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Prepared By
Dr. Ibrahim M. Jomaah
Dr. Abdulrahman M. Basahel
Eng. Egab H. AL Zamanan
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Table Of Contents
Page
1. Introductory Laboratory 1
1.1 introduction 1
1.2 objectives 1
1.3 procedures 2
1.4 Requirements 2
2. Vision Testing 3
2.1 Introduction 3
2.2 Classification Of Jobs And Visual Functions 3
2.3 Objectives 5
2.4 Instruments and Tests 5
2.5 Procedures 8
2.6 Interpretations of The Results 8
3. Audiometry 9
3.1 Introduction 9
3.2 Objectives 11
3.3 Instruments 11
3.4 Procedures 12
3.5 Results 14
4 Anthropometric Measurements 15
4.1 Introduction 15
4.2 Objectives 15
4.3 Procedures 16
4.4 Instruments 16
4.5 Testing The Normality of Anthropometric Data ( Test ) 22
4.6 Calculation of The Percentiles 26
5. The Use Of Anthropometric Data In Designing An Office Work
Station 28
5.1 Introduction 28
5.2 Objectives 28
5.3 Procedures 29
5.4 Design Principles Applying Anthropometric Data 29
5.5 General Gioidelines Of Work Station Design 31
5.6 Using Anthropometric Data In Work Station Design 34
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5.7 Illustration Example 35
6. The Evaluation Effect of Awkward Posture on the
Performance of the Musculoskeletal System 38
6.1 Introduction 38
6.2 Objectives 40
6.3 Instrument 40
6.4 Experiment Procedures 42
6.5 Results of the Experiment 43
7. NIOSH Lifting Equation and Material Handling 44
7.1 Introduction 44
7.2 Objectives 50
7.3 Instrument 50
7.4 Experiment Procedures 52
7.5 Results of the Experiment 53
8. Physical Work Capacity (I) 54
8.1 Introduction 54
8.2 Heart Rate 54
8.3 Objectives 56
8.4 Instruments & Tests 56
8.5 Procedures 60
8.6 Results 60
9. Physical Work Capacity (II) 63
9.1 Introduction 63
9.2 Methods Of Determination Of Maximum
Oxygen Consumption 64
9.3 Objectives 64
9.4 Instruments 66
9.5 Procedures 67
9.6 Results 73
10. Measurement Of Reaction Time 74
10.1 Introduction 74
10.2 Types Of Reaction Time 75
10.3 Objectives 76
10.4 Instruments 76
10.5 Procedures 77
10.6 Results 78
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11. Strength Measurements 80
11.1 Introduction 80
11.2 Objectives 81
11.3Instruments 81
11.4 Procedures 83
11.5 Results 85
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1. INTRODUCTORY LABORATORY
1.1 Introduction
This laboratory session is an introductory laboratory in which students obtain
a general knowledge on human factor engineering as well as the nature of
experiments and laboratory exercises that are covered throughout the
semester. Safety instructions that must be followed during each laboratory
session will be explained and discussed with students. In addition video films
about human factors engineering and its profession as well as video films
about the human body and its major systems, particularly the muscular,
skeletal, circulatory, respiratory and nervous systems; will be shown to the
students during this laboratory session. These information are anticipated to
provide students with sufficient knowledge on human factor engineering and
work systems with emphasis on human body and its role in any work system.
1.2 Objectives
The objectives of this laboratory session are summarized in the following
points:
1. Gaining a basic knowledge and understanding of the human factor
engineering area.
2. Understanding the nature of experiments and laboratory exercises that
are covered throughout the semester.
3. Reviewing and understanding the safety instructions that must be
followed during each laboratory session.
4. Acquainting students with the major human body systems, particularly
the muscular, skeletal, circulatory, respiratory and nervous systems.
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1.3 Procedure
The procedure of this introductory laboratory session is summarized in the
following steps:
1. Explain to students what is human factors engineering, its profession,
applications and uses.
2. Explain the type and the nature of the experiments and laboratory
exercises that are covered throughout the semester. Answer any
question that might arise.
3. Explain and discuss with students the safety instructions that must be
followed during each laboratory session.
4. Show a video film about human factors engineering and ask students to
take notes.
5. Show video films about human body and its major systems, particularly
the muscular, skeletal, circulatory, respiratory and nervous systems and
ask students to take notes.
1.4 Requirements
Students are requested to present short reports about the following:
The human factor engineering area, its definitions, objectives and
applications.
Gross anatomy and functions of the following:
(a) Muscular system.
(b) Skeletal system.
(c) Nervous system.
(d) Respiratory system.
(e) Circulatory system The report might be submitted in Arabic language; however, the English
nomenclature of all the body parts and scientific terminology should be
included.
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2. Vision Testing
2.1 Introduction
Eyes are used daily in countless seeing tasks . Employees meeting the vision
requirements of their jobs learn job sooner , have fewer accidents , do better
work , and are less likely to become dissatisfied . in short , they are better
fitted to their jobs . statistical analyses of vision and job performance has
proved a definite connection between adequate visual efficiency and
successful performance on the job . in terms of productivity , maintenance of
quality ,and safety , efficient seeing is important on the job . the vision
requirements of each job are determined by analysis of the job descriptions or
by an actual in-plant study. Anyone who is not able to maintain comfortable
seeing that is equal to the visual task presented by the occupation is laboring
under a handicap usually needlessly .
2.2 Classification Of Jobs & Visual Functions
Years of study at the Occupational Research Center at Purdue University
,and later at the Bausch & Lomb plant , have revealed that industrial jobs fall
into six board categories or "job families " these categories are :
1. clerical and administrative ; which includes visual job family involving
general office , paper or desk work , and office- machine operation .
Managerial , administrative and certain technical occupations are also
included in this visual job family
2. inspection and close machine work which includes jobs involving the
inspection of small parts . machine operating jobs in which the work is done at
a very close distance and assembly jobs involving very small parts such
watches , radio tubes , and electronic equipments are also in the visual job
family .
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3. Operators of Mobile Equipment; which includes jobs requiring the operation
of moving vehicles. It is desirable for the safety of the operator and for
prevention of damage to his equipment or plant property. Jobs included are;
truck drivers and operators of cranes and fork lifts
4. Machine operators; which includes visual job family involving the routine
operation of machines in which the visual tasks are within arm's length, such
as lathes, drill presses and spinning …etc
5. Unskilled Laborers: which includes jobs of a relatively unskilled nature. It
also aids in assuring the safety of other employees and in protecting
equipment in the same work area . this visual job family includes porter ,
janitor , guards , hand truckers, sweepers …etc
6. Mechanic and Skilled Tradesmen ;which involve non-routine jobs of
mechanical nature , such as automobile mechanics , machine fixture . this job
family also include skilled trades , such as toolmaker , electrician
,plumber….etc
Researches revealed that there are 12 visual functions that are important to
success in most occupation . The B&L vision tester used in this experiment
tests these functions . the test falls under 4 basic classifications as follows
a) phoria or binocular action of the eyes ( vertical and lateral muscle balance-
at the FAR & NEAR testing distance – four tests )
b) Acuity , or fitness of visual discrimination ; (both eyes , right eye , and left
eye at both testing distance – six tests )
c) Stereopsis , or perception of depth ; (at FAR distance – one test )
d) Color discrimination ; (at FAR distance – one test )
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2.3 Objectives
The objectives of this experiment may be summarized in the following points ;
1. To study and understand the six categories of jobs and the 12visual
functions
2. To learn a simple and accurate method of measuring the 12visual functions
3. To study how to compare the measured 12visual functions with the visual
standard that are required for the student selected job and determining
whether the student visual skills are adequate , below or seriously lowered for
the job visual standard .
2.4 Instruments and Tests
The B&L vision tester provides near point measurements of the above stated
2 functions that express eye acuity and binocular balance . the instrument
contains a variety of inter-changeable slides which have been developed to fit
various FAR&NEAR testing situations and are moved by the test dial which is
easily turned . the slides are illuminated by 4 lamps . the FAR tests are
presented at an optical distance of 20 Ft , the NEAR test at 14 inches . A
green pilot light is the reference point for dial numbers for FAR testing ; an
amber light for NEAR testing . one lens system is used for both FAR&NEAR
tests . it is raised or lowered by the Lens Lever ; its position is further
identified by lettering on the side of the instrument body . the testing slides are
designed as follows
1. Lateral Phoria ; the test ( muscle balance) measure the tendency of the
eyes to turn in or out when the stimulus to fusion is low . the slides consist of
an arrow before the left eye and a row of numbered dots before the right .the
arrow moves to the phoria position
2. Vertical Phoria ; a red dotted line before the left eye will fuse with the top of
one of numbered stair steps before the right .
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3. Acuity Tests ; the test objects consists of a large square with its diagonals
at 900 and 1800 respectively . the square is divided into 9 smaller squares ;
the 4 smaller squares at corners are usable for testing targets . The targets
area itself consists of checkerboard with the individual squares of a size to
give the required visual angle suitable for each acuity level with this design
the check board can be located only when the squares are resolvable. Acuity
targets are in 12steps of progressive difficulty over a range equivalent to
Sneller Rating of 20/200 to 20/17 .
4. Depth tests; measure the ability to judge distance. the vision tester slide
presents a distance target with certain details , which are optically located
closer to the eyes of the observer . these ate seen as projections at 9 varying
distances before the target .
5. Color slides; is a transparent color reproduction of four highly selective
pseudoisochromatic plates .
The B & L vision tester and its main components are shown in figure 2..
Figure 2.1 Human Eye Schematic diagram
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Figure 2.2 The B & L Vision Tester and its Main Components
2.5 Procedures
The B & L vision tester is used to test 12 visual functions mentioned above .
The procedure of the experiment may be summarized in the following points ;
1. Switching The B & L vision tester on using the master switch
2. Setting the lens lever at FAR OR NEAR position depending on the test
3. A student should place his hand snugly on the hand rest tissue
4. using the Test Dial to change from one test to another test (the question to
be asked for each test is provided in the instrument manual with their answer
model )
5. Recording the score of each question on the scorecard provided with the
instrument
2- head rest tissues 1-Instrument body
4- Easy "FAR " & "NEAR" change 3- lens system
6 –tension knobs 5- instrument base
8- "FAR " & "NEAR" indicators 7- test dial
10- convenient carrying handle 9- observation windows
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6. After testing , the scorecard is positioned behind the appropriate ,
transparent Job Vision Standard sheet provided with the instrument . this tells
at a glance if any of the test scores fall below the vision standard required for
the job .
2.6 Interpretation Of The Results
The result of the test is concluded as:
a) Visual skills adequate the standard (clear area of template)
b) Visual skills below the specific standard (yellow area of template))
c) Seriously lowered visual skills for the job performance (red area of
template)
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3. AUDIOMETRY
3.1 Introduction
Understanding how humans hear is a complex subject involving the fields of
physiology, psychology and acoustics. Sound enters the ear as mechanical
energy. Sensory cells within the inner ear, called "hair cells" because of their
hair-like appendages, convert the mechanical energy of sound into electrical
energy. These electrical impulses are then transmitted to accompanying
nerve cells, which carry them to the brain for decoding. The outcome of this
process is known as the perception of sound. A breakdown in this system,
whereby the hair cells or nerve fibers cease to function, leads to sensor neural
hearing loss.
People are born with approximately 15,000 sensory cells and 30,000 nerve
fibers within each ear. Each hair cell is individually tuned to a specific range of
sound frequency. When hair cells or nerve fibers die - due to age, noise
trauma or a variety of other reasons - the result is loss of hearing in that
frequency region. The greater the number of hair cells that die, the greater the
hearing loss. Once a hair cell dies, evidence shows that, in time, the
accompanying nerve fiber will also die. In a smaller percentage of cases of
sensor neural hearing loss, the nerve fiber dies, while the accompanying hair
cell remains intact.
The ear consists of three basic parts - the outer ear, the middle ear, and the
inner ear. Each part of the ear serves a specific purpose in the task of
detecting and interpreting sound. The outer ear serves to collect and channel
sound to the middle ear. The middle ear serves to transform the energy of a
sound wave into the internal vibrations of the bone structure of the middle ear
and ultimately transform these vibrations into a compressional wave in the
inner ear. The inner ear serves to transform the energy of a compressional
wave within the inner ear fluid into nerve impulses, which can be transmitted
to the brain. The three parts of the ear are shown in (figure 3.1).
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3.2 Objectives
The objectives of this lab exercise can be summarized in the following points:
1. To study and understand the structure of the major components of
the ear involved in processing sound.
2. To learn a simple and accurate method of measuring the hearing
level and compare it with the hearing threshold level (the least sound
level that can be perceived) at different frequencies.
3. To understand the importance of measuring the hearing level at
different frequencies in terms of :
a) Providing valuable information concerning the worker’s ability to
perform the job safely and effectively.
b) Detecting early symptoms of hearing loss.
c) Assessing the hearing conservation program in the plant or factory.
Figure 3.1: The Three Parts of Ear
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3.3 Instrument
The instrument used in measuring hearing level in decibel (dB) at different
frequencies is the Audiometer type 1800. The Audiometer is a device used for
evaluating person’s hearing acuity. It is basically an X-Y recorder with a built-
in test signal generator. The X-axis represents the test frequency and the
deflection is controlled primary by the instrument itself. The Y-axis deflection,
which represents the hearing level of the tested subject, is controlled by
means of a hand switch operated by the tested subject. The switch operates
an automatic attennator, which controls the level of the signal supplied to the
ear phone worn by the tested subject. The Audiometer type 1800 is shown in
figure. (3.2).
Figure 3.2: The Audiometer Type
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3.4 Procedures of The Experiment
The procedures of the experiment can be summarized in the following
steps:
1. Switching the Audiometer type 1800 on.
2. Filling the information requires on the audiogram chart (see figure 3)
and slides the pen to its far left position by pushing the RETURN
switch. The chart can now be positioned on the chart bed with the
diagram side up with the two holes nearest its center line over the re-
gistration pins.
3. Before starting the test, it is important to instruct the tested subject so
that he clearly understands what is expected from him. For the sake
of uniformity it is advisable to give the same instructions to all tested
subjects, for instance:
“Your ears are going to be tested with a series of tones. You can
control their level by means of the hand switch button. Press the
button as soon as you hear a tone and release it as soon as the tone
disappears. Do not let the tone grow loud and do not leave it
inaudible too long.”
4. It is therefore important to remove all obstructions between the
earphone and the ear, such as hair, eyeglasses, earrings, hearing
aids, etc.
5. Adjust the head band so that it rests on the top of the tested subject’s
head.
6. Center the earphones over both ears and ensure that the earphone
with the red label (or shell) is on the right ear and the one with the
blue label (shell) is on the left ear. Also take care to eliminate any
visible gap between the earphone cushions and the tested subject’s
head.
7. Select the desired test signal mode, CONT. or PULSE, with the TONE
switch and press the TEST button. The X-axis drive will now start on
the first response from the tested subject.
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8. After all fifteen frequencies have been presented to the patient the
signal will be turned off, the writing pen retracted, lifted, and returned
to its start position ready for a new test.
The data collection form of this experiment is shown in appendix II.
3.5 Results of The Experiment
Each student has to perform the experiment and record his hearing level
in decibel (dB) at different frequencies.
Each student has to calculate the mean, standard deviation, the 5th, 50th
and 95th percentiles of the hearing level of the whole class students at
each frequency and comment on the results.
Figure 3.3 : The Audiogram Chart
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Figure 3.4 : Hearing Impairment Calculation Worksheet
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4. ANTHROPOMETIC MEASUREMENTS
4.1 Introduction
Engineering Anthropometry deals with the application of scientific physical
measurement methods to human subjects for the development of engineering
design standards. Dimensions, capabilities, and limitations of humans are
inherited. Since too little can be done to change them, humans dimensions
and capabilities should be taken as the basis for designing the machines,
products and environment around in the work place. So, the designer needs
information about anthropometric data for different populations. Also
information about the variations of anthropometric data within a specific
population is needed in order to produce different types of products to match
most of the members within this population.
Human factors engineers are concerned in getting the correct information
about the anthropometric data for the different population groups in order to
assess their dimensions and physical capabilities. Such information is needed
for the design of work place, work stations, equipment and tools, as well as of
clothing and all other objects used by a human being. Also, with this
information the human factors engineers can assign tasks within the
capabilities of human beings.
4.2 Objectives
The objectives of this lab. exercise can be summarized in the following points:
1. Gaining basic understanding of rationales, applications and
interpretations of the anthropometric measurements and their
frequently used methods.
2. Understanding the methods of collecting the anthropometric data and
the of instruments required for taking these measurements.
3. Understanding the methods of analyzing the collected anthropometric
data. This includes: checking the normality of the collected
anthropometric data and calculating the 5th, 50th and 95th percentile.
20
4.3 Procedures
The studied variables included 36 anthropometric parameters as well as some
basic parameters including: age, ethnic origin, father’s occupation and family
size; the latter two parameters may be used as indicators of the socio-
economic status, ethnic origin is an indicator for heredity. The studied
parameters are summarized in Table (1) and Figure (4.1). The procedures of
this lab. exercise can be summarized in the following points:
1. Students are divided into groups. Each group consists of two students.
2. Each student of the two should take the 36 anthropometric measures
of the other one and record them in the attached data collection form.
3. The collected 36 anthropometric measures are assigned to the
students so that each student will take one of the 36 anthropometric
measures of the class to analyze it.
4. The analysis includes:
a) Testing the normality of each anthropometric measure.
b) Calculating the 5th, 50th and 95th percentile.
4.4 Instruments
The instruments used in this lab. exercise include the following:
1. Metric Scale, which is of the physician’s type. It has a movable rod in
the range of 75 cm to 195 cm with an incremental scale of 1 cm. It is
used to measure the stature; the eye standing, the shoulder standing,
and elbow standing height. The metric scale is also equipped with a
weighing balance of up to 160 kg capacity an incremental unit of 100
gm (0.1 kg). The weight measurements are recorded to the nearest 0.5
kg. The Metric Scale is shown in figure (4.2).
2. Chest Depth Caliber, which is of the physician’s type. It has a movable
rod in the range of 1cm to 60 cm with an incremental scale of 1cm. It is
used to measure the chest depth, chest breadth, waist depth, waist
breadth, head length, head breadth and neck breadth. The Chest
Depth Caliber is shown in figure (4.3).
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3. Breadth Scale, which is of the physician’s type. It has a movable rod in
the range of 1 to 100 cm with an incremental scale of 1 cm. It is used to
measure the shoulder breadth, hip breadth, upper limb breadth,
forward grip reach, elbow finger tip length, shoulder elbow length, thigh
thickness, buttock-knee length, foot length, foot breadth, hand length
and hand breadth. The Breadth Scale is shown in figure (4.4).
4. Fat Caliper (Skin Fold Caliper), which is adjustable from 1 to 60 mm
with increment of 1 mm. It is used to measure fatness. The Fat Caliper
is shown in figure (4.5).
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Table (4.1) : The selected anthropometric parameters
No. Variable Name
*
3 Age
4 Ethnic Origin
5 Father’s Occupation
6 Family Size
7 Weight
8 Height
9 Eye Height Standing
10 Shoulder Height standing
11 Elbow Height Standing
12 Waist Height Standing
13 Standing Vertical Grip Reach
14 Height Setting
15 Eye Height Sitting
16 Shoulder Height Sitting
17 Elbow Height Sitting
18 Sitting Vertical Grip Reach
19 Overknee Height From Floor
20 Underknee Height From Floor
21 Chest Depth
22 Chest Breadth
23 Waist Depth
24 Waist Breadth
25 Head Length
26 Head Breadth
27 Neck Breadth
28 Shoulder Breadth
29 Hip Breadth
30 Upper Limb Length
23
Table (4.2) : The selected anthropometric parameters
No. Variable Name
31 Forward Grip Reach
32 Elbow Finger Tip Length
33 Shoulder Elbow Length
34 Tight Thickness
35 Buttock Knee Length
36 Buttock to Hollow of Knee Length
37 Foot Length
38 Foot Breadth
39 Hand Length
40 Hand Breadth
41 Fat Thickness
42 Chest circumference
43 Waist circumference
24
Figure 4.1: The Selected anthropometric measurements
25
Figure (4.2) The Metric Scale
Figure (4.4) Chest depth caliper
Figure (4.6) Shoulder caliper Figure (4.5) Flexible tape measure
Figure (4.3) Skinfold caliper
26
4.5 Testing the Normality of Anthropometric Data (2א Test)
The Chi-square test of goodness of fit can be used to determine how well
theoretical distribution (such as normal distribution) fit empirical distributions
i.e. those obtained from sample data. So the Chi-square test of goodness of fit
is a method of using sample data to test the hypotheses that this data is
collected from a population that follows certain statistical distribution. This
technique is used in this lab. exercise to test the hypotheses that the
collected 36 anthropometric measures follow the normal distribution.
The normal distribution is a continuous distribution so to conduct this test one
must first group the collected data into certain number of intervals. The steps
of conducting this test can be summarized in the following points:
1. Choose C, the number of intervals.
2. Find the z-value corresponding to the upper limit of each interval. For
the first interval, P(z) = 1/C; for the second interval, P(z) = 2/C; for the
third interval, P(z) = 3/C; and so on. The last interval (like the first
interval) is open-ended.
3. Calculate the x-values of the class limits, using the following equation:
X = µ + z σ ( if µ and σ are unknown they can be estimated from the
sample) .
4. After determining the class limits, the expected frequencies (E) of each
interval should be calculated. Every interval is associated with the
same proportion (1/C), so the expected frequency in every interval is E
E =N (1 / C) where N is the total number of observations.
5. Calculate the actual or observed frequencies (O) of each interval based
on the class limits for the collected data.
6. Calculate the Chi-square 2א from the following equation:
2 / E( O – E ) = 2א
7. The degree of freedom of the Chi-square distribution is calculated as
follows: v = C – No. of parameters estimated – 1
So, if µ and σ are estimated then v = C – 2 – 1 or C – 3 .
27
As an example consider the following data which represent the breadth of hand
measurements (in cm) of 125 individuals (male) arranged in ascending order:
10.10 10.34 10.39 10.42 10.48 10.48 10.49 10.52 10.52
10.54 10.55 10.57 10.59 10.59 10.59 10.61 10.61 10.62
10.64 10.65 10.67 10.68 10.69 10.69 10.70 10.70 10.70
10.71 10.72 10.72 10.73 10.74 10.74 10.74 10.74 10.75
10.75 10.75 10.76 10.78 10.79 10.79 10.79 10.79 10.80
10.80 10.80 10.81 10.82 10.82 10.84 10.85 10.86 10.87
10.89 10.89 10.91 10.91 10.92 10.93 10.93 10.93 10.93
10.95 10.97 10.99 11.00 11.01 11.01 11.02 11.02 11.03
11.03 11.04 11.04 11.04 11.05 11.05 11.06 11.06 11.07
11.08 11.08 11.08 11.08 11.08 11.08 11.08 11.09 11.09
11.10 11.10 11.11 11.12 11.13 11.13 11.14 11.14 11.15
11.16 11.16 11.17 11.17 11.17 11.18 11.18 11.20 11.21
11.22 11.26 11.27 11.30 11.31 11.32 11.33 11.34 11.35
11.40 11.41 11.43 11.55 11.57 11.58 11.58 11.61
To test the normality of the above data the following steps should be followes:
1. Choosing the number of intervals C = 6 (C can be any number but in this case
C selected to be six ).
2. Finding the z-value corresponding to the upper limit of each interval. For the
first interval, P(z) = 1/6 so from the standard normal distribution table z = -0.965
for the second interval, P(z) = 2/6 and z = -0.445 for the third interval, P(z) = 3/6
and z = 0.0 and so on. The last interval (like the first interval) is open-ended.
28
-z +z 1 2 -1 -2 0
3. Calculating the x-values of the class limits, using the following equation:
X = µ + z σ. Since µ and σ are unknown they can be estimated from
the sample as X and S. The X of the sample is 10.94 and S = 0.286.
Based on that the class upper limit of the first interval is:
X1 = X + Z1 S = 10.94 + ( -0.965) * (0.286) = 10.664
The class upper limit of the second interval is:
X2 = X + Z2 S = 10.94 + (-0.445) * (0.286) = 10.813
The class upper limit of the third interval is:
X3 = X + Z3 S = 10.94 + (0.000) * (0.286) = 10.94 and so on.
4. Calculating the expected frequencies (E) of each interval. Every interval
is associated with the same proportion (1/6), so the expected frequency
in every interval is E = N (1 / C) = 125*(1/6) = 20.833. For each interval
the actual (observed) frequency (O) should be calculated and the
following table should be constructed:
1
2
3 4
5
6
29
Table(4.3) illustrate the Z values of the standard normal distribution
corresponding to the commonly used percentiles.
5. The degree of freedom (v) = C – 1 – 2 = 6 – 1 –2 = 3 and if α = 0.05 the
table value of 2א with v = 3 is 7.815 so the calculated 2א value of 7.04 ( from
the above table) is less than the table value of 2א which is 7.815 so we
conclude that the breadth of hand measurements are normally distributed.
The intervals Observed
Freq. (O)
Expected
Freq. (E) ( O – E )2 2א = ( O – E )2 / E
Less than 10.664 20 20.833 0.69 0.033
10.664 - 10.813 28 20.833 51.4 2.47
10.813 - 10.94 15 20.833 34.02 1.63
10.940 - 11.10 27 20.833 38.03 1.82
11.10 - 11.22 18 20.833 8.03 0.38
11.22 and more 17 20.833 14.70 0.705
Total 125 125 146.833 7.04
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4.6 Calculation of the Percentiles
The Kth percentile can be define as the value at or below which fall K percent
of the observations and above which no more than (100 – K) percent of the
observations. For the normal distribution the any percentile can be calculated
using the following formula:
Xp = X + Zp * S where
Xp is the percentile value
X is the average value of the sample data
Zp is the value of Z from the standard normal distribution table that
corresponding to the desired percentile
S is the standard deviation value of the sample data
As an example consider the previous example of the breadth of hand
measurements. The 5th percentile can be calculated as follows:
X0.05 = X + Z0.05 * S
X0.05 = 10.94 + (- 1.64) * (0.286) = 10.47cm
The 50th percentile can be calculated as follows:
X0.50 = X + Z0.50* S
X0.50 = 10.94 + (0.00) * (0.286) = 10.94cm
The 95th percentile can be calculated as follows:
X0.95 = X + Z0.95* S
X0.95 = 10.94 + (1.65) * (0.286) = 11.41cm
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Percentile P Zp
1st 0.01 -2.33
2.5th 0.025 -1.96
5th 0.05 -1.64
10th 0.1 -1.28
17th 0.17 -0.955
50th 0.5 0.00
83rd 0.83 0.955
90th 0.9 1.28
95th 0.95 1.64
97.5th 0.975 1.96
99th 0.99 2.33
Table (5.1): The Z values of the standard normal distribution corresponding to the
commonly used percentiles
32
5. ANTHROPOMETIC DATA IN DESIGNING AN OFFICE WORK STATION
5.1 Introduction
The human is the most important element in work systems,. The design
process, therefore, should proceed 'from the human user outward'. To do this,
we need information on human body dimensions, physical strengths,
limitations and capabilities as well as the working environment, job and task
characteristics. The use of such data allows the workplace to be designed so
as to suit those who will carry out the operations or the tasks.
The job may consist of simple tasks such as assembling an electronic circuit
for a color TV or may consist of complex tasks such as flying an aircraft.
Whatever may be the nature of task or work, simple or complex, the design of
the workplace should be such that the person does not have to, for example,
exert more force than is necessary or adopt undesirable awkward posture,
which may affect his/her manipulative skills. In other words, workplace should
be optimal for the person and the task.
The systematic application of anthropometry can minimize the requirement for
people to adapt to unfavorable working situations, which in turn reduce
musculoskeletal stresses on the body. Anthropometry permits us to develop
standards and specific requirements (bench marks) against which a product,
machine, tool or equipment can be evaluated to ensure their suitability for the
user population.
5.2 Objectives
The objectives of this lab. exercise can be summarized in the following points:
1. Gaining basic understanding of the use of anthropometric
measurements.
2. Understanding the three principles of the application of the
anthropometric data in the work station design.
3. Understanding the general guidelines of designing the work station.
4. To obtain hands-on experiences and training on common
anthropometric methods and their uses in the design.
33
5.3 Procedures
After studying the methods of collecting and analyzing the anthropometric
data including checking the normality of the data as well as calculating the
different percentiles, it is very important to learn how to use these data in
designing a work station. The procedures of this lab. exercise can be
summarized in the following points:
1. Discussing the importance of the anthropometric measurements in the
work station design.
2. Discussing the three principles of the application of the anthropometric
data in work station design.
3. Discussing the general guidelines of work station design.
4. Each student have to design an office work station and specifying the
dimensions of the designed work station based on the following:
a) The anthropometric measurements of the student individually.
b) The anthropometric measurements of the whole class as a
population.
5.4 Design Principles of the Application of Anthropometric Data
In the application of anthropometric data there are three principles that may
be relevant, each one being appropriate to certain types of design problems.
These principles are as follows:
Design for Extreme Individuals: Theoretically the work station should be
designed to accommodate the largest and smallest people in the population;
however, this is not always feasible. A more common approach is to design
for the first, fifth, ninety fifth or ninety ninth percentiles. The Kth percentile can
be define as the value at or below which fall K percent of the observations and
above which no more than (100 – K) percent of the observations (see figure
5.1). A minimum dimension (clearance dimension), of a facility would usually
be based on an upper percentile value of the relevant anthropometric feature
of the sample used, such as the 95th percentile. Perhaps most typically a
minimum dimension would be used to establish clearances, such as for doors,
escape hatches, and passageways. On the other hand, maximum dimensions
(reach dimension) of some facility would
34
be predicted on lower percentiles (say, the 5th) of the distribution of people on
the relevant anthropometric feature. The distance of control devices from an
operator is an example; if those with short functional arm reach can reach a
control, persons with longer arm reach generally could also do so. In setting
such maximums and minimums it is frequently the practice to use the 95th
and 5th percentile values, if the accommodation of 100 percent would incur
trade-off costs out of proportion to the additional benefits to be derived.
Design for Adjustable Range: Certain features of equipment or facilities
preferably should be adjustable in order to accommodate people of varying
sizes. The forward-backward adjustments of automobile seats and the vertical
adjustments of typists’ chairs are examples. In the design of adjustable items
such as these, it is fairly common practice to do so for the range of cases from
the 5th to the 95th percentiles.
Design for the Average: In the domain of human anthropometry there are
few, if any, people who would really qualify as average in each and every
respect. Since the concept of the average person is something of a myth,
there is some rationale for the common proposition that physical equipment
should not be designed for this mythical individual. Recognizing this, however,
we would like to make a case here for the use of average values in the design
of certain types of equipment or facilities, specifically those for which, for
Figure 5.1: The 5th, 50th and 90th Percentiles
35
legitimate reasons, it is not appropriate to pitch the design at an extreme
value (minimum or maximum) or feasible to provide for an adjustable range. It
is also possible to apply the of designing for the average when the designer
primarily concern with one dimension. Designing the lecture room chair may
be an example of this type of designing.
At this stage it is very important to illustrate that the discussion of the above
principles generally refers to the application of anthropometric data for single
dimension and to what percentage of individuals would be accommodated
with specified specifications in terms of such dimensions. The accommodated
percentage can be determined in a straightforward manner for individual
dimension, but the problem becomes more complex when several dimensions
need to be considered in combination. The complications arise from the
interrelationships between and among the dimensions, some of which have
low correlations with each other. Thus, an individual who falls within an
accommodated percentage on one dimension might fall outside the
accommodated percentages on another.
5.5 General Guidelines of Work Station Design
The general guidelines of work station design can be summarized in the
following points:
1. Minimize static loads. Loads on body members due to static work
components may cause strain on muscles, tendons, ligaments and
spinal discs. The resulting physical pains may be reversible and
vanish after the static load is removed, but some ailments may be of
a persistent nature. Example of static loads to be avoided is holding,
lifting or carrying objects with the hands, especially when arms are
outstretched.
2. Every employee should be provided with an adjustable and properly
designed chair, meeting the following requirements:
a) The height of the seat and backrest should both be adjustable.
b) Back support is particularly required for the lower back (lumbar
region).
c) The seat should be cushioned and give way about 2.5 cm (1inch)
36
d) Fabric rather than plastic should be used as a cover material for
the seat and backrest.
e) The recommended depth and width of the seat are, respectively,
about 38 to 40 cm (15 to 16 inch) and 40 to 45 cm (16 to 18
inch). With arm rests, a distance of at least 48 cm (19 inch)
between the arms is recommended.
f) An angle of about 1000 between the backrest and the seat is a
common recommendation. There is less of a consensus
regarding the desired angle of the seat, although the majority
opinion among ergonomists seems to be that the seat should
slope backward slightly (about 10 to 50 ).
g) Arm rests are not generally recommended for industrial chairs
since they are liable to restrict movement. In some
circumstances, arm rests may be appropriate as arm support for
reducing tremor, for example, during fine manipulative tasks.
The recommended distance between the top of the arm rest and
the compressed seat is about 20 cm (8 inch), although this
distance should ideally be adjustable.
h) Foot rests may be necessary for comfortable posture with
approximately horizontal thighs and feet and vertical lower legs.
3. The work surface should be about 5 cm (2 inch) below the elbow for
both sitting and standing postures.
4. The worker should be able to, at his or her discretion, alternate be-
tween a sitting and standing posture. This may require that the work
surface be of adjustable height.
5. Both arm and foot movements should be used, while considering the
following points:
a) Movement speed and accuracy tend to favor arm movements,
especially for complex tasks.
b) When arm and foot movements require considerable attention, such
simultaneous movements should be avoided since the attention re-
quirement may exceed human capability and lead to potential
safety hazards.
37
c) Foot movements tend to reduce the speed and accuracy of arm
movements.
d) Avoid having both feet move simultaneously.
6. Both arms should move simultaneously and in such a way that the
two movements are symmetrical and opposite in direction (away
from and toward the center of the body) if visual attention is not
required during or at the end of each movement or parallel if
visual control is required.
7. Arm movements should be continuous and curved. Straight
movements with sudden changes in direction and velocity are
inefficient and fatiguing.
8. Keep arm movements within the normal work area. The normal
work area in the horizontal plane may be defined as the area
determined by the two arcs drawn by the hands when the forearms
are moved about relaxed upper arms (with the angle between
upper arm and the horizontal plane being approximately 650 ). The
normal work area in the vertical plane may be similarly determined
by the arcs drawn by the hands during vertical sweeps of the lower
arms while pivoting about the elbows and with the upper arms
remaining relaxed.
9. Arm movements should pivot about the elbow rather than the
shoulder (that is, rather than using cross-body movements of the
entire arm).
10. The preferred hand should be used since it is generally faster,
stronger and capable of more accurate manipulations than the
nonpreferred hand
11. Twisting motions should be performed with the elbow bent to
prevent overstressing of muscles and tendons.
12. Fixed locations should be used for tools, materials and controls.
This principle eliminates the need for such ineffective task
elements as search and select.
13. A work station should be so designed that it is compatible with the
physical dimensions and strengths of the individual user or
38
potential user population. Anthropometric data should be used for
determining user population characteristics.
14. Each hand-operated tool and device should be made to fit the
hand and in such a way that it can be used with the hand in the
neutral position (that is, in line with the forearm), it can be used by
either hand, it has properly designed hand grip (at least 10 cm (4
inch) in length and approximately 5 cm (2 inch) in diameter for
good power grip) and it utilizes the appropriate muscle groups and
avoids single-finger repetitive action (thumb action is less
undesirable than index-finger action).
5.6 Using Anthropometric Data in Work Station Design (A Step By Step Approach)
The use of anthropometric data for design of workplaces, machines,
equipment and product should proceed in a systematic manner to achieve the
best results. A step-by-step procedure is outlined as below.
1. Select the user population. This essentially means determining the
gender (male, female or both), age (children, young adult, elderly),
occupation, nationality or ethnicity and cultural aspects of the user
population.
2. Determine what body dimensions are needed for the design. For
example, the design of a computer work station may require popliteal,
elbow and knee heights. For the design of a control panel, the
forward reach is a required data. Further, in this step, it should also
be checked that all relevant data are available. If any data are
missing, steps should be taken to get them.
3. Determine what “principle” should be applied (e.g., design for
extreme individuals, for an adjustable range, or for the “average”).
39
4. When relevant, select the percentage of the population to be
accommodated (e.g., 90 percent, 95 percent) or whatever is relevant
to the problem.
5. Develop anthropometric tables appropriate for the population, and
extract relevant values.
6. If special clothing is to be worn, add appropriate allowances
7. If possible set up a full size mock-up. This is a key step in the design
process and is useful in revealing design faults. Mock-ups of the
equipment can be made of cheap materials such as card board,
plastics, etc. Mock-up trials should involve real life conditions, that is ,
representative tasks, users and conditions so that when the final
product or facility is manufactured, it will work as intended. If mock-up
tests reveal any problems, the design process should be repeated
until an acceptable match is obtained.
5.7 Illustration Example
The primary workspace dimensions and their anthropometric determiners are
as follows:
a) Seat height S is popliteal height plus heel height.
b) Table height T is seat height plus thigh thickness plus tabletop thickness.
c) An angle of about 250 is a commonly recommended for the Footrest.
d) Eye height E is seat height S plus eye height (sitting) minus slump. When
leaning back against a suitable high backrest at π = 1050, eye height
needs to be corrected for this angle.
e) Display height is determined by the eye height E, viewing angle α against
the horizontal, and viewing distance V. The visual target (the center of the
display) is at a height d over the support surface, which in turn is at a
height D above the floor.
Figure 2 shows these dimensions schematically. The following equations can
be used to calculate the variables listed above:
1. Seat height S = Popliteal Height + Heel Height
(Heel height is assumed to be 2 cm)
40
2. Table height T = S + Thigh Thickness + Tabletop Thickness
(Tabletop thickness is assumed to be 2 cm)
3. An angle of about 250 is a commonly recommended for the Footrest.
4. Eye Height E = Eye Height x sin π - slump
π = 900 for upright sitting π = 1050 for reclined sitting Slump is assumed to be 2 cm 5. Display Support Height D = S + E - d - V x sin α
d is the height of the center of the display above D V is the viewing distance, assumed to be 40 cm
α is the preferred viewing angle, above (+) or below (-) horizontal, in the
lateral view. In recent experiments (Kroemer), the viewing angle has been
found to be:
For upright sitting π = 900 : α = -28.60
For reclined sitting π = 1050 : α = -19.580
41
Figure 5.2: Work Station Dimensions
42
6. The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal System
6.1 Introduction
The musculoskeletal system of the human body includes the bones, muscles
and connective tissues. The most important function of this system is to
maintain posture and produce joint movement. Additionally it supports the
human body by producing heat and maintaining body temperature. According
to the United States Occupational Safety and Health Administration (OSHA,
2002) about 60 percent of overexertion injuries reported annually in the United
States are due to improper lifting, repetitive tasks (e.g., working on an
assembly production line) or using awkward posture while performing a task.
As well musculoskeletal pain and injuries most commonly occur in the lower
back and upper extremities (e.g., the arms, wrists, neck and shoulders).
Awkward posture is one of the most important factors that lead to
musculoskeletal disorders as well as a heavy physical workload. Ergonomics
defines the term ‘awkward posture’ as a deviation of a joint from the preferred
neutral position, in other word, performing a task with different body parts
(e.g., back, joints) twisted or bent backward or forward rather than in the
neutral position (the normal position of body parts), causing transient
discomfort and fatigue. Awkward posture is the result of a mismatch between
the workplace design and the dimensions of the human body and can lead to
musculoskeletal problems, particularly lower back disorders. Examples of
awkward postures include performing tasks with back flexion (a stooping
posture), kneeling and overhead tasks.
Various methods and techniques are used to evaluate the impact of awkward
posture on the performance of the musculoskeletal system. These methods
are divided broadly into two types: firstly objective measures of performance,
physiology (e.g., heart rate, muscles activity, blood pressure) and force on
body parts; and secondly assessment tools for subjective measures, including
the Rapid Upper Limb Assessment Tool (RULA; see Figure 6.1a) and
43
Category-Ratio Borg Scale (Borg CR-10; see Figure 6.1b). RULA is one of the
most common methods used to evaluate the musculoskeletal risks of poor
posture in upper body parts, particularly the neck, trunk and upper limbs. This
method easily calculates the rating of musculoskeletal loads in tasks that
present a risk of neck and upper-limb loading. The tool generates a single
score as a snapshot of the task which is a rating of the required posture, force
and movement. The risks are calculated into a score from 1 (low) to 7 (high).
These scores are grouped into four action levels that indicate the time frame
in which it is reasonable to expect risk control to be initiated.
Figure 6.1a: RULA tool form. (adapted from www.ergo-plus.com)
44
6.2 Objectives
The objectives of this laboratory experiment are as follows:
1. To gain knowledge about awkward postures
2. To learn about common methods (performance, physiological and
subjective) used to assess the effect of awkward posture on the
musculoskeletal system and its performance
3. To understand how to implement the RULA method as a common
technique to assess musculoskeletal risks while performing a task
4. To learn how to compare the musculoskeletal risks of two different
working postures and to educate students about musculoskeletal
risks posed by these working postures
6.3 Instrument
A wooden plate and two uprights have small wooden plates with 6 bolts for
each upright plate and each bolt has nuts and washers (Hand tool dexterity
test, model 32521, Lafayette Instrument, US; see Figure 2) for a total of 12
bolts. The device has the following dimensions: 0.76×0.40×0.40 m. The
0 Nothing at all “No P”
0.3
0.5 Extremely weak Just
noticeable 1 Very weak
1.5
2 Weak Light 2.5
3 Moderate 4
5 Strong Heavy 6
7 Very strong 8
9
10 Extremely strong “Max P” 11
ϟ
● Absolute maximum Highest
possible
Figure 6.2 1b: Borg-CR10 rating scale range. (adapted from Borg, 1998)
45
wooden plate simulates the assembly task because this type of task is
common in many different factory jobs, particularly in the industrial sector, and
the operator can assume an awkward posture to perform this type of task.
Two types of hand tools (10-inch Crescent wrench and screwdriver) are used
to fix the bolts to the wooden plate (see Figure6. 2).
In addition an A&D Medical heart rate (HR) and blood pressure (BP; systolic and
diastolic blood pressure) monitor (UA 767-PLUS-30 Memory, US) features a
suitably sized, high-definition crystal display, large 30 memory and average
reading function. It also includes a standard slim-fit cuff with an upper arm
circumference of 22 cm to 32 cm (See Figure 6.3).
A digital stopwatch (Dad-7141, Japan) also records the time to complete a
task. The stop watch has these features: 60 lap and split memory with
1/100sec memory recall during operation, calendar and time (12/24 hour
format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water
resistance (See Figure6. 4).
Figure 6.2: Assembly wooden plate, hand tools and bolts with
nuts and washers.
46
6.4 Experiment Procedures
The experiment procedures are as follows:
1. Participants are given a brief introduction to the experiment in order
to familiarize them with the procedure.
2. They are provided with instructions and advise on how to assemble the
wooden plates.
3. The participants are then asked to affix the digital A&D Medical
heart rate monitor to their left hand so that it records the heart rate for
each participant at resting level and at the end of each minute while
performing the assembly task.
4. Next the participants start the assembly task in two different
postures (two conditions): first a stooped or awkward posture in which
the back is leaned forward without the knee bent; secondly a sitting
posture in the neutral posture. In each posture the participant needs to
fix 12 bolts on both upright plates (see Figure 2) within the 5 min of
allotted time.
5. The accuracy and the actual time required to complete the task are
recorded.
6. Finally immediately after completing each condition in the 2- to 3-minute
break between each task condition, the participants are asked to
complete the Borg-CR10 scale (see Figure 1b).
Figure 6.3: Digital A&D Medical heart rate and blood pressure monitor. (UA
767-PLUS-30 Memory)
Figure 6.4: Digital stopwatch.
(Dad-7141, Japan)
47
6.5 Results of the Experiment
a. The groups are required to perform a statistical analysis and find the
significant impact of each postures on the following measures:
i. Accuracy and time to complete the task
ii. Heart rate (HR)
iii. Borg-CR10 score
iv. RULA method score
Note: You need to use analysis of variance (ANOVA) repeated measures
analysis to find the effect of the two postures on the measures.
b. The participants need to determine the relationships between the
accuracy, time of task, heart rate and Borg-CR10 measures by
Pearson’s correlation (r) technique.
c. Each group has to calculate the mean, standard deviation, the 5th, 50th
and 95th percentiles of the completed time of task and heart rate of each
participant for each task condition.
48
7. NIOSH Lifting Equation and Material Handling
7.1 Introduction
A decade after the first NIOSH lifting guide, NIOSH revised the technique for
assessing overexertion hazards of manual lifting. NIOSH developed an
equation (1981) to assess the impact of lifting load on low back (L5/S1) and to
help ergonomists and occupational safety analyze lifting demands and find
the amount of force on low back. The purpose of equation is to prevent or
reduce the occurrence of lifting –related low-back pain and injuries. The
equation in 1981 provides two weight limits action limit (AL) & maximum
permissible limit (MPL). The new document of equation was developed in
(1991) and calculate one parameter which is called recommended weight limit
(RWL) no longer contains two separate weight limits (Action Limit (AL) and
Maximum Permissible Limit (MPL)). It represents the maximal weight of a load
that may be lifted or lowered by about 90% of American industrial workers,
male or female, physically fit and accustomed to physical labor.
Three main criteria are considered in creation of NIOSH lifting equation:
Biomechanics Criteria
• The biomechanical criterion selects 3.4 kN as the compressive force at
the L5/S1 disc that defines an increased risk of low back injury
• The 3.4 kN limit established on the basis of epidemiological data and
cadaver data.
• Epidemiological data from industrial studies provide quantitative
evidence that there is a relationship between lifting-related low back
pain and injury with high compressive force at the L5/S1 disc.
• The back problems increases 1.5 times while the compressive forces
at the L5/S1 between 4.5 kN and 6.8 kN greater than while the
compressive forces below 4.5 kN.
Physiology Criteria
The physiological criteria were selected to limit loads for repetitive
lifting.
49
Activities such as walking, load carrying, and repeated load lifting use
more muscles groups than infrequent lifting tasks so, they require large
energy expenditures.
The physiological criteria were selected to limit loads for repetitive
lifting.
The maximum limit of energy expenditure for a lifting task occurs at 2.2
to 4.7 kcal/min.
Psychophysics Criteria
Psychophysics Criteria is developed on the basis of measurement of
the maximum acceptable weight of lift (MAWF).
In the Psychophysics criteria the maximum acceptable weight of lift
identifies depend on the workers judgment.
The optimum conditions for lifting task (NIOSH, 1991) are:
• The lifting task should perform with a symmetric lifting position with no
torso (trunk) twisting since; twisting torso is more harmful than
symmetric lifting.
• Good handles and coupling to help grab and easy to lift the load.
• The vertical distance of lifting should be ≤ 25 cm.
• The horizontal distance between the load and spine should be
decrease.
• The vertical distance of the originating height of the load is around 75
cm above the floor.
• The optimum frequencies of lifting are 4 times per minute.
The new equation resembles the 1981 formula for AL, but includes new
multipliers to reflect asymmetry and the quality of hand-load coupling. The
1991 equation allows as maximum a “Load Constant” (LC) - permissible
under the most favorable circumstances -- with a value of 23 kg (51 lb.). The
equation that uses to compute the RWL is:
RWL = LC*HM*VM*DM*AM*FM*CM
LC - load constant of 23 kg or 51 lb.
50
** Each remaining multiplier may assume a value [0, 1]
HM - the horizontal multiplier: H is the horizontal distance of the hands from the ankles (the midpoint of the ankles) VM - the Vertical Multiplier: V is the vertical location (height) of the hands above the floor at the start and end points of the lift. DM - the Distance Multiplier: where D is the vertical travel distance from the start to the end points of the lift AM - the Asymmetry Multiplier: where A is the Angle of asymmetry, i.e., the angular displacement of the load from the medial (mid-saggital plane) which forces the operator to twist the body. It is measured at the start and end points of the lift. Note: the representation of the required dimensions is illustrated in Figure 1. FM - the frequency multiplier: where F is the frequency rate of lifting, expressed in lifts per minute (See Table 2.). CM - the coupling multiplier: where C indicates the quality of coupling
between hand and load (See Table 3.).
The value of the first five components can be determined with formulas in the
Table 1. The values of FM and CM multipliers can be found in Tables 2 and 3,
respectively.
To quantify the degree to which a lifting task approaches or exceeds the
RWL, a lifting index (LI) was proposed for the 1991 NIOSH lifting equation,
which defines as the ratio of the load lifted to the RWL. So, in order to
determine the Lifting Index (LI) the following equation is used:
LI = Weight of object / RWL
The LI can be used to estimate the risk of specific lifting tasks in developing low-back disorder.
If the lifting tasks with LI < 1, no risks for low back LI > 1, risks for low back will occur for some workers and it is
recommended to redesign the lifting task LI > 3, high risks for most of workers and it is necessary to make an
immediately redesign for the lifting task
51
Figure 7.1 Graphics representation the required dimensions for NIOSH equation
and represent the hands locations and angle of asymmetry (A)
52
Table 7.1 Definition of Components of NIOSH Lifting Equation
53
Table 2. Frequency Multiplier (FM)
Table 7.3. Coupling Multiplier (CM)
54
7.2 Objectives
The objectives of this laboratory experiment are as follows:
7. To gain knowledge about NIOSH lifting equation
8. To learn about common methods (NIOSH Lifting equation) used to
assess the effect of material handling and lifting tasks on low back in
particular, the impact of lifting tasks on
9. To understand how to implement the equation in order to reduce the
impact of lifting task on low-back (L5/S1) disc.
10. To learn how to analyze the lifting task practically and use the NIOSH
equation to calculate the recommended weight limit (RWL) and lifting
index (LI) in lifting task scenario.
7.3 Instrument
Two wooden boxes were used in this experiment and sets of loads (see
Figure 7.2) in order to induce the physical workload and lifting task scenario.
The box to be lifted had the following dimensions: 0.35×0.35×0.30 m, where
0.30 m was the distance between cut-out handles. There were two cut-out
handles 0.25 m above the bottom, with dimensions 0.20×0.08 m and with
weight 2.5 kg. These box dimensions were selected to be identical to the
standard lifting box size guidelines. The physical task was lifting boxes with
inside loads, since this is more applicable to real life than the cycling task. The
lifting boxes simulate the lifting task because this type of task is common in
many different factory jobs, particularly in the industrial sector, and that type of
task can impact significantly on workers low-back as well as leads to back
injury.
In addition, the GONIMETER (Lafayette gollehon extendable, model 01135,
USA) (See Figure 7.3) was used to determine the torso angle while lifting and
transfer the boxes from first location (floor) to the second position (table).
Also, the anthropometric tape (Lafayette, model J00305, USA) was used to
determine the dimensions while performing the lifting task.
Moreover, the A&D Medical heart rate (HR) monitor (UA 767-PLUS-30 Memory,
US) with features a suitably sized, high-definition crystal display, large 30 memory
55
and average reading function was used to record the heart rate. It also includes a
standard slim-fit cuff with an upper arm circumference of 22 cm to 32 cm (See
Figure 7.4).
A digital stopwatch (Dad-7141, Japan) also records the time to complete a
task. The stop watch has these features: 60 lap and split memory with
1/100sec memory recall during operation, calendar and time (12/24 hour
format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water
resistance (See Figure 7.5).
Figure 7.2 Wooden box and loads
Figure 7.3 Goniometer and anthropometric tape
56
7.4 Experiment Procedures
The experiment procedures are as follows (group work):
11. Participants are given a brief introduction to the experiment in order to
familiarize them with the procedure and complete the health
questionnaire in order to check any previously back injury for the
students (healthy volunteer).
12. They are provided with instructions and advise on how to lift the
wooden boxes in appropriate posture (squat posture).
13. The participants are then asked to affix the digital A&D
Medical heart rate monitor to their left hand so that it records the heart
rate for each participant at resting level and at the end of each minute
while performing the lifting.
14. There are two boxes with 8 kg of loads for each box and the
participant needs to pick up the first box directly in front of him from
the floor (first location). After lifting the box, the subject must twist
approximately 90 degrees at the waist to place the box on a table.
15. Then, the participant needs to repeat this lifting task with
second box and at this time other student in the group needs to return
the first box from the table to the first location. The subject is required
to perform this task approximately 5 times per minute for 5 min
allocated time.
Instructions: You will need one subject to perform the lift task,
one student to take the required task dimensions as mentioned
Figure 7.4 Digital A&D Medical heart rate and blood pressure monitor. (UA
767-PLUS-30 Memory)
Figure 7.5 Digital stopwatch.
(Dad-7141, Japan)
57
previously and complete the NIOSH equation worksheet (see
Figure 7.6). You will also need one student to keep time and tell
when the heart rate is to be taken. and the rating of perceived
exertion is to be collected.
16. Finally immediately after completing the lifting task, the participant is
asked to complete the Borg-RPE scale.
7.5 Results of the Experiment
a. The groups are required to calculate the Recommended Weight Limit
(RWL) and Lift Index (LI) (use the attached NIOSH worksheet).
b. Each group need to propose a valuable recommendation and
interventions to reduce the impact of lifting task on low-back.
c. Using the numeric values for the RPE determine if there is a correlation
between H.R. and the values obtained for the RPE.
d. Each group has to determine the differences between HR at rest level
and HR during performing the lifting task via t-test analysis.
Figure 7.6 NIOSH Lifting Equation Job Analysis Worksheet
58
8. Physical Work Capacity (I)
Measurement of Heart Rate
8.1 Introduction
Physical work capacity (p w c) plays a central role in the process of carrying out
the ergonomic stress analysis in industry. The objectives of applying ergonomic
principle in the work place to maintain a balance between job stress requirement
and PWC . if PWC is exceeded the worker is at risk of overexation if the job stress
is less than PWC ,the worker in underutilized and there a productivity loss
.Physical work capacity is the functional capacity of an individual to perform a
certain task that requires muscular activity over a period of time . the length of time
may vary from a few seconds ( e.g. strength ) to several hours ( e.g. endurance )
Personal, task , and environmental parameters are important factors that affect the
physical work capacity of an individual . some of the most important personal
factors are ,age ,gender ,body weight ,and fitness level .
It is well established that Physical work capacity declines with individual's age . the
maximum Physical work capacity is usually achieved in the age of range of 25 – 35
years .The Physical work capacity of an individual who is over 60 years of age is
about 50 % of the values attained around 25-35 years . on average , the female
Physical work capacity is about two thirds of the male capacity . fitness level can
significantly improve Physical work capacity of an individual . the capacity of a very
fit person may reach as high as two to three times that of the least fit person .
8.2 Heart Rate
Physical work demand adjustments and adaptation , which affect nearly all
the organs , tissues and fluids of the body . the most important of these are
(a) deeper and more rapid breathing
(b) increased heart rate , accompanied by an initial rise cardiac capacity and
an increased output per minute .
59
(c) vasomotor adaptation , with dilatation of the blood vessels in the organs
involved ( muscles and heart ) , while other blood vessels contract
This diverts blood from the organs not immediately concerned into those
which need more oxygen and nutrients .
(d) rise in blood pressure , increasing the pressure _gradient from the main
arteries into the dilated vessels of the working organs , therefore .
Speeding up the flow of blood
(e ) increase supply of sugar , by releasing sugar into the blood from liver
(f) rise in body temperature and increased metabolism . the rise in body
temperature speeds up the chemical reaction of metabolism , and ensure that
more chemical energy is converted into mechanical energy ( for this reason
athletes warm up before a contest ) .
Measuring the heart rate ( taking the pulse ) is one of the most useful ways
assessing the workload , because it can be done so easily . when the work is
comparatively light , the heart rate increases quickly to a level appropriate to the
effort , and then remains constant for the duration of the work . when work ceases ,
the pulse returns to normal after few minutes .
With more strenuous work , however , the heart rates goes on increasing until
either it is interrupted , or the operator is forced to stop from exhaustion . figure 1
shows diagrammatically the behavior of the heart pulse during certain work studies
.
60
8.3 Objectives
The objectives of this experiment may be summarized in the following points ;
1. Studying a method of measuring the work rate and energy using the Ergocycle .
2. Learning a method of measuring the heart rate during rest , physical effort and
rest
3. Studying the relation between the heart rate and the time ( duration ) of
physical effort using regression .
4. Studying a method of evaluation the Physical work capacity using the heart rate
.
8.4 Instruments
In this experiment three instruments are used . these are ;
1. Bicycle Ergometer ( figure 8.1)
2. Heart rate monitor ( figure 8.2 )
3. Stop watch ( figure 8.3 )
Figure 8.1 Bicycle Ergometer ( Fitness Bike E 3200)
61
Figure 8.2 Digital A&D Medical heart rate and blood pressure
monitor (UA 767-PLUS-30 Memory
Figure 8.3 : Digital stopwatch (Dad-7141, Japan)
62
Bicycle Ergometer
The term ' ergometery '' stems from the Greek ''ergon'' (work ) , and ''metron ''
(measurement) and may be translated rather literally as " work measurement
".in this experiment a Monrak ergometer , model 818E is used . Monrak
ergometer model 818 , is a test cycle provided with a brake , whose brake
resistance can be read in Newton (N) or Kilopond (Kp) ( 1kp is the force
acting on the mass of 1 kg at normal acceleration of gravity ; 100
kpm/min=16.35 watts ) . the brake power can be read in watts at two different
pedaling speeds , 50 and 60 pedals revolution / minute respectively .
The energy that a person must develop during a certain amount of time in
order to get over this brake power can thus be calculated . the energy is
usually expressed in kj (kilo joule ) or kcal (kilo calories)
Monrak ergometer model 818Eis also equipped with an electronic meter
showing an imagined cycling speed in km per hour , a covered distance in km
,pedal revolutions per minute and time .
When pedaling the test person supplies the flywheel with a certain kinetic
energy . this is braked by means of a brake belt which runs around the bigger
part of the brake surface of the flywheel . the brake power is changed either
by using another pedaling speed or by increasing or decreasing the tension of
the brake belt against the flywheel by means of the load adjustment wheel .
the height of the saddle is adjusted so that , when you set comfortably with
your foot exactly above the pedal axle and with the pedal in its down position ,
your knee is only slightly bent . the adjustment of the handlebar should give a
comfortable ride . when cycling for a long time , it may be suitable sometime
during the exercise to change the adjustment of the handlebar . the gearing
and the circumference of the Monk ergometer , model 818E wheel have been
so dimensioned that one complete turn of the pedals moves a point of thr rim
6 meters . the braking power (kp)set by adjustment of belt tension ,multiplied
by distance pedaled (m) , gives the amount of work in kilopond meters (kpm).
If the distance is expressed per minute , then the rate of work (the power ) in
kpm per minute will be obtained . Monrak ergometer , model 818E is shown in
figure 1 .
63
Heart rate monitor
Heart rate monitor model A&D is a full automatic digital electronic heart rate /
blood pressure monitor , using a microelectronic circuit , is equipped with a
broad Liquid Crystal Display (LCD) with high definition . the monitor , using
oscillography as the testing mechanism beasts of little deviation , high anti-
interference and high precision . heart rate , low pressure and high pressure
can be measured at the same time . 7 groups of data can be saved for one
time . the important features of heart rate monitor model can be summarized
in the following points ;
i- measurement of heart rate , low and high pressure
ii- memory function
iii- using Oscillography mechanism
iv- large LCD display
v- auto shut-off
The heart rate model A&C is shown in Figure 8.2 .
Stop Watch
In this experiment digital stop watch is used which includes 1/100
chronograph with split/lap time , normal time , hour-minute-second-month-
date-day of week display , daily alarm and hourly chime with neck cord . the
digital stop watch is shown in figure 3
64
8.5 Procedures
The procedure of the experiment may be summarized in the following points ;
Measure heart rate (HR) at rest by allowing the subject to set on a chair
for 3 minute without movement or any activity . measure the heart rate during
the last 10 seconds of each minute
The bicycle ergometer should be set so that the knees are almost
completely extended when the foot is at the bottom of the pedaling cycle
Set the brake resistance of the bicycle ergometer at 2 kp ( 2 kg or 20N)
Set the pedaling speed at 50 revolution per minute
Start pedaling at the above speed on the same time start the stopwatch to
record time
Continue pedaling for 5 minutes and measure the heart rate during the
last 10 seconds of each minute
Stop pedaling after 5 minutes ( he should stay on bicycle ergometer)
Take rest on bicycle ergometer for the next 5 minutes and measure heart
rate during the last 10 seconds of each minute
Record the results of the experiment in the attached form , which is
presented in appendix (1)
8.6 Results
Each student have to perform the experiment and record the results in the
attached form
The work rate should be measured using the following equation ;
Work rate=resistance(kg) *(2п*radius ) (m)*speed (rev./min.)
(2п) * radius of the Monrak bicycle ergometer = 6 meters .
1 watt = 6.12kg.m/min . ( kg. m / min = kp . m/min )
So, the work load in watt can be easily calculated as follows ;
Work rate (watt) = brake resistance (kp) * pedaling speed (rev./min.)
The results of the experiment should be interpreted as follows ;
65
If the time during which the heart rate returns to its rest level (recovery
time after the physical effort ) is equal to the time period of the physical effort
then the subject is fitted to the applied work load .
If the time during which the heart rate return to its rest level ( rest level
period after the physical effort) is more than the time period of the physical
effort then the subject is not fitted to the applied work load .
The approximate energy consumption in kcal should be estimated using
table 1 . for example if the brake power was 50 watts and the exercise has
been going on for one hour and 15 minutes you read , in this case , according
to the arrows on the table , an energy consumption of 375 kcal is obtained
Each student has to study the relationship between the heart rate that
measured during the last 10 seconds of each minute of the physical effort
time and the physical effort time using regression .
Each student has to draw a graph relating the heart rate with the rest ,
physical work and recovery time as shown in figure 1
66
Table 8.1 Estimation of energy consumption in kcal based on The Work Rate
Calorie consumption
Watt Time
Min 350 300 250 200 150 100 50
115
230
345
460
575
690
805
920
1035
1150
1265
1380
1495
1610
1725
1840
1955
2070
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
85
170
255
340
425
510
595
680
765
850
935
1020
1105
1190
1275
1360
1445
1530
70
140
210
280
350
420
490
560
630
700
770
840
910
980
1050
1120
1190
1260
55
110
165
220
275
330
385
440
495
550
605
660
715
770
825
880
935
990
40
80
120
160
200
240
280
320
360
400
440
480
520
560
600
640
680
720
25
50
75
100
125
150
175
200
225
250
275
300
325
350
375
400
425
450
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
67
9. Physical Work Capacity (II)
Estimation of Maximum Oxygen Consumption
9.1 Introduction
Aerobic power is one of the components of physical fitness ,and perhaps the
one variable most extensively studied Cardiovascular endurance depends ,to
a large extent , on the ability of respiratory , cardiovascular , and skeletal
muscles working together to take in oxygen from the atmosphere transport it
to the muscles , and use it in aerobic metabolism . generally speaking , the
greater the ability of these three systems to perform their roles in the transport
and utilization of oxygen , the greater the amount of work that can be
performed without undue fatigue . with an increase in the amount of work that
can be performed , cardio respiratory endurance is , by definition , increased .
maximal oxygen uptake (Max VO2 or VO2max ) is an index of the maximal
functional capacity of these systems . it may be defined as the maximal
amount of oxygen that a person can consume during physical work while
breathing air at sea level . maximal oxygen consumption has become the
primary criterion used to assess cardio respiratory endurance . measurements
of maximal oxygen consumption is often expressed as the volume consumed
per minute (L/min) this is called absolute maximal oxygen consumption .
However , when used to compare the endurance capacity of the individual to
another , it is usually expressed relative to body weight (ml/ kg ҳ min ) this is
called relative maximal oxygen consumption .
Average values range from about the 30 ml per kg minute in 40 to 50 year-old
sedentary men to a high of 75-80 in young endurance runners . the values for
women typically tend to be 20% lower , primarily because of difference in
body consumption
68
9.2 Methods of Determination of maximal oxygen
consumption
The most effective way of maximal oxygen consumption is to do it directly . in
modern laboratories this is usually accomplished by measuring the volume of
air expired and the oxygen and the carbon dioxide concentrations of inspired
or expired air with computerized instruments . this is done during a " symptom
limited " (more later ) maximal graded exercise test on treadmill or bicycle
ergometer . Despite the fact that this type of test is ideal , its application to
testing of large groups and assessment of general physical fitness levels
across different ages , states of training and genders is seldom practical .The
equipment is expensive , the procedures require trained technicians to
operate the instruments , test are quite time-consuming , and
The subjects must be highly motivated and sufficiently fit to work hard enough
to
Reach an actual maximum. T he most significant problem is that any maximal
exercise tests conducted on men over 40 years old and women over 50 years
old , or on any individual with two or more cardiovascular risk factors , must
be supervised by a physician with skills in exercise test administration and
interpretation . In contrast, physician supervision it is not required when
submaximal estimation of VO2is performed on men or women of any age and
risk status as long as they do not have overt symptoms or disease . Therefore
, submaximal assessments of cardiovascular function are often employed in
health clubs , corporate fitness programs , and in other situations where mass
testing is required and/or where equipment and personnel with advanced
training are not available . Due to the demand and popularity of submaximal
estimation of max VO2 , a number of procedures for its use have been
developed .Such tests have the advantage of being relatively inexpensive ,
they require little training of testing personnel to obtain reliable results , they
are easy to do in large groups , and they have short test durations. In addition
, they do not demand a maximal work effort by the subject , which makes
them low risk , an attending physician is not required , and they can be used
to document changes in cardio respiratory endurance that occur with training .
69
submaximal tests do have disadvantages .maximal heart rate , blood pressure
and oxygen consumption are not measured directly .This means that errors of
10 to 20% in predicted values can occur . Nonetheless , for large groups of
people with wide disparity in demographics and fitness levels , submaximal
tests are extremely useful
The ability to predict maximal oxygen consumption for submaximal exercise is
entirely dependent on the validity of the assumption of linear relationship
between heart rate, oxygen consumption, and workload. Fortunately, there is
much research to support this claim as long as the intensity of the exercise is
above a level where stroke volume reaches its maximal value . For most
subjects this means an average intensity above 40% of maximal oxygen
consumption or heart rate. For example , in a 20 year-old individual ,assuming
the maximal heart rate is approximately 220-chronological age ,this would
correspond to a heart rate of about 200 beats per minute .The major
determinant of oxygen consumption is cardiac output .This value equals the
product of heart rate and stroke volume . Thus, it follows that above the
exercise intensity , which demands maximal stroke volume , the major
increase in cardiac output and consequently oxygen consumption is directly
related to the increase in heart rate that occurs as workload increases .In
these submaximal tests , relatively high exercise intensities should be avoided
since the relationship between heart rate and oxygen consumption can
become somewhat curvilinear near maximal heart rate . A departure from
linearity would severely confound interpretation of the
Test .for this reason, it is recommended that any submaximal test should be
conducted at working intensity that will elicit a steady state heart rate between
115 and 150 beats per minute. in most cases this will fall in that critical area
where heart rate workload , and oxygen consumption are all linearly related .
it must be also noted that when heart rates are recorded to be used in the
calculation of Max VO2 , this must be at steady state for the test to be valid .
this is accomplished by assuring that the subject exercises long enough to
achieve steady state ;approximately minutes .
protocols for the estimation of maximal oxygen consumption using sub
maximal work have been developed for use on treadmill , in bench-stepping
exercise ,and on the stationary bicycle ergometer . In this laboratory the
70
bicycle ergometer will be used for the estimation of maximal oxygen
consumption because bicycling has proved to be a very suitable work form ,
since , among other things , at a given load , (submaximal) , it demands about
the same energy output , whether the subject be young or old , trained or out
of condition , elite bicyclist or unfamiliar with the sport…..in addition to varying
protocols for use on different instruments , there are also numerous protocols
for use on the bicycle ergometer .For example : the "Astrand- Rythmig " test is
a single stage test in which a nomogram or several tables are used to predict
maximal oxygen consumption from the heart rate response to a one 6-minute
sbmaximal workload . A second type of this test is multi-stage YMC
protocol . in this protocol , 3to4 consecutive three-minute stages are used to
raise the heart rate to level between 110 and 150 bpm .Two recorded heart
rates in this range at different workloads are required to predict maximal
oxygen consumption . A third type of this test is Fox linear equation . In this
laboratory Astrand-Rhythming test as well as Fox method , will be used to
determine the maximal oxygen consumption .
9.3 Objectives
The objectives of this experiment may be summarized in the following points:
1. Studying two methods of estimating the maximal oxygen consumption
. namely Astrand method and Fox method
2. Studying a method of estimating the energy consumption using
oxygen consumption
3. Studying a method of evaluating the physical work capacity using the.
maximal oxygen consumption
9.4 Instruments
In this experiment three instruments are used .
These are ;
1. Bicycle Ergometer
71
2. Heart Rate Monitor
3. Stop Watch
For details of instruments, please see section 8.4 of the eighth laboratory .
Exercise.
9.5 procedures
The procedure of the experiment may be summarized in the following points ;
1. The bicycle Ergometer should be set so that the knees are
almost completely extended when the foot is at the bottom of the pedaling
cycle
2. Set the brake resistance of the bicycle ergometer at 2 kp ( 2 kg or 20N)
3. Set the pedaling speed at 50 revolution per minute
4. Start pedaling at the above speed on the same time starts the stopwatch to
record time
5. Continue pedaling for 6 minutes (as a rule about 6 minutes is sufficient to
adapt the heart rate to the task being performed) and measure the heart rate
during the last 10 seconds of each minute.
Find the average heart rate between the 5th and the 6th minutes
6. If the difference between the last heart beats exceeds 5 beats , ask subject
to continue for 7th minute and take average of the 6th and 7th minutes .
7. Use the average heart rate of the 5th and the 6th minutes and check table 1
to find corresponding maximum absolute VO2
8. To obtain the relative maximal oxygen uptake in ml/kg . min, multiply the
maximal oxygen uptake by 1000 ( to convert liters to milliliters )and divide by
body weight in kilograms
9. Correct maximal oxygen uptake using the correction factors presented in
table2
10. Use table 3 to classify the subject ability or fitness to the applied workload.
11. Use the heart rate that has been measured after 5 minutes
to estimate maximal oxygen consumption using Fox equation as follows;
vo2 max . = 6.3 – ( 0.0193* heart rate after 5 minutes )
72
Note: energetic body activity should not be engaged in during the hours
preceding the work test nor should the test be performed earlier than about an
hour after a light meal , or after a longer time if a heavier meal has been taken
.Furthermore , the subject should not smoke for the last 30 minutes prior to the
commencement of the test
Table 9.1 Maximal Oxygen Uptake (max vo2) Estimates For the Astrand
Rhyming Test in Liters per Minute (L/min)
WR WR WR WR wome
n
WR WR W
R
Me
n
900 750 600 450 300 1500 120
0
900 60
0
300 HR
4.8 4.1 3.4 2.6 4.8 3.4 2.2 120
4.8 4.0 3.3 2.5 4.7 3.4 2.2 121
4.7 3.9 3.2 2.5 4.6 3.4 2.2 122
4.6 3.9 3.1 2.4 4.6 3.3 2.1 123
4.5 3.8 3.1 2.4 6.0 4.5 3.3 2.1 124
4.4 3.7 3.0 2.3 5.9 4.4 3.2 2.0 125
4.3 3.6 3.0 2.3 5.8 4.4 3.2 2.0 126
4.2 3.5 2.9 2.2 5.7 4.3 3.1 2.0 127
4.8 4.2 3.5 2.8 2.2 5.6 4.2 3.1 2.0 128
4.8 4.1 3.4 2.8 2.2 5.6 4.2 3.0 1.9 129
4.7 4.0 3.4 2.7 2.1 5.5 4.1 3.0 1.9 130
4.6 4.0 3.4 2.7 2.1 5.4 4.0 2.9 1.9 131
4.5 3.9 3.3 2.7 2.0 5.3 4.0 2.9 1.8 132
4.4 3.8 3.2 2.6 2.0 5.3 3.9 2.8 1.8 133
4.4 3.8 3.2 2.6 2.0 5.2 3.9 2.8 1.8 134
4.3 3.7 3.1 2.6 2.0 5.1 3.8 2.8 1.7 135
4.2 3.6 3.1 2.5 1.9 5.0 3.8 2.7 1.7 136
4.2 3.6 3.0 2.5 1.9 5.0 3.7 2.7 1.7 137
4.1 3.5 3.0 2.4 1.8 4.9 3.7 2.7 1.6 138
4.0 3.5 2.9 2.4 1.8 4.8 3.6 2.6 1.6 139
73
4.0 3.4 2.8 2.4 1.8 6.0 4.8 3.6 2.6 1.6 140
3.9 3.4 2.8 2.3 1.8 5.9 4.7 3.5 2.6 141
3.9 3.3 2.8 2.3 1.7 5.8 4.6 3.5 2.5 142
3.8 3.3 2.7 2.2 1.7 5.7 4.6 3.4 2.5 143
3.8 3.2 2.7 2.2 1.7 5.7 4.5 3.4 2.5 144
3.7 3.2 2.7 2.2 1.6 5.6 4.5 3.4 2.4 145
3.7 3.2 2.6 2.2 1.6 5.6 4.4 3.3 2.4 146
3.6 3.1 2.6 2.1 1.6 5.5 4.4 3.3 2.4 147
3.6 3.1 2.6 2.1 1.6 5.4 4.3 3.2 2.4 148
3.5 3.0 2.6 2.1 5.4 4.3 3.2 2.3 149
3.5 3.0 2.5 2.0 5.3 4.2 3.2 2.3 150
3.4 3.0 2.5 2.0 5.2 4.2 3.1 2.3 151
3.4 2.9 2.5 2.0 5.2 4.1 3.1 2.3 152
3.3 2.9 2.4 2.0 5.1 4.1 3.0 2.2 153
3.3 2.8 2.4 2.0 5.1 4.0 3.0 2.2 154
Table 9.1 Cont. Maximal Oxygen Uptake (vo2 Max ) Estimate for Astrand-
Rhyming Test in Liters per Minute (L/min)
WR WR WR WR women WR WR WR WR MEN
900 750 600 450 300 1500 1200 900 600 300 HR
3.2 2.8 2.4 1.9 5.0 4.0 3.0 2.2 155
3.2 2.8 2.3 1.9 5.0 4.0 2.9 2.2 156
3.2 2.7 2.3 1.9 4.9 3.9 2.9 2.1 157
3.1 2.7 2.3 1.8 4.9 3.9 2.9 2.1 158
3.1 2.7 2.2 1.8 4.8 3.8 2.8 2.1 159
3.0 2.6 2.2 1.8 4.8 3.8 2.8 2.1 160
3.0 2.6 2.2 1.8 4.7 3.7 2.8 2.0 161
3 2.6 2.2 1.8 4.6 3.7 2.8 2.0 162
2.9 2.6 2.2 1.7 4.6 3.7 2.8 2.0 163
2.9 2.5 2.1 1.7 4.5 3.6 2.7 2.0 164
74
2.9 2.5 2.1 1.7 4.5 3.6 2.7 2.0 165
2.8 2.5 2.1 1.7 4.5 3.6 2.7 1.9 166
2.8 2.4 2.1 1.6 4.4 3.5 2.6 1.9 167
2.8 2.4 2.0 1.6 4.4. 3.5 2.6 1.9 168
4.4 3.5 2.6 1.9 169
Table 9.2 Age Based Correction Factor For Maximal Oxygen Uptake
Correction
Factor
Age Correction
Factor
Age
0.830 40 1.11 14
0.820 41 1.10 15
0.810 42 1.09 16
0.800 43 1.08 17
0.790 44 1.07 18
0.780 45 1.06 19
0.774 46 1.05 20
0.768 47 1.04 21
0.762 48 1.03 22
0.756 49 1.02 23
0.750 50 1.01 24
0.742 51 1.00 25
0.734 52 0.987 26
0.726 53 0.974 27
0.718 54 0.961 28
0.710 55 0.948 29
0.704 56 0.935 30
0.698 57 0.922 31
0.692 58 0.909 32
0.686 59 0.896 33
0.680 60 0883 34
0.674 61 0.870 35
75
0.668 62 0.862 36
0.662 63 0.854 37
0.656 64 0.846 38
65 0.838 39
Table 9.3 Classification of the levels of fitness to the physicals work based on
the Maximal Oxygen consumption
Astrand Bicycle Ergometer Test VO2 Max Normative Data-Males
Very high high average Below
average
Low
>4.00
>57
3.70-3.99
52-56
3.10-3.69
44-51
2.80-3.09
39-43
<2.79
<38
20-29 years
(l/min)
(ml. kg /min)
>3.70
>52
3.40-3.69
48-51
2.80-3.39
40-47
2.50-2.79
35-39
<2.49
<34
30-39years
(l/min)
(ml. kg/min)
>3.40
>48
3.10-3.39
44-47
2.50-3.9
36-43
2.20-2.49
31-35
<2.19
<30
40-49years
(l/min)
(ml. kg/min)
>3.10
>44
2.80-3.09
40-43
2.20-2.79
32-39
1.90-2.19
26-31
<1.89
<25
50-59years
(l/min)
(ml. kg/min)
>2.80
>40
2.50-2.79
36-39
1.90-2.49
27-35
1.60-1.89
22-26
<1.59
<21
60-69years
(l/min)
(ml. kg/min)
76
9.6 Results
1. Each student has to perform the experiment and estimate his maximal
oxygen consumption using Astrand method and Fox method and compare the
results . results should bd recorded in the attached form Appendix ІІ
2. The work rate is measured using the following equation ;
Work rate=resistance(kg) *(2п*radius ) (m)*speed (rev./min.)
(2п) * radius of the Monrak bicycle ergometer = 6 meters .
1 watt = 6.12kg.m/min . ( kg. m / min = kp . m/min )
So, the work load in watt can be easily calculated as follows ;
Work rate (watt) = brake resistance (kp) * pedaling speed (rev./min.)
3. The approximate energy consumption in kcal is estimated based on the
maximal oxygen consumption . for every liter of oxygen consumed in .
77
10. MEASUREMENT OF REACTION TIME
10.1 Introduction
We take many everyday actions for granted, from blinking our eyes to picking
up a phone to driving a car. Most actions, except for the simplest reflexes,
involve a large amount of brain activity: receiving and processing sensory
information, integrating and interpreting that information, and controlling of
muscle activity to produce movements in response to the information. This
process is called reaction process.
The study of reaction time was one of the first major topics of experimental
research in Psychology, although the practical importance of reaction time
was acknowledged long before Psychology developed as a separate
discipline. It is important to understand the distinction between reaction time,
response time and movement time.
Reaction time is the amount of time required for the nervous system to
receive and integrate incoming sensory information and then
causes the body to respond i.e. it is the time interval between the
presentation of a stimulus and the Initiation of Movement.
Response time is the time interval between the presentation of a stimulus and
the completion of any movement performed in response to that
stimulus.
Movement time is the time interval during which the subject or individual make
the movement. It is the time difference between Response time
and Reaction time.
In humans, the nervous system and the muscular system work together to
produce a reaction to a stimulus. The main function of the
nervous system is to collect information gathered by the sensory
system and then transmit these information to the muscular
system to produce a reaction. The nervous system collects and
transmits information through a series of nerve cells called
neurons. Neurons are composed of four parts: the dendrites, a
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soma, an axon, and axon terminals called terminal buttons.
These parts are shown in Figure 10.1.
10.2 Types of Reaction Time
There are several categories of reaction time, have been established and
studied in experimental psychology. These categories are:
1. Simple reaction time
2. Discrimination reaction time
3. Choice reaction time
In a simple reaction time experiment, the subject is presented with one
simple stimulus, such as a light, and instructed to perform one simple
response, such as pressing a button. In a discrimination reaction time
experiment, the subject is presented with one of two or more different stimuli,
such as a red light and a green light, and instructed to perform a response to
only one of the stimuli, such as pressing a button when the red light is
presented but not when the green light is presented. In a choice reaction
time experiment, the subject is presented with one of two or more different
stimuli, such as a red light and a green light, and instructed to perform
different responses depending upon which stimulus is presented, such as
pressing a red button when the red light is presented and pressing a green
button when the green light is presented. There are other types, and many
variations of reaction time experiments.
Figure 10.1 The Parts of a Neuron cell
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10.3 Objectives
The objectives of this experiment can be summarized in the following points:
1. To study and understand the concept and importance of reaction and
movement time.
2. To study and understand the different types of reaction time.
3. To learn a simple and accurate method of measuring the reaction and
movement time.
4. To understand how to analyze and use the collected data of the
reaction and movement times.
10.4 Instrument The instrument used in measuring reaction and movement time in this experiment
is Double Reaction / Movement Timer Model 63017. This instrument discriminates
between pure reaction time and movement time. The system consists of the
following:
1. A control console containing two independently operating digital
electronic stop clocks (1/1000 second, readings from 0 to 9.999
seconds in 0.001 second increments).
2. A visual response selector (three colours; red, green, blue).
3. A 2800 Hz sonalert auditory stimulus.
4. A one second ready signal with variable delay period (1-10 seconds) to
stimulus onest.
5. Two telegraph keys connected to the instrument with 12 feet cord.
Also included, a selector switch to alternate or reverse the reaction Vs.
movement key and a ready signal light for trial initiation. The Double Reaction
/ Movement Timer Model 63017 is shown in figure (10.2).
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10.5 Procedures of The Experiment
The procedures of the experiment can be summarized in the following points:
1. Switch the Double Reaction / Movement Timer tester on.
2. Select one of the two possible response keys, which are: visual
response key (includes three type of light stimuli red, blue or green)
and auditory response key (includes a 2800 Hz sonalert auditory
stimulus).
3. The student should maintain focused attention to the display screen in
order to visually perceive a light stimulus and respond to it as quickly
as possible.
4. At the beginning of the experiment the student should put his hand on
one of the telegraph keys. When a stimulus is displayed (visual
stimulus) or heard (auditory stimulus), the student should release one
telegraph key and presses the second key.
5. After responding to the visual or auditory stimuli the digital electronic
stop clock (millisecond timer) records reaction time, the second timer
displays total time from stimulus start to second key press. The
difference of the two times allows movement time to be measured.
The data collection form of this experiment is shown in appendix III.
Figure 10.2 The Double Reaction / Movement Timer Model 63017
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10.6 Results of The Experiment
1. Each student has to measure his reaction time using both the auditory and
the visual displays, and report his results.
2. The measurements of reaction time of the whole class will be assigned to
each student to analyze it and calculate the 5th, 50th and 95th percentile
and comments in the use of these measurements.
3. Each student has to use his reaction time to calculate the distance his
car will move before he press the car brake when he drive his car at a
speed of 120 k/h and he see a red traffic light. Comment in the results.
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MEASUREMENT OF REACTION TIME
Student Name: Height : cm
Com. No. Weight : kg
Age: Years
Measurements of The Student Reaction Time:
Readings Visual Reaction Time
(Sec.) Auditory Reaction Time
(Sec.)
Average
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11. Strength measurements
11.1 Introduction Strength is the maximal force muscles can exert isometrically in single
voluntary effort, that is, the muscular capacity to exert force under static
conditions. Static conditions occur under the following conditions:
1. If a high level of effort is maintained for 10 seconds or more.
2. If moderate effort persists for 1 minute or more.
3. If slight effort (about one third of maximum force) lasts for 5 minutes or
more.
A major objective in design and tools should be to minimize or abolish
altogether the need to grasp and hold things (i.e. to reduce static effort) .Along
continued and excessive static work load can lead to deterioration of joints ,
ligaments and tendons . Strength can be measured in a variety of ways:
a) Directly at the muscle.
b) By indirect methods.
c) At the interface between the human body and the external resistance
against which strength is exerted .
One method of measuring strength directly at the muscle is by the use of
(EMG) Eletromyographic techniques .An Eletromyogram is a measure of the
electric activity of the muscle . the amount of muscular contraction is
measured by measuring the increase in electrical activity by means of sensors
on the skin surface of the muscle group being contracted .
Indirect measures of strength measurement include Metabolic Rates ( heart
rate , blood pressure , etc . ) or subjective ratings of perceived exertion . the
subject rates the relative difficulty of the exertion on a scale of 6 to 20 .
Strength can be measured at the interface through the use of a Dynamometer
(an instrument used for measuring force ) .
Another technique that has become popular lately is to measure strength by
measuring the maximum duration –of static muscular effort in relation to the
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force being exerted . Rohmet gives the following table relating % maximum
force versus duration of effort
Duration ( minutes ) % Of Maximum Force
0.1 100
0.35 75
1 50
3.5 25
The latest two methods will be used in this experiment to measure the
muscular strength of the students .
11.2 objectives
The objectives of this lab exercise can be summarized in the following points :
1. To understand the concept and important of muscular strength
2. To study and understand the methods of measuring muscular strength .
3. To study the factors that affect the muscular strength using regression
analyses.
11.3 Instruments
The instruments used in this lab .exercise are as follows;
1. The Hand Dynamometer which is a hand held instrument for measuring
grip strength. the handle of the instrument is adjustable to fit the grip length of
the hand . The Hand Dynamometer measures grip strength up 100 kilo grams
in 500 gram graduations. Two dial hands move up together, but one “freezes
“at the maximum grip achieved, while the other follows the grip up or down to
show the current squeeze strength. The Hand Dynamometer is shown in
Figure 11.1
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2. Back and Leg Dynamometer which includes 600-pounds pull
Dynamometer for testing subjects with normal strength, a4 ' chain, a
solid aluminum –lifting bar with comfortable hand grips and a lifting
platform. The solid lifting platform, measuring 24" x 24" , is small
enough for easy transportation . The pull Dynamometer has several
heavy-duty springs for long-lasting accuracy and range of 50 to 600
pounds, in 5-pound increments. the Back And Leg Dynamometer is
shown in Figure 11.2
3. Stop Watch which includes 1/100 second chronograph with split/lap
time, normal time, hour-minute-second-month-date-day of week
display, daily alarm and hourly chime with neck cord as shown in
Figure 11.3
Figure 11.1 The Hand Dynamometer
Figure 11.3 Digital stopwatch.
Figure 11.2 Back and Leg Dynamometer
86
11.4 Procedures
In this lab. Exercise the hand grip, thighs and back strength are measured
using two methods namely: dynamometer and maximum duration – of static
muscular effort in relation to the force being exerted .the dimensions of hand;
thighs and back are also measured in order to study the relationship between
these dimensions and the strength of the hand grip, thighs and back.
The procedure of the experiment may be summarized in the following points;
1. Measuring the grip strength of the hands using The Hand Grip
Dynamometer by exerting the maximum possible force in the hand. The hand
should be located beside the body and muscles should be extended. Three
measurements are taken and the average of them is calculated. The time that
subject can hold 75% and 50% of Max strength are also measured in the
same manner.
The following points should be taken in consideration during measuring the
hand strength;
Before this test is administered, the handle of the dynamometer must be
adjusted for the size of each individual subject. The handle should fit
comfortably in the hand with enough allowance for a good grip. Record the
setting found on the inside gauge if follow-up testing is to occur.
Place the subject's arms at their sides keeping it away from the body with
the elbow bent slightly (approximately 20 °). Illustrate the use of the
instrument to the subject prior to testing
The test is to be administrated with dominant hand first and then with the
non- dominant hand. The examiner should be confident the subject's
maximum grip strength is being measured. Emphases on “squeeze as hard
as you possibly can “and other forms of encouragement may be necessary for
87
maximum effect. Allow three trials with each hand , right and left hand
alternately , but introduce a brief pause of about 10to20 seconds between
each trial to avoid excessive fatigue .
Record the amount registered at each trial. If the difference between the
scores of each is within 3 kg, (considering the scores of each hand
separately) the test is complete. If a difference of more than 3 kg is noted the
test is repeated after a sufficient rest period. Calculate the averages for each
hand separately. It is important that the dials be returned to the "0" position
after every trial. Readings are taken to the nearest whole kilogram.
2. Measure the thigh strength using Back And Leg Dynamometer. Grasp the
handle between hands and try to lift it up using the thighs' muscles. Note that
the handle should be at level of hip joints, knee angle should be 90° (angle
between thighs and legs), and keeping the back as straight as possible
(Try not to use the hand and back muscles ) . Three measurements should be
taken and their average of them is calculated
3. Measure the back strength using Dynamometer. Grasp the handle
between hands and try to lift it up using the back' muscles. Note that the
handle should be at level of hip joints, knee angle should be 180° (angle
between thighs and legs).(try not to use the hand and thighs muscles ) . Three
measurements should be taken and their average of them is calculated .the
data collection from this experiment is shown in appendix III
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11.5 Results
1. Each student has to measure the strength of his hand grip , thighs and
back as well as their dimensions as illustrated above .
2. The whole class measurements of hand grip, thighs an back strength as
well as their dimensions will be assigned to the students analyze them as
follows:
a) Calculating the 5th, 50th and 95th percentile of hand grip, thighs and back
strength.
b) Using regression techniques to study the relationship between the
following:
◘ Hand strength vs. upper circumference of the hand
◘ Hand strength vs. rest circumference of the hand
◘ Hand strength vs. hand length
◘ Thighs strength vs. circumference of the thighs
◘ Thighs strength vs. buttock knee length
◘ Back strength vs. shoulder height standing
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