Various grades of work

GRADES OF WORK

PRESENTED BY

RAM KUMAR R

SAHUL HAMEED H

BASIC CONCEPTS

MUSCLE PHYSIOLOGY

There are three types of muscles namely

1. Striated or skeletal muscles

2. Cardiac muscles

3. Smooth muscles

Most vigorous activities are carried out by skeletal muscles, which are attached to the bones.

Cardiac muscles are present on the walls of the heart.Smooth muscles are seen on the walls of blood vessels

and internal organs.

MUSCLE METABOLISMEnergy is required for muscles to contract, this energy is

provided by the food that we eat and digest, primarily the carbohydrates and fats.

Carbohydrates are converted to glucose and stored in liver.

In liver the glucose or glycogen is broken down to liberate energy for muscle contraction.

The muscles does not consume the energy directly but through conversion of ATP to ADP, which releases energy required for cells.

Cretinine Phosphate (CP) is a immediate source of energy useful only for short duration.

BASAL METABOLISM

Metabolism is a chemical process by which foodstuffs are converted into heat or mechanical energy.Muscles convert 30% of energy liberated into mechanical

work and remaining 70% as heat.Body requires a certain amount of energy just to stay alive

without doing any physical work, this is called Basal Metabolic Rate (BMR)

For 70 kg male – 1.2 kcal/minFor 60 kg female – 1.0 kcal/min

BMR depends on Body size Age Sex

RESPIRATORY RESPONSE

The respiratory response is to increase the rate of breathing and volume of air inspired with each breathAt rest oxygen consumption is less than 0.5 L/minAt extremely heavy work it is about 5.0 L/min

The body cannot instantaneously increase the amount of oxygen consumption, it occurs in gradual stages.

During this period the anaerobic glycolysis and depletion of ATP and CP stores provide energy to the muscles and the body experience oxygen debt.

“Oxygen debt is the amount of oxygen required by the muscles after the beginning of work, over and above which is supplied to

them during work activity”

This debt is repaid during the resting period

CARDIO VASCULAR RERSPONSE

Increased cardiac output

In order to provide more oxygen, more blood must flow to the muscles, to do this the heart must pump more blood per unit time.

It can be done in two waysBy increasing heart rateBy increasing stroke volume

Cardiac output at rest is about 5 L/min

Cardiac output during heavy work 25 L/min

INCREASED BLOOD PRESSURE

The consequence of increased cardiac output is increase in blood pressure during physical work

The adrenal glands release hormone called catecholomines that strengthen the heart beat and increase blood pressure.

REDISTRIBUTION OF BLOOD FLOW

Accompanied by increase in cardiac output and blood pressure there is a redistribution of blood flow throughout the body

DISTRIBUTION OF BLOOD DURING REST AND WORK

Part of the body Blood flow distribution (%)

Resting Heavy work

Muscles 15-20 70-75

Skin 5 10

Brain 15 3-4

Bones 3-5 0.5-1

Kidneys 20 2-4

Digestive system 30-25 3-5

Heart muscle 4-5 4-5

MEASURES OF PHYSIOLOGICAL STRAIN

Oxygen consumption (uptake)

one litre of oxygen liberates approximately 5 kcal of energy, thus by measuring the oxygen consumption we can directly estimate the energy consumption

EXPERIMENTAL DATA- International Journal of Physical Education, Fitness and Sports

Parameters Service sector (n

=136) Mean (±SD)

Manufacturing sector (n = 49) Mean (±SD)

Experimental group (Service

sector + Manufacturing

sector) (n =185) Mean (±SD)

Validation group (n =100) Mean (±SD)

Age (yrs) 46.7 (±8.10)

44.4 (±10.88)

46.1 (±8.95) 49.4 (±9.74)

Height (cms)

164.4 (±6.36)

165.6 (±4.78)

164.7 (±5.99) 165.0 (±5.3)

Weight (kgs)

63.1 (±11.54)

66.1 (±10.72)

66.1 (±10.72) 66.1 (±10.40

Physical Characteristics

Parameters Service sector Mean (±SD)

Manufacturing sector Mean

(±SD)

Experimental group Mean

(±SD)

Validation group Mean

(±SD)

Resting HR (beats.min-1)

72.2 (±16.29) 71.0 (±7.96) 72.3 (±16.69) 71.5 (±16.49)

Resting VO2 (ml.kg-1.min-

1)

5.5 (±1.30) 5.0 (±2.26) 5.6 (±1.27) 5.3 (±1.27)

HR max (beats.min-1)

154.0 (±17.00) 166.0 (±15.99) 158 (±21.84) 159 (±21.11)

VO2 max (ml.kg- 1.min-

1)

27.3 (±4.15) 34.8 (±5.99) 33.0 (±5.61) 31.5 (±5.99)

Pre-work and maximum values of heart rate and oxygen consumption

Maximum Aerobic Power

Maximum Aerobic Power is defined as the highest oxygen intake an individual can attain during exercise while breathing air at sea level

Increasing the rate of work causes a linear increase in oxygen intake, to a point , after which oxygen uptake level off. Further increase in work rate will no longer increase oxygen uptake.

Heart Rate

There is a linear relationship between oxygen consumption and heart rate.

A few wires attached to a person and a telemetry or recording can easily measure heart rate, that can be used to estimate oxygen consumption, which in turn can be converted to energy expenditure.

GRADES OF WORK

• Grades of work is the measurement of energy required to

carryout the task

• The energy requirement varies from individual to

individual based on physical structure, sex, age.

• The energy requirement for same work differs based on

the geographical location and the working environment.

GRADES OF PHYSICAL WORK BASED ON ENERGY

EXPENDITURE LEVEL

Grade of work

Energy expenditure,

kcal/min

Energy expenditure,8 h (kcal/day)

Heart rate, beats per

minute

Oxygen consumption,

L/min

Rest (sitting) 1.5 <720 60-70 0.3

Very light work

1.6-2.5 768-1200 65-75 0.3-0.5

Light work 2.5-5.0 1200-2400 75-100 0.5-1.0

Moderate work

5.0-7.5 2400-3600 100-125 1.0-1.5

Heavy work 7.5-10.0 3600-4800 125-150 1.5-2.0

Very heavy work

10.0-12.5 4800-6000 150-180 2.0-2.5

Unduly heavy work

>12.5 >6000 >180 >2.5

ENERGY COST PER DAY FOR VARIOUS OCCUPANTS

occupation energy expenditure (kcal/day)

Mean Minimum maximum

Laboratory technicians

Male 2840 2240 3820

Female 2130 1340 2540

University students

Male 2930 2270 4410

Female 2290 2090 2500

Male only

Construction worker

3000 2440 3730

Steel workers 3280 2600 3960

Coal miners 3660 2970 4560

ENERGY EXPENDITURE FOR DAY TO DAY ACTIVITIES

Activity Energy expenditure (kcal/min)

Sleeping 1.3

Sitting 1.6

Standing 2.25

Walking(level) 2.1

Cleaning/ironing 2.0-3.0

Cycling(16kmph) 5.2

ENERGY REQUIREMENT FOR VARIOUS ACTIVITIES IN INDUSTRY

ACTIVITIES ENERGY(kcal/min)

Inspection 1.6

Testing(sitting) 2.2

Testing(standing) 2.7

Construction 4.0

Driving 4.2

Manual material handling

5.0

Cutting 6.8

Pushing 7.7

Lifting 8.5

Working near furnace

10.2

FACTORS AFFECTING ENERGY CONSUMPTION

Methods of work

The energy cost for certain type of work vary with the manner in which the work is carried out.

The methodology of work carried out varies based on the method of carrying load and oxygen consumption rate associated with it.

WORK POSTURE

The posture of workers while performing some task is another factor which influence the energy consumption.

Musculoskeletal disorders (MSDs) are common health problem throughout the world. Assessment of exposure levels to MSD risk factors can be an appropriate base for planning and implementing interventional ergonomics programs in the workplace.

In many rapidly developing countries, where labor is cheap, proper occupational hygiene and posture analysis methods are often neglected. Proper sitting arrangements and work environment are seldom provided

Continued…

Repetitive processes and manual material handling are the major problems in the hand tool manufacturing. Therefore, musculoskeletal disorders (MSDs) are related to such high repetitive processes and working in bad posture.

Thus, to improve the efficiency of the workers their posture needed to be assessed and corrective measures should be adopted to avoid the musculoskeletal disorders

WORK RATE

• Another factor that affect the energy consumption is work rate or the pace of work

• Repetitive work can be carried out upto certain pace until which heart rate is maintained, above which heart rate increases appreciably and the work load can cause fatigue and other physiological changes in the human body

CASE STUDY-AN ANALYSIS OF EXPERTS' RATINGSOF ERGONOMIC STRESS (International Journal of Industrial Ergonomics)

INTRODUCTION

Jobs which expose workers to excessive ergonomic

stresses can cause a variety of occupational health problems including fatigue, discomfort, and disability. These stresses may result from awkward posture, excessive force demands, highly repetitive actions and/or excessive energy expenditure.

In the United States, musculoskeletal disorders are ranked near the top of conditions requiring medical treatment: Specifically, musculoskeletal disorders are ranked:

• Second among reasons for seeing a physician,

• Third among disorders requiring hospital

surgery, and

• Fifth among reasons for visiting hospitals.

KEY FINDINGS

Chaffin (1972) found that jobs requiring repeated moderate or heavy whole body exertions can lead to discomfort, loss of coordination, loss of strength, and strain on the cardiovascular system.

Jobs requiting sustained postures or repeated use of specific muscle groups can lead to a general loss of coordination, localized muscle discomfort, and cardiovascular strain

Eight out of ten adults experience back pain during their working careers, resulting in significant medical and compensation costs

ERGONOMIC STRESSES OF INTEREST

1.Manual materials handling (MMH) activities

This category included stresses associated with strength-demanding materials handling tasks (e.g. Lifting, carrying,pushing,pulling,etc.) which could lead to overexertion injuries of the back and other body regions.

Analysts were instructed to focus their attention on the magnitude of the forces exerted and the body geometry maintained during materials handling tasks in order to estimate the likelihood of overexertion musculoskeletal injuries.

2. Upper Extremity (UE) activities

This category included stresses associated with actions of the hands, arms, and shoulders that could lead to cumulative trauma disorders, such astendinitis, synovitis, and carpal tunnel syndrome. Analysts were instructed to focus their attention on the frequency, force, and posture associated with hand-intensive tasks. Other factors, such as exposure to vibration and localized mechanical stresses were also considered when estimating the likelihood of an upper extremity injury.

3. Posture

This category included non-neutral postures of the trunk, neck, and/or shoulders that could lead to localized muscle fatigue and/or musculoskeletal disorders.

Analysts were instructed to focus their attention on the trunk (flexion, lateral bending, or twisting), the neck (flexion, extension, twisting, or lateral bending), and the shoulder (flexion or abduction). Temporal aspects, such as frequency and duration of these non-neutral postures, were also considered by the analysts in order to estimate the

potential for injury.

4. Metabolic energy expenditure and whole body fatigue

This category included work activities requiring high levels of energy expenditure which could lead to excessive loading of the cardiovascular system and whole body fatigue, such as climbing or repetitive/prolonged lifting of heavy loads.

Analysts were also instructed to consider environmental effects (e.g., heat stress) when estimating the potential for job-induced whole body fatigue.

SCORING SYSTEM ADOPTED

Insignificant. Jobs given this rating were judged to be free of potentially harmful ergonomic stresses in the category of interest. The expert believed that the job was sufficiently safe that no follow-up action (i.e., additional analyses and/or job modifications) would be required or necessary.

Moderate. Jobs given this rating were judged to present moderate ergonomic stresses in the category of interest. The expert believed that follow-up analyses using quantitative methods were justified to confirm perceptions and to determine the necessity for design and/or work methods changes.

High. Jobs given this rating were judged to present major ergonomic stresses in the category of interest. This rating indicated that the expert believed the probability of injury was sufficiently high to justify immediate, detailed follow-up analyses. Furthermore, the expert believed that high priority should be given to redesigning the job in order to eliminate or reduce the level of ergonomic stress

CONTINUED..

CASE STUDY-A STUDY ON PUSH-PULL ANALYSIS ASSOCIATED WITH AWKWARD POSTURE AMONG WORKERS IN AEROSPACE INDUSTRY (International Journal of Research in Engineering and Technology)

INTRODUCTION

Manual material handling (MMH) such as lifting heavy products, reaching materials, bending forward their back when doing tasks, and pushing or pulling excessive loads because those tasks require a stable position and large degree of freedom. Pushing and pulling activities are one of the activities for MMH that can increase the risks of back pain problem. The pushing and pulling activities is a frequent activity for a great segment of the workforce, including hospital workers, manufacturing workers, construction workers, forest workers, etc. Moreover, both of these activities are associated with the awkward posture.

Awkward posture can be theorized as a discomfort

posture because it is harmful position for human body

when a joint is not in its neutral range of postures and

make muscles are either shorter or longer than resting

length. When joints are exposed to postures that involve

range of movement near the extreme positions, the

muscles around the joint are stretched or compressed. If

the exposure to extreme postures is prolonged, the

muscles do not immediately return to their resting length

AWKWARD POSTURE AMONG WORKERS IN AEROSPACE INDUSTRY

TOOL USED FOR ANALYSIS OF POSTURE

The analysis of posture is done using CATIA ergonomic analysis tool

The analysis is used to analyze the maximum acceptable and sustainability force when workers push or pull each mould.

The feature used from this tool to do the analysis is Push-Pull Analysis feature. Besides that, the comfort level of the working posture also analyzed by using this tool. But, the comfort level is analyzed by using RULA feature.

Demographic of workers participated in the study

Criteria Mean (SD)

Gender Male

Age 25.7 (5)

Mass (kg) 64.5 (10.9)

Height (cm) 174.2 (7.3)

Experience (year) 4.7 (2.7)

Awkward posture for pushing and pulling activity

RESULTS AND DICUSSION

Push-Pull Analysis from CATIA V5R19 software

RULA analysis of right body region for push-pullactivity

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