AppliedBiomechanicsBiomechanics

Pascal Madeleine

http://www.hst.aau.dk/~pm/ab/ab.html

FormålAt give indsigt i Biomekanik i relation til design og konstruktion af apparater

IndholdNewton mekanikNewton mekanikBiomekaniske målemetoderAntropometriIdrætErgonomiModellering

AB

mm 5 Human factors and systemsAnthropometri

Applied Biomechanics

mm 7 Applications in ErgonomicsConcepts, cumulative disorders

mm 8 Optimization in Ergonomics

Cumulative trauma disorders –repetitive stress injuriesp jOptimization in Ergonomics

mm8Pascal Madeleine AB

Neckshoulder

Biopsies: moth-eaten fibres

Model

MOTORCONTROL

OCCUPATIONALSETTINGS

PAIN INDEEP STRUCTURE

Risk factorsBoth physical and psychosocial factors are of interest and will influence the outcome.

The known physical factors are: - relatively fixed erect posture, - repetitive arm movements, - repetitive arm movements, - heavy work,- insufficient rest, - static posture and- vibrations- cold

Low load repetitive work

–Pressure pain threshold (PPT)

–Work task timing (duration)–Work task timing (duration)

–Cutting forces

–Surface electromyographic (EMG) activity of four shoulder muscles

–Displacement of the center of pressure

–Arm and trunk 3D movements

Referred pain

Injection site

Local pain

Referred pain

Sensory aspectsPain location

Referred pain

Injection site

Local pain

Referred pain

Sensory aspectsPressure algometry (part iii)

Mean ± SE pressure pain thresholds

0 month 6 months

Effects of employment duration (‡) andneck-shoulder complaints (†)

0 month 6 months

Pain group (kPa) 200.2 ± 32 281.5 ± 45.8

Non-pain group (kPa) 327.3 ± 49.6 348.1 ± 81.6

‡,†

*, † p<0.05

Increased muscle tenderness or hyperalgesiatend to give credit to:– hyperactivity theories (Travell et al. 1942, Schmidt

et al. 1981, Johansson and Sojka 1991) explainingthe propagation of pain from one muscle to other

Sensory aspects

the propagation of pain from one muscle to othermuscles and

– underline central or spinal interaction responsible forthe widespread of musculo-skeletal pain.

Increased sensitivity to pressure in newlyemployed butchers might also be importantprognostic factors for WMSD development.

LH1

CUT1 CUT2

LH2

LH1

Amplitude (V)

Motor Task Timing EffectsWorking Rhythm

Time (s)

0 1 2 3 4 5

TLH1

TLH1CUT1

TCUT1 TCUT2 TLH2

TCUT1CUT2 TCUT2LH2

TCyc

TLH2LH1

Z dir.

X dir. Origo-Arm

Olecranon

Y dir.

X dir.

Y dir.

X dir.

Y dir.Z dir.TMaT/AnT

TAnA/MaA

TMaA/Lab

Z dir.

L2

TLab/MaT

AnCSTrunk AnCSArm

MaCSTrunk MaCSArm

Z dir.

X dir.

Y dir.

Origo-Trunk

ArmBody

Z dir.

(III)

(II)(I)

(IV)

[ ] [ ][ ] [ ]y R x dx y= +

3D analysis[ ] [ ][ ]y T xx y=

X dir.

Y dir.

LaCS

( )T R dMaT AnT MaT AnT MaT AnT/ / /,

( )T R dAnA MaA AnA MaA AnA MaA/ / /,

( )T R dMaA Lab MaA Lab MaA Lab/ / /,

( )T R dLab MaT Lab MaT Lab MaT/ / /, R R R R RArm AnA MaA MaA Lab Lab MaT MaT AnT= / / / /

R R RTrunk AnT MaT MaT Lab= / /

Effects of employment d iduration

0

1

2

3

4

5

6

7

ius

tus

nt.

ed.

Frm

s (µ

V/N

)

a

**

Motor aspects

EMGEffects of

employment duration

Del

toid

eus

Med

. (µV

)

50

100

150

200

250

Del

toid

eus

Ant

. (µ V

)

50

100

150

200

250

70

EMG activation profiles

0

5

10

15

20

30

40

50

60

70

MPF

(H

z)R

atio

rm

s activ

e/rm

s non-

activ

e

**

Tra

pezi

u

Infr

aspi

natu

Del

toid

eus

Ant

Del

toid

eus

Med

Tra

pezi

us

Infr

aspi

natu

s

Del

toid

eus

Ant

.

Del

toid

eus

Med

.

b

c

*

*

Experienced

Inexperienced

* p<0.05

Infr

aspi

natu

s (µ

V)

10

20

30

40

50

60

70

Time (s)

0 1 2 3 4 5

Tra

pezi

us (

µ V)

20

30

40

50

60

70

80

Flex

ion-

Ext

ensi

on A

ngle

( o )

0

5

10

15

20

25

dduc

tion

Ang

le (

o )

10

15

20

25

30

0

0

5

10

15

20

25

30

35

40

45a b

Flexion

Forward Flexion

Right LateralFlexionAbduction

Arm Trunk

lexi

on A

ngle

( o

)Fl

exio

n-E

xten

sion

Ang

le (

o )

Kinematics

Motor aspects

Abd

uctio

n-A

dd

-5

0

5

10

0 1 2 3 4 5

Rot

atio

n A

ngle

( o

)

-30

-25

-20

-15

-10

-5

0

5

10

15

-5

0 1 2 3 4 5

-10

-5

0

5

10

15

20

25

30

Time (s) Time (s)

OutwardRotation

Clock-wiseBody Rotation

Rot

atio

n A

ngle

( o

)L

ater

al F

leExperienced

Inexperienced

Effects of employment duration

Differences in motor learning and motor control strategies may be of importance as they could be leading to WMSD development.

Pain-free experienced butchers seemed to have Pain-free experienced butchers seemed to have developed a protective motor strategy, that might be an important prognostic factor.

Such studies may be valuable for better understanding why some workers develop chronic WMSD, while others performing the same work tasks do not.

Effects of neck-shoulder

ipain

Del

t. M

ed. (

µV)

25

50

75

100

125

Del

t. A

nt. (

µV)

25

50

75

100

125

50

50

100

150

200

250

50

100

150

200

a bClinical Study Experimental Study

EMGEffects of acute and

chronic neck-shoulder pain

Motor aspects

Infr

. (µV

)

10

20

30

40

50

20

40

60

80

100

Time (s) Time (s)

0 1 2 3 4 5

Tra

p. (

µV)

20

30

40

50

60

70

0 1 2 3 4 5

30

40

50

60

70

80

90

Before pain/controls

During pain/patients

* p<0.05

shoulder pain RM

S non-

acti

ve

b

2 . 0

2 . 5

1 . 0

1 . 5

2 . 0

A f t e r 6 m o n t h sA t 0 m o n t h

Nor

mal

ized

RM

S acti

ve

a

†*

At 0 month After 6 months

EMGEffects of

neck-shoulder complaints (†)

Motor aspects

No Complaint group

Complaint group

*, † p<0.05

RM

Sac

tive/R

MS

non-

acti

ve

rat

io

c

Tra

pezi

us

Infr

aspi

natu

s

Del

toid

eus

Ant

.

Del

toid

eus

Med

.

Tra

pezi

us

Infr

aspi

natu

s

Del

toid

eus

Ant

.

Del

toid

eus

Med

.0

2

4

6

8

1 0

1 2

Nor

mal

ized

RM

1 . 0

1 . 5

*†

†

Sagg

ital p

lane

(de

g.)

0

5

10

15

20

pla

ne (

deg.

)

15

20

25

0

0

5

10

15

20

25

Arm Movement Trunk Movement

Kinematics

Motor aspects

Fro

ntal

pla

0

5

10

0 1 2 3 4 5

Tra

nsve

rse

plan

e (d

eg.)

-25

-20

-15

-10

-5

0

5

10

-10

-5

0 1 2 3 4 5

0

5

10

15

20

25

Time (sec.) Time (sec.)

Controls

Patients

Effects of neck-shoulder pain

The findings underlined:– interaction between neck-shoulder pain and motor control

and– the importance of the neck-shoulder pain status.

and emphasized the known physical risk factors:– repetitiveness, cutting force level, EMG activity amplitude,

arm and trunk posture and movement amplitude associatedwith low load repetitive work.

EMG amplitude level might be a prognostic factor forWMSD development

Upper extremity loads during pushing and pulling of waste containerEffects of the handle orientation

COLLABORATION WITH AHTS, R98,…

Kinetic & Kinematics

Y-dir

Z-dir

X-dir

Example: Refuse collection

Kinematics

YZ

X

YZ

X

YZ

X

YZ

X

YZ

X

Z

Y

Z

X

YZ

X YZ

X

Y

Z

X

labloclocanatseg RRR //=Lab. coordinate system

Kinetic & Kinematics

YZ

X

Fx

Fy

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡=⎥

⎥

⎦

⎤

⎢⎢

⎣

⎡=

z

y

x

zhånd

yhånd

xhånd

FFF

håndsensFFF

hånd RF __

__

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡×+⎥

⎥

⎦

⎤

⎢⎢

⎣

⎡=⎥

⎥

⎦

⎤

⎢⎢

⎣

⎡=

z

y

x

z

y

x

zhånd

yhånd

xhånd

FFF

håndsenshåndsensMMM

håndsensMMM

hånd RdRM ____

_

_

Fz

Fx

Conclusion

0 1 2 3 4 5 6 7-25

-20

-15

-10

-5

0

5

Lateral tilt (roll)

Positive: Towards right

Forw/backw tilt (pitch)

Positive: Forward

Rotation (yaw)

Positive : Right side forward (seen from back)

Increased range of motion and hand load with vertical handles and with 240-litres container

Refuse collection work is asymmetrical

Relative low load on the upper limbs

Computerwork

Computer work

COLLABORATION WITH AMI

Procid results

Computer work

AMI

Procidproject

Computer work tips EMGBiofeedback

Hermens et al. 2004

Before

Immediately after

Four weeks after

Biofeedback

0

2

4

6

8

10

12

EMG RMS (%ref)

Aud Vis Control

Left trapezius

Feedback source

*

*

12*Biofeedback

0

10

20

30

40

50

60

70

80

90

100Agree that feedback is usefulDisargee that feedback is usefulTim e above feedbackthreshold%

0

2

4

6

8

10

12

EM G M M G Control

Feedback source

*

EMG RMS (%ref)

Hypothesis

Ris

kR

isk

Same MUs

Samemuscle parts

Median subject

‘repeaters’‘repeaters’

Mathiassen SE 2003

Fixed,no break

Fixed,breaks

Short cyc.Control.

Short cyc.Autonom.

Long cyc.Autonom.

Samemuscles

Differentmuscles

‘replacers’‘replacers’

Trunk variability

* *

Arm variability Trunk variability

Increased degree of variability in experienced butchers

Motor variability during repetitive arm movement

* *

Variability as a preventing tool for work-related musculo-skeletaldisorders

Madeleine et al. 2008

The human task interface

Motor skillsSpeed, accuracy and control of human movements

Control and acquisition of motor responsesSpeed of movement:Fast movements take 200 ms or less. “let them fly”Slow movements (>200 ms) enable correction processes.processes.

Closed loop vs. Open loop theories

Motor programs

Reaction timeSimple/choice reaction time

Variables influencing reaction time: - Stimulus modality (auditory/tactual vs. visual)- Stimulus detectability- Spatial frequency- Spatial frequency- Expectancy of a signal- Age- Stimulus location

Ervilla et al. 2003

Reaction timeChoice reaction time

Other factors influencing reaction time: - Compatibility between stimulus & responses- Practise- Warning- Warning- Type of movement- More than one stimulus

Movement timeDirection of movement, distanceand accuracy required

Accuracy of movementMovement controlled by visual feedback:Target location, distance of movement, speed of movement

Human control of systemsThe human receives information, processes it, selects an action, and executes it.

Compatibility: relationship between displays and controlsTracking: continuous controlTracking: continuous controlSupervisor control: Supervision of automated processes (CAM techniques)

CompatibilityFour types: conceptual, spatial, movement and modality compatibility.

Designing and taking compatibility into consideration lead to: (i) learning is faster, (ii) reaction is faster, (iii) fewer errors are made, (iv) user reaction is faster, (iii) fewer errors are made, (iv) user satisfaction is higher.

Spatial compatibilityDeals with physical similarities (controls/displays) or arrangement of displays and their controls

Movement compatibilityMovement of a control device to:

- to follow the movement of a display- to control the movement of a display- that produces a specific system response

Movement of a display indication without any related responseresponse

TrackingTracking task require continuous control and are present in many daily life activities

SystemInputs(constant or variable)

Outputs

Input: “target”Movement: “course”

Output: “controlled element”

Human limitations in tracking tasks are processingtime, band width and anticipation.

Supervisory controlSupervisory control in the context of human computer systems derives from the human analogy (supervisor/subordinate interactions).Attributes: planning, teaching, monitoring, intervening and learning

Skill-, knowledge-, rule-based behaviour

Controls and data entry devicesExamination of the more common types of control devices and some of the factors which influence their use by humans.See appendix B for recommendations.

Function of controls: Transmit control information Function of controls: Transmit control information (either discrete or continuous) to some device, mechanism, or system.

Factors in control designIdentification of controls – shape, texture,size, location, color, label coding of controls

Exampleofcontroldevices

Visual, perception, handicap, maintenance

Control response ratio (C/R ratio)In continuous control tasks, a specified movement of the control will result in a system response (C/R ratio).

No form for C/R ratio computation

Data entry devicesIn terms of efficiency, reduction of entry time and of errors, keyboard have clear cut advantages compare with knobs, levers, …

Most data entry keyboard are sequential (individual characters are entered in a sequence).characters are entered in a sequence).

Keyboard arrangement: Alphabetickeyboards (qwerty) and numerickeyboards

Keyboard feel

Keypads (membrane)

Keyboard

Split and tilted keyboard

Handwritten and gestural data entry

Cursor positioning devicesTouch screen, light pen, graphic tablets,…

Tab 11.5

Controls and Data entries devices

Hand tools and devicesMany hand tools and devices are not designed for efficient, safe operation by humans especially for repetitive tasks.

Injuries based on a traumatic event (knives, hammers), and cumulative trauma disordershammers), and cumulative trauma disorders

Principle of hand tool design: Maintain the wrist straight (carpal tunnel syndrome)

Hand tools and devicesPrinciple of hand tool design: Avoid tissue compression stress (ischemia, numbness), avoid repetitivefinger action, design for safe operation,remember women and left-handers

Hand tools and devicesEvaluation of alternative design: Example: toothbrush design, multiple function dental syringe

Take home messages

Optimization in ergonomics Manual Material HandlingManual Material HandlingMotor skillsHuman control of SystemControl and data entries devicesHand tool and devices