L11 - Work and Biomechanics Flashcards by Sofia Courtis

What are the professional roles of OTs, PTs, Kinesiologists and ergonomists? (3)

Assess the physical demands of a client’s job
Help to reintegrate a client back to work
Suggest modification of equipment/methods used at work (ex. modify office chair)

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What is the professional role of biomechanical researchers?

Perform experiments in a more controlled lab setting with more sophisticated equipment.

Results can then be applied to work settings.
–> ex:. spine loads during lifting

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What is the professional role of governmental agencies and epidemiologists?
Name examples of agencies. (3)

Identify and study risk factors, incidence, prevention methods
Providing work related regulations and norms.

Example:
- CNESST
- IRSST (research arm of CNESST)
- Canadian Centre for Occupational Health and Safety (federal)

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Name examples of types of questions that government agencies ask?

Example of types of questions:
1. incidence of carpal tunnel syndrome and textile workers
2. definition of repetitive work)

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Name some worksite evaluation methods. (4)

Kinematic assessment
Questionnaires: occupational self-assessment
Force evaluation: Chatillon dynamometer
Surface EMG

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Worksite Evaluation Methods
Name examples of kinematic assessements. (3)

Task analysis from interview and observation
Range of motion
Video analysis

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What 5 variables are assessed in the Revised Strain Index?

Intensity of exertion
Frequency of exertion
Duration per exertion
Hand/wrist position
Duration of the task per day

See NDC p.30 for an example of a Strain Index Scoring Sheet

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What is dartfish?

Movement analysis software using imported video images.

Protocols for utilization recommended to optimize
reliability and interpretability.

See NDC p.31 for illustration

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What goes on at the DeGroot Motion Analysis Lab in NYC?

High level musicians come in and she studies their biomechanics.

Treatment + prevention goals

See NDC p.32 for illustration/video

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What are the factors that can contribute to work-related musculoskeletal disorders (WMSD)?

Work organization and technology
Biomechanical factors
Psychosocial factor
–> ex: your job affects other’s jobs

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What are the types of work risk factors? (8)

Biomechanical
Mechanical
Environmental
Organizational
Psychosocial
Recent Work Changes
Other Employment
Work History

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Work Risk Factors
What are the biomechanical risk factors?

Posture
Movement and repetition
Force

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What are the 2 harms involving posture?

Extreme postures: flexed, extended or twisting
posture rather than neutral position.
Prolonged static posture

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Risks Involving Posture
What are the guidelines for extreme posture?

US dept. of Labour: task carried out with joint at 90-
100% of ROM amplitude.
–> ex: overhead work (farmers, electricians)

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Risks Involving Posture
What is the risk involved in prolonged static posture?

Muscles do not relax.
Posture held for >1min
Ex. seat with no arm rests

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Risks Involving Posture
What are the risks involved in working with arms in elevation above 90° (overhead)? (2)

Amount of time working with arms in elevation above 90 degrees associated with shoulder and neck pain.
Number of months working with arms in elevation above 90 degrees associated with alterations in supraspinatus tendon.

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What are the 2 risks involving movement and repetition?

Extreme movements
Repetitive movements

Risks Involving Movement and Repetition
What are extreme movements?

Work task carried out with extreme movement.
ex: reaching on assembly line, twisting neck to look at computer

(Canadian Centre for Occupational Health and Safety)

Risks Involving Movement and Repetition
What are repetitive movements?

Number of cycles of the work task carried out on the same day.
Cadence must be considered.

(Canadian Centre for Occupational Health and Safety)

According to the Dictionary of Occupational Titles, what is considered repetitive, frequent, occasional?

Repetitive: greater than 2/3 of workday
Frequent: 1/3 to 2/3 of workday
Occasional: 1/3 or less of workday

What is exertion?
What is the influence of repetition?

The amount of force required to carry out a task.

If the task is repetitive, a small increase in the required force may cause physical symptoms.
–> ex: change to stiffer keyboard

What determines the worker’s risk for injury?

The combination of required force and number of muscle contractions.

What is a risk factor for a worker having lifting requirements for a job?

Imbalance between their actual lifting strength and the
lifting requirements of job.

What exposure increases biomechanical risk?

From least to worse:
1. Repetition OR force OR posture
2. Repetition AND force OR posture
3. Repetition AND Force AND posture

See NDC p.43 for illustration

See NDC p.46 What are the biomechanical risk factors for this women?

1. Repetitive motion 2. Neck kyphosis 3. No arm support

What are the biomechanical risk factors associated with tool use?

1. Local pressure 2. Impact/vibration

What are the 4 general principles for reducing biomechanical risk factors with tool use?

1. Tools should effectively perform the intended function --> ex: a knife is not a screwdriver 2. Appropriate proportion to body size --> ex: small hand size grasping large pliers 3. Appropriate for strength and capacity of worker --> ex: weight of tool vs. physical capacity 4. Design should minimize fatigue --> ex: lightweight material)

What are the hand tool considerations? (8)

1. handle shape 2. handle length 3. handle diameter 4. texture 5. grip span 6. right or left hand 7. glove use 8. vibration See NDC p.48 for illustration

What is the biomechanical risk with local pressure?

Sustained pressure or friction during work task = pain --> ex: manual therapy techniques and therapists! Wajon and Ada 2003: Evaluated 155 physiotherapists who perform spinal manual therapy techniques. --> 83% complained of thumb pain

What are evidence based interventions to diminish biomechanical risk factors? (6)

1. Modification of workstation components (ex. hand tools, keyboard design, assistive devices) 2. Modification of work method (ex. mini-breaks, lower weight loads, alternating sitting and standing posture, set-up with lean principles) 3. Exercise programs (ex. individual or group) 4. Education programs (ex. back posture during lifting) 5. Work hardening programs after injury (ex. task simulation and duration of workday) 6. Modification of work wear (ex. shock absorbing insoles)Reduce exposure to risk factor (ex. vibration)

Describe the ideal posture when sitting?

1. Feet on floor 2. Knee at 90° flexion 3. Hip at 90° flexion 4. Butt in back of chair 5. Back on back rest 6. Arms supported 7. Elbows at 90° 8. Wrists straights 9. Top of screen straight view from eyes See NDC p.54 for illustration

What is the biomechanical risk factor with sitting?

Sitting uses near end range flexion of the spine. --> static posture in near-end ROM!

What are the guidelines for sitting? (4) Why? (2)

1. Use of lumbar support 2. Inclining back rest 3. Arm rests 4. Size of chair should match size of worker Why? 1. Helps to reduce disc pressure. 2. EMG activity reduced when back rest inclination closer to seat.

What are some modifications that can be done to the sitting environment? (2)

1. Seat pan tilt and lumbar support improve seated posture 2. Sit-Stand Work Stations 3. Perching

What are the benefits of perching sitting? (2)

1. Moderate support and moderate movement. 2. Helped to reduce spinal load and discomfort.

What are the impacts of arm and wrist support? (4)

1. 16% reduction in disc pressure when arms comfortably supported 2. Lower EMG activity in trapezius 3. Low to moderate level evidence supporting benefit of arm rests in reducing shoulder and neck pain 4. Increased keystroke ability if wrists supported

Name 2 arm muscles involved as a risk factor in unsupported typing.

1. EDC fatigue after one hour of typing (EMG) 2. Biceps fatigue reduced by use of wrist support with keyboard (EMG)

See NDC p.61 What are the biomechanical risk factors for this woman?

1. Petite = big chair 2. Feet dangling, so book underneath 3. Back rest not fit to her

What are the guidelines for screen use? (2) What is the suggestion with a laptop?

1. Should be face to face and approximately 60- 70cm from worker 2. Top of screen at eye level Elevated laptop and use plug-in keyboard. See NDC p.63-64 for illustration

What is a biomechanical risk with keyboard use? What are the guidelines for keyboard use? (2)

Risk of excessive pronation and ulnar deviation 1. Ideal angle of keyboard 0 to 25 degrees 2. Dished (indented) keys with light resistance facilitated typing performance

What are the biomechanical risks factors with mouse use?

1. 48% of standard mouse users keep finger(s) in extension 2. Mouse placement far from keyboard risk factor for upper extremity disorders 3. Postural mobility (mouse) vs prolonged static posture (touch pad on laptop) need to be considered. Well placed mouse preferable.

See NDC p.70 What are the biomechanical risk factors for this woman?

1. No arm support 2. Monitor is not at eye-level 3. Writing, answering phone, using mouse = leaning forward a lot