Environmental/Occupational Health & Safety Office
Ergonomics
Written by: Jessica Berrigan ‘10
“The science of fitting the work environment, work demands and work practices
to the capabilities of the working population to maintain safety, productivity
and quality of work” Ergonomics at Work Inc., 2002.
Defining the Science of Ergo
Ergonomics also known as “human factors” is derived from the Greek “ergon” meaning work
and “nomos” meaning laws. It is essentially a “science of work” which can be applied to all
aspects of human activity to optimize human well-being. Ergonomic applies a holistic approach
encompassing not only the physical and environmental, but also social, cognitive, organizational and any other relevant factors.
The primary objective of ergonomics is to minimize the risk of work-related musculoskeletal
disorders (WRMSD’s) through planning, designing, assessing and evaluating tasks, jobs, tools
and systems. This is essential to ensure the work environment is compatible with an individuals abilities or limitations or is a best fit/adjustable for the majority of the demographic. The
major factors that are considered during an assessment include: the environment (i.e. floor
type, tools, temperature, lighting etc.), mental demands (i.e. stress, mutlitasking, fatigue etc.),
physical demands (i.e. pace, muscle fatigue, awkward postures, repetition etc.), and task demands (i.e. objectives, deadlines etc.).
Musculoskeletal Disorders
Table of Contents
WRMSD Statistics........................ 2
Non Work-Related Factors.......... 2
Primary Risk Factors.................... 2
Static vs Dynamic Postures ......... 3
Secondary Risk Factors ............... 4
Recommendations ...................... 4
Musculoskeletal disorders is an “umbrella term” encompassing overuse and repetitive disorders and injuries involving muscles, tendons, nerves and ligaments. These disorders are
strongly linked to hazards in the workplace that can be prevented.
References/Resources ................ 6
Cause: Due to a single event (acute) or repeated exposure (cumulative or chronic) to activi-
Acute vs. Chronic
ties that cause strains and sprains of muscles, tendons and soft tissues until the stress exceeds
the strength of the tissue (i.e. carpal tunnel, tendonitis etc.).
Signs: Shaking of hands after working with an object or tool, Rubbing arms, hands etc. Swelling/redness of areas of tension, Avoidance of tasks that stress certain body parts.
Symptoms: Tightness, tingling, discomfort, Soreness, fatigue, Loss of strength or clumsiness
Progression of Injury: In the first stage, pain only appears during the activity and disappears after the activity is stopped. In the second stage, pain will continue after the activity for
several hours. This may affect sleep and require one or more nights to recover. In the third
stage, pain will be experienced even when not performing the activity and may become
chronic. Pain will affect sleep and will not recover over a weekend.
Request an Ergo Assessment ...... 6
Acute injuries occur suddenly
during an activity (i.e. sprained
ligaments or strained muscles).
Several acute injuries may develop
into a chronic condition
Chronic injuries persist/develop
over time and are usually due to
overuse or repetitive stress or
activities (i.e. WRMSD’s).
www.wlu.ca/eohs
WRMSD Statistics
In 2008, 296.774 claims were filed
through the Work place Safety Insurance
Board (WSIB).
Closely followed by upper extremity
injuries of the wrist, hand arm and
fingers (20.9%).
Primarily due to overexertion (22.7%)
and repetitive movements(12.6%).
Work-related musculoskeletal disorders
(WRMSD’s) are the number one cause of
lost time in the workplace; representing
approximately 50% of all WSIB lost time
claims and accounting for more than
60% of annual costs reported for 2008.
Work-related musculoskeletal disorders
are a serious issue in the workplace.
Prevent MSD’s by recognizing the hazards/concerns and implementing/
evaluating controls.
Back injuries accounted for 28.6% of
these claims, in particular low-back
injuries (21.1%).
Statistics reported here were taken from the WSIB
statistics for 2008, retrieved June, 2010.
“Be PROACTIVE and spot the Risk Factors!” Sadi, 2007
Non Work-Related Factors
MSD’s: Primary Risk Factors
Gender/Age:
1. Awkward Postures:
Muscle strength differences
Load tolerances of spine,
Vision
Information processing
Ability to recover from
strenuous/prolonged work or
injuries
Neck/Trunk:
Flex.
Joint type: Pivot/semi-mobile
Movement: All three planes.
Ext.
Flexion > 20°/ Extension > 30°
> 20° Lateral Bending
Rotat.
Rotation > 45°
Lifestyle:
Flex.
Lat. Bend
Ext.
Physical activity levels
Nutrition and diet
Attire ( i.e. high heels,
glasses)
Knee:
Hyp. Ext.
Psychosocial:
Joint type: Hinge joint
Movement: In one plane.
Flex.
Workplace morale
Full Flexion/ Hyperextension
Employee relationships
Job satisfaction
Definitions
Shoulder:
Circumduction: complete rotation
of the shoulder joint in a circle.
Extension: movement such that
the joint angle increases.
Flexion: movement such that the
joint angle decreases.
Joint type: Ball and socket,
Movement: Great flexibility, less stability
Abd.
Flexion > 60 ° /Extension
Abduction > 60° /Adduction
(elbows not crossing midline)
Circumduction (repetitive)
Elevation (static or repetitive)
2
Circ.
Flex.
Ext.
Add.
Elev.
Recommended Dimensions for Standing Work
Static vs Dynamic Postures
Static Posture
A neutral standing posture will minimize strain on the back, shoulders and neck. Proper work surface heights, depending on type
of work, are required to minimize the risk of prolonged awkward postures. A foot rest will decrease loading on the lower back
and allow for changes in standing posture (Modified from (WSIB Resource: Repetitive Strain Injuries, retrieved June 2010).
Recommended Dimensions for Seated Work
When a posture is held stationary for a long period of
time: muscles exert a force
while maintaining an isometric contraction (i.e. the muscles do not lengthen or
shorten).
Static postures are more
problematic if held for long
periods or repeated often,
even at lower levels of force/
exertion.
A neutral seated position will also minimize strain on the back, shoulders and neck. Chairs and work surfaces should be adjusted
so that ankles, knees, hips and elbows should be around 90° to minimize muscle fatigue. Work should be located within a field of
view that allows for a neutral head/neck posture. Workstations should be organized so that things used most often are closest to
minimize reaching (Modified from WSIB Resource: Repetitive Strain Injuries, retrieved June 2010).
MSD’s: Primary Risk Factors Cont.
Sup.
Flex.
Elbow/ Forearm:
Joint type: Hinge joint/pivot
Movement: In one plane.
Extreme Flexion/Extension
Pron.
Rad. Dev.
Hand and Wrist
Joint type: Ellipsoid
Movement: In two planes
Extreme or static Flexion/Extension
Ext.
Dynamic Postures
When a posture is not held
for long periods of time,
muscles exert force while
undergoing concentric and
eccentric contractions (i.e.
muscles are shortening and
lengthening).
Hyp. Ext.
90° Pronation/ Supination
Flex.
Example: Holding a box at
waist height with straight
arms is a static posture for
the back and shoulders.
Uln. Dev.
Static or repetitive Ulnar and Radial
Deviation
2. Forceful Exertions
Forceful exertions are that which overloads our muscles, tendons, joints or tissue, one or
many will increase your risk for WRMSD’s. The force needed to complete a task can depend
on an individuals stature/gender, the task/ muscle size relationship, posture and lifting
strategies used, and the moment or torque created ( reaching, lifting). Force will also increases with pace or rapid changes in direction.
3. Repetition
The effect of repetition depends on the force exerted, duration and postures exhibited. A
task is considered repetitive if a cycle between tasks is shorter than 30 seconds.
Shoulder: more than 2.5 times/min
Upper arm/elbow: more than 10 times/min
Forearm/wrist: more than 10 times/min
Fingers: more than 200 times/min
Example: Lifting a box from
the floor to a table top.
During static postures, there is a
reduction in the amount of blood
flow to the muscles compared to
dynamic postures. Therefore, less
oxygen is delivered and less waste
is removed causing muscles to
fatigue faster. Over time this will
cause stress on primary and secondary muscles resulting in pain,
discomfort and inflammation.
Definitions
Adduction: Movement towards
the midline of the body
Abduction: Movement away from
the midline of the body
Pronation: Rotation of the forearm
so that the palm faces downwards
Supination: rotation of the forearm so that the palm faces upwards.
3
Stretch Break Guidelines
Here are some general guidelines for safe stretching:
Secondary Risk Factors
1. Mechanical Contact Stress
3. Climate
Cause: Continuous or repeated contact with
Cause: Extreme cold (office: < 18˚C) or hot
Try to include all the major
muscle groups.
a sharp or hard surface (i.e. desk, edge of
seat, tools ect.).
temperatures (depends on humidity, source
of heat, work demands ect.)
Perform stretches on both
sides of the body equally.
Contact stress may pinch nerves, muscles and
tendons causing strain which may lead to
pain/discomfort and/or inflammation
Cold stress will lead to muscle rigidity and
circulation problems. Heat stress can eventually cause muscle cramping and dehydration.
These stresses can lead to low productivity,
and result in serious injury and/or death.
Stretch muscle pairs evening;
agonist and antagonist.
Majority of stretches should
be static.
Stretches should be held to
the point of tension; light
discomfort not pain.
Hold the stretch for 10-15
seconds.
Rest for 10-15 seconds between each stretch.
Repeat each stretch 2-3
times.
Remember to breathing
normally during a stretch.
Avoid:
Bouncing.
Contracting the muscle or
muscle group you are
stretching.
Forceful or hard stretching,
may cause stiffness and muscle tightness.
2. Lighting
Cause: Glare may be from a direct source
shining on your work, such as the sun or task
lighting, or an indirect source (i.e. overhead
lighting).
Poor and/or excessive lighting causes glare,
eyestrain and increased visual demands, and
possible physical demands from bending, or
twisting neck/torso to see work.
Recommendations: Minimize Risk of
WRMSD’s
1. Stretch it Out
Stretching before and during the work day will warm-up cold muscles, improve blood
flow, increase flexibility and decrease your risk or injury. Schedule stretch breaks every
hour throughout your day. Take a ten minute break and stretch a major muscle group. Next
break stretch a different group. By the end of the day you will have completed your entire
stretching program! See stretch break guidelines and example stretches.
If stretching sore muscles:
Use light stretches away from
the discomfort.
Example Stretches: Neck
Hold stretches 5-10 seconds.
Rest for 5-10 seconds between each stretch.
Extensors: Slowly lower your chin to your chest and
hold.
Repeat stretches 2-3 times.
Flexors: Maintain a straight neck posture and look up
towards the ceiling. Focus on pointing your chin out
and up. Hold. Avoid tilting your head back such that
your spine is compressed
Remember to stay within your
limits to avoid injury. Stretching should not cause prolonged
pain or soreness
Extensors
Flexors
Rotators: Start by looking straight ahead and then
rotate your head bringing your chin close to your
shoulder. Drop your chin and slowly rotate your head
to look over the other shoulder. Repeat
Rotators
4
Lateral Flexors/Extensors: Start looking straight ahead
and then tilt your ear towards your shoulder. Alternate
sides.
Lateral Flex/Ext
Recommendations Cont.
2. Break Time
Taking frequent breaks will introduce more movement into your day if you are stationary
seated or standing. This has been shown to improve mood, increase productivity and decrease risk of MSD’s. Lunch and snack breaks should be taken away form your desk or
workstation to allow for a change in posture, and a mental break from work. Task rotation
such as switching from computer work to file documents will introduce a break from repetitive postures and movements.
3. Limit Awkward Postures
Use proper postures to minimize strain on muscles. Limit time spent in these postures as
well as static awkward postures. Have your workstation ergonomically assessed and designed. Adjust your workstation to fit your body size to minimize risk of stress and strain
from awkward postures.
“Remember: Insufficient physical activity potentially far exceeds the risk of
WRMSD due to sedentary computer/office work. Exercise has number of physical
and psychosocial benefits! “ Stracker, 2009.
4. Minimize Repetitive/Forceful Exertions
Try to minimize repetitive and forceful exertions by taking necessary breaks, task rotations
and stretching. Use proper techniques to minimize risk of injury (i.e. Safe Lifting Guidelines:
bend at knees, use legs to lift, hold object close to body). Use of ergonomically designed
workstations and tools to assist with tasks (i.e. mechanical lifts.
5. Share the Workload
Certain tasks require the use of your dominant hand, arm or leg etc. Try using your nondominant hand for tasks that do not require a large amount of precision (i.e. mousing,
gripping and lifting objects). This will decrease the overload normally associated with repetitive tasks with the dominant side allowing for more rest and balance.
6. Organize your Workplace
Objects and documents that are used most often should be within reach. Clutter should be
removed on and below workstations. Avoid overreaching for things, stand up to access
things that are just out of reach. Place things most often used at waist height on shelves.
Heavy boxes should be kept lower and light boxes higher avoid heavy lifting above your
head.
7. Report the Hazards
It is your role as a worker to minimize your risk and report the hazards to a supervisor.
Offer your suggestions on how to minimize or improve working conditions. Be aware of the
risks and symptoms if you begin to experience them.
5
Request an Assessment
To request an ergonomic
assessment of your workstation, please complete
the Ergonomic Workstation
Assessment Request Form
at www.wlu.ca/eohs and
forward to:
Donna Kubica, EOHS office,
BA103.
For further information,
please contact:
[email protected].
References
1.
Association of Canadian Ergonomists (ACE), About ergonomics, http://www.aceergocanada.ca/index.php?contentid=142, retrieved June, 2010.
2.
Ergonomics at Work Inc., Introduction to office ergonomics, 2002.
3.
International Ergonomics Association (IEA), What is ergonomics, http://
www.iea.cc/ browse.php?contID=what_is_ergonomics, retrieved June, 2010.
4.
Sadi, j et al. A 13-year cohort study of musculoskeletal disorders treated in an
autoplant, J Occup Rehabil 17: 610– 622, 2007.
5.
Stracker, L et al. The effects of walking and cycling computer workstations on
keyboarding and mouse performance, Human Factors 5 (6): 831-844, 2008.
6.
Taylor’s Ergonomics Inc., Physical demands descriptions, 2010.
7.
Workplace Safety & Insurance Board (WSIB), Ontario MSD Prevention Guidelines
and Repetitive Strain Injuries, http://www.wsib.on.ca, retrieved June, 2010.
www.wlu.ca/eohs
“The EOHS office is committed to promoting an environmentally responsible, safe and
healthy work environment for all community members, while striving to ensure compliance
with relevant regulations and support the university's mission of teaching and research“
Stephanie Kibbee Director,
Environment/Occupational
Health and Safety
Bricker Academic Building BA103
75 University Avenue West
Waterloo, ON, N2L 3C5
Phone: 519-884-0710 x2874
Fax: 519-884-2781
E-Mail: [email protected]
Ergonomic Resources
Workplace Safety & Insurance Board (WSIB)
http://www.wsib.on.ca/
http://www.preventionpractices.com/
Ministry of Labour
http://www.labour.gov.on.ca/index.php?/english/hs/
Association of Canadian Ergonomics (ACE)
http://www.ace-ergocanada.ca
International Ergonomic Association (IEA)
http://www.iea.cc/