Transcript Hand Tools Robert Stuthridge Ergonomist National

Assistive Technology:
Hand Controls
AgrAbility Webinar
22 February, 2010
Robert W. Stuthridge B.Sc., M.Sc.
Purdue University
National AgrAbility Project
Agenda
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The need for hand-operated (AT) controls
Design options
Hazards and risks
Design considerations
Usage considerations
Hazard and risk assessments
Need for hand-operated (AT) controls
• US Ag. high rate of permanent disability (Deboy 2008;
NIOSH 2009)
• Types of disabilities (through AgrAbility) (Willcomm,
2004)
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23% Orthopedic (including musculoskeletal).
16% Amputation.
13% Neuromuscular.
21% Spinal Cord injury.
27% Other.
• Any of these may involve reduced lower-limb
functionality.
Need for hand-operated (AT) controls
• Over 70% of agricultural
workers with disabilities
continue to work by
modifying their work
environment using
‘assistive technology
devices’ (Gruver at al. 1997)
Hazards and risks
• AT may increase primary user’s risk of
developing “secondary injuries” (Willkomm 1997; Yoder,
Kingman et al. 2001; Willkomm 2004; Mathew 2009).
• AT injuries may occur as a consequence of
inappropriate design of AT, preceded by
incidents such as:
• Slips
• Trips
• Falls
• Incidental contact with AT (Willkomm 1997).
Hazards and risks
• May also increase risk of similar injuries for
secondary users (family members, other
employed workers including seasonal/casual)
(Willkomm 2004; Mathew 2009).
• Slips, falls and incidental contact result in acute
injury.
• Possible to attribute injury to immediately
precedent event.
• May lead to:
• Redesign of AT
• Limitation or cessation of use of AT
• Change in workers’ behavior when using AT
Hazards and risks
• Most agricultural injuries are not acute - no clear cause
effect relationship between an incident and an injury
(Walker-Bone and Palmer 2002).
• Work-related musculoskeletal disorders WMSD are
most prevalent form of agricultural injury (Walker-Bone and
Palmer 2002).
• WMSD arise from repeated or prolonged exposure to
occupational hazards such as:
• whole body vibration,
• segmental (e.g. hand-arm) vibration,
• awkward working postures,
• heavy lifting, and
• use of excessive force (Mehta, et. al., 2000; Muzammil et.al., 2004;
Rautiainen, et.al., 2004; O'Sullivan, et. al., 2009).
Design considerations
Design Considerations: Wrist Posture
• Handles designed to
promote neutral
wrist/arm postures
Design Considerations: Force
Nonslip cushioned grips must be suited
to all likely climatic conditions.
Don’t make handles too large in diameter:
Optimum handle span largely dependent on hand length.
Small hands <6.7 inches long and medium hands 6.7-7.5 inches long exert
most force at ≤2.0 inch handle span.
Large hands >7.5 inches long exert most force at 2.4 inch handle span.
Usage considerations
Usage Considerations: Repetition
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Even initially ‘comfortable’
postures and forces can cause
pain with enough duration or
repetition, e.g. laying, sitting,
standing.
Need to balance
mobility/movement with a
need to avoid repetitive
movements.
Variation of posture is key.
Rest/recovery pauses and
breaks.
Steering Ball can provide
postural options…suitable
for fitting to steering wheels
of tractors and other
vehicles.
Hazard and risk assessment
Definition of Terms Used
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“Assistive Technology (AT)” means “technology designed to be utilized in an assistive technology device or
assistive technology service.” Assistive Technology Act (1998). Assistive Technology Act of 1998. 105-394,
S.2432. US Congress. Washington DC.
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“Disability”: This presentation uses the definition applied by the Americans with Disabilities Act, As
Amended, 2008 ADA (2008). Americans With Disabilities Act of 1990 As Amended 2008 42.126.12101 P.L.
110-325 US Congress, Washington DC. The ADA defines "disability" with respect to an individual as:
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“Assistive Technology Device”: “The term `assistive technology device' means any item, piece of equipment, or
product system, whether acquired commercially, modified, or customized, that is used to increase, maintain, or
improve functional capabilities of individuals with disabilities.” Assistive Technology Act (1998). Assistive Technology
Act of 1998. 105-394, S.2432. US Congress. Washington DC.
“Assistive technology service”: The term `assistive technology service' means “any service that directly assists an
individual with a disability in the selection, acquisition, or use of an assistive technology device. .” Assistive
Technology Act (1998). Assistive Technology Act of 1998. 105-394, S.2432. US Congress. Washington DC.
A physical or mental impairment that substantially limits one or more major life activities of such individual;
A record of such an impairment; or
Being regarded as having such an impairment.
In determining whether a person is disabled within the meaning of the Act, ‘major life activities’ are defined as
follows: “Major Life Activities include, but are not limited to, caring for oneself, performing manual tasks, seeing,
hearing, eating, sleeping, walking, standing, lifting, bending, speaking, breathing, learning, reading, concentrating,
thinking, communicating, and working. A major life activity also includes the operation of a major bodily function,
including but not limited to, functions of the immune system, normal cell growth, digestive, bowel, bladder,
neurological, brain, respiratory, circulatory, endocrine, and reproductive functions” ADA (2008). Americans With
Disabilities Act of 1990 As Amended 2008. 42.126.12101 P.L. 110-325,. US Congress. Washington DC,..
Disabilities may arise due to trauma, disease, aging, genetic conditions (Deboy et al, 2008).
“ Hand Controls” here infers only equipment controls modified for operation with the hands or arms,
where the operation would not ordinarily involve the use of the hands or arms. It specifically includes for
this presentation only those controls modified to meet the needs of agricultural workers with disabilities.
“Secondary injury” is an injury “caused wholly or partially by limitations associated with disability
conditions and/or resulting from the use of modified practices or AT to compensate for disabling
conditions. The cause of the original disability can be a previous injury or any other condition.” Mathew, S.
N. (2009).
References
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Deboy, G. R., Jones, P.J., Field, W.E., Metcalf, J.M. and Tormoehlen, R.L. (2008) "Estimating the Prevalence of Disability
within the U.S. Farm and Ranch Population." Journal of Agromedicine 13(3 ): 175-189.
Gruver, M.L., Allen, P. B., Field, W. E., Schweitzer, J. (1997) Potential health and safety risks of farming/ranching with a
disability. In Plowshares #27. 1997, Breaking New Ground Resource Center, Purdue University: West Lafayette, IN..
Mathew, S. N. (2009). “An assessment process to estimate the secondary injury potential of assistive technology adopted by
farmers with disabilities.” (PhD Thesis). West Lafayette, IN., Purdue University.
Mehta, C.R., Shyam, M., Singh, P., Verma, R.N., (2000) Ride vibration on tractor-implement system. Applied Ergonomics,
2000. 31(3): p. 323-8.
Muzammil, M.S., Siddiqui S.S. and F. Hasan, (2004) Physiological effect of vibrations on tractor drivers under variable
ploughing conditions. Journal of Occupational Health., 2004. 46(5): p. 403-9.
NIOSH (2009). "Agricultural Safety." NIOSH Safety and Health Topic http://www.cdc.gov/niosh/topics/aginjury/default.html
Rautiainen, R.H., Lange, J.L., Hodne, C.J., Schneiders, S., Donham, K.J., (2004) Injuries in the Iowa Certified Safe Farm
Study. Journal of Agricultural Safety and Health, 2004. 10(1): p. 51-63.
Walker-Bone, K. and K. T. Palmer (2002). "Musculoskeletal disorders in farmers and farm workers." Occup Med (Lond)
52(8): 441-450.
Willkomm, T. (1997). “Risks in using modified tractors by operators with spinal cord injuries and their co-workers.” PhD
Thesis. Pittsburgh, PA, University of Pittsburgh.
Willkomm, T. (2004) "Farming and Ranching with a Disability
http://nasdonline.org/static_content/documents/1832/d001767.pdf."
Yoder, A., Kingman, D.M., Field, W.E. (2001) Influences of disabling conditions on the nature and frequency of farm/ranchrelated injuries. National Ag Safety Database 2001 11/27/2009; Available from:
http://nasdonline.org/document/1833/d001768/influences-of-disabling-conditions-on-the-nature-and.html.