Workers who were exposed to higher frequencies (≥ 5 exertions per minute) and longer durations (≥ 15 percent of duty cycle) of forceful exertions (pinch grip ≥ 2 lbs; power grip, object weight lift, or push/pull force ≥ 10 lbs) were 6 and 3 times more likely, respectively, to have dominant hand sided lateral epicondylitis according to a recently published cross sectional design study by the Washington State Department of Labor and Industries.
The research, involving 733 full time workers from 12 different manufacturing and health care worksites, also showed that the odds of having dominant hand sided lateral epicondylitis were significantly higher if tasks involved longer durations of forceful lifting (≥ 0 percent of the time), forearm supination ≥ 45° (≥ 5 percent of the time), or a combination of forceful lifting and forearm supination.
Data revealed that other significant personal/workplace risk factors for lateral epicondylitis included being:
• middle age (36-50 years)
• a smoker
• at a workplace with low social support
Surprisingly, a weak or not relationship was found between lateral epicondyltis and:
• wrist flexion or extension ≥ 45°, ≥1 percent of the time
• wrist radial deviation < 5° or ulnar deviation ≥ 20°, ≥ 4 percent of the time
• power grip force > 0 percent of the time
• pinch grip force > 0 percent of the time
• vibration hand-held tool use > 0 percent of the time
The Bottom Line – How This Applies To Ergonomists
Although this study design – cross sectional – does not indicate causal relationships, findings can be applied to similar work environments (manufacturing and health services) with confidence. Based on this study, ergonomists can apply effective prevention and worksite modification practices for lateral epicondylitis by concentrating on reducing the frequency/duration of high exertions, forceful lifting, forearm supination, and combination of forceful lifting/supination.
Other Key Points
Among the 733 subjects, lateral epicondylitis was found on the dominant side (n = 32), on the non-dominate side (n = 17), and on both sides (n = 6) of the subjects.
Sixty-six percent of those who had lateral epicondylitis had at least one other upper extremity musculoskeletal disorder. The authors point out that this may suggest a transfer of strain to other upper extremity body regions as compensation when one area is painful.
The low participation rate (64.5 percent) could skew study findings (the difference between those who completed the study and those who did not is unknown). Also, the healthy worker effect may have played a role in this research.
Study ergonomists performed a worksite walk through and classified jobs using the hand activity level of the American Conference of Governmental Industrial Hygienists (hand force – low, high; hand repetitiveness – low, medium, and high). To be included in the study, a facility had to have at least three out of the six exposure categories (hand force/hand activity combinations).
Of all workers who qualified for the study, 64.5 percent enrolled.
Interviews were conducted to collect data on personal factors and work history including age, gender, race, education, duration of employment, smoking status, and presence of chronic disease. Information was also collected about leisure activities that involved high force/high repetition such as playing golf, gardening, knitting/sewing, weightlifting, and video/computer work.
A case definition of lateral epicondylitis was determined by having the subject:
• Complete a symptom questionnaire
• Be examined by a study-prepared occupational physician, registered nurse, or physical therapist blinded to the self-reported health status
Job demands, decision latitude, job security, and job satisfaction were assessed through a psychosocial questionnaire completed by each volunteer. Study ergonomists evaluated work organization (i.e., pacing, job rotation, team coordination) by using an observational tool.
Physical load factors (the duration/frequency of awkward postures, repetitive movements, and force intensity) were determined through observation and by videotaping each participant from two angles. Analysis was conducted at the task level. About 95 percent of the participants performed cyclical mono-task jobs. Equipment weights and push/pull forces were measured at the workplace.
This position paper can be acquired at: http://www3.interscience.wiley.com/journal/122296569/abstract
Article Title: Quantitative Exposure-Response Relations Between Physical Workload and Prevalence of Lateral Epicondylitis in a Working Population
Publication: American Journal of Industrial Medicine, 52:479-490, 2009
Authors: Z J Fan, B A Silverstein, S Bao, D K Bonauto, N L Howard, P O Spielholz, C K Smith, N L Polissar, and E Viikari-Juntura
This article originally appeared in The Ergonomics Report™ on 2009-06-17.