title: The association between combination of hand force and forearm posture and incidence of lateral epicondylitis in a working population.
abstract: OBJECTIVE
  The objective of this prospective study is to investigate the exposure-response relationships between various workplace physical exposures of force, repetition, and their combination assessed at an individual level with lateral epicondylitis (LE).
  
  
  BACKGROUND
  Workplace upper extremity musculoskeletal disorders (UEMSDs) are prevalent, disabling, and expensive. LE is one of the major UEMSDs in active workers.
  
  
  METHODS
  We used detailed health history, symptoms, and physical examination for identifying incidence and detailed exposure assessment to capture work tasks of each worker and to measure quantitative mechanical workload. We used counting process style input of proportional hazards regression for modeling cumulative incidence that accounts for changed exposure estimates during the follow-up period when respondents change jobs.
  
  
  RESULTS
  The incidence rate of LE on the dominant side was 4.91 per 100 person-years. Adjusted for age and gender, the combined effect of forearm pronation > or = 45 degrees for > or = 40% of time and time spent with forceful exertion, including any power grip (hazard ratio [HR] = 2.8, 95% confidence interval [CI] = [1.35-5.77]), lifting for > or = 3% of time (HR = 2.50, 95% CI = [1.19-5.24]), and duty cycle for forceful exertion for > or = 10% (HR = 2.25, 95% CI = [1.09-4.66]), were significant predictors of dominant side LE, whereas neither the awkward posture nor the forceful exertion alone was significant. Older workers with jobs requiring a high percentage of time working with force in combination with awkward postures of forearm were more likely to predict LE.
  
  
  CONCLUSIONS
  This study shows the evidence of the etiologic role of strenuous manual tasks in the occurrence of LE.
authors.forename: Z Joyce
authors.initials: ZJ
authors.lastname: Fan
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Silverstein
authors.forename: Stephen
authors.initials: S
authors.lastname: Bao
authors.forename: Dave K
authors.initials: DK
authors.lastname: Bonauto
authors.forename: Ninica L
authors.initials: NL
authors.lastname: Howard
authors.forename: Caroline K
authors.initials: CK
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D005542:Forearm / Q000503:physiopathology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000209:etiology* / Q000503:physiopathology*; D009790:Occupations; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013716:Tennis Elbow / Q000209:etiology* / Q000503:physiopathology*