title: Examining the interaction of force and repetition on musculoskeletal disorder risk: a systematic literature review.
abstract: OBJECTIVE
  Our aims were (a) to perform a systematic literature review of epidemiological studies that examined the interaction of force and repetition with respect to musculoskeletal disorder (MSD) risk, (b) to assess the relationship of force and repetition in fatigue failure studies of musculoskeletal tissues, and (c) to synthesize these findings.
  
  
  BACKGROUND
  Many epidemiological studies have examined the effects of force and repetition on MSD risk; however, relatively few have examined the interaction between these risk factors.
  
  
  METHODS
  In a literature search, we identified 12 studies that allowed evaluation of a force-repetition interaction with respect to MSD risk. Identified studies were subjected to a methodological quality assessment and critical review. We evaluated laboratory studies of fatigue failure to examine tissue failure responses to force and repetition.
  
  
  RESULTS
  Of the 12 epidemiological studies that tested a Force x Repetition interaction, 10 reported evidence of interaction. Based on these results, the suggestion is made that force and repetition may be interdependent in terms of their influence on MSD risk. Fatigue failure studies of musculoskeletal tissues show a pattern of failure that mirrors the MSD risk observed in epidemiological studies.
  
  
  CONCLUSIONS
  Evidence suggests that there may be interdependence between force and repetition with respect to MSD risk. Repetition seems to result in modest increases in risk for low-force tasks but rapid increases in risk for high-force tasks. This interaction may be representative of a fatigue failure process in affected tissues.
authors.affiliation: Department of Industrial and Systems Engineering, Auburn University, Auburn, AL, USA. seangallagher@auburn.edu
authors.forename: Sean
authors.initials: S
authors.lastname: Gallagher
authors.forename: John R
authors.initials: JR
authors.lastname: Heberger
mesh_terms: D012090:Cumulative Trauma Disorders / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D017116:Low Back Pain / Q000453:epidemiology / Q000209:etiology*; D018763:Muscle Fatigue; D053580:Muscle Strength; D009140:Musculoskeletal Diseases / Q000453:epidemiology / Q000209:etiology*; D009141:Musculoskeletal System / Q000293:injuries*; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology; D012307:Risk Factors; D016526:Workload