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.

Method: 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.

Figure 1

Results of seven cross-sectional epidemiological studies allowing 2 × 2 analysis of force and repetition and that exhibit a Force × Repetition interaction: (a) Silverstein, Fine, and Armstrong (1987); (b) Armstrong, Fine, Goldstein, Lifshitz, and Silverstein (1987); (c) Marras et al. (1993; data reported in Zurada, Karwowski, & Marras, 1997); (d) Haahr and Andersen (2003); (e) Thomsen et al. (2007; additional data analysis provided by J. F. Thomsen, personal communication, November 18, 2011); (f) Frost et al. (2002); (g) Nathan, Meadows, and Doyle (1988).

Figure 2

Data on fatigue failure of spinal motion segments by force and cycles of repetition (Brinckmann, Biggemann, & Helweg, 1988).

Figure 3

Data on fatigue failure of human extensor digitorum longus tendons by force and cycles of repetition (Schechtman & Bader, 1997). UTS = ultimate tensile strength.

Figure 4

Force × Repetition quadrants superimposed on a fatigue failure curve. LFLR = low force, low repetition; LFHR = low force, high repetition; HFLR = high force, low repetition; HFHR = high force, high repetition.

Figure 5

Conceptual model of the effects of force and repetition on musculoskeletal disorder development and recovery. A + indicates an increased likelihood of a following event (more + signs indicate higher likelihood); a − indicates decreased likelihood of a following event.