Visual analogue scale correlates of musculoskeletal fatigue

Visual analogue scale has been shown to reflect subjective feelings but rarely has it been used for musculoskeletal fatigue so in the present study VAS ratings were used to quantify musculoskeletal fatigue. A total of 20 students underwent a fatigue protocol (M age = 21.3 yr., SD = 1.0). A series of randomized external loads at 0, 5, 10, 15, 25, 35, and 50% of the maximum voluntary contraction was generated by the BTE Primus and applied at the distal end of the dominant arm, which was sustained at the 90degrees forward flexion position. After 60 sec. of force exertion for each loading, the subject marked the scale to reflect their extent of fatigue at the shoulder muscle. Analysis showed fatigue scores were significantly correlated with the percentages of maximum load applied (r = .73, p less than or equal to .01). The correlation between higher external loads (25-50% maximum load) and fatigue scores was .57 (p less than or equal to .01) and that for lower external loads (0-15% maximum load) was .44 (p less than or equal to .01). The validity of using a visual analogue scale as a measure of musculoskeletal fatigue requires further study, particularly for a low load.