Psychologic Contribution to Non-local Fatigue

Non-local fatigue occurs when one muscle group causes the fatigue of a different muscle group within a training session. This phenomenon is commonly studied among exercise physiologists who have potentially overlooked the possibility of a psychological effect of knowingly participating in what is supposed to be a fatigue study. PURPOSE: Therefore, the purpose of the study is to determine what subjects think will happen to lower body performance when upper body exercises are added, and if that affects the actual non-local fatigue result. METHODS: One lower-body workout (LB) consisted of five sets of leg extension (quadriceps only exercise) at 90% of their maximum strength with 3-minutes between the beginning of each set. Another whole-body workout (WB) consisted of five sets of leg extension, and four sets of bench press and lat- pulldown was performed between bench press sets in an alternating manner, at 80% of maximal strength. For all exercises, sets 1-4 were performed for submaximal repetitions, and the fifth leg extension set was performed to exhaustion. Total number of completed repetitions of the last knee extension set was counted and recorded. R via RStudio was used to run a mixed model and linear model to analyze the effect of prediction and condition on number of reps to failure. RESULTS: There was no significant interaction between subjects’ predicted result and the effect of condition (LB vs WB) (p=0.28, R^2=0.13). For subjects predicting impairment to occur, WB resulted in 1.2 (1.5) repetitions less than LB. Those predicting no change to occur, WB resulted in 0.2 (1.3) repetitions less than LB. There was no significant main effect of condition (p=0.14). CONCLUSION: In conclusion adding lat pulldown and bench press did not result in significant non- local fatigue in the leg extension exercise. Furthermore, what the subjects predicted would occur did not help explain the non-local fatigue results, despite a medium effect size.