The Effects of Upper - Body and Lower - Body Fatigue on Standing Balance

The purpose of our study was to analyze the effects of upper-body fatigue and lower-body fatigue on post-exercise standing balance. Force plates were used to assess static balance by measuring the displacement of the Center of Pressure (COP) while subjects stood on the plate. Ten healthy male undergraduate students (mean age 20.7 years, SD = 1.3) each participated in one session. All subjects were considered to be physically fit, as determined by self-reported vigorous physical activity in hours per week (mean activity 7.1 hours, SD = 3.7). During sessions, participants performed two control trials and two fatigue trials, with each trial consisting of subjects standing motionless on a force plate for 20 seconds. Participants completed one upper-body fatiguing protocol and one lower-body fatiguing protocol in random order. Standing balance trials were completed before and immediately following each fatigue protocol. Lower-body fatigue was achieved by participants performing a maximum number of body-weight squats, while upper-body fatigue was attained by participants performing a maximum number of push-ups. Subjects reported their Rate of Perceived Exertion (RPE), which was used to determine individuals’ subjective level of exhaustion on a scale of 6-20 (mean squat RPE = 14.9, SD = 2.2; mean push-up RPE = 15.4, SD = 1.3). Each subject was required to rest during a 15-minute recovery period between each fatigue protocol. The upper-body fatigue protocol produced significant (p < 0.05) mediolateral variability of the COP when compared to the control condition, and additionally, the lower-body fatigue protocol resulted in a significantly greater path length in comparison to the control trials. There was no significant difference in standing balance between upper and lower-body fatigue trials. The most paramount findings of the present study indicate that the selective fatigue of upper-body musculature greatly impairs standing balance, particularly by causing significant mediolateral deviations.