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Effects of self-regulatory strength depletion on muscular performance and EMG activation


  • We thank John Moroz, Arif Jetha, and Courtney Clayton for their assistance with the study apparatus and data acquisition. This research was supported by a Standard Research Grant awarded to Kathleen A. Martin Ginis and Steven R. Bray by the Social Sciences and Humanities Research Council of Canada.

Address reprint requests to: Steven R. Bray, Ph.D., Department of Kinesiology, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4K1, Canada.


The purpose of the present study was to examine the effects of a self-regulatory strength depletion manipulation on performance of a physical endurance (isometric handgrip) task. In addition, the effect of depletion on EMG activity in the working forearm muscles during the endurance task was explored. Sedentary undergraduates (N=49) were randomly assigned to either a cognitive depletion condition (modified Stroop task) or a control (color word) group and completed two maximal isometric exercise endurance trials separated by the cognitive task. Participants in the depletion group showed significant (p<.05) degradations in performance and exhibited higher EMG activation on the second endurance trial (p<.05) compared to controls. Results are consistent with the limited strength model of self-regulation and are interpreted in light of the central fatigue hypothesis.