Theses and Dissertations

Date of Award


Document Type


Degree Name



Exercise Science

Committee Chair

Ryan Colquhoun, Ph.D.


The purpose of the current study was to compare sex-differences in quadriceps fatigability following both high- and low-intensity repeated, isometric contractions. Twenty-four (12 males, 12 females) participants completed two experimental visits consisting of repeated, isometric contractions of the knee extensors at 30% (LT) and 70% (HT) of maximal voluntary force (MVIC) until failure. Prior to, and immediately following the fatiguing contractions, strength, voluntary activation (VA), and peak twitch torque (PTT) were assessed while measuring surface electromyographic amplitude of the vastus lateralis (VLAMP) and vastus medialis (VMAMP ). Fatiguing bouts were assessed via mean torque (TQMEAN), total repetitions completed, torque coefficient of variation (TQcv ), EMG amplitude (VLAMP; VMAMP) and integrated EMG (iEMG) signal, and torque impulse (TQ1MP). Repeated measures Analysis of Variance analyses indicated females completed nearly double the repetitions of males during LT contractions (p = 0.001 ). Greater central fatigue was experienced during the LT contractions than HT (p = 0.050), despite having lower EMG amplitude throughout the fatiguing bout (p < 0.001). A sex difference may be present during LT repeated isometric contractions, but further investigation is needed.