BACKGROUND: The purpose of this investigation was to compare the accuracy of muscle excitation and torque production at 25, 50, and 75% of perceived maximum effort in males and females. METHODS: Twenty-four trained males and females (n=12) completed a familiarization and an experimental visit separated by at least 48 hours. During the experimental visit, participants were seated in an isokinetic dynamometer with their dominant leg attached to the arm of the dynamometer at 90º of knee flexion. Muscle excitation was assessed via a surface EMG sensor was placed on the vastus lateralis (VL). Following a brief 5-minute warm-up on a cycle ergometer, subjects completed 3 separate 3-5 second warm-up contractions at 25, 50, and 75% of their perceived maximum voluntary isometric contraction (MVIC) strength. No feedback of any kind was provided to the subjects. Peak torque (PT) and EMG amplitude of the VL (VLAMP) were calculated during the highest 500 ms window of each repetition and averaged across the 3 repetitions at each intensity. The average PT and VLAMP were normalized to MVIC and expressed as the percent error from the target (i.e., 25%, 50%, 75% MVIC) to examine the accuracy of the variables (nPTERROR and nVLERROR, respectively). Only data from the experimental visit was used in the analysis. Separate 3 (intensity) × 2 (sex) repeated measures ANOVAs were run for each dependent variable. Alpha was set a-priori at 0.05 and all data was analyzed in SPSS. RESULTS: There were no significant interaction effects for either nPTERROR (p=0.564) or nVLERROR (p=0.343). However, there were main effects for intensity for both variables (p<0.001 for both). Post-hoc analyses indicated that, when collapsed across sex, participants displayed significantly more negative nPTERROR and nVLERROR at 75% (nPTERROR: -29.6%±16.7%; nVLERROR: -30.3±16.5%) when compared to both 25% (nPTERROR: -2.4%±13.2%; nVLERROR: -2.9±11.3%; p<0.001 for both) and 50% (nPTERROR: -19.1±14.4%; nVLERROR: -18.1±14.1%; p<0.001 for both). Additionally, both nPTERROR and nVLERROR were significantly more negative at 50% when compared to 25% (p<0.001). CONCLUSIONS: Our results suggest that participants displayed more accurate peak torque and muscle excitation in the vastus lateralis at lower submaximal intensities and the amount of error increased with increases in perceived effort. Importantly, biological sex does not appear to influence this relationship.

This document is currently not available here.