Effects of Maximal Versus Submaximal Intensity Fatigue-Protocols on Maximal Torque Responses of the Leg Extensors

Abstract

Declines in muscular strength are commonly reported as a consequence of strength-based exercises. However, few studies have investigated the effects of different intensities of isometric fatigue protocols on maximal torque post-fatigue recovery responses. PURPOSE: The purpose of this study was to investigate the effects of a fatigue-inducing bout of submaximal, and maximal intermittent isometric contractions on maximal torque recovery responses of the leg extensors in college-aged females. METHODS: Twenty (mean±SD: (age=21.23±1.41years) sedentary females participated in a familiarization trial followed by two experimental fatigue sessions, separated by seven (±1) days. All sessions began with participants performing maximal voluntary contractions (MVCs) followed by a randomly assigned fatigue-inducing protocol consisting of intermittent isometric contractions of the leg extensors using a 0.6 duty cycle (6 s contraction, 4 s relaxation) at either 50% or 100% of MVC until 50% of volitional fatigue was achieved. All MVC and fatigue protocols were performed on an isokinetic dynamometer with the leg angle set at 60° below the horizontal plane of the right leg. MVCs were again performed at 0, 7, 15, and 30 minutes post fatigue. A two-way repeated measures ANOVA (intensity [submaximal vs. maximal] × time [Pre- vs. Post0 vs. Post7 vs. Post15 vs. Post30]) was used to analyze all PT data. An alpha value of P ≤ 0.05 was considered statistically significant for all comparisons. RESULTS: There was no significant two-way interaction (P = 0.281); however, there was a main effect for time (P = 0.001) where PT was lower at all post-fatigue time periods compared to Pre- (P = 0.001-0.002). CONCLUSIONS: These findings showed similar fatigue-induced PT effects and recovery responses for the leg extensors for both submaximal and maximal intensities. The sustained decreases in PT during recovery may have important injury and performance implications in a variety of populations and settings, and these effects may be similarly incurred at both submaximal and maximal contraction intensities.