Effects of Submaximal Fatigue on Maximal and Rapid Torque Characteristics of the Leg Extensors

Abstract

Recent studies suggest that muscular fatigue may lead to decreased maximal and rapid torque characteristics. However, it is unknown how these fatigue-induced responses would affect anaerobically trained individuals post fatigue. PURPOSE: The purpose of this study was to examine the effects of a fatigue-inducing bout of submaximal intermittent isometric contractions on maximal and rapid torque characteristics of the leg extensors in anaerobically trained college-aged females. METHODS: Twenty-one (mean ± SD: age = 22.58 ± 4.36 years) anaerobically trained females (resistance trained 4 days·wk-1 for the past 2 years) participated in a familiarization trial followed by one day of testing, separated by seven (±1) days. Peak torque (PT) and rapid torque development at 30 milliseconds (RTD30) and 100-200 milliseconds (RTD100-200) were assessed on an isokinetic dynamometer with the leg angle set at 120° of knee flexion of the right leg. All sessions began with participants performing maximal voluntary contractions (MVCs) followed by a fatigue-inducing protocol consisting of intermittent isometric contractions of the leg extensors using a 0.6 duty cycle (6s contraction, 4s relaxation) at 50% of MVC until volitional fatigue. Participants performed MVCs before (Pre), immediately post (Post0), seven (Post7), fifteen (Post15) and thirty (Post30) minutes following the fatigue protocol. Isometric PT was determined as the highest 0.5 s epoch during the entire 3-4 s MVC. A one-way repeated measures ANOVA (Pre vs. Post0 vs. Post7 vs. Post15 vs. Post30) was used to analyze all PT and RTD variables. RESULTS: PT was significantly lower at Post0, Post7, and Post15 (P = 0.001- 0.015) compared to Pre. RTD30 was significantly lower only at Post0 (P = 0.001), and RTD100-200 was significantly lower at Post0, Post7, and Post15 (P = 0.000-0.009) compared to Pre. CONCLUSIONS: These findings showed similar fatigue-induced PT and RTD100-200 recovery responses post fatigue, while RTD30 recovered more rapidly after a submaximal fatigue protocol. These findings may have important performance and injury risk implications, as the ability to apply maximal and rapid torque may be diminished up to 15 minutes following fatiguing tasks.