Sex Differences in Recovery from Extreme and Severe Intensity Exercise

Abstract

Previous protocols investigating neuromuscular fatigue have typically discarded the first 2 of 6 electrical stimulation sets in recovery and have reported the average of the remaining force values. However, our lab has recently shown that central (as measured by maximal voluntary contraction force, MVC; and voluntary activation, VA) and peripheral fatigue (as measured by potentiated twitch force, Qtw) had significantly recovered within 90 s following extreme intensity exercise and would otherwise be missed using contemporary protocols. PURPOSE: The purpose of this study was to test the hypothesis that MVC, VA, and Qtw immediately following task failure of extreme intensity exercise would be significantly lower than those measured 2 min into recovery in both men and women, while remaining suppressed following severe exercise. METHODS: Two men (26 ± 5 yrs; 109 ± 9 kg; 179 ± 1 cm) and two women (23 ± 2 yrs; 55 ± 3 kg; 159 ± 1 cm) performed 2 intermittent isometric knee extension tests to exhaustion at 40% (severe intensity) and 70% (extreme intensity) MVC in random order. Neuromuscular measurements were made every 30 s beginning immediately after task failure for a total of 6 sets. The last two MVC, VA, and Qtw were averaged and compared to the first measurement immediately following task failure using paired t-tests. RESULTS: Qtw and MVC significantly decreased following severe and extreme exercise (p<0.01). However, VA was not different across severe or extreme exercise. VA was not different across recovery following severe or extreme exercise. MVC was not different following severe, however, had increased following extreme (p=0.02) exercise. Qtw was significantly recovered after severe (p<0.01) and extreme (p<0.02) exercise. Further, qualitative analysis suggests women may be able to recover MVC and Qtw faster than men following extreme exercise, while these differences may not be evident following severe exercise. CONCLUSIONS: These current data suggest central fatigue (as measured by VA) does not significantly impact exercise tolerance during severe or extreme exercise. Importantly, these data suggest that the measurements typically used to represent the condition of the muscle are taken too far post-exercise such that much of the recovery of the muscle has already occurred, especially following extreme exercise.