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The Sexes Do Not Differ for Neural Responses to Submaximal Elbow Extensor Fatigue
Alexandra F Yacyshyn1, Chris J McNeil
1Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada.
Medicine and Science in Sports and Exercise
|March 21, 2020
Summary
This study found no sex-related differences in isometric muscle fatigue of elbow extensors. Muscle afferent feedback and motoneuronal excitability were similar between males and females during sustained contractions.
Area of Science:
- Exercise Physiology
- Neuroscience
- Muscle Physiology
Background:
- Investigating sex-based differences in neuromuscular fatigue is crucial for understanding human performance.
- Group III/IV muscle afferent feedback plays a role in modulating motoneuronal excitability during fatiguing contractions.
Purpose of the Study:
- To determine if sex influences group III/IV muscle afferent feedback during isometric fatigue.
- To assess the impact of sustained submaximal elbow extensor contraction on motoneuronal excitability and voluntary activation in males and females.
Main Methods:
- 24 participants (12 males, 12 females) performed a 15-min submaximal elbow extensor contraction.
- Cervicomedullary motor evoked potentials (CMEP) and motor evoked potentials (MEP) were recorded to assess motoneuronal and cortical excitability.
- Voluntary activation (VA) was measured post-fatigue using superimposed and resting tetani.
Main Results:
- Despite males being stronger, no sex differences were observed in fatigue-related changes in CMEP, MEP, or VA.
- Unconditioned CMEP remained unchanged, while conditioned CMEP decreased by ~50%.
- MEP (both unconditioned and conditioned) significantly increased, indicating altered cortical excitability.
Conclusions:
- Isometric fatigue of elbow extensors does not elicit sex-related differences in muscle afferent feedback or motoneuronal excitability.
- Metabolite buildup and group III/IV afferent activity appear similar between sexes during this type of fatiguing exercise.
