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Central and peripheral fatigue during passive and exercise-induced hyperthermia
Julien D Périard1, Corinne Caillaud, Martin W Thompson
1Aspetar, Research and Education Centre, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. julien.periard@aspetar.com
Medicine and Science in Sports and Exercise
|March 3, 2011
Summary
Prolonged exercise and passive heating in heat stress impair quadriceps force production due to central and peripheral fatigue. Exercise exacerbates this decline, alongside significant cardiovascular strain limiting performance.
Area of Science:
- Exercise Physiology
- Environmental Physiology
- Neuromuscular Physiology
Background:
- Understanding the impact of heat stress on neuromuscular function is crucial for athletes and military personnel.
- Previous research has not fully isolated the effects of exercise versus passive heating on muscle performance under hyperthermia.
Purpose of the Study:
- To differentiate the effects of exercise-induced hyperthermia (ExH) from passive hyperthermia (PaH) on quadriceps neuromuscular function.
- To investigate the role of cardiovascular strain in limiting endurance performance during heat stress.
Main Methods:
- Eight males underwent maximal voluntary isometric contractions (MVCs) after cycling to exhaustion (ExH) or passive water immersion (PaH) in hot conditions (38°C, 60% RH).
- Rectal temperature (Tre) reached ~39.8°C during ExH and 39.5°C during PaH.
- Voluntary activation and force production were assessed pre- and post-intervention using superimposed electrical stimulation.
Main Results:
- Force production significantly decreased after both ExH and PaH, with a greater reduction following ExH.
- Voluntary activation was depressed post-intervention but maintained around 90% during MVC.
- Cardiovascular strain at exhaustion included increased heart rate (~96% max) and reduced stroke volume (25%) and mean arterial pressure (10%).
Conclusions:
- Loss of force production during hyperthermia results from both central and peripheral fatigue.
- Exercise in heat exacerbates neuromuscular decline compared to passive heating.
- Increased thermal and cardiovascular strain during exercise in heat significantly impairs neuromuscular function and limits performance.
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