Physiological models to understand exercise fatigue and the adaptations that predict or enhance athletic performance

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• The prevailing cardiovascular/anaerobic model suggests fatigue arises when oxygen supply to muscles fails during high-intensity exercise.
• This model is challenged by evidence suggesting the heart, not skeletal muscles, would be affected first by anaerobiosis.
• Existing research has not definitively proven muscle anaerobiosis, hypoxia, or ischemia during maximal exercise.

Purpose of the Study:

• To critically evaluate the limitations of the cardiovascular/anaerobic model of exercise fatigue.
• To introduce and discuss alternative models that better explain exercise limitations under various conditions.
• To provide a comprehensive overview of factors influencing exercise performance.

Main Methods:

• Review and critique of the cardiovascular/anaerobic model.
• Exploration of four alternative models: energy supply/depletion, muscle power/recruitment, biomechanical, and psychological.
• Synthesis of physiological, metabolic, and biomechanical factors affecting exercise.

Main Results:

• The cardiovascular/anaerobic model fails to explain fatigue in diverse scenarios like prolonged exercise, heat exertion, altitude, and chronic diseases.
• Key physiological measures like VO2 max and anaerobic threshold are poor predictors of exercise capacity in similar athletes.
• Alternative models offer a more holistic explanation for exercise limitations.

Conclusions:

• A broader perspective incorporating multiple models is necessary for a complete understanding of exercise fatigue.
• Factors beyond oxygen supply, including energy availability, muscle activation, biomechanics, and psychological state, are crucial.
• Considering these diverse models enhances our understanding of training adaptations and exercise performance limits.