Critical Power: An Important Fatigue Threshold in Exercise Physiology

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• The power-duration relationship in exercise is hyperbolic and conserved across species.
• Critical Power (CP) and W' are key parameters defining this relationship, predicting exercise tolerance.
• CP integrates respiratory, metabolic, and contractile physiological responses.

Purpose of the Study:

• To highlight the scientific and practical utility of the CP concept.
• To demonstrate how CP unifies systemic and intramuscular responses.
• To explain CP as a "fatigue threshold" separating exercise intensity domains.

Main Methods:

• Analysis of the hyperbolic power-duration relationship.
• Integration of physiological profiles (respiratory, metabolic, contractile) around CP.
• Comparison of exercise intensity calibration relative to CP versus other physiological markers (e.g., lactate threshold, V̇O2max).

Main Results:

• CP and W' accurately predict tolerable exercise duration above CP.
• Exercise intensity relative to CP unifies physiological responses.
• CP identifies exercise domains where physiological responses can or cannot be stabilized, indicating fatigue loci.

Conclusions:

• The CP concept provides critical insights into fatigue development and mechanisms of physiological control during exercise.
• CP serves as a "fatigue threshold," differentiating exercise intensity domains.
• CP has significant potential for optimizing athletic training, performance, and managing chronic diseases.