The relationship between power and time to fatigue in cycle ergometer exercise

Area of Science:

• Exercise Physiology
• Sports Science
• Biomechanics

Background:

• Critical power (Pcrit) is a key physiological determinant of endurance exercise performance.
• Accurate modeling of the power-time relationship is crucial for understanding exercise capacity.
• Existing models for critical power vary in complexity and physiological interpretability.

Purpose of the Study:

• To evaluate and compare three distinct critical power (Pcrit) models.
• To determine the most accurate and physiologically meaningful model for the power-time relationship.
• To assess the parsimony and descriptive capabilities of hyperbolic and exponential models.

Main Methods:

• Ten university students underwent exercise tests to fatigue (2-10 minutes).
• Power and time data were fitted to 2-parameter hyperbolic, 3-parameter hyperbolic, and 3-parameter exponential models.
• Model performance was assessed using R-squared values and physiological interpretability of parameters.

Main Results:

• All models demonstrated strong fits to the power-time data (R² ≥ 0.995).
• The 2-parameter hyperbolic model yielded physiologically meaningful Pcrit (187 ± 38 W) and anaerobic work capacity (20.4 ± 9.0 kJ).
• The 3-parameter exponential model's parameters lacked clear physiological meaning, and the additional parameter in the 3-parameter hyperbolic model was superfluous.

Conclusions:

• The 2-parameter hyperbolic model provides an adequate and parsimonious description of the power-time relationship within the studied exercise durations.
• This model offers superior physiological interpretability compared to more complex alternatives.
• The findings support the use of the 2-parameter model for estimating critical power and anaerobic work capacity in similar exercise contexts.