Approximation equation for oxygen uptake kinetics in decrement-load exercise starting from low exercise intensity

Area of Science:

• Exercise Physiology
• Human Physiology
• Sports Science

Background:

• Oxygen uptake kinetics during exercise are crucial for understanding physiological responses.
• Decrement-load exercise (DLE) presents unique challenges in modeling oxygen uptake due to oxygen debt repayment.
• Existing models may not fully capture the complexities of Vo2 during DLE.

Purpose of the Study:

• To determine the fitting accuracy of an approximation equation for oxygen uptake (Vo2) in decrement-load exercise (DLE).
• To investigate the relationship between Vo2 in DLE and incremental-load exercise (ILE).
• To develop and validate a predictive model for Vo2 kinetics during DLE.

Main Methods:

• Participants performed DLE starting at 120 watts, decreasing by 15 watts/min.
• Initial DLE work rate was set at 72±10% of the anaerobic threshold work rate from ILE.
• Vo2 data from DLE were compared to ILE, and an approximation equation combining constant-load exercise (CLE) and ILE models was tested.
• The impact of incorporating a time delay parameter into the approximation equation was evaluated.

Main Results:

• Vo2 in DLE initially increased, peaked, then decreased linearly.
• Vo2 during DLE was generally higher than in ILE at equivalent work rates, attributed to oxygen debt repayment and oxygen deficit.
• An approximation equation incorporating a time delay parameter showed a high degree of fit (94-98%) for Vo2 in DLE.
• The developed equation effectively approximated Vo2, including oxygen debt, during DLE.

Conclusions:

• The proposed approximation equation, considering time delay, accurately models oxygen uptake during decrement-load exercise.
• This model provides a valuable tool for understanding and predicting physiological responses to DLE.
• The findings highlight the importance of accounting for oxygen debt in exercise physiology models.