Sources of variation in oxygen consumption during a stepping task

Area of Science:

• Exercise Physiology
• Human Performance

Background:

• Submaximal exercise tests are commonly used to estimate maximal oxygen uptake (VO2max).
• The modified Canadian Aerobic Fitness Test (CAFT) utilizes stepping exercise at age- and heart rate-determined cadences.
• Accurate prediction of VO2max relies on understanding the factors influencing oxygen demand during submaximal activities.

Purpose of the Study:

• To identify factors determining oxygen uptake during stepping exercise.
• To assess the variability in oxygen demand within a given stepping cadence.
• To evaluate the predictability of oxygen demand from subject characteristics.

Main Methods:

• 66 women and 55 men performed the modified CAFT protocol.
• Oxygen demand was measured twice for each stepping cadence.
• Regression analysis was used to examine relationships between oxygen demand and subject characteristics (age, leg length, body mass, VO2max).

Main Results:

• Oxygen demand measurements showed moderate reliability (intraclass correlation coefficient = 0.51).
• The coefficient of variation for oxygen uptake at a given cadence was 10.4%.
• Subject characteristics like age, aerobic fitness, leg length, and adiposity explained only a small portion of the variation in oxygen demand (maximum R2 = 0.34).

Conclusions:

• Significant variation exists in the oxygen demand of stepping exercise.
• This variability is a major source of error when predicting VO2max from submaximal stepping tests.
• Predicting the oxygen demand of stepping exercise from individual characteristics is challenging due to limited explanatory power.