Homestead, E. P., Peterman, J. E., Contini, E. J., Kane, L. A., & Bynes, W. C. (2013). Alterations in the VO2-power relationship above the lactate threshold during a graded-bicycling exercise protocol. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 590.

This study examined the changes in oxygen uptake (VO2) to power and energy expenditure to power relationships below and above the lactate threshold. Ss (M = 15; F = 15) performed a graded-exercise protocol on a bicycle ergometer. Initial power outputs were determined based upon S size and training status. Workloads were increased by 30-Watt increments every four minutes until exhaustion. Indirect calorimetry and blood lactate measures were performed during each stage. Only 18 subjects (M = 13; F = 5) had a sufficient number of data points below and above lactate threshold to adequately describe the linear regressions.

The individual coefficient of determination values for the oxygen uptake to power and energy expenditure to power relationships at both below and above lactate threshold were 0.96 or higher. The mean VO2-power slope and intercept for above the lactate threshold were significantly steeper and lower than the mean for the below lactate threshold slope and intercept. The mean energy expenditure to power slope and intercept for above lactate threshold were significantly steeper and lower than the mean below lactate threshold slope and intercept. No gender effect was observed on the changes in slope or intercept for either relationship.

Implication. The relationships between power and oxygen uptake or energy expenditure during a graded bicycle test suggest an increased oxidative energy requirement relative to power above the lactate threshold.

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