Quantifying Running Economy in Amateur Runners: Evaluating VO and Energy Cost with Model-based Normalization.

Submaximal oxygen uptake (VO) scaled by ratio is commonly used to evaluate running economy (RE) to reflect metabolic consumption at a given submaximal-intensity velocity. However, this method is questionable due to its neglect of substrate-related issues and the inherent mathematical discrepancies in ratio scaling. This study aimed to investigate the validity of ratio-scaled VO as a measure of RE by comparing it with allometric-scaled energy cost (E, kcal/kg/min). Sixty-nine recreationally active college students underwent VO tests and discontinuous submaximal running assessments at three %VO intensities. A 1000-meter test assessed running performance. One-way repeated-measures ANOVA compared changes in VO or E with increasing running intensities. Regression analysis explored methods for metabolic data standardization. Pearson correlation coefficient evaluated the effectiveness of standardization and the correlations between sports performance and RE scaled by different measures. Magnitude-based inferences were used to assess sex differences and probabilities of RE at each running intensity. Both VO and E significantly increased with increasing intensities, suggesting that VO is a valid quantification of RE. Allometric scaling is more suitable than ratio scaling for removing the influence of body weight on both E and VO, with females showing better RE. Allometric-scaled E was sensitive in detecting correlations with performance, strongest at 65% VO. While VO is a valid quantification of RE, allometric scaling, rather than ratio scaling, should be used to normalize the RE quantification before performing reliable interindividual comparisons. The 2/3 law can be considered as the exponent b value for body weight. Additionally, 65%VO intensity is recommended as the submaximal testing intensity in the RE test. Nonetheless, more studies with diverse samples are needed to confirm the validity.