Quantifying Running Economy in Amateur Runners: Evaluating VO₂ and Energy Cost with Model-based Normalization

Area of Science:

• Exercise Physiology
• Sports Science
• Human Metabolism

Background:

• Submaximal oxygen uptake (VO2sub) scaled by ratio is a common but questionable method for assessing running economy (RE).
• Ratio scaling neglects substrate issues and has mathematical discrepancies, questioning its validity for comparing metabolic cost.
• Allometric scaling offers a potentially more accurate method for normalizing energy expenditure data.

Purpose of the Study:

• To investigate the validity of ratio-scaled VO2sub for measuring RE by comparing it with allometric-scaled energy cost (Ec).
• To determine the most suitable scaling method (ratio vs. allometric) for normalizing metabolic data in RE assessment.
• To identify optimal submaximal intensity and evaluate sex differences in RE.

Main Methods:

• Sixty-nine college students performed VO2max tests and discontinuous submaximal running at three %VO2max intensities.
• Running performance was assessed via a 1000-meter test.
• Statistical analyses included ANOVA, regression, Pearson correlation, and magnitude-based inferences to compare VO2sub and Ec, assess standardization effectiveness, and evaluate performance correlations.

Main Results:

• Both VO2sub and Ec significantly increased with running intensity, confirming VO2sub's validity for RE quantification.
• Allometric scaling proved more effective than ratio scaling in removing body weight influence on Ec and VO2sub.
• Females demonstrated better RE, and allometric-scaled Ec showed stronger correlations with performance at 65% VO2max.

Conclusions:

• Allometric scaling is recommended over ratio scaling for normalizing RE quantification to enable reliable interindividual comparisons.
• The exponent 'b' for body weight in allometric scaling can be approximated by the 2/3 law.
• 65% VO2max is suggested as the optimal intensity for submaximal RE testing, though further validation is needed.