Minimum cost of transport in human running is not ubiquitous

This study explores recent claims that humans exhibit minimum cost of transport (CoTmin) for running, which occurs at intermediate speed, and assesses individual physiological, gait, and training characteristics.

Twelve healthy participants with varying levels of fitness and running experience ran on a treadmill at six self-selected speeds in a discontinuous protocol over three sessions. Running speed (km·h), VO2 (mL·kg·km), CoT (kcal·km), HR (bpm), and cadence (steps per minute) were continuously measured. VO2max was measured on the fourth testing session. The occurrence of CoTmin was investigated, and its presence or absence was examined with respect to fitness, gait, and training characteristics.

Five participants showed clear CoTmin at intermediate speed and a statistically significant (P < 0.05) quadratic CoT-speed function, whereas the other participants did not show such evidence. Participants were then categorized and compared with respect to the strength of evidence for CoTmin (ClearCoTmin and NoCoTmin). The ClearCoTmin group displayed a significantly higher correlation between speed and cadence, more endurance training and exercise sessions per week, and a marginally nonsignificant but higher aerobic capacity than the NoCoTmin group. Some runners still showed CoTmin at intermediate speed even after subtraction of resting energy expenditure.

The findings confirm the existence of optimal speed for human running in some but not all participants. Those exhibiting COTmin undertook higher volume of running, ran with a cadence that was more consistently modulated with speed, and tended to be aerobically fitter. The ability to minimize energetic CoT seems not to be a ubiquitous feature of human running but may emerge in some individuals with extensive running experience.