The energetics of endurance running

Maximal O₂ consumption ( \(\dot V_{O_{_2 max} } \) and energy cost of running per unit distance (C) were determined on the treadmill in 36 male amateur runners (17 to 52 years) who had taken part in a marathon (42.195 km) or semi-marathon (21 km), their performance times varying from 149 to 226 and from 84 to 131 min, respectively. \(\dot V_{O_{_2 max} } \) was significantly (2p<0.001) greater in the marathon runners (60.6 vs 52.1 ml · kg⁻¹ · min⁻¹) whileC was the same in both groups (0.179±0.017, S.D., mlO₂ · kg⁻¹ · m⁻¹ above resting), and independent of treadmill speed. It can be shown that the maximal theoretical speed in endurance running (vEND) is set by \(\dot V_{O_{_2 max} } \) , its maximal sustainable fraction (F), andC, as described by:vEND=F · \(\dot V_{O_{_2 max} } \) ·C ⁻¹. SinceF was estimated from the individual time of performance,vEND could be calculated. The average speed of performance (vMIG) andvEND (m · s⁻¹) were found to be linearly correlated:vMIG=1.12+0.64vEND (r ²=0.72;n=36). The variability ofvMIG explained byvEND, as measured byr ², is greater than that calculated from any one regression betweenvMIG and \(\dot V_{O_{_2 max} } \) (r ²=0.51),F · \(\dot V_{O_{_2 max} } \) (r ²=0.58), or \(\dot V_{O_{_2 max} } \) ·C ⁻¹ (r ²=0.63). The mean ratio of observed (vMIG) to theoretical (vEND) speeds amounted to 0.947±0.076 and increased to 0.978±0.079 (±S.D.;n=36) when the effects of air resistance were taken into account. It is concluded thatvEND=F · \(\dot V_{O_{_2 max} } \) ·C ⁻¹ is a satisfactory quantitative description of the energetics of endurance running.