Energetics of running in top-level marathon runners from Kenya

Abstract

On ten top-level Kenyan marathon runners (KA) plus nine European controls (EC, equivalent to KA), we measured maximal oxygen consumption ($\dot{V}{\text{O}}_{{ 2 {\text{max}}}}$) and the energy cost of running (C _r) on track during training camps at moderate altitude, to better understand the KA dominance in the marathon. At each incremental running speed, steady-state oxygen consumption ($\dot{V}{\text{O}}_{ 2}$) was measured by telemetric metabolic cart, and lactate by electro-enzymatic method. The speed requiring $\dot{V}{\text{O}}_{ 2} = \dot{V}{\text{O}}_{{ 2 {\text{max}}}}$ provided the maximal aerobic velocity (v _max). The energy cost of running was calculated by dividing net $\dot{V}{\text{O}}_{ 2}$ by the corresponding speed. The speed at lactate threshold (v _ΘAN) was computed from individual Lâ_b versus speed curves. The sustainable $\dot{V}{\text{O}}_{{ 2 {\text{max}}}}$ fraction (F _d) at v _ΘAN (F _ΘAN) was computed dividing v _ΘAN by v _max. The F _d for the marathon (F _mar) was determined as F _mar = 0.92 F _ΘAN. Overall, $\dot{V}{\text{O}}_{{ 2 {\text{max}}}}$ (64.9 ± 5.8 vs. 63.9 ± 3.7 ml kg⁻¹ min⁻¹), v _max (5.55 ± 0.30 vs. 5.41 ± 0.29 m s⁻¹) and C _r (3.64 ± 0.28 vs. 3.63 ± 0.31 J kg⁻¹ m⁻¹) resulted the same in KA as in EC. In both groups, C _r increased linearly with the square of speed. F _ΘAN was 0.896 ± 0.054 in KA and 0.909 ± 0.068 in EC; F _mar was 0.825 ± 0.050 in KA and 0.836 ± 0.062 in EC (NS). Accounting for altitude, running speed predictions from present data are close to actual running performances, if F _ΘAN instead of F _mar is taken as index of F _d. In conclusion, both KA and EC did not have a very high $\dot{V}{\text{O}}_{{ 2 {\text{max}}}}$, but had extremely high F _d, and low C _r, equal between them. The dominance of KA over EC cannot be explained on energetic grounds.