Energetics of running in top level marathon runners from Kenya.

On ten top-level Kenyan marathon runners (KA) plus nine European controls (EC, equivalent to KA), we measured maximal oxygen consumption ( _V O2max) and the energy cost of running (Cr) 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 ( _V O2) was measured by telemetric metabolic cart, and lactate by electroenzymatic method. The speed requiring _V O2 ¼ _V O2max provided the maximal aerobic velocity (vmax). The energy cost of running was calculated by dividing net _V O2 by the corresponding speed. The speed at lactate threshold (vHAN)was computed from individual Laˆb versus speed curves. The sustainable _V O2max fraction (Fd) at vHAN (FHAN) was computed dividing vHAN by vmax. The Fd for the marathon (Fmar) was determined as Fmar = 0.92 FHAN. Overall, _VO2max (64.9 ± 5.8 vs. 63.9 ± 3.7 ml kg-1 min-1), vmax (5.55 ± 0.30 vs. 5.41 ± 0.29 m s-1) and Cr (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, Cr increased linearly with the square of speed. FHAN was 0.896 ± 0.054 in KA and 0.909 ± 0.068 in EC; Fmar was 0.825 ± 0.050 in KA and .836 ± 0.062 in EC (NS). Accounting for altitude, running speed predictions from present data are close to actual running performances, if FHAN instead of Fmar is taken as index of Fd. In conclusion, both KA and EC did not have a very high _V O2max, but had extremely high Fd, and low Cr, equal between them. The dominance of KA over EC cannot be explained on energetic grounds.