Energetics of running in top-level marathon runners from Kenya

On 10 top level Kenyan marathon runners (KA), plus 9 European controls (EC, equivalent to KA), we measured maximal oxygen consumption (VO2max) 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 (VO2) was measured by telemetric metabolic cart, lactate by electro-enzymatic method. The speed requiring VO2= VO2max provided the maximal aerobic velocity (vmax). Cr was calculated dividing net VO2 by the corresponding speed. The speed at lactate threshold (vΘAN) was computed from individual Lâb versus speed curves. The sustainable VO2max fraction (Fd) at vΘAN (FΘAN) was computed dividing vΘAN by vmax. The Fd for the marathon (Fmar) was determined as Fmar = 0.92 FΘAN. 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. FΘAN was 0.896+0.054 in KA and 0.909+0.068 in EC; Fmar 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 FΘAN instead of Fmar is taken as index of Fd. In conclusion, both KA and EC had not a very high VO2max, but had extremely high Fd, and low Cr, equal between them. The dominance of KA over EC cannot be explained on energetic grounds.