Running economy of elite east African runners

Endurance running velocity (v) is equal to: v = (Fâ¢Vâ™O2max)/Cr where Vâ™O2max is maximal oxygen uptake, F is the fraction of Vâ™O2max that can be utilised throughout the effort and Cr is the energy cost of running. Therefore, the outstanding results obtained by east African runners in marathon and half-marathon are likely due to their: i) very high Vâ™O2max: ii) low Cr (high running economy); iii) large F, or by the interplay of these three factors. PURPOSE: To assess Vâ™O2max and Cr in a group of top level Kenyan marathon runners. In addition, on the basis of the average v maintained during marathons, individual F values were also estimated. METHODS: Experiments were carried out on track (Eldoret, Kenya, altitude 2000 m asl) on 13 elite Kenyan runners (29.8 yy ± 3.3; 58.3 kg ± 4.7; 173 cm ± 9.3, average record v during marathon: 19.6 km/hr ± 0.36). Cr was assessed by measuring Vâ™O2 at steady state (Vâ™O2ss) at constant speed during an incremental test. Initial v was set at 12 km/hr, each step lasted 4 minutes and v was increased by 2 km/hr at each step. Blood lactate concentration ([La]b) was measured after each step. Vâ™O2max was defined by the plateau attained in the Vâ™O2ss vs v relation above a given v. Net Cr in mL O2/kmâ¢kg was calculated as the ratio of net Vâ™O2ss to the corresponding average v. F was then calculated for each subjects: i) as F = (vâ¢Cr)/Vâ™O2max)/Cr knowing individual marathon best performances; and ii) calculating the Vâ™O2 corresponding to the v found at a La]b of 2 mM (v2). RESULTS: Maximal v during the test was 19.9 km/hr ± 0.36. Vâ™O2max corrected to sea level condition amounted to 62.6 mL O2/minâ¢kg ± 5.6 and Cr turned out to be equal to 173 mL O2/kmâ¢kg ± 13.2. F estimated from record v, Cr and Vâ™O2max was equal to 0.90 ± 0.06 and agreed with that estimated from v2 (0.89 ± 0.07). The present runners had a Vâ™O2max on average about 21 % smaller than, and a Cr equal to, that previously found in younger less competitive Kenyan runners. No comparison with previous F values was possible. CONCLUSIONS: Results indicate that elite Kenyan marathoners: i) have a relatively low Vâ™O2max; ii) have a very low Cr; and iii) have an extremely high F in comparison with elite Caucasian runners. Both ii) and iii) compensate for i) and thus may entirely explain their excellent performances.