Endurance running velocity (v) is equal to: v = (F•V’O2max)/Cr where V’O2max is maximal oxygen uptake, F is the fraction of V’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 V’O2max: ii) low Cr (high running economy); iii) large F, or by the interplay of these three factors. PURPOSE: To assess V’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 V’O2 at steady state (V’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. V’O2max was defined by the plateau attained in the V’O2ss vs v relation above a given v. Net Cr in mL O2/km•kg was calculated as the ratio of net V’O2ss to the corresponding average v. F was then calculated for each subjects: i) as F = (v•Cr)/V’O2max)/Cr knowing individual marathon best performances; and ii) calculating the V’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. V’O2max corrected to sea level condition amounted to 62.6 mL O2/min•kg ± 5.6 and Cr turned out to be equal to 173 mL O2/km•kg ± 13.2. F estimated from record v, Cr and V’O2max was equal to 0.90 ± 0.06 and agreed with that estimated from v2 (0.89 ± 0.07). The present runners had a V’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 V’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.

### Running Economy Of Elite East African Runners

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*TAM, ENRICO;*

##### 2008

#### Abstract

Endurance running velocity (v) is equal to: v = (F•V’O2max)/Cr where V’O2max is maximal oxygen uptake, F is the fraction of V’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 V’O2max: ii) low Cr (high running economy); iii) large F, or by the interplay of these three factors. PURPOSE: To assess V’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 V’O2 at steady state (V’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. V’O2max was defined by the plateau attained in the V’O2ss vs v relation above a given v. Net Cr in mL O2/km•kg was calculated as the ratio of net V’O2ss to the corresponding average v. F was then calculated for each subjects: i) as F = (v•Cr)/V’O2max)/Cr knowing individual marathon best performances; and ii) calculating the V’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. V’O2max corrected to sea level condition amounted to 62.6 mL O2/min•kg ± 5.6 and Cr turned out to be equal to 173 mL O2/km•kg ± 13.2. F estimated from record v, Cr and V’O2max was equal to 0.90 ± 0.06 and agreed with that estimated from v2 (0.89 ± 0.07). The present runners had a V’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 V’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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.