Superior fatigue resistance of elite black South African distance runners

Black athletes currently dominate long-distance running events in South Africa. In an attempt to explain an apparently superior running ability of black South African athletes at distances >3 km, we compared physiological measurements in the fastest 9 white and 11 black South African middle- to long-distance runners. Whereas both groups ran at a similar percentage of maximal O2 uptake (%V̇O(2 max)) over 1.65 · 5 km, the %V̇O(2 max) sustained by black athletes was greater than that of white athletes at distances >5 km (P < 0.001). Although both groups had similar training volumes, black athletes reported that they completed more exercise at >80% V̇O(2 max) (36 ± 18 vs. 14 ± 7%; P < 0.005). When corrections were made for the black athletes' smaller body mass, their superior ability to sustain a high %V̇O(2 max) could not be explained by any differences in V̇O(2 max), maximal ventilation, or submaximal running economy. Superior distance running performance of the black athletes was not due to a greater (±50%) percentage of type I fibers but was associated with lower blood lactate concentrations during exercise. Time to fatigue during repetitive isometric muscle contractions was also longer in black runners (169 ± 65 vs. 97 ± 69 s; P < 0.05), but whether this observation explains the superior endurance or was due to the lower peak muscle strength (46.3 ± 10.3 vs. 67.5 ± 18.0 Nm/l lean thigh volume; P < 0.01) remains to be established.