African runners exhibit greater fatigue resistance, lower lactate accumulation, and higher oxidative enzyme activity

Nine African and eight Caucasian 10-km runners resident at sea level volunt eered. Maximal O-2 consumption and peak treadmill velocity (PTV) were measu red by using a progressive test, and fatigue resistance [time to fatigue (T TF)] was measured by using a newly developed high-intensity running test: 5 min at 72, 80, and 88% of individual PTV followed by 92% PTV to exhaustion . Skeletal muscle enzyme activities were determined in 12 runners and 12 se dentary central subjects. In a comparison of African and Caucasian runners, mean IO-km race time, maximal O-2 consumption, and PTV were similar. In Af rican runners, TTF was 21% longer (P < 0.01), plasma lactate accumulation a fter 5 min at 88% PTV was 38% lower (P < 0.05) and citrate synthase activit y was 50% higher (27.9 +/- 7.5 vs. 18.6 +/- 2.1 mu mol.g wet wt(-1).min(-1) , P = 0.02). Africans accumulated lactate at a slower rate with increasing exercise intensity (P < 0.05). Among the entire group of runners, a higher citrate synthase activity was associated with a longer TTF (r = 0.70, P < 0 .05), a lower plasma lactate accumulation (r = -0.73, P = 0.01), and a lowe r respiratory exchange ratio (r = -0.63, P < 0.05). We conclude that the Af rican and Caucasian runners in the present study differed with respect to o xidative enzyme activity, rate of lactate accumulation, and their ability t o sustain high-intensity endurance exercise.