Physiological differences between black and white runners during a treadmill marathon

Summary

To determine why black distance runners currently out-perform white distance runners in South Africa, we measured maximum oxygen consumption (V _{O 2max}), maximum workload during a V _{O 2max} test (L _max), ventilation threshold (V _Thr), running economy, inspiratory ventilation (V _I), tidal volume (V _T), breathing frequency (f) and respiratory exchange ratio (RER) in sub-elite black and white runners matched for best standard 42.2 km marathon times. During maximal treadmill testing, the black runners achieved a significantly lower (P<0.05) L _max (17 km h⁻¹, 2% grade, vs 17 km h⁻¹, 4% grade) and V _I max (6.21 vs 6.821 kg^−2/3 min⁻¹), which was the result of a lower V _T (101 vs 119 ml kg^−2/3 breath⁻¹) as f _max was the same in both groups. The lower V _T in the black runners was probably due to their smaller body size. The V _Thr occurred at a higher percentage V _{O 2max} in black than in white runners (82.7%, SD 7.7% vs 75.6%, SD 6.2% respectively) but there were no differences in the V _{O 2max}. However, during a 42.2-km marathon run on a treadmill, the black athletes ran at the higher percentage V _{O 2max} (76%, SD 7.9% vs 68%, SD 5.3%), RER (0.96, SD 0.07 vs 0.91, SD 0.04) and f (56 breaths min⁻¹, SD 11 vs 47 breaths min⁻¹, SD 10), and at lower V _T (78 ml kg^−2/3 breath⁻¹, SD 15 vs 85 ml kg^−2/3 breath⁻¹, SD 19). The combination of higher f and lower V _T resulted in an identical V _I. Blood lactate levels were lower in black than in white runners (1.3 mmol l⁻¹, SD 0.6 vs 1.59 mmol l⁻¹, SD 0.2 respectively). It appeared that the only physiological difference that may account for the superior performance of the black runners was their ability to run at a higher percentage V _{O 2max} max during competition than white runners.