Anthropometric Characteristics Account For Time To Exhaustion In Cycling

This study examined the relationship between the phenotypic and anthropometric characteristics and the cycling time to exhaustion (T-lim) at the maximal aerobic power output (P-max). 12 (7 men, 5 women) physically-active participants performed a square-wave test at P-max to determine the maximal time limit. Muscle histochemistry, enzymatic activities and buffer capacity were determined from a vastus lateralis muscle biopsy, lean body mass (LBM) by hydrostatic weighing, and total (TV) and lean (LV) volumes of the thigh by anthropometric measurements. The mean (+/- SD) T-lim was 235 +/- 84s (score range: 108-425s). No relationship was found between T-lim and any muscle phenotypes. However, we observed a strong, linear relationship between T-lim and LBM (r=0.84, P<0.05). Thigh TV and LV displayed weaker correlation coefficients with T-lim (r=0.66 and r=0.73, respectively; P<0.05). We further estimated the femur length and found this measure to correlate with T-lim (r=0.81, P<0.05). This study suggests that muscle phenotypes may not be representative of T-lim. Rather, anthropometric characteristics account for such performance by conferring a biomechanical advantage in cycling. We conclude that, in addition to metabolic factors, anthropometric characteristics with reasonable accuracy predict T-lim in cycling, and may account for the large inter-subject variability observed in previous studies.