HERITABILITY OF AEROBIC POWER AND ANAEROBIC ENERGY GENERATION DURING EXERCISE

Twenty-nine pairs of monozygotic twins and 19 pairs of dizygotic twins, all male, ages 18-31 yr, performed a graded uninterrupted exercise test on the bicycle ergometer to exhaustion. By use of path analysis, the genetic variance of measured peak O2 uptake was estimated at 77% (P < 0.001), at 71% (P < 0.001) after adjustment for weight and skinfold thickness, and at 66% (P < 0.001) after additional adjustment for weekly hours of sports participation. O2 uptake at a heart rate of 150 beats/min, a submaximal estimate of exercise capacity, showed less genetic variance, i.e., 61% (P < 0.001) before and 50% (P < 0.001) after weight adjustment and only 16% (NS) after correction for life-style factors. Similarly, the heritability of peak O2 uptake, when estimated from submaximal data, was 68% (P < 0.001), 40% (P = 0.05), and 26% (NS), respectively. Mechanical efficiency had no significant genetic component. O2 uptake at the respiratory exchange ratio of 0.95 and the slope of the curvilinear relationship between CO2 output and O2 uptake, used to assess the anaerobic energy generation during progressive exercise, showed significant (P < 0.001) genetic variance before (72 and 74%) and after adjustment for weight (67 and 69%) and sports participation (63 and 57%). The heritability of peak aerobic power remained significant (58%; P < 0.001) after adjustment for these expressions of anaerobic energy generation. In conclusion the genetic variance of measured peak O2 uptake is significant and persists after adjustment for anthropometric characteristics, lifestyle factors, anaerobic energy generation, and mechanical efficiency. Estimated peak O2 uptake and O2 uptake at heart rate of 150 beats/min show a lower genetic variability.