Aim: The aim of this study was to estimate the genetic and environmental contribution to the variation observed in the rate of torque development (RTD), which is considered an important determinant of sport performance.
Methods: Nine monozygotic (MZ) and seven dizygotic (DZ) twin pairs, of both sexes aged 19-26 years, performed three isometric maximal voluntary contractions with the knee at 70 degrees and 40 degrees of flexion (0 degrees=terminal extension) on a Contrex Isokinetic dynamometer. The RTD was extracted from the force time curves and calculated in two different ways, giving rise to two indices, the maximal rate of torque development (MRTD), and the torque at the first 100 msec (F100msec). Heritability estimates (h2) were derived on the basis of intrapair variances between MZ and DZ twin pairs.
Results: A significant genetic influence (P<0.05) was found for both RTD indices (h2=0.99, and 0.93 for MRTD, and F100msec respectively) at only 40 degrees of knee flexion, an angle associated with intensive neural activation.
Conclusion: The maximal rate of torque development of knee extensor muscles during the initial phase of their contraction and at enhanced neural activation, is under strong genetic influence.