Leg dominancy in relation to fast isometric torque production and squat jump height

We hypothesized that maximal unilateral isometric knee extensor torque, the rate of torque development during maximally fast isometric contractions and unilateral squat jump performance would be better with the dominant than non-dominant leg. Limb dominancy was established using the step up, balance recovery, and ball kick test. On two days, eight men (21.5 +/- 2.2 years, means +/- SD) performed unilateral maximal isometric contractions with their knee extensors (120 degrees knee angle) with superimposed electrical stimulation to determine maximal torque and voluntary activation for both limbs. In addition, maximally fast isometric contractions without countermovement and unilateral squat jumps (SJ) starting from 120 degrees knee angles were performed. Torque time integral (contractile impulse) over the first 40 ms after torque onset (TTI40) and maximal rates of torque development (MRTD) during voluntary and maximal electrical nerve stimulation were used to quantify initial torque rise. Limb dominancy tests were very consistent, but none of the parameters was (or tended to be) significantly different between limbs, neither during maximal electrical stimulation nor during voluntary attempts. Between limbs there were significant relationships for voluntary TTI40 (r (2) = 0.94) and maximal SJ height (r (2) = 0.88) and both parameters were significantly related in both limbs (r (2) = 0.69 and 0.75). In conclusion, unilateral fast torque generating capacity, muscle activation and squat jump performance were similar in both limbs, but differed substantially among subjects, with strong correlations between fast voluntary isometric torque development and jump height. These findings further challenge the concept of lower limb dominancy in dynamometry testing in sports and rehabilitation.