Strength capabilities of knee extensor muscles in junior speed skaters

BACKGROUND: The present study aimed to investigate the gender- and age-related profiles of junior speed skaters in strength capabilities during both single and repetitive maximal contractions. METHODS: The subjects were 19 male (age = 17.1 +/- 0.2 years, X +/- SE) and 13 female skaters (16.9 +/- 0.2 years). Isokinetic knee extension torque (T) developed concentrically in a single contraction at three constant velocities of 1.05, 3.14 and 5.24 rad/sec and 50 repetitive maximal contractions at 3.14 rad/sec was measured using an isokinetic dynamometer. In addition, a B-mode ultrasound apparatus was used to determine the cross-sectional area (CSA) of the quadriceps femoris muscle at mid-thigh. RESULTS: For the junior skaters, T values at three velocities of 1.05, 3.14 and 5.24 rad/sec and the mean value of isokinetic torque (MT) for every five consecutive trials in the first 25 maximal contractions were similar in both genders when they were expressed relative to the product of the cross-sectional area (CSA) of the quadriceps femoris muscle and lower limb length, T/CSAL and MT/CSAL, respectively. However, the males showed significantly higher MT/CSAL values than the females in the last 25 repetitions of the endurance test. In the comparisons between junior and reference senior skaters, T/CSAL for both genders and MT/CSAL for the females showed little age-related difference. For the males, however, MT/CSAL values in the first 15 repetitions of the endurance test were significantly lower in the junior skaters than in the senior ones. CONCLUSIONS: The present results indicate that the strength capabilities of junior speed skaters in a single maximal contraction will be similar in both genders when the difference in muscle size is normalized. However, the junior male skaters may be less fatiguable than the junior female ones in repetitive maximal contractions. Moreover, the comparison between junior and senior skaters suggests that, in postadolescence, males might be more trainable than females to improve torque output during short-term repetitive maximal contractions beyond that achieved during adolescence.