Effects of velocity of isokinetic training on strength, power, and quadriceps muscle fibre characteristics

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Twenty young men trained the right knee extensors and flexors on an isokinetic dynamometer three times weekly over a 10-week period. During each session, 10 men in the slow training group completed three sets of 8 maximal contractions at a rate of 1.05 rad s−1, whereas the other 10, the fast group, completed three sets of 20 contractions at a rate of 4.19 rad s−1. Subjects were pre- and post-tested for peak torque and power on an isokinetic dynamometer at 1.05, 3.14, and 4.19 rad s−1. Proportions of muscle fibre-types and fibre cross-sectional areas were determined from biopsy specimens taken before and after training from the right vastus lateralis. When testing was conducted at 1.05 rad s−1, the slow group improved (P<0.05) peak torque by 24.5 N m (8.5%), but no change was noted for the fast group. Power increased (P< 0.05) by 32.7 W (13.6%) in the slow group and 5.5 W (2.5%) in the fast. At 3.14 rad s−1, both groups increased (P<0.05) peak torque and power. At 4.19 rad s−1, the fast group increased (P<0.05) peak torque by 30.0 N m (19.7%), whereas no training effect was observed in the slow group. There was no significant change in power in either group at 4.19 rad s−1, No significant changes were observed over the 10-week training period in percentages of type I, IIa and IIb fibres, but both groups showed significant increases (P<0.05) in type I and IIa fibre areas. No differences were noted between groups, and no hypertrophy of type IIb fibres was observed.