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

Summary

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.