2005 Volume 50 Issue 1 Pages 1-11
This study examined the changes in joint moment and joint power of the lower limbs during double-leg hop (DLH) training. Six untrained male subjects were given DLH training 3 days per week for 8 weeks. The height of the hurdle was fixed at 90% of the maximum. The subjects were measured for three types of vertical jump, rebound jump and isokinetic strength before and after training. Ground reaction force and 24 body positions were recorded simultaneously and analysis of these data led to classification into two phases (a negative phase and a positive phase). The contact time in DLH was reduced after training (p<0.01). The height of the body's center of gravity did not change during take-on and take-off, but changed significantly during the minimal phase (p<0.01). Body stiffness was significantly increased in both the negative phase (p<0.01) and positive phase (p<0.01). The peak joint moment and joint power at the ankle increased significantly, but those of the hip and knee did not change during the contact phase. The peak joint power at the hip appeared in the early contact phase after training, and the stiffness of the ankle increased significantly (p<0.05). However, these changes in joint moment and joint power were not transferred to vertical jump performance, rebound jump height or isokinetic strength. Only the contact time of the rebound jump was shortened. In conclusion, it was clarified that DLH training induced an increase in the peak joint moment and stiffness of the ankle joint. Moreover the peak muscle power of the hip appeared in the early contact phase.