DECREASED IMPACT FORCES AND INCREASED HAMSTRINGS TORQUES IN FEMALE ATHLETES WITH PLYOMETRIC TRAINING 321

Abstract

The purpose of this study was to test the effect of a jump training program on landing mechanics and lower extremity strength in females involved in jumping sports. These parameters were compared before and after a six week training program with those of untrained males using a force plate and an opto-electrically digitized system and an isokinetic dynamometer. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block decreased 22% (p < 0.01), while knee adduction and abduction moments decreased approximately 50%(p < 0.05). Multiple regression analysis revealed that these moments were significant predictors of peak landing forces (p < 0.01). Females demonstrated lower landing forces than males, and lower adduction and abduction moments following training. Male external knee extension(hamstrings) moments were three-fold higher than females (p < 0.01). Hamstrings power increased 44% with training (p < 0.0001) on the dominant side, and 21% in the non-dominant (p < 0.05). Hamstrings to quadriceps peak torque ratios increased 26% on the non-dominant side (p < 0.01), and 13% on the dominant (p < 0.05), correcting side-to-side imbalances. Male peak torque ratios were significantly greater than untrained, but similar to trained females. Training resulted in a 9.2% mean increase in vertical jump height (p < 0.05). In conclusion, neuromuscular training decreased impact forces by reducing medial and lateral torque at the knee, increased power and decreased hamstrings strength imbalances, and increased vertical leap in female athletes. This training may have a significant effect on knee stabilization and prevention of serious knee injury in this high-risk population.