Plyometric Training in Female Athletes

The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. 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 jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-toquadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21 % on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes. At our center, we have noted a large number of adolescent female athletes with serious knee injuries caused by jumping and cutting sports such as soccer, volleyball, and basketball. In a recent study on the incidence of injury in indoor soccer players, researchers at our center reported that the incidence of serious knee injury was approximately sixfold higher in female than in male players. 18 A number of studies have corroborated the higher incidence of serious knee injury in female participants in jumping sports compared with male participants.’, 10, 11, 13, 17,19, 31, 32 Chandy and Grana,~ in a 3-year study of 24,485 male and 18,289 female high school students participating in paired sports, reported that the incidence of season-ending knee injuries in female athletes was 4.6 times that of male athletes. Female athletes in jumping sports had significantly more injuries and more severe injuries. The National Athletic Trainers of America Symposium reported that 18% of girls’ injuries were knee-related in a population of 333,149 high school girls, compared with 10% of injuries in 380,783 high school boys. They also report that 89% of surgeries performed on female basketball players were for knee injuries. Ferretti et al.10 reported a fourfold higher incidence of serious knee ligament injuries in female versus male National Championship level volleyball players. Zelisko et a1.32 reported in a 2-year study that the incidence of knee injuries in professional female basketball players was 2.2 times higher than that in professional male basketball players. It was suggested that even though these women were as well trained as their male counterparts, differences in knee injury frequency remained. Haycock and Gillette 14 reported similar total injury rates for male and female collegiate athletes, although they did indicate that female athletes had higher rates of injury involving the patella and joints. They attributed any differences to differing levels of training and coaching and not to anatomic or physiologic differences. Whiteside 31 also reported similar overall injury rates for men and women, although the rate of significant knee injuries * Presented at the 21 st annual meeting of the AOSSM, Toronto, Ontano, Canada, July 1995 t Address correspondence and repnnt requests to Timothy E Hewett, PhD, The Cincinnati Sportsmedicine Research and Education Foundation, Deaconess Hospital, 311 Straight Street, Cincinnati, OH 45219 No author or related institution has received any financial benefit from research in this study by TIM E HEWETT on June 8, 2009 ajs.sagepub.com Downloaded from