Ford, K. R., Myer, G. D., & Hewett, T. E. (2010). Longitudinal effects of maturation on lower extremity joint stiffness in young athletes. Presentation 888 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

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This study determined if the neuromuscular risk factors related to knee stiffness diverge between the genders during the adolescent growth spurt. It was hypothesized that pubertal males would demonstrate increased knee stiffness, while pubertal females would not. In addition, it was determined whether post-pubertal females would have significantly lower knee joint stiffness compared to post-pubertal males. Ss (N = 315) participated in two testing sessions one year apart. Ss were classified based on their maturation status as either pubertal or post-pubertal. Sagittal plane ankle, knee, and hip angles and moments were used to calculate active joint stiffness parameters during a drop vertical jump. Stiffness was calculated as the slope of the moment-angle curve from a least squares linear regression during the stance phase.

All Ss showed increased active knee stiffness during landing between the first and second year. No similar increase was found when stiffness was normalized to body mass. Males demonstrated greater magnitudes of ankle and hip active stiffness. Peak ankle and hip moments in post-pubertal males were significantly greater than post-pubertal females. Females had a higher knee to hip moment ratio compared to males.

Implication. Gender divergence in ankle and hip stiffness begins slightly prior to the adolescent growth spurt. Differences in hip joint posture at initial contact (greater flexion in males) and external hip flexion moment (greater flexion magnitude in males) indicate that males utilize a different hip strategy during drop vertical jumps compared to females.

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