ABSTRACT
The purpose of this study was to investigate the relationship between toe muscular strengths and single and/or repetitive jump performances on different directions (vertical or horizontal) in athletes. Thirty two male collegiate students participated (athletes group n=24, control group n=8). Two types of measurements were performed to evaluate toe muscular strengths: toe pushing force (TPF) with the metatarsophalangeal joint (MPJ) at neutral position (0°) and the MPJ in the dorsiflexed position (45°). Jump performances were assessed by press jump (vertical jump and standing broad jump) that measures jumping height or distance, and rebound jump (rebound jump and repetitive hopping) that measures “RJ-index” (the jumping height divided by the contact time). Pearson correlation coefficients were used to determine the relationship between the toe muscular strengths and the performances of each jumping test. There were significant correlations between TPF with the MPJ in the dorsiflexed position and the performances of the repetitive hopping and rebound jump in athletes (P<0.05), but no significant correlations were found in controls. Also, there were no significant correlation between TPF and the performances of vertical jump and standing broad jump of all groups. These results suggest that, TPF in the dorsiflexed positions is one of the indicators that affect repetitive jump performance.
ABSTRACT
The factors influencing ankle range of motion were investigated for 185 middle-aged and elderly subjects (116 women and 69 men, aged 48-86 years) . Each subject was seated with the right knee extended, and the ankle joint was passively dorsiflexed by a dynamometer with torque just tolerable for each subject, to measure the maximal dorsiflexion angle. During passive loading, elongation of muscle fibers in the gastrocnemius and Achilles tendon was determined in vivo by ultrasonography. There was a difference between women and men for the passive dorsiflexion angle (men smaller than women), which negatively correlated with muscle thickness of the posterior portion of the leg determined by ultrasonography. Both in women and men, the passive dorsiflexion angle negatively correlated with age, even after normalizing for maximal voluntary plantar flexion torque. Both elongation of muscle fibers and tendon was related to the passive dorsiflexion angle, and the ratio of tendon elongation to muscle fiber elongation positively correlated with the passive dorsiflexion angle. The active dorsiflexion angle, measured separately with the subject maximally dorsiflexing the ankle with no load, correlated with the passive dorsiflexion angle but not with age, and there was no gender difference. From the results it was suggested 1) that the mobility of the ankle joint is affected by elongation of both muscle fibers and tendon, but with the effect of the tendon being greater than that of muscle fibers, and 2) that muscle mass negatively affects passively-induced joint range of motion. Actively performed joint range of motion would be affected by elongation of the muscle-tendon corn plex and force-generating capability of the ankle. Gender difference in joint range of motion and the aging effect are related to these factors.