身体不活動による垂直跳能力の変化
−筋力萎縮を補う運動の調整について−
深代 千之 長野 明紀 野田 幹子 船渡 和男 鈴木 洋児 福永 哲夫
Change in a vertical jump ability following prolonged bed rest
Senshi FUKASHIRO, Akinori NAGANO, Mikiko NODA, Kazuo FUNATO, Youji SUZUKI and Tetsuo FUKUNAGA
Decrease in strength and atrophy of skeletal muscles has been recognized after a prolonged bed rest (BR) . However, it has not been clear how the behavior of free movements like jumping against gravity changes after BR. It may be possible that loss of strength is compensated by neuromuscular coordination in free movement. The present study investigated the change in vertical jump ability after BR. Five male subjects participated in 20 days BR. Every day during BR, maximal knee extension training in only one leg using a Cybex machine was performed under 60 deg/s of angular velocity with 2 sets of 50 repetitions per day. The jump tests described below were carried out before and immediately after 20 days BR. The subjects were asked to perform maximal vertical jumps on a Kistler force-plate ; one leg and two leg jumps from a squatting position without counter-movement or arm swing. Subjects performed 3 trial jumps in each condition. The jumping height of the body center of gravity during flight was calculated from a vertical velocity at take-off, which was obtained from the integrated vertical ground reaction force. The joint torque, power and work during jumping were estimated using inverse dynamics.
The means of the jumping heights before and after BR were 0.297m and 0.240m in the two-leg jump, 0.115m and 0.084m in the jump by untrained leg, and 0.119m and 0.093m in the jump by the trained leg, respectively. Significant decreases were observed in the two-leg and untrained leg jumps. However, regarding the parameters in the joint torque, power and work, the influence of the trained leg was not observed in each jump after BR. Although the mechanical work in ankle joint decreased significantly in both left and right leg jumps, that of the hip joint increased slightly after BR. Therefore, it was suggested that the large decrease in ankle joint work might be compensated by increase of hip joint work after BR.
東京大学大学院生命環境科学系 Department of Life Sciences. The University of Tokyo
