高齢者の跳躍動作における下肢関節のパワー発揮

Abstract

In an aging society, it is important to study the states and mechanisms of decline in body functions with aging and of changes in motion with aging. It is especially valuable to investigate the functions of the lower extremities, since they are main factors determining safety as well as competitiveness in almost all sports activities. The purpose of this study is to cross-sectionally investigate the changes in joint moment and power of lower extremities for the elderly during a standing long jump using a force platform and a high-speed VTR camera. The subjects of this study were thirty-three healthy elderly males (62yr. to 86yr.). They were divided into three age groups: the 60s(n=12), 70s(n=14), and 80s(n=7). They were videotaped at 200 frames per second with high-speed VTR camera while they were performing the standing long jump from a force platform with maximal effort. Using ground reaction force data from the force platform and coordinate data of seven body landmarks (toe, ball of the foot, heel, ankle, knee, great trochanter, and suprasternale) from VTR images, equations of motion for thigh, shank, and foot were solved, and then joint moments, powers, and mechanical works were calculated. Joint moment curves and power curves were evaluated after being normalized by time from the start of the jump (ST) to the takeoff (OFF) and averaged for each group. For the hip and knee joint extensor's moment acted predominantly from ST to the point of about 90% completion of the jump, and then flexor's moment acted predominantly up to the OFF. For the ankle joint, extensor's moment acted predominantly through-out the jump. The power curve for the hip and knee has three peaks. The first one was power by extensor's eccentric contraction (EEh, EEk), the second was power by extensor's concentric contraction (ECh, ECk), and the third was power by flexor's eccentric contraction (FEh, FEk). The power curve for the ankle has only two peaks (EEa, ECa). From the investigation of these curves and these maximum values, the following results were obtained. 1) Although the magnitude of downward kicking force in a standing long jump hardly changed with aging, magnitude of backward kicking force decreased with aging, and jumping distance for the elderly also decreased proportionately. 2) Maximum extensor's moment and maximum power of joints in lower extremities decreased with aging. The magnitude of decrease was the largest in the hip joint, the second largest in the ankle joint, and smallest in the knee joint. 3) The power by concentric contraction of the extensors in the standing long jump was influenced by aging and decreased. The power by eccentric contraction of the extensors, however, was hardly influenced by aging. 4) In a standing long jump, which requires that the body be largely inclined at the takeoff, elderly people tended to jump with smaller forward incline of their bodies to avoid being in an unstable situation.