ドロップ着地における関節モーメントによる回転安定性の姿勢制御

抄録

In drop landing studies, control of rotary stability based on the net effect of the three joint moments has not been previously investigated. Ashby & Heegaard(2002) quantified rotary stability in a standing long jump study by using the moment about the center of mass by ground reaction force (M_CM). The purpose of the present study was to investigate rotary stability by M_CM and the lower extremity joint moments, as well as the effects of the joint moments on rotary stability. Ten healthy male sublects(age;22.9±0.99yr, body mass;mass 68.2±7.00kg, and height;174.5±3.57cm)participated.A fbrce platform(Kistler type 9287BA&9281CA, Kistler Instnlments, Switzerland)was used to measure ground reaction fbrces(GRF)at 1kHz. Also, two high speed cameras(FASTCAM, Photron, Japan)were used to record human motions at 0.25kHz. Each subject performed stiff and soft drop landings from a platfbrm (0.48m). In stiff landing, as much as possible, the subjects did not flex their joints. On the other hand, in soft landing the subjects used joint flexions to attenuate impact. Joint moments were calculated using an inverse dynamic analysis. In addition, M_CM was calculated by vector product of the position vector from the whole body center of mass to the center of pressure and GRF. The M_CM in backward direction was larger in stiff landing than in soft landing. In addition, when the hip joint moment increased, the knee joint moment decreased. On the contrary, when the hip joint moment decreased, the knee joint moment increased. Thus, these findings indicate that the coordination of knee flexion joint moment and hip extensor joint moment is an important factor for controlling rotary stability during drop landings.