| Summary: | 碩士 === 國立成功大學 === 體育健康育與休閒研究所 === 96 === Most of previous studies about in-line skating have focussed on the investigation of injury and the effect of using a guard. However, there have been no researches to study the mechanics of injury. In-line skating jump landing was similar to stop-jump landing. Stop-jump consists of a 2-3 steps approach run and a two-footed landing followed by two-footed takeoff to maximum height and two-footed landing again. However, no study has been involved to investigate the second two-footed landing after the takeoff. The studies of drop landing indicated that knee, ankle joints and plantarflexor played important roles in landing cushioning. In-line skating boots will constrain the motion of plantar-flexion, however, the influence of in-line skating boots on ground reaction force, kinematics, and muscle activation of lower limbs during landing has been unknown. Therefore, the purpose of this study tried to describe the movement characteristics of lower limbs during landing with stop-jump and in-line skating jump and compare the effect on lower limbs motion under ankle constrain.
Eight subjects were asked to perform three jump landing tasks: stop-jump with barefoot (BF), stop-jump with ankle constrain (AC) and jump with in-line skating boots (IS). Landing movements in sagittal plane were recorded by one high speed camera. One force plate and EMG system were used to measure the ground reaction force and the activation of four muscles during landing.
The results indicated that hip joint had more and quicker flexion, and the knee joint had less and slower flexion under IS. This landing strategy was used to lower the center of gravity of the body to keep the movement steadily, but could not absorb the shock during landing. Therefore, the in-line skating boots seems to play an important role to reduce the impact during landing. Because the ankle was constrained under IS, the range of motion was lower than BF and AC During pre-landing phase, the activation of rectus femoris and tibialis anterior was the largest under IS, but the activation of gastrocnemius was the lowest under IS, and the co-contraction ratio (biceps femoris/( biceps femoris+rectus femoris)) was also lowest. These characteristics might cause higher loading in knee joint, especially on anterior cruciate ligament, and increase the risk of injury. Therefore, the in-line skating boots with well cushioning could reduce the landing impact and reduce the falling injury while the human use the landing strategies to keep stability.
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