A study of the lower limbs movement of elderly adults by vibratory somatosensory stimulation applied to the ankle tendon

Normal walking on staircases is a very important ordinary activity. It is a complicated motion that requires a big muscular strength and moment, and a big joint exercise scope. Due to such characteristics, staircase walking may be an obstacle to those with weakened lower limb muscle strength, and actually, fall injury accidents occur. Existing studies focus on dynamic changes in staircase walking. However, this study aimed to analyze staircase-walking characteristics evidenced when applying vibratory somatosensory stimulus to the ankle joint in a bid to reduce the risk of fall injuries associated with staircase walking. Five elderly male subjects, who had no disease related to the musculoskeletal system, participated in experiments. Experiments were held in a motion analysis laboratory equipped with 3-D motion analysis systems, force platforms, etc. In order to gather motion data, subjects wore markers and vibratory stimulation devices designed to apply somatosensory stimulus to ankle joints, and climbed down a staircase with the height adjusted appropriately. Using motion data gathered from staircase-walking, the ankle joint, knee joint and hip joint angles were obtained, and thus each joint's contribution to the motion was calculated. In the case of vibratory somatosensory stimuli being applied to the Achilles's tendon, the ankle joint contributed more to the motion of climbing down a staircase than the knee joint and the hip joint did. On the other hand, in the case of vibratory somatosensory stimulus being applied to the anterior tibialis, the ankle joint contribution was lowered, and to make up for it, the knee joint and the hip joint contribution increased. This outcome revealed that the effect of the vibratory somatosensory stimulation applied to the ankle joint can appear in not only the ankle joint, but also in the whole lower limbs due to chain reaction.