This study investigated foot pressure patterns between experienced skiers and intermediate skiers during alpine skiing. Five experienced skiers and five intermediate skiers participated in this study. Foot pressure measurement system was used to measure vertical ground reaction force (vGRF) and contact area under the six plantar regions. Each participant was asked to perform basic parallel turns and carved turns on a 18 o groomed slope. Each right turn was divided into the initiation phase, the steering phase 1 and 2. For the initiation phase of the basic parallel turns, significantly greater contact area was found on the LRF and RRF of the intermediate skiers (p<.05) and significantly greater vGRF was found on the LRF of the intermediate skiers (p<.05). Also significantly greater vGRF and contact area were found on the LRF and RRF of the intermediate skiers at the steering phase 1 (p<.05) and on the LRF of the intermediate skiers at the steering phase 2 (p<.05). For the carved turns, significantly greater vGRF and contact area were found on the LRF and RRF of the intermediate skiers at all three phase (p<.05). On the other hand, significantly greater vGRF was found on the RFF of the experienced skiers at the steering phase 1 (p<.05). Also significantly greater vGRF and contact area were found on the RMF of the experienced skiers at the steering phase 2 (p<.05). In order to increase performance, we suggest that the intermediate skiers should be unweighted at the initiation phase and shift the body weight to the forefoot of the outer foot at the steering phase 1. Also, the outer ski should be loaded more than the both skis at the steering phase 1 and 2.
Objective: To investigate rotation movement of segment for performing each position and its effect on knee/hip angulation, COM inclination, and edging angle changes.Method: Twelve Alpine skiers (age: 25.8±4.8 years, height: 173.8±5.9 cm, weight: 71.4±7.4 kg, length of career: 9.9±4.6 years) participated in this study. Each skier was asked to perform counter-rotation, neutral, and rotation positions.Results: Shank and thigh were less rotated in the counter-rotation position than in other positions, whereas the trunk and pelvis were more counter-rotated (p<.05). Hip angulation, COM inclination, and edging angle were significantly greater in the counter-rotation position than in other positions (p<.05).
Conclusion:Our finding proved that the counter-rotation position increases hip angulation, COM inclination, and edging angle. Consequently, we suggest that skiers should perform counter-rotation of the trunk and pelvis relative to the ski direction in the vertical axis for the counter-rotation position. Further analysis will continue to investigate the effects of the counter-rotation position in real ski slope with kinetic analysis.
PURPOSE The purpose of this study was to compare the dynamic postural control of youth athletes with and without a history of lateral ankle sprains. METHODS Twenty-eight youth athletes (14 lateral ankle sprain, 14 healthy control) participated in this study. All participants answered the Foot and Ankle Ability Measure questionnaire and were subject to the Star Excursion Balance Test (SEBT) for dynamic postural control evaluation to collect the joint angles of the lower extremity, a center of pressure (COP) path, and COP velocity. Independent sample t-test or Mann-Whitney U-test were performed to analyze the difference between the groups. RESULTS The lateral ankle sprain group (LAS) was found to have a long experience in participating in sports, and low Foot and Ankle Ability Measure scores were identified when compared to the healthy control (CON; <i>p</i><0.05). LAS was observed with a short reach distance, less hip flexion, and dorsiflexion angles during the anterior direction of SEBT when compared to CON (<i>p</i><0.05). Furthermore, LAS showed a slower anteroposterior and mediolateral center of pressure velocities in the posteromedial aspect of SEBT and a slower anteroposterior COP velocity in the posterolateral aspect of SEBT when compared to that of CON (<i>p</i><0.05). There were no differences between the groups with respect to the other variables (<i>p</i>>0.05). CONCLUSIONS Based on these results, decreased anterior reach distance of SEBT may be affected by changing the dynamic posture control strategy of the lower extremity joint on the sagittal plane in LAS.
Purpose The purpose of this study was to investigate the effect of auditory stimulus using white noise on stability and balance during sit-to-stand and standing tasks of chronic stroke patients. Methods Eighteen chronic stroke patients participated in this study. They asked to perform the tasks of sit-to-stand, standing with eyes open and standing with eyes closed before and after listening to white noise. Eight infrared cameras and one force plate were used to evaluate the stability and balance before and after the white noise stimulus during each task. Results There was no significant difference between before and after white noise stimulus in all tasks. On the other hand, the anteroposterior range of CoP was significantly decreased after white noise stimulus in standing with eyes-closed (p<.05), and the sagittal angle of CoP-CoM was significantly decreased after white noise stimulus in standing with eyes-open and eyes-closed (p<.05). Conclusion Auditory stimulus using white noise improves the balance of chronic stroke patients. Therefore it is thought to be helpful for the independent daily life of chronic stroke patients.
Purpose The purpose of this study was to investigate the three dimensional joint angles of the ankle, knee and hip during basic long turn, carving long turn, basic short turn and carving short turn. Methods Fourteen alpine ski instructors from Korea Ski Instructor Association participated in this study. Each skier asked to perform 4-types of turning technique, classified by radius and level. 8 inertial measurement units were used to measure three-dimensional joint angles of the ankle, knee and hip joint. Results Significant differences were found the lower extremity joint angles on the mediolateral and vertical axis during long-turn and carving-turn (p<.05). significant differences were found the lower extremity joint angles on the anteroposterior axis in the steering phases 1, 2 and complete phase (p<.05). Conclusions In the Alpine skiing, the short turn requires a complex movement of the lower limb joint compared to the long turn. When performing a long turn, the movement of the ankle joint on the vertical axis are required compared to the short turn. And the carving and short turn need to the movements of the lower limb joint on the mediolateral axis.
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