Purpose The purpose of this study was to compare the technique and power of the Korean national athletes and international athletes in the start phase of the 500 m speed skating to improve the performance and to understand the relationship between the biomechanical variables affecting the record. Method The subjects were 8 Korean national athletes (Korean athletes) and 6 international athletes (international athletes). For the three dimensional motion analysis, 5 high-speed cameras were used to capture the 40 m start phase of the athletes participating in the international competition. The variables selected for analysis were the kinematic chain, 100 m net time, time to 9 strokes, horizontal position of center of mass after 2.5 sec, range of motion of trunk, knee, push-off angle, net power output, total power loss. Results The correct kinematic chain ratio of Korean athletes was 61.2%, which was lower than 76.0% of international athletes. The time to 9 strokes was 2.82±0.25 sec for Korean athletes, which was significantly lower than 2.53±0.11 sec for international athletes (p=.001). The range of motion of the push-off angle was 60.15±2.75° for Korean athletes, which was significantly lower than 64.76±2.55° for international athletes (p=.001). The net power output was 887.2±269.9 W for Korean players and 1103±264.1 W for international players (p=.021). The variables related to the 100 m net time were the horizontal position of center of mass after 2.5 sec (r=-.956, p=.001), the net power output (r=-.931, p=.001), and the total power loss (r=-.904, p=.001). Conclusion In order to improve the start performance of Korean athletes, it is necessary to maximize the efficiency of skating through skill training to use the correct kinematic chain. Also power enhancement training is needed to improve leg power because the net power output related with 100 m net time.
PURPOSE This study aims to analyze the effects of injury prevention video feedback on kinetic variables of the knee joint during the cutting maneuver. METHODS Twenty-eight healthy men participated and motion and force data were collected using infrared cameras, a force plate, and a Witty timing system. Paired t-tests were employed for data evaluation using the SPSS 26.0 program. RESULTS Results showed increased abduction and lateral rotation angles of the knee joint at the lower height of the center of mass (COM) (p<. 05). The lateral rotation of the knee joint decreased at initial ground contact (p<.05). Flexion angular velocity increased at initial ground contact after video feedback (p<.05) and decreased at the lower height of COM (p<.05). Abduction angular velocity decreased at the lower height of COM (p<.05), and internal rotation angular velocity was increased on the initial ground contact (p<.05). Maximum ground reaction force for anterior-posterior and medial-lateral directions increased after video feedback (p<.05). Flexion and internal rotation moments increased, and adduction moment also increased (p<.05). CONCLUSIONS In conclusion , video feedback effectively reduced knee load during the cutting maneuver, contributing to injury prevention for the knee joint.
PURPOSE This study aimed to analyze the dynamic posture stabilization and kinematic variables between visual feedback and Y-balance training groups during jump-landing. METHODS Thirty-eight male players (age: 22.6 ± 1.12 years, height: 175 ± 3.54 cm, weight: 65.5 ± 5.11 kg) were included in this study, and chronic ankle instability was checked using Cumberland Ankle Instability Tool (CAIT) and Balance Error Scoring System (BESS). They were randomly assigned to the Visual biofeedback (Training group: TG, n = 19) and Y-balance groups (Control group: CG, n = 19) for four weeks. TG performed balance training using the Biodex balance system (BBS) and CG performed training using the Y-balance system. During jump landing, time to stabilization (TTS), force plate (COP, GRF); joint angle and moment were collected and analyzed. All analyses were performed with SPSS 21.0, and Bonferroni was used for repeated measured ANOVA and post-hoc. RESULTS The results indicated that there was an interaction between TG and CG in terms of AP and ML directions of TTS (p < 0.05). AP/ML TTS of the TG for the post-test was smaller than that for CG (AP: p = 0.000; ML: p = 0.046). ML TTS of the TG for post-test was smaller than at pre-test (p = 0.041), and AP TTS of the CG for ankle joint moment (p < 0.05). There was an interaction between TG and CG in terms of dorsiflexion (DF) and plantarflexion (PF) of joint moment (p < 0.05). Ankle moment of the CG for post-test decreased than at pre-test (DF: p = 0.040, PF: p = 0.032), and ankle dorsiflexion moment of the CG for post-test was decreased than at pre-test (p = 0.046). CONCLUSIONS Balance ability was achieved more effectively through visual biofeedback training than Y-balance training. Therefore, we recommend balanced training with visual feedback on chronic ankle instability.
