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플랫폼 다이빙 앞으로 서서 앞으로 1<sup>1</sup>/<sub>2</sub>회전 동작의 운동역학적 분석
전경규,Jeon, Kyoung-Kyu 한국운동역학회 2013 한국운동역학회지 Vol.23 No.3
This study was to perform the kinetic analysis of forward $1\frac{1}{2}$ somersault on the platform diving. Six men's diving players of the Korea national reserve athletes participated in this study. The variables were analyzed response time, velocity, center of mass (COM), angle, center of pressure (COP) and ground reaction force (GRF) of motion. For measure and analysis of this study, used to synchronized to 4 camcorder and 1 force plate, used to the Kwon3D XP (Ver. 4.0, Visol, Korea) and Kwon GRF (Ver. 2.0, Visol, Korea) for analyzed of variables. The results were as follows; Time factor were observed in maximum knee flexion depending on the extent of use at phase 1 of take-off to execute the somersault. This enabled the subject to secure the highest possible body position in space at the moment of jumping to execute the somersault and prepare for the entry into the water with more ease. Regarding the displacement of COM, all subjects showed rightward movement in the lateral displacement during technical execution. Changes in forward and downward movements were observed in the horizontal and vertical displacements, respectively. In terms of angular shift, the shoulder joint angle tended to decrease on average, and the elbow joints showed gradually increasing angles. This finding can be explained by the shift of the coordinate points of body segments around the rotational axis in order to execute the half-bending movement that can be implemented by pulling the lower limb segments toward the trunk using the upper limb segments. The hip joint angles gradually decreased; this accelerated the rotational movement by narrowing the distance to the trunk. Movement-specific shifts in the COP occurred in the front of and vertical directions. Regarding the changes in GRF, which is influenced by the strong compressive load exerted by the supporting feet, efficient aerial movements were executed through a vertical jump, with no energy lost to the lateral GRF.
전경규,김규완,현승현,류재청 한국운동역학회 2018 한국운동역학회지 Vol.28 No.2
Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stance-phase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.
탄성 발목 보호대 착용 유무가 전방 점프 착지 시 하지 관절의 역학적 변인 차이 비교
전경규,안세지,정형도 국민체육진흥공단 한국스포츠정책과학원 2023 체육과학연구 Vol.34 No.3
PURPOSE This study aimed to investigate the effect of an ankle strap on kinetic variables of the lower limb during forward jump landing. METHODS Twelve healthy adult men (mean age, 23.58±2.22 years; mean height, 177.83±5.37 cm; mean weight, 75.00±7.72 kg) participated. The participants stood barefoot on both legs at a horizontal distance of 40% of their body height from the center of the force plate, then jumped forward and landed on the force plate with their dominant or non-dominant leg over a 30-cm hurdle while wearing or not wearing an ankle strap. Joint angle, peak vertical force, loading rate, and leg stiffness were calculated. Paired t-test and repeated-measures two-way analysis of variance with Bonferroni’s post hoc tests were used to compare the characteristics of both lower limbs and the effect of wearing an ankle strap. The significance level was α < .05 RESULTS Our results showed significant differences in kinematic variables between the dominant and non-dominant legs without the ankle strap. With the ankle strap, the inversion angles at the ankle joints of both lower extremities were significantly decreased, and an interaction effect between both legs and the ankle strap occurred in the internal rotation angle of the ankle joint. Kinetic variables did not differ significantly. CONCLUSIONS The ankle strap did not completely compensate for ankle instability in the non-dominant leg, but it significantly reduced the angle of internal rotation at the ankle joint. Thus, we recommend that correct wearing of the ankle strap in sports since it reduces the possibility of lateral ankle sprains to some extent.
Effects of ankle instability type and bilateral leg on lower extremity kinetics during drop-landing
전경규,현승현 국민체육진흥공단 한국스포츠정책과학원 2021 International Journal of Applied Sports Sciences Vol.33 No.1
The purpose of this study was to investigate the analysis of the postural stability and leg stiffness according to the ankle instability types and bilateral legs during drop landing. Methods: Total 14 male athletes (n=7: mechanical ankle instability, n=7: functional ankle instability) Participants in the experiment. The leg stiffness, leg length, peak vertical force, loading rate, as well as the DPSI (medial-lateral [ML], anterior-posterior [AP], vertical [V], dynamic postural stability index) during drop landing were calculated. To analyze the variables measured in this study, SPSS version 21.0 was used to calculate the mean and standard deviation, while a two-way ANOVA was used to evaluate the ankle instability types (MAI, FAI) with landing leg (left: dominant, right: non-dominant leg) results. Dimensionless leg stiffness and change of leg lengths showed increased with significantly in non-dominant leg and MAI type than in dominant leg and FAI type. This resulted from decrease in the leg lengths with leg stiff. MLSI showed increased with significantly in dominant leg than in non-dominant leg during drop landing. Mechanically unstable individuals demonstrated increased leg stiffness, which may increase risk of musculoskeletal. Also, mechanically unstable participants demonstrated greater loading rate variability, which may indicate difficulty mitigating landing forces with lax ligaments.