• 대한기계학회논문집B
• /
• 제41권4호
• /
• pp.277-283
• /
• 2017

본 연구에서는 높이에 따른 점프 전략 변화를 이해하기 위해 반동을 이용한 수직 점프 시 상변화 시점에서의 지면반력 벡터가 높이에 따라 어떻게 변하는지 분석하였다; 반동과 추진 구간에서 유사한 힘 작용선을 갖는 수직 점프의 경우, 상변화 시점에서 반동의 이득을 나타내는 합력 벡터의 크기와 방향이 일정한 경향성을 가지고 높이에 따라 변화할 것이라 가정하였다. 9명의 청년군 모두는 정해진 5 종류의 높이를 총 5세트에 걸쳐 랜덤 방식으로 점프하였으며, 해당 높이를 유도하기 위해 지면으로부터 191 cm에서 221 cm 사이에 일정한 간격을 두고 마커를 배치하였다. 점프 높이가 증가함에 따라 반동 시 무게중심을 낮추고, 수평, 수직 방향의 힘을 증가시키는 것이 관찰되었는데, 이는 추진일을 증가시키기 위해 관절의 가용범위를 넓히고 초기 힘(또는 가속도) 이득을 늘리기 때문으로 생각된다.

• 한국운동역학회지
• /
• 제23권3호
• /
• pp.209-218
• /
• 2013

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.

• 한국인터넷방송통신학회논문지
• /
• 제19권2호
• /
• pp.143-149
• /
• 2019

플로팅 홀로그램은 광고나 콘서트와 같이 넓은 공간에서 현장감과 실존감이 뛰어난 3D 입체영상을 제공하면서, 3D 안경의 불편함, 시각적 피로, 공간 왜곡 현상 발생을 감소할 수 있는 기술이다. 따라서 본 논문은 좁은 공간에서도 사용가능한 플로팅 홀로그램 환경에서 캐릭터 조작을 위한 사용자 제스처 인식 시스템을 구현한다. 제안된 방법은 하르 특징기반의 캐시케이드((Harr feature-based cascade classifier) 분류기를 이용하여 얼굴 영역을 검출하고, 검출된 얼굴 영역을 기준으로 실시간으로 체스쳐 차영상으로부터 사용자 제스쳐의 발생 위치 정보를 이용하여 사용자 제스쳐를 인식한다. 그리고 각각 인식된 제스쳐 정보는 플로팅 홀로그램 환경에서 생성된 캐릭터 움직임을 조작하기 위하여 상응하는 행위에 맵핑된다. 제안된 플로팅 홀로그램 캐릭터 조작을 위한 사용자 제스처 인식 시스템의 성능평가를 위해서는 플로팅 홀로그램 디스플레이 장치를 제작하고, 몸 흔들기, 걷기, 손 흔들기, 점프 등의 각 제스처에 따른 인식률을 반복 측정한 결과 평균 88%의 인식률을 보였다.

• 대한물리치료과학회지
• /
• 제29권1호
• /
• pp.47-54
• /
• 2022

Background: Plyometric exercise is an exercise exerting forceful power in a brief period using isotonic activation. It is effective to improve reaction of muscle, agility, endurance and athletics performance. Weight training is an exericse improving muscular strength, endurance and respirating ability applying diversely in frequency and load of exercise Plyometric exercise and Weight training is to facilitate the athletics performance though improving the function of lower limb muscle, there is a difference that Plyometic jump squats is the way to improve agility and Weight training is the way to improve muscular strength. Therefore, it is necessary to know how this difference effects on athletics performance as measuring ankle, ROM, and jumping ability. Design: Randomized controlled trial. Method: This study was conducted with the voluntary participation of 40 university students, who were randomly assigned to jump squat and calf raise groups (n=20 per group). For each subject, we measured the range of motion of the ankle joint before and after exercise, as well as a standing broad jump and vertical jump test performance. We compared the performance indices before and after exercises using paired t-tests, and between groups using independent-samples t-tests. Conclusions: Both jump squat and calf raise exercises improved ankle joint dorsiflexion and plantar flexion, as well as standing broad jump and vertical jump height performance. However, there were no significant differences before versus after exercise, or between exercise types. Although jump squats and calf raises have different purposes, it is thought that, in combination, these exercises improve performance more effectively than either alone, and that such a combined exercise program improves the quality of training in both the general public and athletes in various sports.

• The Journal of Korean Physical Therapy
• /
• 제34권1호
• /
• pp.12-17
• /
• 2022

Purpose: Ankle dorsiflexion is an essential element of normal functions, including walking, activities of daily living and sport activities. The tibialis anterior (TA) muscle functioned as a dorsiflexor and as a dynamic stabilizer of the ankle joint during walking and jumping. This study aimed to compare TA muscle thickness using ultrasonography according to the four different toe and ankle postures for the selective TA strengthening exercise. Methods: This study were recruited 26 (males: 15, females: 11) aged 20-30 years, with no injury ankle and calf in the medical history, had normal dorsiflexion and inversion range of motion (ROM). The thickness of the TA muscle was measured by ultrasonography in the four different toe and ankle postures: 1. Ankle dorsiflexion with all toe extension and ankle inversion (ITEDF); 2. Ankle dorsiflexion with all toe flexion and ankle inversion (ITFDF); 3. Ankle dorsiflexion with all toe extension and neutral position (NTEDF); 4. Ankle dorsiflexion with all toe flexion and neutral position (NTFDF). One-way repeated analysis of variance (ANOVA) and Bonferroni correction were used to confirm the significant difference among conditions. The level of statistical significance was set at α=0.01. Results: TA muscle thickness with ITFDF was significantly greater than in any other ankle positions, including ITEDF, NTFDF, and NTEDF (p<0.01). Conclusion: Among the four toe and ankle postures, isometric contraction in ITFDF postures showed the greatest increase in thickness of TA rather than ITEDF, NTEDF, and NTFDF postures. Based on these results, ITFDF can be recommended in an efficient way to selectively strengthen TA muscle.

• 한국운동역학회지
• /
• 제31권4호
• /
• pp.241-248
• /
• 2021

Objective: The purpose of this study was to investigate the difference in muscle strength, kinematics, and kinetics between injured and non-injured sides of the leg after Achilles Tendon Rupture surgery during walking and running. Method: The subjects (n=11; age = 30.63 ± 5.69 yrs; height = 172.00 ± 4.47 cm; mass = 77.00 ± 11.34 kg; time lapse from surgery = 29.81 ± 10.27 months) who experienced Achilles Tendon Rupture (ATR) surgery participated in this study. The walking and running trials were collected using infrared cameras (Oqus 300, Qualisys, Sweden, 100 Hz) on instrumented treadmill (Bertec, U.S.A., 1,000 Hz) and analyzed by using QTM (Qualisys Track Manager Ver. 2.15; Qualisys, U.S.A). The measured data were processed using Visual 3D (C-motion Inc., U.S.A.). The cutoff frequencies were set as 6 Hz and 12 Hz for walking and running kinematics respectively, while 100 Hz was used for force plate data. Results: In ATR group, muscle strength there were no difference between affected and unaffected sides (p> .05). In kinematic analysis, subjects showed greater ROM of knee joint flexion-extension in affected side compared to that of unaffected side during walking while smaller ROM of ankle dorsi-plantar and peak knee flexion were observed during running (p< .05). In kinetic analysis, subjects showed lower knee extension moment (running at 2.2 m/s) and positive ankle plantar-flexion power (running at 2.2 m/s, 3.3 m/s) in affected side compared to that of unaffected side (p< .05). This lower positive ankle joint power during a propulsive phase of running is related to slower ankle joint velocity in affected side of the subjects (p< .05). Conclusion: This study aimed to investigate the functional evaluation of the individuals after Achilles tendon rupture surgery through biomechanical analysis during walking and running trials. Based on the findings, greater reduction in dynamic joint function (i.e. lower positive ankle joint power) was found in the affected side of the leg compared to the unaffected side during running while there were no meaningful differences in ankle muscle strength and walking biomechanics. Therefore, before returning to daily life and sports activities, biomechanical analysis using more dynamic movements such as running and jumping trials followed by current clinical evaluations would be helpful in preventing Achilles tendon re-rupture or secondary injury.

• 한국운동역학회지
• /
• 제18권4호
• /
• pp.1-19
• /
• 2008

본 연구의 목적은 스노우보더가 플랫폼에서 뛰어내릴 때 경사면에 착지 하는 지면반력 계산을 바탕으로 3가지 종류의 곡선(타원, 원, 브라키스토크론)으로 된 하프파이프의 곡면에 착지할 때의 충격에 대한 역학적 계산의 결과를 해석 하는 것이다. 스노우보더의 착지시 다리의 유연성, 눈이 다져진 정도 경사면의 각도, 초기 속도, 착지 후 동작의 숙련도 등이 충격을 줄여주는 중요한 요소로 작용한다. 그러나 딱딱한 스노우보드용 하프파이프에서는 착지 지점의 곡면에 절대적으로 좌우된다. 이 연구의 역학적 분석 결과 브라키스토크론 곡선이 좀 더 충격 흡수의 효과가 있어 안전한 것으로 판명되었다. 건설의 효율성만을 고려한다면 현재 통용되고 있는 타원형태 이외의 다른 종류의 곡선들은 필요 없다고 생각하기 쉬우나 스노우보더들이 구사하는 기술의 종류와 난이도에 따라서 다양한 기하학적 형태의 시설로 발전되는 것이 바람직하다. 본 연구에서 시행된 연구 방법은 스노우보더 들의 치명적 부강 방지를 위한 하프파이프의 최적 안전 설계 및 사용의 방법과 더불어 스포츠인 들의 사고를 줄일 수 있는 과학적 연구방법에 대한 하나의 모델을 제시 한 것이라고 볼 수 있다.

• 대한족부족관절학회지
• /
• 제18권3호
• /
• pp.108-114
• /
• 2014

Purpose: Ligament reattachment technique using a suture anchor appears to show satisfactory functional outcomes and mechanical stability compared with conventional bone tunnel technique. This study was prospectively conducted in order to evaluate functional outcomes of modified Brostrom procedures using the suture bridge technique for chronic ankle instability in athletes. Materials and Methods: Twenty eight athletes under 30 years of age were followed for more than two years after undergoing the modified Brostrom procedure using the suture bridge technique. Functional evaluation consisted of the foot and ankle outcome score (FAOS), foot and ankle ability measure (FAAM) score. Range of motion and time to return to exercise were evaluated using a periodic questionnaire. Talar tilt angle and anterior talar translation were measured through stress radiographs for evaluation of mechanical stability. Results: FAOS improved significantly from preoperative mean 59.4 points to 91.4 points (p<0.001). Daily living and sport activity scores of FAAM improved significantly from preoperative mean 50.5, 32.5 points to 94.8, 87.3 points, respectively (p<0.001). Talar tilt angle and anterior talar translation improved significantly from preoperative mean $16.8^{\circ}$, 13.5 mm to $4.2^{\circ}$, 4.1 mm at final follow-up (p<0.001). Times to return to exercise were as follows: mean 10.2 weeks in jogging, 15.4 weeks in spurt running, 13.1 weeks in jumping, 11.5 weeks in walking on uneven ground, 9.1 weeks in standing on one leg, 7.2 weeks in tip-toeing gait, 8.4 weeks in squatting, and 10.6 weeks in descending stairs. Conclusion: Modified Brostrom procedure using the suture bridge technique showed satisfactory functional outcomes for chronic ankle instability in athletes. Optimal indication and cost-effectiveness of the suture bridge technique will be studied in the future.

• 한국응용과학기술학회지
• /
• 제39권5호
• /
• pp.701-709
• /
• 2022

본 연구의 목적은 국내 발레단 소속 여자 무용수를 대상으로 연속 회전점프 시 시각선택과 회전순서에 따른 차이를 도약과 착지구간으로 분류하여 비교하였다. 10명의 대상자(연령: 26.0±2.9 yrs, 신장: 163.4±3.3 cm, 체중: 46.8±3.6 kg, 발레경력: 12.3±5.9 yrs)가 연구에 참여하였다. 3차원 동작분석기와 지면반력기를 이용하여 신체중심의 높이와 도약과 착지 시 지면반력을 측정하였다. 시각선택(양눈 사용, 왼눈 사용, 오른눈 사용)과 회전순서(첫번째 회전점프, 두 번째 회전점프)에 따른 차이를 반복측정 이원변량 분석을 통하여 분석하였다. 신체중심의 높이는 첫 번째 회전점프가 높게 나타났다. 도약 시 지면반력의 좌우힘은 좌우발 모두 두 번째 회전점프에서 왼발은 외측힘, 오른발은 내측힘이 강하게 나타났고, 전후힘은 오른발에서 첫 번째 회전점프 시 전방힘이 강하게 나타났으며, 수직힘은 좌우발 모두 차이가 없었다. 착지 시 전후힘은 왼발에서 두 번째 착지에서 후방힘이 강하게 나타났고, 오른발은 왼쪽 시각 사용에서 후방힘이 강하게 나타났다. 수직힘은 왼발에서 두 번째 착지, 오른발은 첫 번째 착지에서 강하게 나타났다.