• Interaction and multiscale mechanics
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• 제5권1호
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• pp.75-90
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• 2012

This paper investigates the effects of sports ground materials on the transfer characteristics of the landing impact force using a coupled foot-shoe-ground interaction model. The impact force resulting from the collision between the sports shoe and the ground is partially dissipated, but the remaining portion transfers to the human body via the lower extremity. However, since the landing impact force is strongly influenced by the sports ground material we consider four different sports grounds, asphalt, urethane, clay and wood. We use a fully coupled 3-D foot-shoe-ground interaction model and we construct the multi-layered composite ground models. Through the numerical simulation, the landing impact characteristics such as the ground reaction force (GRF), the acceleration transfer and the frequency response characteristics are investigated for four different sports grounds. It was found that the risk of injury, associated with the landing impact, was reduced as the ground material changes from asphalt to wood, from the fact that both the peak vertical acceleration and the central frequency monotonically decrease from asphalt to wood. As well, it was found that most of the impact acceleration and frequency was dissipated at the heel, then not much changed from the ankle to the knee.

• 한국운동역학회지
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• 제15권2호
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• pp.103-111
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• 2005

The purpose of this study was to analysis golf swing in accordance with each club using ground reaction force data. The subject of this study was current professional golf players in Korea. Golf clubs used for this study were driver, iron4, iron7, and pitching. The ground reaction force for left and right foot was collected by one Kistler and one Bertec force platforms. Also collected visual data by NC high speed camera to check the phase which was composed of address, top of backswing, impact and finish. Sampling rate was 600Hz both ground reaction forces data and visual data. The conclusion are as follows. 1. An aspect of change for ground reaction force was that the weight between the left foot and right foot were contrary to each other in general as the phase. 2. Without regard to the type of golf club, the ratio of necessary ground reaction forces for each phase in accordance with address, top of backswing, impact, and finish was comparatively identical. 3. According to the type of golf club, the tendency of Fy was not varied. In terms of Driver, at the moment of impact, the weight of foot-both right and left-was moved to the movement direction of golf because of the rotation force from swing.

• The Korean Journal of Physiology
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• 제18권1호
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• pp.81-96
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• 1984

As the crippled persons work mostly in a sitting position and would be engaged in a foot-pressing job, it is necessary to assess their degree of participation of important muscles in various modes of foot activities. In this regard, it deems to be urgent to establish the reference standards for healthy persons. The present study has been undertaken to determine the degree of participation of the M. tibialis anterior, M. gastrocnemius and M. soleus in heel pressing, foot-flat pressing and forefoot pressing motion under varying forces, and in order to compare the electrical activities of three muscles with each other, and to analyse the time sequence between force and appearance or disappearance of EMG recording. Sixty-three healthy young women ranging from age of 18 to 23 were examined. The results obtained were as follows: 1. Participation of three muscles in foot movement under varying forces: A) Both gastrocnemius muscles or left soleus muscle did not contribute to heel pressing motion. Activity of both tibialis anterior muscles was the greatest among three muscles at heel pressing motion and the degree of their activities was proportional to force. B) Activities of left tibialis anterior muscle and both gastrocnemius muscles were negligible under 3 kg force at foot-flat pressing movement. Left gastrocnemius muscle did not contribute to foot-flat pressing under 6 or 9 kg force. Although activities of both soleus muscles and both tibialis anterior muscles were small, the degree of their activities increased with force at foot-flat pressing movement. C) Activities of both tibialis anterior muscles were negligible under 3 kg force at forefoot pressing motion. Activity of both soleus muscles was the greatest among 3 muscles and the degree of their activities increased with force at forefoot pressing motion. Both tibialis anterior muscles participated in forefoot pressing motion with severe exertion. 2. Electrical activities by foot movement under varying forces : A) Electrical activities were prominent in both tibialis anterior muscles and the level of their activities was linear with force at heel pressing motion. The degree of participation of both soleus muscles was small at heel pressing motion. B) Electrical activity of tibialis anterior muscle was the greatest among 3 muscles at foot-flat pressing movement and was followed by that of soleus muscle. Level of electrical activities increased with force in left soleus muscle and right tibialis anterior muscle at foot-flat pressing movement. C) Electrical activity of both soleua muscles was the greatest among 3 muscles at forefoot pressing movement and that of tibialis anterior muscle was next to soleus muscle. Level of electrical activities was proportional to force in left tibialis anterior muscle, right gastrocnemius muscle and both soleus muscles at forefoot pressing movement. 3. Time between starting signal and initiation of contraction of heel pressing and forefoot pressing motion in 3 muscles was longer than that of foot-flat pressing movement. Time of relaxation in 3 muscles was longer than that of contraction under varying forces. EMG recording appeared before initiation of contraction in both tibialis anterior muscles at heel pressing motion and in both soleus muscles at forefoot pressing movement under varying forces. Time of initiation of contraction was similar in both sides of tibialis anterior muscles under varying forces and time of onset of contraction at foot-flat pressing motion was the shortest. 4. Forefoot pressing movement would be encouraged in paralysis of tibialis anterior muscle, while heel pressing motion would be encouraged in paralysis of triceps surae muscle.

• 한국운동역학회지
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• 제27권1호
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• pp.25-33
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• 2017

Objective: The purpose of this research was to establish the differences of ground reaction force variables and sensations according to the foot types and the structures of the inner arch support band during $2^{nd}$ vertical ballet jump. Method: 12 Female ballet majors in their twenties who have danced for more than 10 years and had no injuries were selected for this research. Independent variables consist of the foot type (pes rectus, pes planus) and the structure of the inner arch support band (no band, x-shaped, linear shaped). Dependent variables consist of ground reaction force variables and relative wearing sensation. Results: The impact decreased the most when x-shaped bands were used on pes rectus and rigid pes planus. When linear-shaped bands were used on flexible pes planus, the impact decreased. Conclusion: The bands also helped reduce the impact on pes rectus. Furthermore, it is clear that according to the foot type, the impact reducing band structures perform differently. The inner arch support bands were necessary for jump training for any foot type.

• 로봇학회논문지
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• 제5권1호
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• pp.48-54
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• 2010

Ankle-foot orthosis with a pneumatic rubber actuator, which is intended for the assistance and the enhancement of ankle muscular activities was developed. In this study, the effectiveness of the system was investigated during plantarflexion motion of ankle joint. To find a effectiveness of the system, the subjects performed maximal voluntary isokinetic plantarflexion contraction on a Biodex-dynamometer. Plantarfexion torque of the ankle joint is assisted by subject's soleus muscle that is generated when ankle joint do plantarflexion motion. We used the muscular stiffness signal of a soleus muscle for feedback control of ankle-foot orthosis as physiological signal. For measurement of this signal, we made the muscular stiffness force sensor. We compared a muscular stiffness force of a soleus muscle between with feedback control and without it and a maximal plantarflexion torque between not wearing a ankle-foot orthosis, without feedback control wearing it and with feedback control wearing it in each ten elderly adults. The experimental result showed that a muscular stiffness force of a soleus muscle with feedback control was reduced and plantarflexion torque of an ankle joint only wearing ankle-foot orthosis was reduced but a plantarflexion torque with feedback control was increased. The amount of a increasing with feedback control is more higher than the amount of a decreasing only wearing it. Therefore, we confirmed the effectiveness of the developed ankle-foot orthosis with feedback control.

• 한국운동역학회지
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• 제15권3호
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• pp.31-49
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• 2005

The purpose of this study was to analyze the weight transfer patterns under the different golf swing types which are full swing control swing and putting stroke. Two women golfers participated in this study, one(165cm, 94.3kg)being classified as a low-handicap(LH)player, the other(165cm, 54.5kg) being classified as a high-handicap(HH) player. Both players are right-handed. Two force plates(Kistler, 9286AA) were synchronized with a motion capture system(Qualisys ProReflex MCU240). Anteriorposterior, mediolateral, and vertical forces were used as an indicator of the pattern of swing. Four discrete positions which are address, top of backswing impact, and finish were identified as an event and three phases which are backswing downswing, and follow-through between he events were also identified. The results showed that, at impact, the total force was 1.24BW ring the full swing 1.17BW during the control stroke, 1.00BW during the putting stroke. Depending on the golf swing types, the differences are existed. At impact, the distribution of forces is different with a low-handicap(LH) player and a high-handicap(HH) player. A LH player has 26% in right foot and 74% in left foot during the full swing 49% in right foot and 51% in left foot during the control swing 49% in right foot and 51% in left foot during the putting stroke. A HH, on the other hand, has 74% in right foot and 26% in left foot during the full swing 62% in right foot and 38% in left foot during the control swing 54% in right foot and 46% in left foot during the putting stroke. From address to top of backswing the amount of vertical forces are changed 43:57(right foot: left foot) to 76:24 during the full swing 47:53(right foot: left foot) to 75:25 during the control swing 50:50(right foot: left foot) to 54:46 during the putting stroke. The biggest weight transfer pattern took place in full swing and the control swing is next, and the putting stroke is the final.

• Structural Engineering and Mechanics
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• 제66권1호
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• pp.1-14
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• 2018

Column is usually floating on the stone base directly with or without positioning tenon in traditional Chinese timber structure. Vertical load originated by the heavy upper structure would induce large friction force and compression force between interfaces of column foot and stone base. This study focused on the mechanical behaviors of column foot joint with consideration of the influence of vertical load. Mechanism of column rocking and stress state of column foot has been explored by theoretical analysis. A nonlinear finite element model of column foot joint has been built and verified using the full-scale test. The verified model is then used to investigate the mechanical behaviors of the joint subjected to cyclic loading with different static vertical loads. Column rocking mechanism and stress distributions of column foot were studied in detail, showing good agreement with the theoretical analysis. Mechanical behaviors of column foot joint and the effects of the vertical load on the seismic behavior of column foot were studied. Result showed that compression stress, restoring moment and stiffness increased with the increase of vertical load. An appropriate vertical load originated by the heavy upper structure would produce certain restoring moment and reset the rocking columns, ensuring the stability of the whole frame.

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

• 한국운동역학회지
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• 제26권4호
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• pp.343-351
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• 2016

Objective: The purpose of this study was to help improve game performance and provide preliminary data to enhance the efficiency of the kick and stability of the support foot by comparing the kinematic characteristics of the repeated side kick (geodeupyeopchagi) in poomsaeKoryo between expert and non-expert groups. Method: The subjects were divided into 2 groups according to proficiency in Taekwondo, an expert group and a non-expert group (n = 7 in each group), to observe the repeated side-kick technique. Four video cameras were set at a speed of 60 frames/sec and exposure time of 1/500 sec to measure the kinematic factors of the 2 groups. The Kwon3D XPprogramas used to collect and analyze three-dimensional spatial coordinates. Ground reaction force data were obtained through a force plate with a 1.200-Hz frequency. An independent samplesttest was performed, and statistical significance was defined as .05. The SPSS 18.0 software was used to calculate the mean and standard deviation of the kinematic factors and to identify the difference between the experts and non-experts. Results: The angular displacement of the hip joint in both the expert and non-expert groups showed statistical significance on E1 and E4 of the left support foot and E5 of the right foot (p<.05). The angle displacement of the knee joint in both groups showed statistical significance on E4 of the left support foot, and E1 and E2 of the right foot (p<.05). The angular velocity of the lower leg in both groups showed no statistical significance on the left support foot but showed statistical significance on E2 and E6 of the right foot (p<.05). The angular velocity of the foot in both groups showed no statistical significance on the left support foot but showed statistical significance on E2 of the right foot (p<.05). The vertical ground reaction force in both groups showed statistical significance on E2 (p<.05). The center of pressure in all directions in both groups showed statistical significance (p<.5). Conclusion: While performing the repeated side kick (geodeupyeopchagi), the experts maintainedconsistency and stability of the angle of the support leg while the kick foot moved high and fast. On the other hand, the angle of the support foot of non-experts appeared inconsistent, and the kick foot was raised, relying on the support leg, resulting in unstable and inaccurate movement.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.297-298
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• 2009