• 한국운동역학회지
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• 제17권1호
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• pp.29-39
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• 2007

This study were obtained elapsed time phase-by-phases, displacement, user angle, velocity and angular velocity to analyse kinematically contributing factors at impact of forehand drive motion, on targeting three male players. The results of the study were presented as follows; In the forehand drive swing, the elapsed time by phases was a total of .52 seconds: .30 seconds from backswing to impact and .22 seconds from impact to follow-through, Considering the mean change in locations of COM of each(part$\rightarrow$body segment) at impact, racket head, left shoulder, right wrist and left hip, the left-right directions(X-axis) were showm to be each $.61{\pm}.03$, $1.19{\pm}.08$, $.66{\pm}.03$, $.94{\pm}.06$, and $.45{\pm}.03m$. The displacement differences of COM of each body segment were shown to be -.57, -.05, -.33, and .16m. For the vertical direction(Z-axis), the center of mass was lowest at impact and highest at E3. For the displacement of the right wrist on the left hip, the right wrist moved to .82m to the lower direction without change in the locations of the hip from E1 from E2. When the left hip moved .02m from E2 to E3, the right wrist moved .7m in the upper direction. In respect to the velocity of each body segment, the hip and the shoulder joint accelerated and then the wrist followed. Then the right wrists of all the subjects and their racket heads showed maximum speed, and an effective swing was observed. At the angle of each part, the angle of the right wrist was the smallest at the backswing and the largest at the moment of the impact. Then it increased gradually in the follow-through section. In respect of angular velocity for subject A, the hip moved and the largest change occurred. Immediately before the impact, the subject made a swing using his right wrist, his hip, and the shoulder joint, showing the maximum value, which was judged to be effective.

• The Journal of Korean Physical Therapy
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• 제35권4호
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• pp.111-116
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• 2023

Purpose: Pneumoconiosis is a chronic lung disease in which the lungs become hardened due to the accumulation of fine mineral dust that has been breathed in at industrial sites. The lungs are unable to function properly, resulting in complications of several respiratory diseases. Methods: The subjects were 36 elderly adults (pneumoconiosis patients 18, healthy elderly 18) over the age of 65 years. The respiratory function was assessed using a spirometer to measure forced vital capacity (FVC), first second of forced expiration (FEV1), FEV1/FVC, and peak expiratory flow n(PEF). The static balance function test was determined by the center of mass (COM), ankle angle range, hip angle range, sway parameters, and reciprocal compensatory index (RCI). Cognitive function was measured by applying MoCA-k. Results: Comparison of respiration functions between the two groups showed statistically significant differences in FVC, FEV1, FEV1/FVC, and PEFs (p<0.05). Cognitive abilities showed statistically significant differences due to higher cognitive skills in the control group as compared to the patient group (p<0.05). Most results of the static balance capability measurements showed statistically significant differences between the groups (p<0.05). However, no statistically significant differences were obtained for COM AP Range, Angle AP Range, RCI ML Range, and AP Range (p>0.05). Conclusion: The results of the current study indicate that patients suffering from pneumoconiosis have less cognitive ability and balance function as compared to healthy elderly people. Therefore, we expect an improvement in the balance ability and cognitive function through systematic management and strengthening lung function training to improve the quality of life of pneumoconiosis patients.

• 한국운동역학회지
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• 제17권4호
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• pp.89-98
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• 2007

The purpose of this study was to evaluate the trunk motion and knee joint moment during deep stand to sit and sit to stand according to the trunk weight increase. These experimental subjects were 9 males, who had no skeletal muscular disease. They were performed a SATS(stand to sit), STS(sit to stand) according to the trunk weight increase. Trunk weight increase were classified into 4 bearing trunk weight of 0%, 8%, 16%, 24% of the subject' weight. 1-way(4) RM ANOVA is applied to get the difference of trunk displacement movements and knee joint moments according to he trunk weight increase. significant level of each experiment is set as $\alpha$=.05. 1. Significant difference was classified into 3 bearing trunk weight of 0%, 16%, 24% in maximum forward backward displacement of trunk COM(center of mass). Significant difference was classified into 4 bearing trunk weight of 0%, 8%, 16%, 24% in maximum upward downward displacement of trunk COM during the SATS, STS. 2. Significant difference was classified into 4 bearing trunk weight of 0%, 8%, 16%, 24% in maximum extension knee joint moment. Significant difference was classified into 2 bearing trunk weight of 0%, 16% in maximum internal rotation knee joint moment during the SATS, STS. Therefore we expect that biomechanical model of this study will used to study for mechanical characteristics of obese people.

• 한국운동역학회지
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• 제19권1호
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• pp.87-98
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• 2009

본 연구는 남자고등학생 숙련자와 비 숙련자의 던지기 동작을 역학적으로 비교 분석하기 위해 3차원 영상분석 및 지면반력분석을 수행하였다. 연구 결과 숙련자는 공 던지기 동작의 총 소요 시간이 비숙련자보다 짧게 나타났으며, 숙련자는 (1) 왼발 착지 시 신체중심의 수평속도 (2) 전 구간에서 전완 분절의 수평속도 (3) 착지 시 손 분절의 수평속도가 비숙련자보다 빠르게 나타난 반면, 비숙련자는 (1) 착지이후에 신체중심의 수평속도 (2) 왼발이 지면에 닿는 시점에서 손 분절의 수평속도가 숙련자보다 빠르게 나타났다. 전후경각도에서 숙련자는 전 구간에서 후경자세를 취하는 것으로 나타났으나, 비 숙련자는 릴리즈 전까지는 후경자세를 취하다 릴리즈 순간에서는 전경자세를 취한 형태에서 릴리즈를 하는 것으로 나타났다. 또한 숙련자는 공 던지기 동작에서 (1) 어깨각도 (2) 이지 후 오른발의 착지에서 팔꿈치 각도 (3) 최대수직지면반력 (4) 오른발의 착지 시 최대전후지면반력이 비숙련자보다 크게 나타났다. 이와 같은 결과에서 숙련자는 비숙련자보다 안정된 자세로 신체의 중심을 후방에 위치시키는 후경자세를 유지하고 신체의 중심이동을 부드럽게 전환하는 효과적인 던지기 동작이 이루어짐을 알 수 있다.

• 한국운동역학회지
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• 제16권2호
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• pp.1-8
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• 2006

The purpose of this study was to evaluate normalized jerk according to shoes, slope, and velocity during walking. Eleven different test subjects used three different types of shoes (running shoes, mountain climbing boots, and elevated forefoot walking shoes) at various walking speeds(1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 2.11, 2.33m/sec) and gradients(0, 3, 6, 10 degrees) on a treadmill. Since there were concerns about using the elevated forefoot shoes on an incline, these shoes were not used on a gradient. Motion Analysis (Motion Analysis Corp. Santa Rosa, CA USA) was conducted with four Falcon high speed digital motion capture cameras. Utilizing the maximum smoothness theory, it was hypothesized that there would be differences in jerk according to shoe type, velocity, and slope. Furthermore, it was assumed that running shoes would have the lowest values for normalized jerk because subjects were most accustomed to wearing these shoes. The results demonstrated that elevated forefoot walking shoes had lowest value for normalized jerk at heel. In contrast, elevated forefoot walking shoes had greater normalized jerk at the center of mass at most walking speeds. For most gradients and walking speeds, hiking boots had smaller medio-lateral directional normalized jerk at ankle than running shoes. These results alluded to an inverse ratio for jerk at the heel and at the COM for all types of shoes. Furthermore, as velocity increased, medio-lateral jerk was reduced for all gradients in both hiking boots and running shoes. Due to the fragility of the ankle joint, elevated forefoot walking shoes could be recommended for walking on flat surfaces because they minimize instability at the heel. Although the elevated forefoot walking shoes have the highest levels of jerk at the COM, the structure of the pelvis and spine allows for greater compensatory movement than the ankle. This movement at the COM might even have a beneficial effect of activating the muscles in the back and abdomen more than other shoes. On inclines hiking boots would be recommended over running shoes because hiking boots demonstrated more medio-lateral stability on a gradient than running shoes. These results also demonstrate the usefulness of normalized jerk theory in analyzing the relationship between the body and shoes, walking velocity, and movement up a slope.

• 한국운동역학회지
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• 제20권3호
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• pp.319-325
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• 2010

The purpose of this research was to investigate the differences in the ski carving turn motion according to level of expertise. The posture and movement of 6 skiers nearby the fall-line was evaluated with a biomechanical approach focusing the rotational mechanics. The slope was at an angle of $9^{\circ}$ and the following variables were measured and calculated: tangential velocity, change of COM height after passing fall-line, width between feet, angle between upper body and thigh, trunk angle, average radius of curvature and average centripetal force. The expert skiers minimized their center of mass height movement and maintained the width of between their feet after the passing the fall-line in comparison with the beginners and intermediate skiers. The experts restrained themselves from pushing their upper body downward after the turn to maximize the centripetal force. The experts in comparison with the beginners and intermediate skiers during the turn didn't have to reduce their radius of curvature to maintain a high centripetal force. It was concluded, that the most important factor affecting the centripetal force, was for the beginners and intermediate skiers, to minimize their movement while using the appropriate amount of edging.

• 한국운동역학회지
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• 제20권1호
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• pp.49-55
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• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.

• 대한의용생체공학회:의공학회지
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• 제35권2호
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• pp.26-34
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• 2014

Little information is available about the characteristics in revolution gait of hemiplegic elderly, which is frequently represented in daily life. It is also hard to elucidate purely the characteristics due to hemiplegia because of no consideration of aging factors. The aim of study is to identify the alteration characteristics of lower extremity joint angles in both straight and revolution gaits together due to hemiplegia through comparing healthy with hemiplegic elderly. Following Institutional Review Board approval, twelve healthy and hemiplegic elderly were participated and the center of body mass (COM) and lower extremity joint angles were measured during straight and revolution gaits using a computer-aided video motion capture system. The results showed that the gait characteristics were generally altered in both straight and revolution gaits due to hemiplegia (p < 0.05). The gait characteristics were then different between the straight and revolution gaits each other. This study may be valuable by identifying for the first time the alterations of the lower extremity joint angles in both straight and revolution gaits due to pure hemiplegia through comparing healthy elderly with hemiplegic elderly.

• 한국정밀공학회지
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• 제29권4호
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• pp.417-425
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• 2012

This paper presents reference ZMP trajectory generation and implementation for a biped robot via linear inverted dumbbell model (LIDM), which can consider the effect of external momentum on the center of mass (COM) of robot. Based on a reference ZMP trajectory derived by using LIDM, a base trajectory is proposed not only to make the locomotion of robot similar to that of human but also to facilitate its implementation and tuning. In order to realize a dynamic walking using the proposed trajectory, compliance, impedance and ZMP tracking controllers are adopted together. Extensive experiments show that the proposed locomotion of a biped robot is stable and also, similar to that of human. Further researches on balance recovery of a biped robot will be carried out to guarantee its robust locomotion in combination with the proposed trajectory.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1787-1792
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• 2016

Previous walking pattern generation methods could generate walking patterns that allow only straight walking on flat and uneven terrain. They were unable to generate modifiable walking patterns whereby the sagittal and lateral step lengths and walking direction can be changed at every footstep. This paper proposes a novel walking pattern generation method to realize modifiable walking of humanoid robots on unknown uneven terrain. The proposed method employs a walking pattern generator based on the 3-D linear inverted pendulum model (LIPM), which enables a humanoid robot to vary its walking patterns at every footstep. A control strategy for walking on unknown uneven terrain is proposed. Virtual spring-damper (VSD) models are used to compensate for the disturbances that occur between the robot and the terrain when the robot walks on uneven terrain with unknown height. In addition, methods for generating the foot and vertical center of mass (COM) of the 3-D LIPM trajectories are developed to realize stable walking on unknown uneven terrain. The proposed method is implemented on a small-sized humanoid robot platform, DARwIn-OP and its effectiveness is demonstrated experimentally.