• 한국운동역학회지
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• 제20권2호
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• pp.129-137
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• 2010

The purpose of this study is to investigate the effect of a 12-week aquatic exercise on obstacle gait in older women. Originally, 20 healthy female elderly participated this study but 12 of them completed the program. All participants were trained in the aquatic exercise program by an authorized trainer. They had come to the authors' lab three times during training period(0, 6, 12 weeks) and performed obstacle gait with three different height(0, 30, and 50% of leg length). After performed 3-Dimensional motion analysis following results were found. (1) For the CV, MVHC, TC, HC, statistically significances were shown in obstacle height. Although significant training effects were not shown, all variables showed typical patterns and it was considered as efficient motion to overcome the height obstacles. (2) The anterior-posterior and vertical GRF of support leg during support phase were revealed in height effect but in training one. However, differences between Peak 1 and Peak 2 in vertical GRF increased as training period increased. (3) Knee and hip resultant joint moments were affected by training but ankle resultant moments remained unchanged.

• 산업경영시스템학회지
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• 제40권3호
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• pp.66-75
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• 2017

Priority disciplines are an important scheme for service systems to differentiate their services for different classes of customers. (N, n)-preemptive priority disciplines enable system engineers to fine-tune the performances of different classes of customers arriving to the system. Due to this virtue of controllability, (N, n)-preemptive priority queueing models can be applied to various types of systems in which the service performances of different classes of customers need to be adjusted for a complex objective. In this paper, we extend the existing (N, n)-preemptive resume and (N, n)-preemptive repeat-identical priority queueing models to the (N, n)-preemptive repeat-different priority queueing model. We derive the queue-length distributions in the M/G/1 queueing model with two classes of customers, under the (N, n)-preemptive repeat-different priority discipline. In order to derive the queue-length distributions, we employ an analysis of the effective service time of a low-priority customer, a delay cycle analysis, and a joint transformation method. We then derive the first and second moments of the queue lengths of high- and low-priority customers. We also present a numerical example for the first and second moments of the queue length of high- and low-priority customers. Through doing this, we show that, under the (N, n)-preemptive repeat-different priority discipline, the first and second moments of customers with high priority are bounded by some upper bounds, regardless of the service characteristics of customers with low priority. This property may help system engineers design such service systems that guarantee the mean and variance of delay for primary users under a certain bounds, when preempted services have to be restarted with another service time resampled from the same service time distribution.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.132-135
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• 2002

In the present study, an electro-mechanical KAFO (knee-ankle-foot orthosis) which satisfies both the stability in stance and the knee flexion in swing was developed and evacuated in eight polio patients. A knee joint control algorithm suitable for polio patients who are lack of the stability in pre-swing was also developed and various control systems and circuits were also designed. In addition, knee flexion angles and knee moments were measured and analyzed for polio patients who used the developed KAFO with the three-dimensional motion analysis system. Energy consumption was also evaluated for the developed KAFO by measuring the movement of the COG (center of gravity) during gait. From the present study, the designed foot switch system successfully determined the gait cycle of polio patients and controlled knee joint of the KAFO, resulting in the passive knee flexion or foot clearance during swing phase. From the three-dimensional gait analysis for polio patients, it was found that the controlled-knee gait with the developed electro-mechanical KAFO showed the knee flexion of 40$^{\circ}$∼45$^{\circ}$ at an appropriate time during swing. Vertical movements of COG in controlled-knee gait (gait with the developed electro-mechanical KAFO) were significantly smaller than those in looked knee gait(gait with the locked knee Joint). and correspondingly controlled-knee gait reduced approximately 40% less energy consumption during horizontal walking gait. More efficient gait patterns could be obtained when various rehabilitation training and therapeutic programs as well as the developed electro-mechanical KAFO were applied for polio patients.

• 한국운동역학회지
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• 제19권1호
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• pp.27-36
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• 2009

본 연구에서는 수직점프시 몸통운동의 제약이 수직점프의 수행에 미치는 영향을 알아보기 위해 10명의 성인 남성을 대상으로 몸통을 자유롭게 사용한 일반적인 형태와 몸통동작을 제한한 형태의 수직점프를 비교, 분석하였다. 분석 결과 몸통동작을 제한한 경우 비 제약점프에 비해 10% 정도의 수행 손실이 있었는데, 이는 이지 순간의 중심 높이보다는 이 지속도의 차이에 의해 발생하였다. 몸통의 운동은 엉덩관절의 모멘트 파워를 증가시켜 추진의 초기 시점부터 지면반력의 증가에 기여하였는데 이러한 요인이 수행력 증가의 주요한 요인으로 작용하였다. 반면 몸통운동이 제한된 점프에서는 엉덩관절에서의 역학적 출력의 감소를 보상하는 측면에서 무릎관절의 역할이 증가하였으나 충분치 못하였다. 또한 몸통동작의 제한으로 엉덩관절 무릎관절 발목관절의 순차적인 신전패턴과는 상이하게 추진시점 직후 엉덩관절과 무릎관절이 동시에 신전하는 형태의 점프가 이루어져 협응패턴의 변화가 나타났다. 결국 본 연구의 결과 몸통의 적절한 사용은 수직점프의 수행 향상에 효과적으로 기여하는 것으로 나타났다.

• 한국운동역학회지
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• 제19권4호
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• pp.637-645
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• 2009

이 연구는 여성노인의 태권에어로빅스 12주 훈련 후 앞굽이 몸통지르기 동작시 하지관절의 생체역학적 변화를 구명하는 것이다. 대상자는 여성노인 10명이 참여하였으며 카메라(MCU-240) 7대와 지면반력기(Kist1er-9286AA) 2대를 이용하여 데이터를 수집하였다. 유의수준 .10에서 운동전 후 차이는 다음과 같다. 첫째, 최소 관절각의 변화는 발목의 저측/배측굴곡(왼쪽, $p=0.001^*$), 외번/내번(양쪽, $p=0.009^*$, $p=0.04^*$)과 무릎의 외전/내전(왼쪽, $p=0.04^*$) 및 엉덩이의 내측/외측 회전(양쪽, $p=0.07^*$, $p=0.02^*$)에서 통계적으로 유의하게 나타났다. 둘째, 최대 관절모멘트 변화는 발목관절의 외번/내번 모멘트(양쪽, $p=0.05^*$, $p=0.05^*$), 무릎관절의 외전/내전 모멘트(왼쪽, $p=0.08^*$) 및 엉덩이관절의 내측/외측 회전 모멘트(오른쪽, $p=0.09^*$)가 통계적으로 유의하게 나타났다. 셋째, 최대 관절파워의 변화는 엉덩이관절의 굴곡/신전(양쪽, $p=0.05^*$, $p=0.01^*$)과 내전/외전(양쪽, $p=0.02^*$, $p=0.00^*$) 및 무릎의 내전/외전(왼쪽, $p=0.00^*$) 파워가 통계적으로 유의한 차이를 보였다. 결론적으로 태권에어로빅스 몸통지르기동작이 여성노인들의 하지 관절에 부분적인 생체변화를 일으켰다.

• 한국운동역학회지
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• 제22권3호
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• pp.325-332
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• 2012

This study aimed to analyze the effects of external load between male and female on angular velocity, moment, and absorbed energy of the lower-extremity joints during drop landing. The study subjects were 9 male($mass=70.82{\pm}4.64kg$, $height=1.71{\pm}0.04m$, $age=24.5{\pm}1.84years$), 9 female($mass=50.14{\pm}4.09kg$, $height=1.61{\pm}0.03m$, $age=23.6{\pm}2.62years$), without any serious musculoskeletal, coordination, balance, or joint/ligament problems for 1 year before the study. The angular velocity, flexion/extension and abduction/adduction moments, and absorbed energy of the lower-extremity joints were compared between the men and women during drop landing under 4 different conditions of external load(0%, 8%, 16%, and 24%) by using two-way repeated ANOVA(p < .05). The women landed with a greater peak angular velocity of the ankle joint, greater peak inversion moment, and lower peak hip-extension moment than the men did, under all 4 conditions. Additionally, the landing characteristics of the women were distinct from those of the men; the women showed a greater peak knee-adduction moment and greater absorbed energy of the knee joint. These differences indicate that anterior cruciate ligament(ACL) strain was greater in the women than in the men and therefore, women may be at a higher potential risk for noncontact injuries of the ACL with an increase in external load.

• 한국운동역학회지
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• 제20권1호
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• pp.13-23
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• 2010

The purposes of this study was to investigate the biomechanical influence of the walking shoe with a plate spring in the heel and interchangeable heel cushioning elements. Eighteen subjects walked in three conditions: 1) the walking shoes Type A-1 with a soft heel insert, 2) the Type A-2 shoe with a stiff heel insert, 3) a general walking shoe(Type B). Ground reaction forces, leg movements, leg muscle activity and ankle, knee and hip joint loading were measured and calculated during overground walking. During walking, the ankle is a few degrees more dorsiflexed during landing and the knee is slightly more flexed during takeoff with the Type A shoes. As a result of the changes in the walking movement, the ground reaction forces are applied more quickly and the peak magnitudes are higher. Muscle activity of the quadricep, hamstring and calf muscles decrease during the first 25% of the stance phase when walking in the Type A shoes. The resultant joint moments at the ankle, knee and hip joints decrease from 30-40% with the largest reductions occurring during landing.

• Journal of the Korean Wood Science and Technology
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• 제19권1호
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• pp.22-30
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• 1991

This study was carried out to determine the Joint characteristic of L-type specimens. L-type specimens were made of two kinds uf solid woods(Antiaris, Sepetir) and three kinds of wood based materials(plywood, particleboard, medium density fiberboard). They were constructed with PVC anchor and screw, and were discussed with joint strength and stiffness coefficients. The obtained results were as follows: 1. Bending strength showed very high increasing rate from one to three used PVC anchor and screw but was a little rise from three to four used PVC anchor and screw in solid wood. However. in wood based materials, it was unchanged without increasing rate or slight decreased from three to four used PVC anchor and screw. 2. The stiffness coefficients, or Z-values, were in the range from $4.704\times10^{-4}$ to $1.864\times10^{-3}$(rad/kgf-cm). They showed $10^{-3}$ level in one PVC anchor and screw but $10^{-4}$ level in two, three. four PVC anchor and screw. Accordingly, they indicated flexible joints in one PVC anchor and screw and relatively stable joints in two, three. four PVC anchor and screw. 3. Measured ultimate bending moments were 258.70kgf-cm in plywood and 142.68kgf-cm in medium density fiberboard. 4. Comparing with dowel joint. the joint strength used PVC anchor screw was inferior to 8mm and 10mm dowel diameter but differ little from 6mm dowel diameter.

• 한국운동역학회지
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• 제33권4호
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• pp.164-174
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• 2023

Objective: The aim of this study was to quantitatively analyze the impact characteristics of the lower extremity on strike pattern during running. Method: 19 young subjects (age: 26.53 ± 5.24 yrs., height: 174.89 ± 4.75 cm, weight: 70.97 ± 5.97 kg) participated in this study. All subjects performed treadmill running with fore-foot strike (FFS), mid-foot strike (MFS), and rear-foot strike (RFS) to analyze the impact characteristics in the lower extremity. Impact variables were analyzed including vertical ground reaction force, lower extremity joint moments, impact acceleration, and impact shock. Accelerometers for measuring impact acceleration and impact shock were attached to the heel, distal tibia, proximal tibia, and 50% point of the femur. Results: The peak vertical force and loading rate in passive portion were significantly higher in MFS and FFS compared to FFS. The peak plantarflexion moment at the ankle joint was significantly higher in the FFS compared to the MFS and RFS, while the peak extension moment at the knee joint was significantly higher in the RFS compared to the MFS and FFS. The resultant impact acceleration was significantly higher in FFS and MFS than in RFS at the foot and distal tibia, and MFS was significantly higher than FFS at the proximal tibia. In impact shock, FFS and MFS were significantly higher than RFS at the foot, distal tibia, and proximal tibia. Conclusion: Running with 3 strike patterns (FFS, MFS, and RFS) show different impact characteristics which may lead to an increased risk of running-related injuries (RRI). However, through the results of this study, it is possible to understand the characteristics of impact on strike patterns, and to explore preventive measures for injuries. To reduce the incidence of RRI, it is crucial to first identify one's strike pattern and then seek appropriate alternatives (such as reducing impact force and strengthening relevant muscles) on that strike pattern.

• 한국운동역학회지
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• 제25권2호
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• pp.191-198
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• 2015

Objective : The purpose of this study was to conduct biomechanical analysis of varying backpack loads on the lower limb movements during downhill walking over $-20^{\circ}$ ramp. Method : Thirteen male university students (age: $23.5{\pm}2.1yrs$, height: $175.7{\pm}4.6cm$, weight: $651.9{\pm}55.5N$) who have no musculoskeletal disorder were recruited as the subjects. Each subject walked over $20^{\circ}$ ramp with four different backpack weights (0%, 10%, 20% and 30% of body weight) in random order at a speed of $1.0{\pm}0.1m/s$. Five digital camcorders and two force plates were used to obtain 3-d data and kinetics of the lower extremity. For each trial being analyzed, five critical instants were identified from the video recordings. Ground reaction force, loading rate, decay rate, and resultant joint moment of the ankle and the knee were determined by the inverse dynamics analysis. For each dependent variable, one-way ANOVA with repeated measures was used to determine whether there were significant differences among four different backpack weight conditions (p<.05). When a significant difference was found, post hoc analyses were performed using the contrast procedure. Results : The results of this study showed that the medio-lateral GRFs at RHC in 20% and 30% body weight were significantly greater than the corresponding value in 0% of body weight. A consistent increase in the vertical GRFs as backpack loads increased was observed. The valgus joint movement of the knee at RTO in 30% body weight was significantly greater than the corresponding values in 0% and 10% body weight. The increased valgus moment of 30% body weight observed in this phase was associated with decelerating and stabilizing effects on the knee joint. The results also showed that the extension and valgus joint moments of the knee were systematically affected by the backpack load during downhill walking. Conclusion : Since downhill walking while carrying heavy external loads in a backpack may lead to excessive knee joint moment, damage can occur to the joint structures such as joint capsule and ligaments. Therefore, excessive repetitions of downhill walking should be avoided if the lower extremity is subjected to abnormally high levels of load over an extended period of time.