• 한국운동역학회지
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• 제22권1호
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• pp.25-34
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• 2012

The purpose of this study was to determine the effects of landing height on the lower extremity during a counter movement jump. Fourteen healthy male subjects (age: $27.00{\pm}2.94$ yr, height: $179.07{\pm}5.03$ cm, weight: $78.79{\pm}6.70$ kg) participated in this study. Each subject randomly performed three single-leg jumps after s single-leg drop landing (counter movement jump) on a force platform from a 20 cm and 30 cm platform. Paired t-test (SPSS 18.0; SPSS Inc., Chicago, IL) was performed to determine the difference in kinematics and kinetics according to the height. All significance levels were set at p<.05. The results were as follows. First, ankle and knee joint angles in the sagittal plane increased in response to increasing landing height. Second, ankle and knee joint angles in the frontal plane increased in response to increasing landing height. Third, there were no significant differences in the moment of each segment in the sagittal plane for the jumping height increment. Fourth, ankle eversion moment and knee valgus moment decreased but hip abduction moment increased for the jumping height increment. Fifth, Ankle and knee joint powers increased. In percentage contribution, the ankle joint increased but the knee and hip joints decreased at a greater height. Lastly, as jumping height increased, the power generation at the ankle joint increased. Our findings indicate that the height increment affect on the landing mechanism the might augment loads at the ankle and knee joints.

• 디지털융복합연구
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• 제14권6호
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• pp.513-518
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• 2016

다양한 연구결과에도 불구하고 전신진동운동이 인체에 미치는 기전은 명확히 제시되고 있지 않으며, 진동이 하지관절의 운동역학적 변화에 대해 분석한 연구는 미비한 실정이다. 그러므로 이 연구는 어떠한 하지관절의 운동역학적 변인이 수직점프 능력에 영향을 미치는지 분석하고자 한다. 최근 6개월간 하지에 정형외과적 병력이 없는 건강한 성인 남성 5명과 여성 5명은 5분간 30Hz의 전신진동운동을 실시한 전 후로 스쿼트 점프를 각각 3회씩 실시하였고, 수직점프 시 하지관절의 운동역학적 변화를 분석하기 위하여 3D 영상분석 시스템을 활용하였다. 대상자들의 스쿼트 점프 높이는 전신진동운동 처치 이후 향상되는 것으로 나타났으며, 발목과 무릎관절에서 하지관절 모멘트와 파워가 증가하는 것으로 나타났다. 그러나 지면반력 값과 엉덩관절의 모멘트와 파워는 전신진동운동의 처치 전 후에 통계적으로 유의한 차이가 나지 않는 것으로 나타났다. 30Hz의 전신진동운동을 실시한 결과 발목과 무릎관절은 진동이 인체내 긍정적인 영향을 미치는 것으로 나타났으나 엉덩관절의 경우 부정적인 영향을 미치는 것으로 나타났다.

• 대한기계학회논문집A
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• 제34권5호
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• pp.597-604
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• 2010

본 논문에서는 모바일하버의 하역 시스템으로 특화되어 개발한 제로 모멘트 크레인에 적용되는 조인트를 설계하고자 한다. 해당 조인트는 제로 모멘트 포인트의 개념에 기반하여 제로 모멘트 크레인을 안정화시키는데 중요한 역할을 수행한다. 이 목적을 위해서는 크고 다양한 형태의 하중을 견딜 수 있으며, 또한 2 방향의 자유도를 허용할 수 있어야 한다. 통상적인 설계 과정을 거쳐, 유니버셜 조인트와 스피리컬 조인트를 결합한 후 가변형 구름 요소를 적용한 새 디자인을 제안하였다. 구름 요소는 하중을 분산시키며 하역 과정 동안의 동력 손실을 줄여준다. 시스템의 복잡성과 최적화 과정의 효율성을 고려하여, 크리깅 기반 근사 최적화 기법을 선정하였다. 설계된 조인트를 검증하기 위해, 구조 해석을 수행하고, 축소 시제품을 제작하였다.

• 한국운동역학회지
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• 제22권3호
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• pp.305-314
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• 2012

The purpose of this study was to investigate the effects of joint kinetics and coordination on within-individual differences in maximum vertical jump. 10 male subjects aged 20 to 30 performed six trials in maximum vertical jump and with based on jump height the good(GP) and bad(BP) performances for each subject were compared on joint kinetics of lower extremity and coordination parameters such as joint reverse and relative phase. The results showed that maximum moment, power, and work done of hip joint and maximum moment of ankle joint in GP were significantly higher than that in the BP but no significant differences for the knee joint. We could observe a significant difference in joint reverse timing between both conditions. And also the relative phase on ankle-knee and ankle-hip in GP were significantly lower than that in the BP, which means that in GP joint movements were more in-phase synchronized mode. In conclusion, mechanical outputs of hip and ankle joints had an effect on within-individual differences in vertical jump and the inter-joint coordination and coordination including sequence and timing of joint motion also might be high influential factors on the performances within individual.

• Journal of Advanced Marine Engineering and Technology
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• 제28권2호
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• pp.382-392
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• 2004

The usage of constant velocity (CV) joint is effective for motorboats on gliding regime of the motion. During transition on the gliding when angle of the CV differs from null on driving and driven composite shafts there are moments of the second order. Excitation of oscillations of the second order moments occurs when driving shafts transmits a variable torque. which generates through CV joint a lateral moment acting on the bearing. As a result of oscillations from a resonating harmonic of a shafting the harmonic with the greater or periodically varying amplitude for power condition trough transferring to nominal power 144kW. Beating conditions coincide with third mode having frequency 45.486 Hz. In that case there is high increasing of the equivalent stresses. The forming of the stiffness of the composite material is concerned to use most orientation of the layer angle in the range of $\pm$60 degrees relatively of shaft axis. Application of that angles for layer orientation gives possibility to avoid high disturbance of the shafting for motorboat transition regime.

• 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.

• 한국전문물리치료학회지
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• 제25권3호
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• pp.19-26
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• 2018

Background: Genu varum is also known as bow leg. It is a deformity wherein there is lateral bowing of the legs at the knee. it does give rise to pain, and persistent bowing can often give rise to discomfort in knees, hips and ankles. Objects: This study investigated the effect of narrow squats on the knee joint during a gait and distance between the knees of person with genu varum. Methods: This study analyzed 23 patient with genu varum that grade III, 12 narrow squat group and 11 genenal squat group in motion analysis laboratory. The subjects of experiment took gait before and after intervention, the range of joint motion, moment of knee joint adduction, power, distance of the knees were measured. And in order to make an analysis between groups, an paiered t-test and independent t-test was carried out. For statistical significance testing, it was decided that significance level ${\alpha}$ be .05. Results: It was shown that the group of narrow squat exercise significantly decreased in distance of knees (p<.05),In moment of adduction of knee joint, it was shown to significantly decrease in two groups (p<.05), was significantly decreased in adduction, abduction, and rotation (p<.05). In relation of peak-knee adduction moment and valgus angle, there was significant decrease in narrow squat group (p<.05). Conclusion: When the above result of study were examined, a narrow squat exercise given to the genu varum patients significantly decreased the distance between the knees, range of knee adduction and abduction, knee adduction moment, knee power. And stability gains through the decrease of excursion of knee medial part be effective for the correction of genu varum deformation.

• 한국운동역학회지
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• 제24권1호
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• pp.59-66
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• 2014

The purpose of this study was to investigate the effects of knee joint muscle fatigue and overweight on shock absorption during single-leg landing of adult women. Written informed consent forms, which were approved by the human subject research and review committee at Dong-A University, were provided to all subjects. The subjects who participated in this study were divided into 2 groups: a normal weight group and an overweight group, consisting of 15 young women each. Both the normal weight group and the overweight group showed that use soft landing and ankle dominant strategy. The peak vertical ground reaction force, the knee joint absorption power, and eccentric work done, as the increase of knee joint muscle fatigue level, showed a decrease. And the hip joint absorption power and eccentric work done, as the increase of weight, was less than the overweight group showed the normal weight group. In conclusion, the accumulation of the knee joint muscle fatigue and the increase of body weight may lead to an increased risk of injury during landing.

• 한국운동역학회지
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• 제34권2호
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• pp.81-92
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• 2024

Objective: The purpose of this study was to analyze the impact acceleration, shock attenuation and biomechanical variables at various running speed. Method: 20 subjects (height: 176.15 ± 0.63 cm, weight: 70.95 ± 9.77 kg, age: 27.00 ± 4.65 yrs.) participated in this study. The subjects ran at four different speeds (2.5 m/s, 3.0 m/s, 3.5 m/s, 4.0 m/s). Three-dimensional accelerometers were attached to the distal tibia, sternum and head. Gait parameters, biomechanical variables (lower extremity joint angle, moment, power and ground reaction force) and acceleration variables (impact acceleration, shock attenuation) were calculated during the stance phase of the running. Repeated measures ANOVA was used with an alpha level of .05. Results: In gait parameters, decreased stance time, increasing stride length and stride frequency with increasing running speed. And at swing time 2.5 m/s and 4.0 m/s was decreased compared to 3.0 m/s and 3.5 m/s. Biomechanical variables statistically increased with increasing running speed except knee joint ROM, maximum ankle dorsiflexion moment, and maximum hip flexion moment. In acceleration variables as the running speed increased (2.5 m/s to 4.0 m/s), the impact acceleration on the distal tibia increased by more than twice, while the sternum and head increased by approximately 1.1 and 1.2 times, respectively. And shock attenuation (tibia to head) increased as the running speed increased. Conclusion: When running speed increases, the magnitude and increasing rate of sternum and head acceleration are lower compared to the proximal tibia, while shock attenuation increases. This suggests that limiting trunk movement and increasing lower limb movement effectively reduce impact from increased shock. However, to fully understand the body's mechanism for reducing shock, further studies are needed with accelerometers attached to more segments to examine their relationship with kinematic variables.

• 한국운동역학회지
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• 제15권3호
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• pp.9-19
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• 2005

The purpose of this study was to analyze the effects of three different types of preparatory movement(squat, countermovement and hopping) in sideward responsive propulsion movement. 7 healthy subjects performed left and right side movement task by external output signal. 3D kinematics were analyzed The results were followed First, performance time in the countermovement and hopping conditions was shorter(10-20%) than that in the squat condition. The hopping condition that is more related to pre-stretch showed excellent performance. Second, time difference between after turned on the external signal and until take off was the primary factor in performance results among movement conditions. The preparatory phase before the propulsive phase in the squat condition produced more time than that in other conditions. The hopping condition showed the most short time in both the preparatory and the propulsive phase, therefore it was advantage for performance result Third, significant difference was not found in take-off velocity among movement conditions although there was difference of the time required in the propulsive phase. The maximum acceleration in the propulsive phase was larger in order of the hopping. countermovement, and squat condition. The countermovement and hopping conditions showed high take-off velocity although the propulsive phase in those conditions was shorter than that in squat condition. The pre-stretch by preparatory countermovement was considered as the positive factor of producing power in concentric contraction. Fourth, the hopping condition produced large angular velocity of joints. In hopping condition, large amount of moment for rotation movement was revealed in relatively short time and it was considered to cause powerful joint movements. In conclusion, the hopping movement using countermovement is advantage of responsive propulsion movement. It is resulted from short duration until take off and large amount of joint moment and joint power in concentric contraction by pre-stretch.