• 한국운동역학회지
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• 제21권1호
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• pp.9-16
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• 2011

The purpose of this study is to analyze the effects of both various shoe types and bare feet on ground reaction force while walking. Ten first-year female university students were selected. A force platform(Kistler, Germany) was used to measure ground reaction force. Six types of shoe were tested: flip flops, canvas shoes, running shoes, elevated forefoot walking shoes, elevated midfoot walking shoes, and five-toed shoes. The control group was barefooted. Only vertical passive/active ground reaction force variables were analyzed. The statistical analysis was carried out using the SAS 9.1.2 package, specifically ANOVA, and Tukey for the post hoc. The five-toed shoe had the highest maximum passive force value; while the running shoe had the lowest. The first active loading rate for running shoes was the highest; meanwhile, bare feet, the five-toed shoe, and the elevated fore foot walking shoe was the lowest. Although barefoot movement or movement in five toed shoes increases impact, it also allows for full movement of the foot. This in turn allows the foot arch to work properly, fully flexing along three arches(transverse, lateral, medial), facilitating braking force and initiating forward movement as the tendons, ligaments, and muscles of the arch flex back into shape. In contrast movement in padded shoes have a tendency to pound their feet into the ground. This pounding action can result in greater foot instability, which would account for the higher loading rates for the first active peak for padded shoes.

• 한국운동역학회지
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• 제23권3호
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• pp.225-233
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• 2013

The purpose of this study was to estimate the potential injury via analyzing ground reaction force components that were resulted from a prolonged-run-induced fatigue. For the present study, passive and active components of the vertical ground reaction force were determined from time and frequency domain. Shear components of GRF also were calculated from time and frequency domain. Twenty subjects with rear foot contact aged 20 to 30, no experience in injuries of the extremities, were requested to run on the instrumented tread-mill for 160 minutes at their preference running speed. GRF signals for 10 strides were collected at 5, 35, 65, 95, 125, and 155 minute during running. In conclusions, there were no significant difference in the magnitude of passive force, impact load rate, frequency of the passive and active components in vertical GRF between running times except the magnitude of active force (p<.05). The magnitude of active force was significantly decreased after 125 minute run. The magnitude of maximum peak and maximum frequency of the mediolateral GRF at heel strike and toe-off have not been changed with increasing running time. The time up to the maximum peak of the anteroposterior at heel-strike moment tend to decrease (p<.05), but the maximum peak and frequency of that at heel and toe-off moment didn't depend significantly on running time.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.2134-2141
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• 2014

본 연구는 육상 100m 수평속도 요인에 기여하는 지면반력분석을 하기 위하여 여자 단거리 선수 8명을 대상으로 스타트 블록간의 거리를 세 가지(Bunch Start, Medium Start, Elongated Start)유형으로 8주간 출발에 관여하는 운동역학적 요인을 분석하였다. 최대 수평 지면반력은 단거리 경기 진행방향에 대한 추진력으로 전이되는 요인으로서 기록단축에 중요한 수치라고 볼 수 있다. 분석 결과는 앞쪽에 위치한 왼발에서는 우수그룹은 BS, 비우수그룹은 MS가 지면반발력 힘값이 가장 크게, 뒤쪽에 위치한 오른발에서는 우수, 비우수그룹 모두 MS에서 지면반발력 힘값이 가장 큰 결과를 보였다. 뒷발에 위치한 오른발은 우수그룹의 MS(0.83 BW)에서는 BS에서 추진력으로 전이될 때, 가장 유리한 출발 유형이라고 할 수 있다. 최대 수직 지면반력의 분석 결과는 앞쪽에 위치한 왼발에서는 우수그룹은 ES, 비우수그룹은 BS가 지면반발력 힘값이 가장 크게 나타났고, 뒷쪽에 위치한 오른발에서는 우수그룹은 BS, 비우수그룹은 MS에서 반발력 힘값이 가장 크게 나타났다. 지면 반발력이 크게 되면 초기 수평속도를 빠르게 얻을 수 있을 것으로 사료되며, 결국에는 전방 추진력을 크게 하는 자세나 방법을 찾게 되면 초기 기록의 향상을 가져올 수 있어 기록단축을 할 수 있다.

• 제어로봇시스템학회논문지
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• 제22권8호
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• pp.615-618
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• 2016

This paper proposes a method to estimate vertical interaction force to the end of the surgical instrument by measuring reaction force at the part supporting the trocar. Relation between the force to the trocar and the interaction force is derived using the beam theory. The vertical interaction force is modeled as a function of the reaction force to the trocar and the distance between the drape plate and the trocar. Experimental results show that error is induced by the asymmetric shape of the trocar tip because contact position between the instrument and the trocar tip is changed depending on the direction of the interaction force. The theoretical relation, therefore, is compensated and reduced. Average $L_2$ relative error of the estimated force in the x-direction and the y-direction is 5.81 % and 5.99 %, respectively.

• 한국운동역학회지
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• 제15권2호
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• pp.1-10
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• 2005

G. B. LEE, A. S. GWON, The Research for Using methodof GRF (Ground Reaction Force) on Rotational Movement in Arabesque. Korean Journal of Sport Biomechanics, Vol. 15, No. 2, pp.1-10, 2005. As, in relation to all movements of a human being, the movements such as mutually walking, running, rotating, and jumping are attained endlessly through the ground amid the interaction with the ground, in terms of the harmonious movement of the upper limbs and the lower limbs, related to the basic movement in ballet, the type of a movement depends on the size and direction of the force that presses down the ground (Fz, Fx, Fy) amid the interaction with the ground. Therefore, aiming to correctly and efficiently perform a rotational movement in Arabesque, this study analyzed factors of the force manifestation through GRF (Ground Reaction Force), by dividing into preparing, stepping, standing, rotating, and finishing stages (events (1) ${\sim}$ (5)), targeting the subjects of 4 elite female students who majored in ballet. 1. At the No.5 position of the preparing stage, It is necessary that support the ground with left and right foot balance, 2. As the stepping stage is the phase ranging from the event (2), in which a plie movement of bending a knee is started, to the event (3) of stretching a knee, Rebunding motion is not good, and One have a position with ankle and knee flextion condition in order to stretch strengthly in event (3) position 3. At the event (1) position, It is necessary that exert the Fz reaction force at the event (3) position. Because large stretch force help to have a toe on position easily and show a active motion 4. In order to have a stand and rotation motion smoothly, One need a muscle strength training for ankle extension, knee extension, control horizental force

• 대한의용생체공학회:의공학회지
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• 제34권4호
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• pp.197-203
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• 2013

The purpose of this study was to analyze the asymmetry of the reaction forces on lower limbs between dominant and nondominant sides during sit-to-stand movement in normal subjects. Fourteen normal subjects ($22.6{\pm}2.3yrs$, all men) participated in this study. To measure the reaction forces during sit-to-stand movement, two force plates were mounted on the ground and one dual top force plate was mounted on a chair. Five events(movement onset, max thigh reaction force, transition, max hip angle, seat off) were determined from the reaction force and joint angle trajectories. For each of thigh, foot, and total reaction forces, two-way ANOVA was performed with the events and sides as factors. Also investigated was the leg asymmetry expressed as the ratio of the reaction forces of dominant and nondominant sides. The significance of asymmetry was investigated and two-way ANOVA was performed with the events and body parts(foot, thigh and total) as factors. Thigh reaction force and total reaction force showed interaction of events and leg sides(p < 0.01). Post-hoc comparisons showed they were different between sides at the latter stage(transition, max hip angle, and seat off events) (p < 0.01). Asymmetry was also significant at the latter stage(transition, max hip angle, and seat off events) (p < 0.01). Interaction of events and body parts on asymmetry was significant(p < 0.01) and asymmetry was greater in thigh reaction forces than total and foot reaction forces at the events of the latter stage(p < 0.01). The results suggest that asymmetry exist in normal subject and should be fully considered when investigating sit-to-stand strategy of patients.

• 한국운동역학회지
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• 제26권2호
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• pp.153-159
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• 2016

Objective: The purpose of this study was to investigate the effects of joint mobilization on foot pressure, ankle moment, and vertical ground reaction force in subjects with ankle instability. Method: Twenty male subjects (age, $25.38{\pm}3.62yr$; height, $170.92{\pm}5.41cm$; weight, $60.74{\pm}9.63kg$; body mass index (BMI), $19.20{\pm}1.67kg/m^2$) participated and underwent ankle joint mobilization. Weight-bearing distribution, ankle dorsi/plantar flexion moment, and vertical ground reaction force were measured using a GPS 400 and a VICON Motion System (Oxford, UK), and subsequently analyzed. SPSS 20.0 for Windows was used for data processing and paired t-tests were used to compare pre- and post-mobilization measurements. The significance level was set at ${\alpha}$ = .05. Results: The results indicated changes in weight-bearing, ankle dorsi/plantar flexion moment, and vertical ground reaction force. The findings showed changes in weight-bearing distribution on the left (pre $29.51{\pm}6.31kg$, post $29.57{\pm}5.02kg$) and right foot (pre $32.40{\pm}6.30kg$, post $31.18{\pm}5.47kg$). There were significant differences in dorsi/plantar flexion moment (p < .01), and there were significant increases in vertical ground reaction forces at initial stance (Fz1) and terminal stance (Fz2, p < .05). Additionally, there was a significant reduction in vertical ground reaction force at midstance (Fz2, p < .001). Conclusion: Joint mobilization appears to alter weight-bearing distribution in subjects with ankle instability, with resultant improvements in stability.

• 한국운동역학회지
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• 제18권1호
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• pp.129-135
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• 2008

본 연구는 댄스스포츠 라틴댄스 룸바 Backward Walk 동작시 지면반력에 어떠한 영향을 미치는가를 규명하기 위해 지면반력기를 이용하여 결과를 도출하였다. 우수선수와 비우수선수간 t-test를 통해 비교하여 오른발의 동작시 수직(Fz)지면반력의 착지와 이지에서 유의한 차이를 보였고, 왼발에서는 수직(Fz), 좌우(Fx), 에서 착지와 수직(Fz), 좌우(Fx) 이지에서 유의차가 나타났다. 우수선수와 비우수선수간의 차이는 오른발에서 수직(Fz) 지면반력 이외 다른 방향에서는 유의차가 나타나지 않았으며, 왼발은 지면반력의 전후(Fy) 이지에서 유의한 차이가 없음이 밝혀졌다. 이는 일반적으로 왼발 운동능력이 트레이닝을 통하여 훈련된 우수선수 집단에서 더 발달되었음을 알 수 있다. 따라서 이러한 지면 반력의 차이를 이해하고, 비우수선수 및 초보자들의 경우 동작의 반복훈련 및 트레이닝을 통하여 양발을 균형 있게 발달시킴으로써 정확한 동작 수행이 도움을 줄 것으로 사료된다.

• 제어로봇시스템학회논문지
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• 제10권4호
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• pp.350-356
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• 2004

This paper presents a farce manipulability analysis of multi-legged walking robots, which calculates force or acceleration workspace attainable from joint torque limits of each leg. Based on the observation that the kinematic structure of the multi-legged walking robots is basically the same as that of multiple cooperating robots, we derive the proposed method of analyzing the force manipulability of walking robot. The force acting on the object in multiple cooperating robot systems is taken as reaction force from ground to each robot foot in multi-legged walking robots, which is converted to the force of the body of walking robot by the nature of the reaction force. Note that each joint torque in multiple cooperating robot systems is transformed to the workspace of force or acceleration of the object manipulated by the robots in task space through the Jacobian matrix and grasp matrix. Assuming the torque limits are given in infinite norm-sense, the resultant dynamic manipulability is derived as a polytope. The validity of proposed method is verified by several examples, and the proposed method is believed to be useful for the optimal posture planning and gait planning of walking robots.

• 한국정밀공학회지
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• 제20권6호
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• pp.230-237
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• 2003

On this study, we operated the dynamic response for impact load of impact absorbing system for spreader by the finite element analysis and showed respectively the spring constant and the damping coefficient which the reaction force by impact was the lowest value for three types impact absorbing system according to the change of system, also we presented the change of impact reaction force according to the spring constant and the damping coefficient. Additionally, among the three types impact absorbing system according to the change of system, the reaction force of model II was the lowest value and the next model which has higher value than model II was model Iand model III has the highest value in the three types.