• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.19-28
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• 2005

The purpose of this study was to improve the ankle joint to mechanical energy in Crouching start according to the backward block inclined angle(F, F(+1), F(+2)) increase. For purpose of this study the ankle joint was considered as a single hinge joint rotation about a transverse axis. A two-dimensional(sagittal plane) analysis was performed on data collected from 3 spriters(university student). During Crouching start, the ankle joint moment showed a similar patterns according to the backward block inclined angle increase. The peak values of ankle joint moment was plantar flexion approximately 80% throughout the contact phase for Crouching start. The absorbed and generated energy represented different values from the backward block inclined angle increase at ankle joint. On the backward block inclined angle F, subject A($55^{\circ}$) and C($50^{\circ}$) Produced energy generation more than other block inclined angles. On the backward block inclined angle F(+2), subject B($50^{\circ}$) showed largest energy generation.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.85-94
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• 2006

The purpose of this study was to analyze the kinematics variables of during forehand stroke by stance patterns. Eight high school tennis players were chosen for the study, who have never been injured for last six months, in Busan. They performed horizontal swing and vertical swing that it was done each five consecutive trial in the condition of square, open and semi-open stance. It was filmed by 6 video camera and used with 3-dimensional motion analyzer system. The following kinematic variables were analyzed in relation to angle of segment( shoulder, hip and knee joint). The conclusion were as follow: 1. The angle of hip joint represented at impact that horizontal swing was not significant difference by stance patterns but vertical swing was increased in open stance than square and semi-open stance. 2. The angle of both knee was not significant difference between all stance types and swing patterns. 3. The angle of shoulder, hip and knee joint rotation showed that open stance was increased than square and semi-open stance in all swing types and event.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.13 no.1
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• pp.36-43
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• 2007

Purpose: An objective analysis and observations were to be done on hemiplegia patients that are wearing a walking support device, Stroke shoes. Their improvements in walking pace, the reduction of distance between the two knee joint, the increase of curve angle of the knee joint and their steps and the reduction of ankle joint upon swing phase were analyzed using a 20 walking analyzer. Methods: An examination was carried out to see the patients' communication skill and independent walking and then let them walk with the Stroke shoes on to get results before and after wearing it. Simi Reality Motion Systems GmbH (Germany, 2007) was used to analyze the results regarding knee joint and ankle joint angle changes of sagitta plane and coronal plane, stepping distances, distances between the knees and walking pace. Results: 1. The articulation angle of ankle joint during swing phase decreased and knee joint has shown a statistically significant increase in such value(p<0.05). 2. Only knee joint showed a significant increase in articulation angle during heel strike(p<0.05). 3. Knee joint showed a significant increase in articulation angle during toe off(p<0.05). 4. The distance between the two knees as well as their foot steps significantly decreased compared with when Stroke shoes were not worn(p<0.05). 5. Stroke shoes with FES have shown positive effects on the patients in improving their walking styles overall. (p<0.05). Conclusion: There was an improvement in rotation walking pattern by a reduction in the distance between the knees after wearing Stroke shoes with FES. Plantar flexion reduced that occurred in ankle joint during walking and flexion angle increased in knee joint, both of which improved foot drop which was a major problem in hemiplegia patients. Also it is believed that the device will have some positive influences on knee joint stiffening paralysis to aid in improving inefficient walking phases.

• Physical Therapy Korea
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• v.14 no.3
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• pp.90-96
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• 2007

The purpose of this study was to compare the joint position sense at the knee joint at 3 different surface conditions by using the active knee joint angle reproduction test in the standing position. Twenty healthy volunteers (10 males and 10 females) age 20~29 years were recruited for this study. The knee joint position senses were assessed at three different surface conditions: on the floor (stable condition), TOGU (soft condition), and seat fit (unstable condition) in a closed kinetic chain. Testing orders were selected randomly. The absolute angle error was defined as the absolute difference between target angles ($30^{\circ}{\sim}45^{\circ}$ knee flexion) and subject perceived angle of the knee flexion. One way ANOVA was used to compare the absolute angle of error among 3 different conditions. The Independent t-test was used to compare the absolute angle of error between male and female. The error angles were significantly different among surface conditions ($1.3^{\circ}{\pm}1.2^{\circ}$ for the floor, $2.1^{\circ}{\pm}0.9^{\circ}$ for the TOGU, and $4.4^{\circ}{\pm}1.8^{\circ}$ for the seat fit, p<.05). There was no significant difference in error angle between male and female. In conclusion, the joint position sense of the knee joint in the closed kinetic chain decreased at unstable surface conditions. The result of this study indicates that surface conditions should be considered when assessing and training the joint position sense of the knee joint in clinical setting.

• Journal of Korean Physical Therapy Science
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• v.22 no.1
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• pp.43-48
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• 2015

Background : The purpose of this study was find out more effective method for improving muscle strengthening in lower extremities according squatting exercise method among knee joint angle 45, 60, 90 degree and between gym ball behind back and wall. Methods : Participants were 21 university students(males 10, females 11) who didn't have any problem with orthopedic surgery. We divided participants to two groups with gym ball group and wall group. Gym ball group were performance squatting exercise with gym ball behind back. Each group had performance squatting exercise according knee joint angle 45, 60, 90 degree. We collected data from E.M.G of Biceps femoris, Gastrocnemius, Vastus medialis and lateralis, Tibialis anterior in lower extremity according knee joint angle 45, 60, 90 degree of each groups. We analyzed data using by ANOVA and ANCOVA of SPSS PC ver. 12.0 in order to determine more effective method according various squatting exercise. Results : Each groups show significantly difference value of biceps femoris, vastus lateralis and medialis, tibialis anterior, gastrocnemius lateralis and medialis among knee joint angle 45, 60, 90 degree. But there was no significantly difference value between gym ball group and wall group according knee joint angle. Conclusions : We suggested that squatting exercise with gym ball was more effective method improving lower extremity muscle strengthening, and changing knee joint angle was more effective compared than continued knee joint angle.

• Korean Journal of Applied Biomechanics
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• v.32 no.1
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• pp.9-16
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• 2022

Objective: The purpose of this study was to investigate how the chronic ankle instability affects postural control during forward jump landing. Method: 20 women with chronic ankle instability (age: 21.7 ± 1.6 yrs, height: 162.1 ± 3.7 cm, weight: 52.2 ± 5.8 kg) and 20 healthy adult women (age: 21.8 ± 1.6 yrs, height: 161.9 ± 4.4 cm, weight: 52.9 ± 7.2 kg) participated in this study. For the forward jump participants were instructed to stand on two legs at a distance of 40% of their body height from the center of force plate. Participants were jump forward over a 15 cm hurdle to the force plate and land on their non-dominant or affected leg. Kinetic and kinematic data were obtained using 8 motion capture cameras and 1 force plates and joint angle, vertical ground reaction force and center of pressure. All statistical analyses were using SPSS 25.0 program. The differences in variables between the two groups were compared through an independent sample t-test, and the significance level was to p < .05. Results: In the hip and knee joint angle, the CAI group showed a smaller flexion angle than the control group, and the knee joint valgus angle was significantly larger. In the case of ankle joint, the CAI group showed a large inversion angle at all events. In the kinetic variables, the vGRF was significantly greater in the CAI group than control group at IC and mGRF. In COP Y, the CAI group showed a lateral shifted center of pressure. Conclusion: Our results indicated that chronic ankle instability decreases the flexion angle of the hip and knee joint, increases the valgus angle of the knee joint, and increases the inversion angle of the ankle joint during landing. In addition, an increase in the maximum vertical ground reaction force and a lateral shifted center of pressure were observed. This suggests that chronic ankle instability increases the risk of non-contact knee injury as well as the risk of lateral ankle sprain during forward jump landing.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.6 no.2
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• pp.31-38
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• 2000

The influence of the genu varum and the genu valgum in two groups of twenty adult man with deformation on hip joint, knee joint, ankle joint is as follows. 1. Each and all, the statistics that measure tibiofemorial angle indicated the group of the genu varum 168 1.42 and the group of the genu valgum 193 2.21, that was more larger or smaller than normal angle 183 of tibiofemorial. The measure Q-Angle(patellofemorial) indicates the group of the genu varum 9 1.5, the genu valgum 19 2.3, that was larger or smaller than normal angle 13. 2. It showed that range of motion hip joint adduction in the group of the genu varum was more larger than normal range of motion hip joint abduction in the group of the genu valgum was more larger than normal range of motion, hip joint internal rotation in the group of the genu valgum was more larger than normal range of motion, hip joint external rotation in the group of the genu varum was more larger than normal range of motion. 3. range of motion knee joint flexion was simillar to two groups of the genu varum and the genu valgum. On tibial tortion of the leg, the group of the genu varum indicated medial tibial tortion, and the genu valgum indicated lateral tibial tortion. 4. Each groups of the genu varum and the genu valgum in plantarflexion and dorsiflexion of ankle joint. With peak angle, the group of the genu varum showed toe-in that was more smaller than normal angle, and the group of the genu valgum showed toe-out that was more larger than normal angle.

• Korean Journal of Applied Biomechanics
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• v.25 no.3
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• pp.275-281
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• 2015

Objective : In order for Taekwondo athletes to perform destructive kicking performance, they are expected to have Taekwondo-specific muscle properties such as high muscle strength and power. The purpose of this study was to investigate the joint angle-dependent force-producing property of Taekwondo athletes' knee extensor muscles, which is one of the primary muscle groups involved in kicking performance. Method : Ten Taekwondo male athletes (age: $19.9{\pm}0.7yrs$, height: $180.6{\pm}6.2cm$, body mass: $75.9{\pm}8.9kg$, career: $9.2{\pm}2.9yrs$.) and 10 healthy male non-athletes (age: $26.3{\pm}2.6yrs$, height: $174.2{\pm}4.8cm$, body mass: $72.8{\pm}7.7kg$) participated in this study. Subjects performed maximum isometric knee extension at knee joint angles of $40^{\circ}$, $60^{\circ}$, $80^{\circ}$, and $100^{\circ}$ (the full knee extension was set to $0^{\circ}$) with the hip joint angles of $0^{\circ}$ and $80^{\circ}$ (the full extension was set to $0^{\circ}$). During the contractions, knee extension torque using an isokinetic dynamometer simultaneously with muscle activities of the rectus femoris (RF), and the vastus lateralis (VL) and vastus medialis (VM) using surface electromyography were recorded. Based on the torque values at systematically different knee-hip joint angles, the joint torque-angle relationships were established and then the optimal joint angle for the knee extensor was estimated. Results : The results of this study showed that the isometric knee extension torque values were greater for the Taekwondo athletes compared with the non-athlete group at all hip-knee joint angle combinations (p<.05). When the hip joint was set at $80^{\circ}$, the peak isometric torque was greater for the Taekwondo athletes compared with the non-athlete group ($313.61{\pm}36.79Nm$ and $221.43{\pm}35.92Nm$, respectively; p<.05) but the estimated optimum knee joint angles were similar ($62.33{\pm}5.71^{\circ}$ and $62.30{\pm}4.67^{\circ}$ for the Taekwondo athletes and non-athlete group, respectively). When the hip joint was set at $0^{\circ}$, the peak isometric torque was greater for the Taekwondo athletes compared with the non-athlete group ($296.29{\pm}45.13Nm$ and $199.58{\pm}25.23Nm$, respectively; p<.05) and the estimated optimum knee joint angle was larger for the Taekwondo athletes compared with the non-athlete group ($78.47{\pm}5.14^{\circ}$ and $67.54{\pm}5.77^{\circ}$, respectively; p<.05). Conclusion : The results of this study suggests that, compared with non-athletes, Taekwondo athletes have stronger knee extensor strength at all hip-knee joint angle combinations as well as longer optimum muscle length, which might be optimized for the event-specific required performance through prolonged training period.

• The Journal of the Korea Contents Association
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• v.10 no.2
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• pp.268-276
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• 2010

This study was to investigate the knee joint flexion angle and the foot pressure during climbing with different slope. The 24 healthy subjects were participated. And foot pressure was investigated using Parotec system. The knee joint flexion angle were filmed to using a video camera on each slope($0^{\circ},\;3^{\circ},\;6{\circ},\;9^{\circ}$). And knee joint angle was investigated by Dartfish. The data were analyzed ANOVAs. In conclusion, there was significantly different that knee joint flexion angle related on each slope angle. In foot pressure, there was significantly different in lateral heel area(1 cell), medial midfoot area(9 cell), medial forefoot area(15, 16 cell) of left foot, and in lateral heel area(3 cell) of right foot. There was significantly different of foot pressure in lateral and medial heel when knee joint flexion angle is between $10^{\circ}$ and $20^{\circ}$. There was change of gait cycle according to walking slop angle increasing, and the initial contact phase was shorter, the foot pressure in lateral heel was lower.

• Journal of the Korean Society of Physical Medicine
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• v.4 no.1
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• pp.15-21
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• 2009

Purpose : The purpose of this study was to find the effect of ankle joint angle on knee extensor electromyographic activity following knee extension exercise. Methods : Ten male university students participated in the study. The subjects performed isometric maximal voluntary knee extensor contractions (MVC) and knee extensor EMG activity measured in with three different ankle joint angle. The EMG activity of rectus femoris(RF), vastus medialis(VM), vastus lateralis(VL) were measured using surface electromyography. Results : EMG activity of vastus lateralis following the change of ankle joint angle was shown statistically significant difference. Conclusion : Ankle plantar flexion position increase EMG activity of vastus lateralis during knee extension exercise.