• Physical Therapy Korea
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• v.23 no.1
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• pp.20-30
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• 2016

Background: Total knee arthroplasty (TKA) recovers the alignment of the knee joint, but fails to automatically restore the alignment and function of the hip and ankle joints. It may affect the alignment and stability of the knee joint, therefore therapeutic intervention in hip and ankle joint is necessary for the rehabilitation process after TKA. Objects: The aim of this study was to comparison of the effects of the two exercise methods on the coronal plane alignment after TKA. This study conducted an experiment by dividing subjects into a lower extremity isometric co-contraction group (LEIC) and a quadriceps isolated isometric contraction (QIIC) group. Methods: A total of 37 subjects were randomly assigned to the LEIC ($n_1$=19) or the QIIC ($n_2$=18). Exercise was applied to five times per week for three weeks, starting on the eighth day after surgery. Range of motion exercises were performed as a common intervention and then each group performed quadriceps isometric contraction exercises with 10 sets of 5 repetitions. Radiological imaging was performed prior to surgery, one month and six months after surgery. In addition, the hip-knee-ankle angle (HKA) and tibiotalar angle (TTA) were measured. Results: The HKA was close to neutral in the LEIC rather than the QIIC (p<.05). The LEIC showed varus and the QIIC exhibited valgus TTA (p<.05). In a comparison of HKA and TTA over time, there was no significant change in either group (p>.05). According to the comparison of the TTA before surgery, the LEIC showed significant changes in the varus direction (p<.05), while there was no significant change in the QIIC (p>.05). Conclusion: The LEIC method triggered changes in the TTA and brought the HKA close to the neutral. Thus, LEIC is more effective than QIIC in creating stability in the coronal plane alignment of the knee and ankle joints after TKA.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.161-169
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• 2008

The purpose of this study was to investigate kinetic variables of the lower extremity during walking on three different stair widths in healthy adults. Ten healthy college-aged adults($23.5{\pm}3.5$) recruited for this study. Each stairs with the same height and length(l8cm and 90cm) under the Korean Constructional Law but three different widths(26cm, 31cm and 36cm) were conducted for this study. One force plate(9286AA, Kistler Co.) was put on third stairs. One-way ANOVA was performed to find the stair width effects during stair walking and the following findings ware obtained. There was significantly decreased in ankle resultant joint moment at Pull-Up phase(p<.05) and, significantly increased in knee extension moment during mid-stance phase as stair width increase(p<.05), but there was no significance in ankle resultant joint moment was found at Forward Continuance Phase in Ascending Stair Walking and There was significantly increased in ankle resultant joint moment as stair width increase during mid-stance phase(p<.05) and no significance in knee and hip resultant moments among the stair width in descending stair walking.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.201-207
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• 2014

This study investigated the center of mass and lower extremity kinematic patterns between carved and basic paralell turn during alpine skiing. Six experienced skiers (age: $20.67{\pm}4.72yrs$, body mass: $72.67{\pm}7.15kg$, height: $171.00{\pm}5.51cm$) participated in this study. Each skier were asked to perform carved and basic paralell turn on a $22.95^{\circ}$ groomed slope. Each turn was divided into the initiation phase, steering phase 1 and 2. The results of this study show that the carved turn spent significantly less running time than basic paralell turn at all three phases (p<.05). Also vertical displacement of the center of mass was significantly greater in carved turn at all three phases, whereas inward leaning angle of the center of mass was significantly greater in carved turn at the steering phase 1 and 2 (p<.05). Bilateral knee and hip joint angle were significantly greater in basic paralell turn at the initiation phase and the steering phase 2 (p<.05). On the other hand, left knee and hip joint angle were significantly greater in basic paralell turn at the steering phase 1 (p<.05). In order to perform successful carved turn, we suggest that skiers should coordinate bilateral knee and hip joint angles to adjust the center of mass, depending on three ski turn phases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.785-790
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• 2011

The goal of this study is to estimate the force acting on the knee joint in the human body by using the Hilltype muscle model based on a musculoskeletal model of the human lower extremity in the sagittal plane. For estimating the force applied, the human leg is modeled using multi-body modeling. This leg model comprises biarticular muscles acting on two joints of the upper and lower limbs, and the muscles include some of the major muscles such as the hamstring. In order to analyze the uncertainty of the applied forces acting on the knee joint, statistical distributions of human body, leg part, parameters are required and to obtain the parameter's statistical characteristic of the part sample survey method is employed. Finally, by using the sensitivity information of the parameters, the force acting on the knee joint can be estimated.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.2
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• pp.139-147
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• 2020

Purpose : Proprioceptive position sense plays a key role in providing joint stability, and multiple factors are related to proprioceptive position sense. Thus, this study aimed to determine the effects of body composition, particularly skeletal muscle mass on proprioceptive position sense following muscle fatigue. Methods : Healthy female subjects agreed to have their body composition analyzed. Only subjects who had 18.5-22.9 kg/㎡ of BMI (body mass index) were included in this study, and the participants were divided into two groups by skeletal muscle mass level. The experimental group had a level of skeletal muscle lower than the standard level (n=9), while the control group showed a standard or high level of skeletal muscle mass (n=11). To determine the change in proprioceptive position sense of the knee joint, the absolute angle error (AAE) was evaluated following muscle fatigue on low extremity. The muscle fatigue was induced by isokinetic resistance exercise program of Biodex system. AAE was measured by the Biodex system and compared the result before and after muscle fatigue. Results : The experimental group showed a significant AAE difference between before (3.16±2.48 °) and after (5.40±2.61 °) muscle fatigue. In addition, there was a AAE difference between the experimental (5.40±2.61 °) and control groups (3.53±1.67 °) after fatigue; however, there was no significance. Those results indicated that low level of skeletal muscle mass might influence the proprioceptive position sense of the knee joint after muscle fatigue. Conclusion : Thus, maintaining the proper level of skeletal muscle mass is pivotal to reduce the risk of injury following muscle fatigue in ADL or sport activities.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.161-166
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• 2016

Objective: The purpose of this study was to determine the knee and ankle joint kinematics and kinetics by comparing downhill walking with valley-shape combined slope walking. Method: Eighteen healthy men participated in this study. A three-dimensional motion capture system equipped with eight infrared cameras and a synchronized force plate, which was embedded in the sloped walkway, was used. Obtained kinematic and kinetic parameters were compared using paired two-tailed Student's t-tests at a significance level of 0.05. Results: The knee flexion angle after the mid-stance phase, the mean peak knee flexion angle in the early swing phase, and the ankle mean peak dorsiflexion angle were greater during downhill walking compared with valley-shape combined slope walking (p < 0.001). Both the mean peak vertical ground reaction force (GRF) in the early stance phase and late stance phase during downhill walking were smaller than those values during valley-shape combined slope walking. (p = 0.007 and p < 0.001, respectively). The mean peak anterior GRF, appearing right after toe-off during downhill walking, was also smaller than that of valley-shape combined slope walking (p = 0.002). The mean peak knee extension moment and ankle plantar flexion moment in late stance phase during downhill walking were significantly smaller than those of valley-shape combined slope walking (p = 0.002 and p = 0.015, respectively). Conclusion: These results suggest that gait strategy was modified during valley-shape combined slope walking when compared with continuous downhill walking in order to gain the propulsion for lifting the body up the incline for foot clearance.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.173-179
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• 2011

This study aims to analyse difference in biomechanical factors between dominant legs and recessive ones according to muscular imbalance during drop landing targeting talented children in sports. The subjects of the study were ten primary students who are attending to Sports Program for Talented Children organized by C university (age: $12.28{\pm}0.70$ year, height: $1.52{\pm}0.11$ m, and weight: $45.2{\pm}4.9$ kg). Strength legs were classified into dominant side and strengthless legs were classified into non-dominant legs. For three-dimensional analyses of the data collected, 6 video cameras(MotionMaster200, Visol, Korea) were used. To analyse ground reaction force, two force platforms(AMTI ORG-6, MA) were used and to analyse electromyograghy a 8-channeled wireless Noraxon Myoresearch made in USA was used at 1000 Hz for sampling. As a result, it was discovered that the dominants legs controlled knee bending motions more stably than strengthless legs as the maximum vertical ground reaction force was significantly high in dominant legs(p<.05), and joint moment of knee joints of the dominant legs was high(p<.05). Therefore, this study suggested that injury prevention program focusing on muscular balance as well as the existing sports programs for talented children should be developed based on results of the study and it is expected that the results will be useful for improvement of sports programs for talented children.

• Physical Therapy Rehabilitation Science
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• v.8 no.2
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• pp.61-66
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• 2019

Objective: The purpose of this study was to investigate the effects of resistance applied in various directions on lower extremity muscle activity and balance during squat exercise performance. Design: Cross-sectional study. Methods: Forty-one adults (19 males and 22 females) agreed to the study purpose and procedures. All subjects randomly performed squat exercises with an intensity of overcoming 10% of body weight resistance pulled forward, backward and general squats with $60^{\circ}$ of knee joint flexion. Electromyography was used to measure muscle activity of the vastus medialis oblique (VMO), rectus femoris (RF), vastus lateralis oblique (VLO), biceps femoris (BF), and semitendinosus (ST) muscles. The Wii Balance Board was used to assess balance during the three-method squat operation. Each operation was measured three times for 10 seconds. Results: There were significant differences in muscle activities of the VMO, RF, VLO, ST and balance ability with the application of three directions of resistance (p<0.05). Post hoc comparisons revealed that squats performed with resistance pulled in the backward direction resulted in higher VMO, RF and VLO activity than with the resistance placed in a pulled forward direction (p<0.05). In the ST, resistance applied in the pulled forward direction showed greater muscle activity compared to the pulled backward direction (p<0.05). With balance, squats performed with resistance pulled in the forward direction showed greater muscle activity than with resistance applied in the pulled backward direction and during general squat performance (p<0.05). Conclusions: In this study, squat exercises performed with resistance applied in the direction of pulling backwards was found to be the most effective in improving quadriceps muscle strength and balance. It is effective to provide resistance that is placed in the forward when it is difficult to perform a general squat due to weakness of the quadriceps.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.435-441
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• 2006

The anterior cruciate ligament(ACL) is an important stabilizer of knee joint. The ACL injury of knee is common and a serious ACL injury leads to ligament reconstruction surgery. Gait analysis is essential to identify knee condition of patients who display abnormal gait. The purpose of this study is to evaluate and classify knee condition of ACL deficient patients using a nonlinear dynamic method. The nonlinear method focuses on understanding how variations in the gait pattern change over time. The experiments were carried out for 17 subjects(l2 healthy subjects and five subjects with unilateral deficiency) walking on a motorized treadmill for 100 seconds. Three dimensional kinematics of the lower extremity were collected by using four cameras and KWON 3D motion analysis system. The largest Lyapunov exponent calculated from knee joint flexion-extension time series was used to quantify knee stability. The results revealed the difference between healthy subjects and patients. The deficient knee was significantly unstable compared with the contralateral knee. This study suggests an evaluation scheme of the severity of injury and the level of recovery. The proposed Lyapunov exponent can be used in rehabilitation and diagnosis of recoverable patients.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.173-181
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• 2016

This paper reports on the development of a roller-cam clutch mechanism. This mechanism can transfer bidirectional torque with high backdrivability, as well as increase actuation energy efficiency, in electrical exoskeleton robots. The developed mechanism was installed at the robot knee joint and unclutched during the swing phase which uses less metabolic energy, thereby functioning as a passive joint. The roller-cam clutch aimed to increase actuation energy efficiency while also producing high backdrivability by generating zero impedance for users during the swing phase. To develop the mechanism, mathematical modeling of the roller-cam clutch was conducted, with the design having more than three safety factors following optimization. Titanium (Ti-6AL-4V) material was used. Finally, modeling verification was done using ANSYS software.