• Korean Journal of Applied Biomechanics
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• v.23 no.1
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• pp.53-62
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• 2013

The methods of fitting a circle to measured data, geometric fit and algebraic fit, have been studied profoundly in various areas of science. However, they have not been applied exactly to a biomechanics discipline for locating the center of rotation of a human joint. The purpose of this study was to generalize the methods to fitting spheres to the points in 3-dimension, and to estimate the center of rotation of a hip joint by three of geometric fit methods(Levenberg-Marquardt, Landau, and Sp$\ddot{a}$th) and four of algebraic fit methods(Delogne-K${\aa}$sa, Pratt, Taubin, and Hyper). 1000 times of simulation experiments for flexion/extension and ad/abduction at an artificial hip joint with four levels of range of motion(10, 15, 30, and $60^{\circ}$) and three levels of angular velocity(30, 60, and $90^{\circ}$/s) were executed to analyze the responses of the estimated center of rotation. The results showed that the Sp$\ddot{a}$th estimate was very sensitive to the marker near the center of rotation. The bias of Delogne-K${\aa}$sa estimate existed in an even larger range of motion. The Levenberg-Marquardt algorithm of geometric fit and the Pratt of algebraic fit showed the best results. The combination of two methods, using the Pratt's estimate as initial values of the Levenberg-Marquardt algorithm, could be a candidate of more valid estimator.

• Korean Journal of Applied Biomechanics
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• v.22 no.4
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• pp.379-386
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• 2012

The aim of this study was to investigate and identify the differences in lower extremity energy dissipation strategies between drop-landing and countermovement-jump maneuvers. Fourteen recreational athletes(Age : $23.3{\pm}2.1years$, Height : $172.3{\pm}4.0cm$, Weight : $69.2{\pm}4.7kg$) were recruited and instructed to perform drop-landing from 45 cm height and countermovement-jump from 45 cm to 20 cm height. The landing phase was taken as the time between initial contact and peak knee flexion. A motion-capture system consisting of eight infra-red cameras was employed to collect kinematics data at a sampling rate of 200 Hz and a force-plate was used to collect GRF data at a sampling rate of 2000 Hz. Paired t-test was performed to determine the difference in kinematics and kinetics variables between each task. During the countermovement-jump task, all of lower extremity joint ROM and the hip joint eccentric moment were decreased and the ankle joint plantarflexion moment was increased than drop-landing task. In the eccentric work during countermovement-jump task, the ankle joint displayed greater while knee and hip joint showed lesser than drop-landing. Therefore, the knee joint acted as the key energy dissipater during drop-landing while the ankle joint contributed the most energy dissipation during countermovement-jump. Our findings collectively indicated that different energy dissipation strategies were adopted for drop-landing and countermovement-jump.

• Physical Therapy Rehabilitation Science
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• v.3 no.2
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• pp.101-106
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• 2014

Objective: To investigate the appropriate position for abdominal drawing-in maneuver (ADIM) exercise by rehabilitative ultrasound image. Design: Cross-sectional study. Methods: Twenty-eight young adults with no history of low back pain participated in the study. Three positions compared were crook lying position with hip $60^{\circ}$ flexion, standing position with the feet hip width apart and knees straight, and saddle standing positionunsupported with the knees $20^{\circ}$ flexed. Once in the appropriate position, the subjects were verbally cued to draw in their abdominal wall, with the intention of pulling their navel inward toward their lower back. The thickness of each transversus abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles were measured via ultrasound and recorded at the end of inspiration. Results: When compared to the TrA thickness of rest, the TrA thickness was significantly increased in all three positions (crook lying, standing, and saddle standing) during the ADIM (p<0.05). IO thickness was significantly greater in standing and saddle standing than in crook lying (p<0.05). EO thickness was constant in all the three positions. Conclusions: The present study suggests that standing and saddle standing positions could be recommended for the ADIM to maximize recruitment of the TrA and IO activation. Specifically, the saddle standing position with knees flexed to $20^{\circ}$ was observed to increase the TrA activation more than the standing position. These findings should be considered when core stability exercises such as the ADIM are conducted.

• Korean Journal of Applied Biomechanics
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• v.31 no.4
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• pp.297-307
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• 2021

Objective: The aim of this study was to analyze kinetic variables between thermotherapy and dynamic warm-up during drop-landing. Method: Twenty male healthy subjects (Age: 21.85 ± 1.90 years, Height: 1.81 ± 0.06 cm, Weight: 68.5 ± 7.06 kg) underwent three treatments applied on the thermotherapy of femoral muscles and a dynamic warm-up. The thermotherapy was performed for 15 minutes while sitting in a chair using an electric heating pad equipped with a temperature control device. Dynamic warm-up performed 14 exercise, a non-treatment was sitting in a chair for 15 minutes. Core temperature measurements of all subjects were performed before landing at a height of 50 cm. During drop-landing, core temperature, joint angle, moment, work of the sagittal plane was collected and analyzed. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was Bonferroni. Results: Results indicated that Thermotherapy was increased temperature than other treatments (p = .000). During drop-landing, hip joint of dynamic warm-up was slower for angular velocity (p < .005), and left ankle joint was fastest than other treatments (p = .004). Maximum joint moment of dynamic warm-up was smaller for three joints (hip extension: p = .000; knee flexion/extension: p = .001/.000; ankle plantarflexion: p = .000). Negative work of dynamic warm-up was smaller than other treatments (p = .000). Conclusion: In conclusion, the thermotherapy in the local area doesn't affect the eccentric contraction of the thigh. The dynamic warm-up treatment minimized the joint moment and negative work of the lower joint during an eccentric contraction, it was confirmed that more active movement was performed than other treatment methods.

• Journal of the Korean Society of Physical Medicine
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• v.14 no.1
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• pp.53-61
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• 2019

PURPOSE: This study examined the dynamic range of motion (ROM) of the hip, knee, and ankle joint when wearing different shoe sole lifts, as well as the limb asymmetry of the range according to the leg length discrepancy (LLD) during normal speed walking. METHODS: The participants were 40 healthy adults. A motion analysis system was used to collect kinematic ROM data. The participants had 40 markers attached to their lower extremities and were asked to walk on a 6 m walkway, under three different shoe lift conditions (without an insole, 1 cm insole, and 2 cm insole). Visual3D professional software was used to coordinate kinematic ROM data. RESULTS: Most of the ROM variables of the short limbs were similar under each insole lift condition (p>.05). In contrast, when wearing a shoe with a 2 cm insole lift, the long limbs showed significant increases in flexion and extension of the knee joint as well as; plantarflexion, dorsiflexion, pronation, eversion, and inversion of the ankle joint (p<.05). Of the shoes with the insole lifts, significant differences in all ROM variables were observed between the left and right knees, except for the knee internal rotation (p<.05). CONCLUSION: As the insole lift was increased, more ROM differences were observed between the left and right limbs, and the asymmetry of the bilateral lower limbs increased. Therefore, appropriate interventions for LLD are needed because an artificial mild LLD of less than 2.0 cm could lead to a range of musculoskeletal problems of the lower extremities, such as knee and ankle osteoarthritis.

• Korean Journal of Applied Biomechanics
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• v.28 no.4
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• pp.227-236
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• 2018

Objective: The purpose of this study was to investigate the effects of a 12-week combined exercise program on gait parameters in elderly women with osteoarthritis. Method: The subjects of this study were 11 elderly women (age: $67.09{\pm}2.47$, height: $157.35{\pm}4.30cm$, weight: $62.49{\pm}6.36kg$) with knee osteoarthritis. The combined exercise program of this study was divided into aerobic exercise and lower extremity strengthening exercises. The exercises were performed for 60 minutes per session, three times a week, for a total of 12 weeks. The maximum joint moments of the hip, knee, and ankle joints with walking were obtained with 8-3D cameras (MX-T20, Vicon, USA) and 2-force plate (AMTI OR6-7-400, AMTI, USA). SPSS Windows version 23.0 was used for statistical analysis. A paired t-test was used for pre-post comparison. An alpha level of .05 was utilized in all tests. Results: The maximum extension moment was significantly higher in the hip joint after P1 on the X axis. The maximum joint moment of P3 in extension was statistically significantly lower after intervention. On the Z axis, the maximum joint moment was significantly lower after the exercise intervention at P3. There was a statistically significant increase in the extension moment of the left and right knee joints in the X axis after exercise intervention. In the right ankle joint, P1 (plantar flexion moment) showed a statistically significant high moment after exercise intervention. Conclusion: These results suggest that combined exercise, including lower limb and aerobic exercise, may have a positive effect on mobility and walking moments in patients with osteoarthritis of the knee.

• The Journal of Korean Physical Therapy
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• v.34 no.5
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• pp.255-266
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• 2022

Purpose: This study sought to study the effects of cross-legged sitting posture on joint motion. It also examined the correlation between the changes in the joint range of motion, musculoskeletal symptoms, and facial asymmetry. Methods: The Acumar Digital Inclinometer (Lafayette Instrument Company, USA) was used to measure the range of motion (ROM). We measured the flexion and extension of the cervical, thoracic, and lumbar spine using a dual inclinometer, and measured the ROM of the shoulder and hip joint with a single inclinometer. The Likert scale questionnaire was used to investigate musculoskeletal symptoms and facial asymmetry. Results: The data analysis was performed using the Jamovi version 1.6.23 statistical software. After confirming the normality of the ROM with descriptive statistics, it was compared with the normal ROM through a one-sample t-test. Correlation matrix analysis was performed to confirm the association between facial asymmetry and musculoskeletal symptoms. The result of the one-sample t-test showed a significant increase in the thoracic spine extension and right and left hip external rotation (p<0.001^***), while most other joints were restricted. As per the frequency analysis, facial asymmetry was found to be 81.70%. Conclusion: The independent variable, namely cross-legged sitting posture led to an increase in ROM. The study also suggests that facial asymmetry and musculoskeletal symptoms could occur. Therefore, to prevent the increase and limitation of ROM and to prevent the occurrence of facial asymmetry and musculoskeletal symptoms, it is suggested that the usual cross-legged sitting posture should be avoided.

• Korean Journal of Applied Biomechanics
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• v.18 no.2
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• pp.95-104
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• 2008

The purpose of this study was to investigate kinematic coordination and control of lower segments in skill process. For the investigation, we examined the difference of resultant linear velocity of segments and angle vs angle graph. Novice subjects were 9 male middle school students who has never been experienced a taekwondo and expert subjects were 7 university taekwondo players. We analyzed kinematic variables of Dollyochagi motion through videographical analysis and the conclusion were as follows. 1. Examining the graph of novice subjects' maximal resultant linear velocity of the thigh, shank, and foot segment, as it gets closer to the end of the training, the maximal resultant linear velocity in each segment increased. Statistical analysis showed the following results; thigh segment caused the increase of speed, using the trunk segment's momentum in the latter term of learning, while the shank segment utilized the momentum of the adjacent proximal segment at the beginning of learning, and the foot segment in the middle of learning. 2. Until the point where the knee joint angle is minimum, as the novice group learn the skill, the flexion of knee and hip joints has changed into the form of coordination pattern in phase. On the other hand, the expert group showed continual coordination pattern in phase that the movement sequences were smooth. From the knee joint maximal flexion to impact timing, all novice and expert groups showed coordination pattern out of phase. 3. From the knee joint maximal flexion to impact timing, the ankle joint was fixed and the knee joint was extended to all the novice stages and expert subjects.

• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.161-173
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• 2005

Recently among several tennis techniques forehand stroke has been greatly changed in the aspect of spin, grip and stance. The most fundamental factor among the three factors is the stance which consists of open, square and closed stance. The purpose of this study was to investigate the relations between the segments of the body, the three dimensional anatomical angle according to open stance patterns during forehand stroke in tennis. For the movement analysis three dimensional cinematographical method(APAS) was used and for the calculation of the kinematic variables a self developed program was used with the LabVlEW 6.1 graphical programming(Johnson, 1999) program. By using Eular's equations the three dimensional anatomical Cardan angles of the joint and racket head angle were defined 1. In three dimensional maximum linear velocity of racket head the X axis showed $11.41{\pm}5.27m/s$ at impact, not the Y axis(horizontal direction) and the z axis(vertical direction) maximum linear velocity of racket head did not show at impact but after impact this will resulted influence upon hitting ball It could be suggest that Y axis velocity of racket head influence on ball direction and z axis velocity influence on ball spin after impact. the stance distance between right foot and left foot was mean $74.2{\pm}11.2m$. 2. The three dimensional anatomical angular displacement of shoulder joint showed most important role in forehand stroke. and is followed by wrist joints, in addition the movement of elbow joints showed least to the stroke. The three dimensional anatomical angular displacement of racket increased flexion/abduction angle until the impact. after impact, The angular displacement of racket changed motion direction as extension/adduction. 3. The three dimensional anatomical angular displacement of trunk in flexion-extension showed extension all around the forehand stroke. The angular displacement of trunk in adduction-abduction showed abduction at the backswing top and adduction around impact. while there is no significant internal-external rotation 4. The three dimensional anatomical angular displacement of hip joint and knee joint increased extension angle after minimum of knee joint angle in the forehand stroke, The three dimensional anatomical angular displacement of ankle joint showed plantar flexion, internal rotation and eversion in forehand stroke. it could be suggest that the plantar pressure of open stance during forehand stroke would be distributed more largely to the fore foot. and lateral side.

• International Journal of Contents
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• v.8 no.2
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• pp.97-102
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• 2012

The purpose of this study was to investigate the effects of various cool-down exercises on muscular strength and endurance. After receiving a treadmill training for main exercise, the subjects conducted isotonic and isometric cool-down exercises four times for three weeks. Isotonic exercise with leg press of 10kg was repeated by 20 times and isometric exercise was conducted at flexion of hip joint and knee joint with leg press of 10kg by maintaining it for 6 sec and resting for 2 sec by 20 times. Muscular strength after exercise was measured with 1 RM by times and muscular endurance with maximum repetition frequency using time to keep for loading the weight of 10 RM and 65% of maximum muscular strength. As a result of comparing and analyzing measured values, exercise recovery shape of isotonic and isometric cool-down group were more effective than rest recovery shape of the control group. The isometric cool-down group was more effective than isotonic cool-down group. In conclusion, isometric exercise was more effective than isotonic exercise or simple rest on muscular strength and endurance.