• Journal of the Korea Safety Management & Science
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• v.14 no.4
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• pp.93-105
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• 2012

The purpose of this study was to investigate drivers' postures in different car pedal systems and skilled levels under fatigue. Twenty four subjects participated in this experiment. For three-dimensional analyses, six cameras (Proreflex MCU-240, Qualisys) were used to acquire raw data. The parameters were calculated and analyzed with Visual-3D. In conclusion, ROAs of two leg-pedal system were less than one leg pedal system by pattern analysis. Through statistical tests, skilled levels have effects on ROAs(X, Y, Z) of ankle joint at breaking a pedal and ROAs(Y, Z) of ankle joint at accelerating a pedal. Also, car pedal systems have effects on ROAs(Y, Z) of ankle joint, and ROA(Z) of knee joint at accelerating a pedal. In addition, skilled levels and car pedal systems (cross effects) have an effect on ROA(Z) of ankle joint. These findings suggested that we should improve a present single pedal system.

• Journal of the Ergonomics Society of Korea
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• v.35 no.5
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• pp.307-317
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• 2016

Objective: This study looks into biomechanical variables occurring when one moves in a sitting posture, and presents objective references to make improvements in work environments of farm workers. Background: The farmers have more common musculoskeletal disorders compared to other professions, because they are much more exposed to biomechanical risk factors. The sitting posture that is the representative form of the squatted, can cause typical knee joint diseases, such as osteoarthritis or patellofemoral pain syndrome of the knee joint. Therefore, a quantitative study of knee load upon the movement in a squatting posture is required. Method: In order to proceed with its investigation, the study examined movements in a sitting posture with and without a lower body supporter through a threedimensional image analysis and by using Surface EMG. The study compared and analyzed the average muscle activity and the maximum muscle activity as well. Results: Every movement in a sitting posture is related to loads onto the knee joints and, when the farm workers move to sides, the study observed a high level of bowlegged moment. The study also noticed differences in muscle activity of medial gastrocnemius with and without the lower body supporter. Conclusion and Application: The study argues that what has been discussed so far is evidence to prove how the farm working environments should be improved in consideration of these movements observed when the farm workers move in a sitting posture.

• Korean Journal of Applied Biomechanics
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• v.24 no.2
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• pp.131-138
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• 2014

The purpose of this study was to analyse the effect of the drop height on lower extremity and lower back kinematics and kinetics during drop landing with the use of raised heel insole. Furthermore we investigated the change that occurred in our body. Joint ROM, eccentric work and contribution to total work were calculated in 11 male college students performing drop landing with 8 motion analysis cameras and 1 forceplate. The result were as follows. First, the ROM and eccentric work were increased in all joints with the increase of the drop height. Second, the ankle ROM and eccentric work were decreased with the use of the insole. Third, the use of the lower back was increased as the use of the ankle decreased with the insole. Based on these results, we can infer that putting on the insole may contribute to chronic injury. We recommend not to use the insole during physical activity.

• Journal of the Korea Safety Management & Science
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• v.4 no.2
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• pp.11-22
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• 2002

In this study, an asymmetric lifting posture prediction model was developed, which was a three-dimensional model with 12 links and 23 degrees of freedom open kinematic chains. Although previous researchers have proposed biomechanical, psychophysical, or physiological measures as cost functions, for solving redundancy, they lack in accuracy in predicting actual lifting postures and most of them are confined to the two-dimensional model. To develop an asymmetric lifting posture prediction model, we used the resolved motion method for accurately simulating the lifting motion in a reasonable time. Furthermore, in solving the redundant problem of the human posture prediction, a moment weighted Joint Range Availability (JRA) was used as a cost function in order to consider dynamic lifting. However, it is known that the moment weighted JRA as a cost function predicted the lower extremity and L5/S1 joint motions better than the upper extremities, while the constant weighted JRA as a cost function predicted the latter better than the former. To compensate for this, we proposed a hybrid moment weighted JRA as a new cost function with moment weighted for only the lower extremity. In order to validate the proposed cost function, the predicted and real lifting postures for various lifting conditions were compared by using the root mean square(RMS) error. This hybrid JRA reduced RMS more than the previous cost functions. Therefore, it is concluded that the cost function of a hybrid moment weighted JRA can be used to predict three-dimensional lifting postures. To compare with the predicted trajectories and the real lifting movements, graphical validations were performed. The results also showed that the hybrid moment weighted cost function model was found to have generated the postures more similar to the real movements.

• Physical Therapy Korea
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• v.15 no.1
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• pp.38-45
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• 2008

This study investigated gait characteristics, kinematics, and kinetics in the lower extremities between two different shoe conditions (high heeled shoes (7 cm), and high heeled shoes with a total contact insert (TCI)) after lower extremity muscle fatigue. Although TCI shave been applied in high heeled shoes to increase comfort and to decrease foot pressure, no study has attempted to identify the effects of TCI in fatigue conditions. The purpose of this study was to determine the effects of walking in high heeled shoes with TCI after lower extremity muscle fatigue was induced. This study was carried out in a motion analysis laboratory at Hanseo University. A volunteer sample of 14 healthy female subjects participated. All in fatigue conditions, the subjects were divided into two groups. The muscle fatigue was induced by 40 voluntary dorsi- and plantar-flexion exercises and 40 heel-rise exercises of the dominant foot. Surface electromyography was used to confirm the localized muscle fatigue using power spectral analysis of three muscles (tibialis anterior, gastrocnemius medialis and lateralis). The results were as follows: (1) In muscle fatigue conditions, the use of TCI decreased the peak flexion angle of the hip joint significantly in the early stance phase (p<.05) and increased the peak hip flexion moment in the terminal stance phase (p<.05). (2) In muscle fatigue conditions, the application of TCI also increased peak hip power generation in the early stance phase and peak hip power absorption in the terminal stance phase (p<.05). (3) In muscle fatigue conditions, the use of TCI reduced the impact force significantly and increased the secondary peak vertical GRF. These findings suggest that the TCI may provide beneficial effects when muscle fatigue occurs for a high heeled shoe gait. Future research employing the patient population and various types of TCI materials are required to clarify the effects of TCI.

• Korean Journal of Applied Biomechanics
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• v.24 no.1
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• pp.67-74
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• 2014

This study researched into the left-right inclination of the rear foot at the lower limb joints, knee joint angle, angular velocity of the knee joint, angular acceleration and the max. Based on the analysis of kinematics according to the changes in the height of step box (6, 8, 10 inches) during step aerobics of female college students majoring in physical education. The findings of this study are as follows: Then angle of the knee joint decreased as the height of the step box increased the min. Angle was measured right before the right foot was on the step box, and the angle tended to decrease as the step box get heightened. The left-right inclination of the rearfoot angle according to the height of step box increased as the height increased. In the 'pull-up' stage during which the weight was loaded on the right foot the angle increased, while in the right foot stepping stage during which the right foot was on the ground, the left-right inclination of the rearfoot angle increased as the height of the step box increased. The angular velocity of the knee joint according to the height of step box started increasing when the right foot initially stepped on the step box and during the initial stepping section, the angular velocity decreased as the height of step box increased. The changes in angular acceleration of the knee joint according to the height of step box increased as the height of step box increased.

• Journal of the Korean Society of Physical Medicine
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• v.12 no.4
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• pp.1-9
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• 2017

PURPOSE: This study investigated the effect that an elastic therapeutic taping treatment given to patients with chronic ankle instability had on the vertical ground reaction force, center of pressure, and range of motion in the ankle, knee and hip joints, during a Cross-cutting movement from landing. METHODS: This study analyzed 12 able-bodied adults and 12 patients with chronic ankle instability classified by using the Cumberland tool in the motion analysis laboratory, Hanseo University. The experiment was conducted under two conditions elastic taping and no treatment. In order to analyze the difference between the groups. An independent t-test was performed at p>.01. RESULTS: Plying an elastic therapeutic taping to the patients with chronic ankle instability significantly decreased the range of joint motion in the inversion of the ankle joint, the flexion of the knee joint, and the flexion and internal rotation of the hip joint during a cross-cutting movement from landing in comparison with the able-bodied adults p<.01. This restriction in the range of motion decreased the center-of-pressure trajectory length of patients with chronic ankle instability p>.01. CONCLUSION: An elastic therapeutic taping treatment given to patients with chronic ankle instability causes ankle stability to increase during a cross-cutting movement from landing.

• Korean Journal of Applied Biomechanics
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• v.23 no.4
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• pp.347-355
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• 2013

The purpose of this study was to determine the biomechanical effect of wearing the mouthguard on the lower limb during drop landing. Nine male university students who have no musculoskeletal disorder were recruited as the subjects. Linear velocity, angular velocity, vertical GRF, loading rate, joint moment, and lower extremity muscle activity were determined for each subject. For each dependent variable, paired t-test was performed to test if significant difference existed between with mouthguard (WM) and without mouthguard (WOM) conditions (p<.05). The results showed that linear velocity, angular velocity, vertical GRF and loading rate were no significant difference between the two groups. The inversion moment of the ankle joint was increased in WM compared to WOM. Average IEMG values from BF, TA, and LG in WM were significantly greater than corresponding values in WOM during IP phase. This indicates that wearing mouthguard played a vital role in muscle tuning for maintaining joint stability of the lower limb and preventing injury.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.133-140
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• 2017

Objective: The purpose of this study was to determine the relationship between center of pressure (CoP) and local stability of the lower joints, which was calculated based on approximate entropy (ApEn) during walking in elderly women. Method: Eighteen elderly women were recruited (age: $66.4{\pm}1.2yrs$; mass: $55.4{\pm}8.3kg$; height: $1.56{\pm}0.04m$) for this study. Before collecting data, reflective marker triads composed of 3 non-collinear spheres were attached to the lateral surface of the thigh and shank near the mid-segment to measure motion of the thigh and shank segments. To measure foot motion, reflective markers were placed on the shoe at the heel, head of the fifth metatarsal, and lateral malleolus, and were also placed on the right anterior-superior iliac spine, left anterior-superior iliac spine, and sacrum to observe pelvic motion. During treadmill walking, kinematic data were recorded using 6 infrared cameras (Oqus 300, Qualisys, Sweden) with a 100 Hz sampling frequency and kinetic data were collected from a treadmill (Instrumented Treadmill, Bertec, USA) for 20 strides. From kinematic data, 3D angles of the lower extremity's joint were calculated using Cardan technique and then ApEn were computed for their angles to evaluate local stability. Range of CoP was determined from the kinetic data. Pearson product-moment and Spearman rank correlation coefficient were applied to find relationship between CoP and ApEn. The level of significance was determined at p<.05. Results: There was a negative linear correlation between CoP and ApEn of hip joint adduction-abduction motion (p<.05), but ApEn of other joint motion did not affect the CoP. Conclusion: It was conjectured that ApEn, local stability index, for adduction/abduction of the hip joint during walking could be useful as a fall predictor.

• Korean Journal of Applied Biomechanics
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• v.34 no.2
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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.