• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.21-30
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• 2016

Objective: This study aimed to examine the characteristics of joint kinematics and synchronicity of rowing motion between elite and non-elite rowers. Methods: Two elite and two non-elite rowers performed rowing strokes (3 trials, 20 strokes in each trial) at three different stroke rates (20, 30, 40 stroke/min) on two stationary rowing ergometers. The rowing motions of the rowers were captured using a 3-dimensional motion analysis system (8-infrared camera VICON system, Oxford, UK). The range of motion (RoM) of the knee, hip, and elbow joints on the sagittal plane, the lead time ($T_{Lead}$) and the drive time $T_{Drive}$) for each joint, and the elapsed time for the knee joint to maintain a fully extended position ($T_{Knee}$) during the stroke were analyzed and compared between elite and non-elite rowers. Synchronicity of the rowing motion within and between groups was examined using coefficients of variation (CV) of the $T_{Drive}$ for each joint. Results: Regardless of the stroke rate, the RoM of all joints were greater for the elite than for non-elite rowers, except for the RoMs of the knee joint at 30 stroke/min and the elbow joint at 40 stroke/min (p < .05). Although the $T_{Lead}$ at all stroke rates were the same between the groups, the $T_{Drive}$ for each joint was shorter for the elite than for the non-elite rowers. During the drive phase, elite rowers kept the fully extended knee joint angle longer than the non-elite rowers (p < .05). The CV values of the TDrive within each group were smaller for the elite compared with non-elite rowers, except for the CV values of the hip at all stroke/min and elbow at 40 stroke/min. Conclusion: The elite, compared with non-elite, rowers seem to be able to perform more powerful and efficient rowing strokes with large RoM and a short $T_{Drive}$ with the same $T_{Lead}$.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.77-85
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• 2009

This study is aimed at providing information on injury prevention and skill improvement by inducing the accurate movements in exercise as well as understanding the principles of badminton drive movements. Movement displacement of racket head showed the similar patterns among those surveyed but, it seemed that slight differences resulted from external factors such as height, length of brachial and forearm and individual trend of swing locus. Regarding upper joint angle per phase, the angles of shoulder joint, elbow joint and wrist joint were closely associated in taking drive movements and they supported the segment order theory that power was conveyed from proximal into distal. It was shown that angular velocity of upper joint became larger in follow through movement after impact among all those surveyed, which meant the importance of follow through in racket sports such as badminton. In conclusion, this follow through movement acts as an important factor in racket sports in terms of pose stability maintenance, pose correction of movements and injury prevention of joints. In summary, when swings are made according to segment order theory, efficient movements can be taken.

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.771-778
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• 2009

We aimed to determine the effect of heel height on foot pressure by comparing and analyzing data on foot pressure in shoes with different heel heights. Qn the basis of a previous study, we selected 3cm and 7cm as the shoe heel heights preferred by female college students. We divided 10 female students into forefoot and hindfoot to measure vertical force, maximum pressure, and average pressure. The average pressure on the forefoot was higher and that on the hindfoot was lower in the case of 7cm high-heeled shoes. The maximum pressure on the forefoot was significantly higher in the case of the 7cm heel height (p<.05). The vertical force, maximum pressure, and average pressure on the hindfoot were also significantly higher in the case of the 7cm heel height (p<.05). The results showed that wearing 7cm high-heeled shoes exerted greater maximum pressure on the forefoot and greater vertical force, maximum pressure, and average pressure on the Hndfoot. This leads to increase in confining pressure caused by high pressure distribution over the forefoot and increase in the pressure on the hindfoot, which may cause deformation of toes and heel pain over a long period. Therefore, female college students who wish to wear high heels are recommended to wear 3cm high-heeled shoes rather than 7cm high-heeled shoes.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.67-75
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• 2009

The purpose of this study is to analyze the effects of target position on the bowling motion. Four female high school athletes with more than four years of bowling experiences were recruited to this study. The major results of this study are as follows; When a subject treats the 1st pin, The spin angle of a coxa for the target position is largely kept from the downswing to the backswing peak point. When a subject treats the 7th pin, As the 7th pin exists at the left side for the right shoulder axis of the thrower, the movement of the ball center of the thrower from side to side is the lowest. In addition, the time required and horizontal speed appear the highest in the release section. The slant angle of a shoulder is largely increased as she moves from the backswing peak point to the release section. The twist angle of a shoulder also appears small as a throw motion is made toward the left side. When a subject treats the 10th pin, The spin angle of a shoulder and the twist angle of a body in motion appear the largest in the release section. So, there are the effects of target position on the bowling motion.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.49-58
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• 2009

This study aims to analyze the association between the center of mass(C.O.G) and ocular movement(E.O.G) according to the success and failure in the left turn motion on the balance beam, targeting three female gymnasts. When successful, the left-right C.O.G was moved to the left, which was a rotational direction until such time as the body rotated $180^{\circ}$, whereas there appeared to be a greater movement during failure; thus, it was shown to affect the maintenance of dynamic postural control. In case of the subsequent left-right turning motion of E.O.G, this matches the previous theory that the eyeball moves against the direction of rotation of the body. However, there was a difference at the time of movement, and a clear difference emerged in the success and failure in this study. Also, in the E.O.G in the up-down direction, a movement during failure showed a pattern of down direction in most cases; thus, it is deemed to affect the failure. Therefore, the kinetic postural control and E.O.G are supposed to affect the success and failure in a landing, which is the most importantly evaluated movement on the balance beam, in mutual association.

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.739-748
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• 2009

The purpose of this study was to compare successful and failed trials of the dean and jerk exercise performed by an 2008 Beijing Olympic gold medalist. One successful and one failed trial of an Olympic gold medalist (2008 Beijing Olympic 77 kg event) were investigated for this study. A three-dimensional motion analysis was performed, using three digital camcorders (SF: 6Hz). The events were recorded during the 89th Korean National Athletic Games. After analyzing the jerk motion, the following results were found. The successful trial revealed a shorter performance time at Phase 1 and a longer one at Phase 3 and Phase 4 as compared to the failed trial. The vertical displacement of the knee in failed trial was lower than that m the successful one. The differences in the vertical velocity of barbell and knee between the trials were seen at Phase 3 and Phase 4. A faster COM inferior velocity was seen in the successful trial at Phase 3. A more flexed knee angle was seen in the failed trial as compared to the successful trial at E3.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.37-47
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• 2009

This study develops a technique training program to enhance the completion of Kolman, the high air flight technique, and applies it to two national athletes of the horizontal bar, one of the gymnastic events, for eight weeks. After that, their improvement was measured through 3D motion analysis to help them elevate their performance. The training program includes swing, hand release, twist, and bar hold, and its implementation produced the results stated below. They were made to practice the motion in the following way. After the hand-standing of giant swing which initiates the motion, they lift their body upward a little bit more. Next, they take their body down almost like a vertical descent and make a deep tap swing. Instead of doing the tap swing which widens the flection of hip and shoulder joints, while body revolution is more emphasized in particular, they release the bar as raising the centroid of their body sufficiently. During the flight, they try to narrow every joint in their body. As a result, the bar's elasticity becomes greatly increased, and since the backing rate of their body gets higher, the centripetal force of the swing is improved that they can release the bar in the higher position. In addition, because they can erect their body faster during the flight, they can perform comfortable twist and revolution in the air. They can also adjust the direction of the flight easily without too much concern for the proper timing of hand release as they rise. Thereby, they can not only maintain adequate distance from the bar for the bar hold but also ensure enough distance for body revolution and twist.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.179-186
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• 2009

This works studied to compare gas analyzer with accelerometer and the estimation of energy expenditure based on different attaching position of tri-axial accelerometer such as waist and top of the foot Based on the fact that oxygen intake increases more radically linearly during walking more than 8.0km/hr. 9 male subjects performed walking and running on the treadmill with speed of $1.5{\sim}8.5km$/hr and $4.5{\sim}13.0km$/hr, respectively. Commercially available Nike + iPod Sports kit was used to compare energy expenditure with sensor module attached to their foot. Actual energy expenditure was determined by a continuous direct gas analyzer and two multiple regression equations of walking and running mode for different attaching position were developed. Results showed that estimation accuracy of energy expenditure using waist mounted accelerometer was higher than that of the top of the foot and Nike + iPod Sports kit. Results of energy expenditure based on waist and top of the foot showed that the crossover state of energy expenditure occurred at 7.5km/hr. But Nike + iPod Sports kit could not find intersection of energy expenditure in all nine subjects. Therefore the sensor module attached to the waist and separate multi regression equation by walking and running mode was the best to estimate more accurate prediction.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.167-177
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• 2009

The purpose of this study was to investigate effect of golf shoe design on kinematic variables during golf swing. Five professional male golfers with shoe size 270mm were recruited for the study. Swing motion was collected using 8 high speed camera motion analysis at a sampling of 180Hz. Kinematic variables were calculated by EVaRT 4.2 software. Driver swing was divided into four events; El(adress), E2(top), E3(impact) and E4(finish). Time, peak velocity, velocity of center of mass, velocity of the foot and ankle angle during Phase 1(El-E2), Phase 2(E2-E3), and Phase 3(E3-E4) were analyzed in order to investigate the relationship between golf shoe design and swing performance. The findings indicated that type C golf shoes would be beneficial for stability and control of movement during address and swing performance. Furthermore, faster speed of golf shoes, center of mass, and both feet were observed with Type C golf shoes. It is expected that golfers with Type C golf Shoes provide greater force as they control the center of mass faster and increase rotational force during impact compared to other golf shoes.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.159-166
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• 2009

The purpose of this study was to develop and automatic gait event detection algorithm using single accelerometer which is attached at the top of the shoe. The sinal vector magnitude and anterior-posterior(x-axis) directional component of accelerometer were used to detect heel strike(HS) and toe off(TO), respectively. To evaluate proposed algorithm, gait event timing was compared with that by force plate and kinematic data. In experiment, 7 subjects performed 10 trials level walking with 3 different walking conditions such as fast, preferred & slow walking. An accelerometer, force plate and 3D motion capture system were used during experiment. Gait event by force plate was used as reference timing. Results showed that gait event by accelerometer is similar to that by force plate. The distribution of differences were spread about $22.33{\pm}17.45m$ for HS and $26.82{\pm}14.78m$ for To and most error was existed consistently prior to 20ms. The difference between gait event by kinematic data and developed algorithm was small. Thus it can be concluded that developed algorithm can be used during outdoor walking experiment. Further study is necessary to extract gait spatial variables by removing gravity factor.