• Korean Journal of Applied Biomechanics
• /
• v.14 no.1
• /
• pp.27-40
• /
• 2004

The purpose of this study was to provide basic data for improving athletic performances by analyzing the kinematic variables of the Double Backward Somersault on the Parallel Bars through the 3D motion analysis. The subjects in this study were 5 male gymnasts who were ranked as national athletes. The results are as follows. 1. A total time(Mean Time) of performance showed $2.72{\pm}0.82\;sec$. and flight time to landing after releasing was 0.87sec.(mean). In order to perform better stable flying movement, the flight time should be increased. 2. In the change of velocity of the center of mass, when the increasing ascension velocity of the upper point was high, the position in the top point was high on releasing. 3. In the position variable of the center of mass, the mean of upper-bottom position in horizontal posture was $242.1{\pm}6.5cm$, $232.8{\pm}6.4cm$ in releasing, and $265.0{\pm}5.6cm$ in the highest point. This result is explained that the position of center of mass can be raised by using elastic power when wrist raised the bar in the releasing movement. 4. The angle of shoulder joint was $271.1{\pm}14.0$. Such a big angle influences a negative effect on the releasing velocity, because trunk is not a position in the enough vertical direction. 5. The ankle of hip joint in hand-standing was $191.1{\pm}5.9$, $118.8{\pm}5.3$ in releasing, and $122.3{\pm}5.3$ in taking on. Therefore, the result suggests that trunk should be straightly raised in taking on.

• Korean Journal of Applied Biomechanics
• /
• v.20 no.2
• /
• pp.139-148
• /
• 2010

The purpose of this study was to comparatively analyze the kinematic variables between the squash backhand and racquetball backhand strokes through three-dimensional cinematography. Three expert racquetball players and three expert squash players were involved in the data gathering process. The horizontal, vertical and lateral displacement of racket and trunk segment, intersegmental angular velocity of the wrist, elbow and shoulder joints, and the linear velocity of the racket were descriptively analyzed, and the followings were concluded. The racket of the squash backhand stroke showed an 'U' shaped movement where the racket moved rapidly downward and moved forward to make an impact and followed through to a front-top finish, while the racket of racquetball backhand stroke showed an 'O' shaped movement where the racket showed circular movement through the rear and bottom positions for the impact, and showed rotation through the lower-front and upper front to a upper-rear-ward finish during the follow-through. The peak velocity of racket was found before the impact point in the squash backhand stroke and at the impact point in the racquetball backhand stroke. For the final conclusion, for the squash backhand stoke, instructors might be better to make the racket move downward to make highest velocity before the impact and finished short follow-through, while for the racquetball backhand stroke, to make the racket move forward to make highest velocity at the impact and finished rather long follow-through.

• Steel and Composite Structures
• /
• v.44 no.5
• /
• pp.721-740
• /
• 2022

In this paper, an accurate kinematic model has been developed to study the mechanical response of functionally graded (FG) sandwich beams, mainly covering the bending, buckling and free vibration problems. The studied structure with homogeneous hardcore and softcore is considered to be simply supported in the edges. The present model uses a new refined shear deformation beam theory (RSDBT) in which the displacement field is improved over the other existing high-order shear deformation beam theories (HSDBTs). The present model provides good accuracy and considers a nonlinear transverse shear deformation shape function, since it is constructed with only two unknown variables as the Euler-Bernoulli beam theory but complies with the shear stress-free boundary conditions on the upper and lower surfaces of the beam without employing shear correction factors. The sandwich beams are composed of two FG skins and a homogeneous core wherein the material properties of the skins are assumed to vary gradually and continuously in the thickness direction according to the power-law distribution of volume fraction of the constituents. The governing equations are drawn by implementing Hamilton's principle and solved by means of the Navier's technique. Numerical computations in the non-dimensional terms of transverse displacement, stresses, critical buckling load and natural frequencies obtained by using the proposed model are compared with those predicted by other beam theories to confirm the performance of the proposed theory and to verify the accuracy of the kinematic model.

• Korean Journal of Applied Biomechanics
• /
• v.24 no.1
• /
• pp.11-18
• /
• 2014

The purposes of this study were to analyze the kinematics and electromyographic variables of the upper extremity for the backhand clear motion according to the type of hitting in badminton. Seven elite male university players were selected as the subjects. Four digital video cameras and Noraxon Telemyo 2400 were used to collect the 3D kinematics and electromyographic data. The results were as follows: 1) in the phase of impact, the time of motion for the overhead backhand clear was the longest, 2) in the event of impact, the distance of step toward X direction was the longest and the distance of step toward Y direction was the shortest for the overhead backhand clear, 3) in the event of backswing, the rotation angles of shoulder and pelvis and the flexion angle of shoulder for the overhead backhand clear were the biggest, 4) the maximum flexion angular velocity of shoulder and the maximum extension angular velocity of elbow for the overhead backhand clear were the biggest, and 5) in the phase of impact, mean EMG of the wrist flexor, triceps, and trapezius muscle for the overhead backhand clear was bigger than that for the underhand stroke and in the phase of follow-through, mean EMG of the wrist flexor and extensor, biceps, triceps, and trapezius muscle for the overhead backhand clear was the biggest.

• Korean Journal of Applied Biomechanics
• /
• v.13 no.3
• /
• pp.67-79
• /
• 2003

The purpose of this study is to investigate the effective skill motion through the kinematic analysis of the Yurchenko Streched motion in new horse vaulting. The subjects in this study were 3 male gymnasts who were ranked as national athletes. After the 3D motion analysis, kinematic variables were analyzed to comparison with the difference between this study and the previous study(Yang, D. Y and Lee, C. S, 1999). As a result, the following conclusions was drawn; 1. In the board contact phase, this study showed a shorten contact time to maintain in condition highly extension of hip and hee angle than the previous study. 2. In the pre-flight phase, this study appeared more shortly flight duration time and horizontal flight displacement than the previous study. 3. In the horse contact phase, the contact duration time and horizontal displacement of COG shortened than the previous study, but appeared to the fast horizontal and vertical velocity and highly extension of shoulder an. 4. In the post-flight phase, a stable horse contact appeared to the increase of the flight duration time and the apex height during the post-flight. And it showed that these results have a stable and good landing.

• The Journal of Korean Physical Therapy
• /
• v.18 no.4
• /
• pp.27-40
• /
• 2006

Purpose: This study was to investigate the effect of an arm sling on gait with hemiparesis. Methods: Fifteen patients(8 male, 7 female) with hemiparesis participated in this study and walked self-selected speed over 10m walkway, randomly without arm sling, with Single strap hemisling and Rolyan humeral cuff sling. It were filmed by 5 video camera and used with 3-dimensional motion analyzer system. The following gait variables were analyzed: temporo-spatial parameters, kinematic parameters. Results: In the comparison of temporo-spatial parameters each trial, walking velocity and single support time on affected side was significantly increased and step length on affected side, step length asymmetry ratio, single support time asymmetry ratio was significantly decreased in the Single strap hemisling and Rolyan humeral cuff sling. In the comparison of kinematic parameters each trial, maximal angle of the hip flexion on affected side was significantly increased in the Single strap hemisling and Rolyan humeral cuff sling and maximal angle of the knee flexion on affected side was significantly increased in the Rolyan humeral cuff sling and maximal angle of the ankle dorsiflexion on affected side was significantly increased in the Single strap hemisling. Conclusion: An arm sling improved walking velocity and decreased asymmetry and increased maximal angle of hip, knee, ankle flexion on affected side with hemiparesis caused by stroke.

• Korean Journal of Applied Biomechanics
• /
• v.22 no.1
• /
• pp.95-104
• /
• 2012

The purpose of this study targeted to national cross-country skiers representatives was to implement hypothetical experiment on their patterns of the movements and analysis on kinematic variables occurred while double polling was conducted between starting and finishing phase of 56 meters. Furthermore, it aimed to provide a set of quantitative data to illustrate how to improve one's skill and performance of sprint. In our experiments, we conducted 3-dimension analysis of cycle characteristics, joint angle(hip, knee and elbow), and pole angle. The results showed that at the starting phase, the players did not show a significant difference in attributes of time and distance. In heat 1 where elbow angle and polling starts, the pole angle was noticeably high in heat 1. At the finishing phase, there was a considerable distinction with a high frequency in performing a short polling time and high speed in heat 3. The players showed large extension between the flexion and of the hip angle which indicates high contribution given from the movement of lower body(hip, knee).

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.891-895
• /
• 1996

Performance and efficiency of hybrid (hydraulic-mechanical) pick-up device of deep sea manganese nodules collector are very sensitive to altitude and altitude of pick-up head relative to undulating seafloor. For this reason, motion control of pick-up head relative to the changing deep sea topography and other disturbances is of particular importance in design of pick-up device. The concept of design axiom is applied to a pick-up device of hybrid type. Kinematic analysis conducted in absolute Cartesian coordinates gives position, velocity, and acceleration of the hydraulic cylinders which enable the pick-up head to keep the preset optimal distance from seafloor. Inverse dynamic analysis provides the driving forces of hydraulic cylinders and the reaction forces at each joint. Design sensitivity analysis is performed in order to investigate the effects of possible design variables on the change of the maximum strokes of hydraulic cylinders. The direct differentiation method is used to obtain the design sensitivity coefficients.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.3
• /
• pp.68-74
• /
• 1998

Performance and efficiency of deep seabed collector is a primary factor for feasibility of commercial deep ocean mining. The efficiency of manganese nodules collector depends on vehicle mobility relative to undulating seafloor and is attributed pickup head to keep altitude and elevation of it against seafloor. For this reason, motion control of pickup head relative to the changing deep-sea topography and other disturbances is of particular importance in design of pickup device. The concept of design axiom is applied to a pickup device of hybrid type in order to evaluate the concept design. Kinematic analysis conducted in absolute Cartesian coordinates gives position, velocity, and acceleration of the hydraulic cylinders which enable the pickup head to keep the preset optimal distance from seafloor. Inverse dynamic analysis provides the driving forces of hydraulic cylinders and the reaction forces at each joint. Design sensitivity analysis is performed in order to investigate the effects of possible design variables on the change of the maximum strokes of hydraulic cylinders. The direct differentiation method is used to obtain the design sensitivity coefficients.

• Korean Journal of Applied Biomechanics
• /
• v.16 no.2
• /
• pp.9-19
• /
• 2006

The purpose of this study was to analyze the kinematic variables of the lower limbs joints and the muscle activity for lower limbs during the level and downhill running. The subjects were 6 males of twenties and required to run on the level and downhill which was -7% grade treadmill at 8.3km/h. The running performances were filmed by high speed video camera and EMG signal was gained by ME3000P8 Measurement Unit. Rectus femoris(RF), Vastus lateralis(VL), Gluteus medius(GLU), Biceps femoris(BF), gastrocnemius medial head(GM), gastrocnemius lateral head(GL), Soleus(SO), Tibialis anterior(TA) were selected. The result of this study were as follows: 1. Ankle, knee, hip joint in downhill running showed less movement than the level running but, no significant difference. 2. VL and BF during the support phase in downhill running showed Iess muscle activity than the level running. but RF showed the opposite result. 3. GM, GL, SO adn TA during the supports phase in downhill running showed less muscle activity than the level running.