This study sought to identify biomechanical factors that determine fast and skilful execution of the seoi-nage (shoulder throw) technique by comparing kinematics between elite and college judo athletes. Three-dimensional motion data were captured using a VICON-MX system with 18 cameras operating at 250 Hz as three male elite and seven male college judo athletes performed seoi-nage. No significant difference was found in motion phase time of the turning phase between the two groups, indicating that motion phase time is not necessarily a factor contributing quickness in seoi-nage. The maximum relative velocity of the whole body centre of mass along the anterior-posterior direction was significantly greater in the elite athletes (2.74 ± 0.33 m/s) than in the college athletes (1.62 ± 0.47 m/s) during the turning phase (p = 0.023). The overall angular velocity of the body part lines, particularly the arm line, tended to be greater in the elite athletes (p = 0.068). The results imply that the velocity of the thrower relative to the opponent in the forward drive and turning motion reflects high skill seoi-nage. Coaches should recognise the relative forward velocity as a factor that may contribute to a successful seoi-nage when teaching the judo throw technique.
1The purpose of this study was to elucidate the effects of the lower limb joint moments on 2 the horizontal and vertical velocities of the body mass center during jumping in different 3 directions. Ten male university students performed forward, vertical, and backward jumps, 4 during which their jumping motion (150 Hz) and ground reaction force (600 Hz) were 5 collected. Induced acceleration analysis was performed to quantify the body mass center 6 velocity produced by each joint moment. In all jump conditions, the hip, knee, and ankle 7 joints exerted extension and plantarflexion moments, and most of vertical velocity of the 8 body mass center was produced by the ankle moment. Additionally, the knee moment Advance Publication by J-STAGE
[Purpose] The hybrid assistive limb was developed to improve the kinematics and muscle
activity in patients with neurological and orthopedic conditions. The purpose of the
present study was to examine the long-term sustained effect of gait training using a
hybrid assistive limb on gait stability, kinematics, and muscle activity by preventing
knee collapse in a patient with cerebral palsy. [Participant and Methods] A 17 year-old
male with cerebral palsy performed gait training with a hybrid assistive limb 12 times in
4 weeks. After completion of 12 sessions of hybrid assistive limb training, monthly
follow-up was conducted for 8 months. The improvement was assessed on the basis of joint
angle and muscle activity during gait. [Results] The degree of knee collapse observed at
baseline was improved at 8-month follow-up. Regarding muscle activity, electromyography
revealed increased activation of the vastus lateralis at 8-month follow-up. Moreover, the
hip and knee angles were expanded during gait. In particular, the knee extension angle at
heel contact was increased at 8 months after follow-up. [Conclusion] Gait training with a
hybrid assistive limb provided improvement of gait stability such as kinematics and muscle
activity in a patient with cerebral palsy. The improved gait stability through prevention
of knee collapse achieved with hybrid assistive limb training sustained for 8 months.
The purpose of this study was to investigate joint kinetics of the throwing arms and role of trunk motion in skilled elementary school boys during an overarm distance throw. Throwing motions of 42 boys from second, fourth, and sixth grade were videotaped with three high-speed cameras operating at 300 fps. Seven skilled boys from each grade were selected on the basis of throwing distance for three-dimensional kinetic analysis. Joint forces, torques, and torque powers of the throwing arm joints were calculated from reconstructed three-dimensional coordinate data smoothed at cut-off frequencies of 10.5-15 Hz and by the inverse dynamics method. Throwing distance and ball velocity significantly increased with school grade. The angular velocity of elbow extension before ball release increased with school grade, although no significant increase between the grades was observed in peak extension torque of elbow joint. The joint torque power of shoulder internal/external rotation tended to increase with school grade. When teaching the overarm throw, elementary school teachers should observe large backward twisting of trunk during the striding phase and should keep in mind that young children, such as second graders (age 8 years), will be unable to effectively utilise shoulder external/internal rotation during the throwing phase.
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