UNCONTROLLED MANIFOLD ANALYSIS OF JOINT ANGLE VARIABILITY DURING TABLE TENNIS FOREHAND

The purpose of this study was to evaluate the variance structure of the trunk and racket arm joint angles in the table tennis topspin forehand in relation to the control of racket orientation using the uncontrolled manifold (UCM) approach. Seventeen (9 advanced and 8 intermediate) male collegiate table tennis players performed the strokes against backspin. The UCM analysis was conducted using 30 trial data per each participant. The degree of redundancy exploitation to stabilize the racket vertical and horizontal angles were not significantly different between the two performance levels, suggesting that the ability to exploit joint configuration redundancy may not contribute to achieving higher performance in sport hitting skill. The degree of redundancy exploitation is highest at ball impact and this result may reflect that the table tennis forehand is a fast interceptive task

VARIABILITY OF RELEASE PARAMETERS IN BASKETBALL FREE THROW

The aim of this study is to clarify what kind of variability of release parameters is associated with shot accuracy in basketball free-throw. Eight male right-handed basketball players in college team participated in this study. Participants made 50 shots from the free-throw line after warm-up. A 16-camera motion capture system was used to record the coordinates of the reflective markers attached on the participants’ bodies and the ball. The ball release parameters (i.e. release speed, angle and position) were calculated for the ball at the time of release. TNC-analysis that quantifies Tolerance, Noise, and Covariation cost of a performance (Cohen & Sternad, 2009; Sternad et al., 2011) and a correlation analysis were used to analyse the variability of release parameters. Our results showed that the value of C-cost is smaller for the participant whose shot probability of success was high. Our results suggest that learning various patterns of success in training may be efficient for improvement in free-throw

EFFECTS OF SEGMENTAL ROTATIONS ON VERTICAL AND HORIZONTAL ENERGIES DURING TAKE-OFF OF A LONG JUMP

This study aimed to reveal the effect of segmental rotation on the generation of vertical velocity and loss of horizontal velocity during take-off of a long jump. 3D motion capture system and force plates were used to capture the long jumps by nine male athletes with an approach running distance of approximately 20 m. Forward rotations of the shank and thigh of the stance leg increased vertical energy (Evert) and decreased horizontal energy (Ehori); however, elevation of the free leg side of the pelvis increased Evert (0.53 ± 0.16 J/kg), although pelvic elevation did not decrease Ehori (0.01 ± 0.02 J/kg). It was revealed that although shank and thigh movements involved the loss of horizontal velocity, elevation of the free leg side of the pelvis generated vertical velocity without the loss of horizontal velocity. This study provides evidence for a new technical approach for a long jump

EFFECT OF MECHANICAL PROPERTIES OF THE LOWER LIMB MUSCLES ON MUSCULAR EFFORT DURING TABLE TENNIS FOREHAND

The purpose of this study was to investigate the effect of the maximum isometric forces and the maximum shortening velocities of the lower limb muscles on the muscular effort during the table tennis forehand. Four male collegiate players performed table tennis forehand drives with maximum effort. We used OpenSim’s static optimization algorithm to estimate the activation patterns of lower limb muscles. The cost function was the sum of squared muscle activations for all lower limb muscles, which we will refer to as the muscular effort. The simulations were repeated with the maximum isometric forces or the maximum shortening velocities of each muscle group changed by ±10% of their original values. The results suggest that increasing the maximum isometric forces of the hip extensors and adductors may be most effective to reduce the muscular effort

Optimal coordination of maximal-effort horizontal and vertical jump motions – a computer simulation study

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to investigate the coordination strategy of maximal-effort horizontal jumping in comparison with vertical jumping, using the methodology of computer simulation.</p> <p>Methods</p> <p>A skeletal model that has nine rigid body segments and twenty degrees of freedom was developed. Thirty-two Hill-type lower limb muscles were attached to the model. The excitation-contraction dynamics of the contractile element, the tissues around the joints to limit the joint range of motion, as well as the foot-ground interaction were implemented. Simulations were initiated from an identical standing posture for both motions. Optimal pattern of the activation input signal was searched through numerical optimization. For the horizontal jumping, the goal was to maximize the horizontal distance traveled by the body's center of mass. For the vertical jumping, the goal was to maximize the height reached by the body's center of mass.</p> <p>Results</p> <p>As a result, it was found that the hip joint was utilized more vigorously in the horizontal jumping than in the vertical jumping. The muscles that have a function of joint flexion such as the m. iliopsoas, m. rectus femoris and m. tibialis anterior were activated to a greater level during the countermovement in the horizontal jumping with an effect of moving the body's center of mass in the forward direction. Muscular work was transferred to the mechanical energy of the body's center of mass more effectively in the horizontal jump, which resulted in a greater energy gain of the body's center of mass throughout the motion.</p> <p>Conclusion</p> <p>These differences in the optimal coordination strategy seem to be caused from the requirement that the body's center of mass needs to be located above the feet in a vertical jumping, whereas this requirement is not so strict in a horizontal jumping.</p

INFLUENCE OF TURN RADIUS OF RUNNING ON TORSIONAL LOADING OF THE TIBIA

The purpose of this study was to investigate influence of turn radius of running on the torsional loading of the tibia. Six male subjects ran on a straightway and anti-clockwise corners with different turn radiuses (R=15m and 5m). Data were collected using two high-speed cameras and force platforms. The torsional stresses acting on the inner tibias of runners were compared among each running condition. At beginning, net torsional moments at both ends of the lower leg were calculated. Then, the tibial torsional stresses were estimated, based on equilibrium of those moments. Much larger torsional stress acted on the tibia in later portion of the stance phase of sharper cornering compared to other two running conditions. Mean value of the maximum stress in sharper cornering was also significantly larger (

THE CHALLENEGE OF NEW APPROACHES IN BIOMECHANICS

The target of our biomechanical research is to analyze the mechanics of motion, focusing especially on the behavior of the muscle-tendon complex during dynamic human movements. In our quest to better understand human motion, we have developed the several research methodologies. In the keynote lecture, I will discuss some of the techniques we have used and what we have learned from them. Specifically I will focus on the following: 1. Ultrasonography 2. Computer Simulation 3. Optical vs Inertial Sensor Analysis

Kinetic analysis of fingers during fastball and curveball pitches

This study aims to reveal the function of fingers during fastball (FB) and curveball (CB) pitches of a male adult who had played university baseball pitcher by conducting kinetic analysis on throwing motion with a link-segment model including finger segment. There was no apparent difference in the timing of peak finger joint angle between FB and CB pitches. Peak finger adduction toque in CB pitch occurred just More ball release. In addition, there was an apparent difference more than 30 ms in the timing of peak finger flexion and abduction toque between FB and CB pitches. Previous comparisons of kinematic data for shoulder and elbow revealed similarities between FB and CB pitches. These results suggest that skilled pitcher may minimize visible distinguishing characteristics among pitches and generate different amounts of ball spin at release among pitches adjusting the timing of peak finger torque

DIFFERENT EFFECTS OF APPROACH LENGTH ON SAGITTAL AND FRONTAL JOINT KINETICS DURING A RUNNING SINGLE-LEG JUMP

The approach lengths in running single-leg jumps (RSLJs) vary depending on various sports. We examined the effects of approach length on joint kinetics in RSLJ. We analysed RSLJs for height from the approaches of 1, 3, 5, and 7 steps by 10 male jumpers. The approach length did not have a main effect on hip extension torque (from 3.18±0.46 to 3.41±0.65 Nm/kg), while the hip abduction torque increased with increase in approach length (from 1.84±0.38 to 2.62±0.66 Nm/kg). The lumbosacral lateral flexors behaved similarly to the hip abductors. Results suggest that the greater frontal torques must be exerted from longer approaches whereas the greater hip extensors are important for RSLJs from shorter approaches. The findings provide the information for athletes what torque exertion ability should be trained with a priority depending on their approach lengths