FORCE AND MOMENT EXERTED BY EACH HAND ON AN INSTRUMENTED GOLF CLUB

This article shows an issue of the analysis on golf swing motion, and then introduces an instrumented golf club as a solution for the issue. During the golf swing motion, the upper limbs and a club make a closed multisegment loop, where it is impossible to calculate the forces and moments exerted by each hand via inverse dynamics due to the kinetic redundancy of the closed loop system. An instrumented grip handle equipped with twelve sets of strain gauges was designed to measure the forces and moments exerted by each hand. The results of kinetic analysis for a professional golf instructor indicates that 1 ) the force exerted along the club shaft by the grip-end side hand shows significant large values toward the ball impact, and 2) the forces exerted by both hands in the axes that are perpendicular to the club shaft show coupled force patterns

DYNAMIC CONTRIBUTIONS OF SUPPORT LEG JOINT TORQUES TO THE GENERATION OF THE IPSILATERAL KNEE JOINT MOTION AND GROUND REACTION FORCE IN SPRINTING

This study aimed 1) to quantify the contributions of the support leg joint torques to the generation of the anteroposterior forces, and 2) to clarify major contributors to the support leg knee joint angular velocity in terms of generating factors of the motion-dependent term (MDT) in sprinting. Dynamic contributions of the support leg joint torques in the maximal speed sprinting for elite and sub-elite sprinters were calculated, and the generating factors of the MDT were quantified The results showed that 1) ankle plantar flexion torque is the largest contributor to the generation of propulsive force regardless of performance level, and 2) the major contributors to the support knee flexion for sub-elite sprinter were ankle plantar flexion and hip flexion torques

DETERMINING THE DYNAMIC CONTRIBUTIONS TO KICKING FOOT SPEED IN RUGBY PLACE KICKING

The purpose of this study was to determine the dynamic contributions of joint torques to the generation of kicking foot speed in rugby place kicking. Motion capture and ground reaction force data were recorded from three Japanese rugby players, who were instructed to kick as far and as straight as possible. Each kicker‘s whole body was modelled as a system of 15 rigid-linked segments. The major contributors were calculated using equations of whole-body motion, including consideration of the generating factors of the motion-dependent terms. The flexion torque at the kicking leg hip joint was found to be the largest contributor for all kickers; exerting large flexion torques at the kicking hip joint throughout the final aerial phase of the approach and the subsequent kicking action appears crucial for obtaining a large kicking foot speed

KINETIC ANALYSIS OF EACH HAND IN BASEBALL BATTING MOTION AT DIFFERENT HITTING POINT HEIGHTS

The purpose of this study was to clarify the kinetic features of each hand under conditions of different hitting-point heights in the baseball tee-batting by using a bat with instrumented grip-handle. Twenty-three collegiate male baseball players’ motion were captured with a VICON MX system (12-cameras, 250Hz), and kinetic data at each hand were measured by using the instrumented bat equipped with 28 strain gauges (1000Hz). The vertical displacement of the hitting-point on the bat was mostly dominated by translational movement of the bat. The work of the force of vertical component showed that the positive work of knob-side hand was significantly larger at down swing and level swing phases. These results indicate that the knob-side hand is a great contributor to adjust the bat into the different hitting-point height in each phase

MAIN CONTRIBUTORS TO HIP JOINT MOTION IN SWING LEG DURING MAXIMAL VELOCITY PHASE IN SPRINT

The purposes of this study were 1) to quantify the dynamic contributions of the individual terms; such as, joint torque term, gravitational term, and motion-dependent term (MDT), to the generation of angular velocity of the swing leg hip joint, and 2) to investigate the main contributors to the hip angular velocity considering the generating factor of the MDT. Three male sprinters performed maximal-effort sprinting. Dynamic contributions of the individual terms were calculated, and then the generating factors of the MDT were quantified using a recurrence formula. The results showed that 1 ) the MDT is one of the great contributors to the hip joint angular velocity, and 2) main contributors of the swing leg hip angular velocity are not only instantaneous and cumulative effects of the swing leg hip joint torque but also instantaneous effect of the contralateral hip joint torque

DYNAMIC CONTRIBUTION OF JOINT TORQUES TO THE GENERATION OF SWING LEG MOTION IN SPRINT

The purposes of this study were 1) to investigate the contribution of individual terms such as the swing leg joint torques, motion-dependent term (MDT) and other terms to the generation of the knee joint angular velocity, and 2) to quantify the functional roles of the joint torques in the swing leg motion with consideration of the generating factor of the MDT. The swing leg was modeled as a linked system of three rigid segments in sagittal plane. Dynamic contributions and generating factors of the MDT were calculated using the equation of motion for the swing leg model. The results obtained in this study indicate that 1) the MDT was one of the great contributors to the generation of the knee joint angular velocity, and 2) the main generating factors of the MDT were the swing leg joint torques

EFFECTIVE TIMING OF EXERTING JOINT TORQUES TO OBTAIN BASEBALL BAT HEAD SPEED

The purpose of this study was to quantify the effective timings of exerting joint torques for obtaining a large bat head speed at the ball impact in baseball batting motion. Twelve baseball batters performed hitting a teed ball as strongly as possible. The whole-body segments with bat were modelled as a system of sixteen-rigid linked segments. The kinematic and kinetic data were measured with the motion capture system with 3 force platforms and an instrumented bat. The major contributors were calculated using the equation of the whole-body motion considering the generating factors of the motion-dependent term. Since the instances when the individual contributions show peak values differ among the contributions of the major positive contributors, effective timings of exerting large joint torques exist for obtaining a large head speed at the ball impact

DYNAMIC CONTRIBUTION ANALYSIS ON THE PROPULSION MECHANISM OF SPRINTER DURING INITIAL ACCELERATION PHASE

The purpose of this study was to propose a method that quantifies the functional roles of the support leg joint torques during sprinting acceleration phase. The acceleration of whole-body centre of gravity caused by the joint torques at 1st, 3rd, 5th and 7th steps from the crouch start were calculated based on the equation of motion for the whole body modeled as a linked system of fifteen rigid segments. The generation mechanism of eccentric ankle joint torque was quantified as the contributions of joints torques to the generations of joint angular velocities. The results indicate that 1) the eccentric plantarflexion torque is the largest contributor to the whole-body propulsion, 2) the eccentric plantarflexion torque is generated by the torques of hip and knee joints, and 3) the step number influences the propulsion mechanism

MID-GRIP FORCES AND MOMENTS ESTIMATED FROM POLE DEFORMATION IN POLE VAULTING

The pupose of this study was to propose a method which estimates resultant force and moment from the shape of deformed pole based on a static equilibrium equation. The force and moment were assumed to be exerted at the middle point of both hands on the pole. The pole was modelled as a series of 11 rigid segments connecting its adjacent segment via a virtual rotational joint with a rotational spring component. The stiffness of the spring was identified from a static load test. The resultant mid-grip force and moment were calculated from a static force-moment equilibrium equation. The results indicate that the kinetic values obtained by the proposed method show similar values reported in the previous study which utilized a force plate

KINETIC ANALYSIS OF THE UPPER LIMBS IN BASEBALL TEE-BATTING UNDER LOW HITTING POINT HEIGHT CONDITION

Hitting low height balls is more difficult for baseball batters in comparison to hitting high and middle height balls. The purpose of this study was to investigate the kinetic features of the individual upper limb joints among different skill level players in baseball tee-batting under the low hitting point height condition. Twenty-three collegiate baseball players were instructed to hit three kinds of hitting point height balls. Kinematic and kinetic analyses were implemented together with a motion capture system and an instrumented bat. The findings indicate that highly skilled batters exert great extension torque of the barrel-side (top hand) shoulder joint in the first half of the forward swing period in order to hit low point height balls. It is speculated that the large initial flexion angle of the barrel-side shoulder joint can help to increase the torque and angular velocity of the shoulder joint