THE DIFFERENCES BETWEEN DOUBLE AND SINGLE LEG TAKEOFF ON JOINT KINETICS DURING REBOUND-TYPE JUMP

The purpose of this study was to identify the differences between double and single leg takeoff on joint kinetics during a rebound-type jump. Twelve male track and field athletes performed repeated rebound-type jumps with double legs (DRJ) and a single leg (SRJ). Kinematics and kinetics data were recorded using a high-speed video camera (300 Hz) and force platforms (1000 Hz). The negative and the positive values of the joint torque power about the ankle joint were significantly lower in DRJ than in SRJ. However, the mean joint extension torque, and the negative value of the joint torque power about the hip joint was larger in SRJ than in DRJ. It is suggested that the joint kinetics characteristics, in SRJ as compared to DRJ, reveals a relatively large joint torque and torque power about the hip joint

KINEMATIC ANALYSIS OF CABLE FORCE DURING HAMMER THROWS WITH HEAVIER IMPLEMENTS

The purpose of this study is to compare the differences in cable force between throws with a competition hammer (7.26 kg) and a heavier hammer (8.0 kg). Sixteen male hammer throwers threw the competition and heavier hammers, and three-dimensional motion analyses were conducted. The maximum cable force of the heavier hammer was significantly higher than that of the competition hammer during the double support phase of the 3rd and 4th revolutions. This indicates that throws with the heavier hammer cause a load increase during a particularly important phase of the hammer head’s acceleration. This suggests that throws with a heavier hammer can be an effective training method for improving specific strengths to accelerate of the hammer’s head

EACH BODY SEGMENT FUNCTION DURING THE SUPPORT PHASE OF THE DROP JUMP

INTRODUCTION: The purpose of this study was to investigate each body segment function in the takeoff motion of the drop jump. Ten male athletes performed a drop jump with the height of 40cm. They were instructed to use arm action. Their takeoff motions were filmed at 20OHz with a high speed camera. Two-dimensional coordinates were obtained by digitizing the motion with a sampling frequency of 20OHz. The data was filtered with a Butterworth digital filter at 8.5Hz. BSP of Chandler et al. (1975) were used to estimate the segmental centers of gravity and the mass center of the whole body. This data were used to calculate the generated momenta of the arms trunk (head and trunk), takeoff legs, thighs, shanks and feet in the vertical direction using method of Ae et al. (1985). Accelerative forces were calculated generated momenta by numerical differentiation. RESULTS: The arms showed a positive (but small) accelerative force (accelerating the body upward) in the early half of the support phase, and a small negative force (checking the body downward) in the later half. The trunk showed a negative accelerative force immediately after the touchdown, then gave a twopeaked pattern of positive force in the midpoint of phase and a negative force in the phase immediately before the takeoff. The takeoff legs showed the positive accelerative force throughout the overall takeoff phase, which is especially large immediately after the touchdown and before the takeoff. The force of the takeoff legs was larger than that of other parts. The thighs showed a negative accelerative force immediately after touchdown, then gave a two-peaked pattern of positive one in the midpoint of phase, and the negative one. The thighs showed the same pattern as the trunk. The shanks gave both positive and negative force alternately during takeoff. The feet showed the positive accelerative force throughout the overall takeoff phase, having the larger one immediately after the touchdown and before the takeoff. CONCLUSIONS: The arms are charged with the function of accelerating the body upward in the early half of the support phase. The trunk takes the charge of accelerating around the midpoint of phase. The takeoff legs have the accelerating function throughout the overall takeoff phase. The thighs are charged with the function around the midpoint, the shanks in the phase immediately after the touchdown and before the takeoff, and the feet during the overall takeoff phase. The positive force of the feet is especially large in the phase immediately after the touchdown and before the takeoff, which accelerate the body upward

TECHNICAL FACTORS REQUIRED FOR PROPER BODY TRANSLATION IN THE DISCUS THROW

The purpose of this study was to gain knowledge about technical requirement in male discus throwers, specific to their performance level, by comparing the parameters of body translation. The performances of 22 male discus throwers were analyzed. The subjects were divided into the following three groups based on the distance thrown: advanced, medium, and novice. From the results of this study, it can be concluded that the relevant technical requirement for novice is a dynamic shifting of the center of gravity to the left during the first double support phase. Furthermore, pushing into the ground vigorously before push-off the left foot to drive the body toward the throwing direction during the flight phase would enable novice group to create greater momentum and achieve a higher performance level

CHARACTERISTICS OF STRENGTH AND POWER FOR THE RATE OF FORCE DEVELOPMENT DURING LEG EXTENSION

A multi-strength tester (MST) was developed to assess the rate of force development (RFD) during isometric leg extensions. This study aimed to examine the relationship between RFD measured by MST and strength and power performance. Participants performed isometric leg presses with MST, countermovement jumps, squat jumps (SJ), and concentric squat of 70% of 1 repetition maximum (sq70). Significant correlations were found between the early phases of RFD measured by MST and countermovement jump. There were no significant correlations found in SJ. The late phase of RFD measured by MST significantly correlated with sq70. The present results suggest that the early phases of RFD with MST relate with countermovement during jump performance. The late phase of RFD with MST relate with the ability of generating force under heavy resistance

COMPARISON OF WORLD ELITE AND JAPANESE ELITE THROWERS IN THE DISCUS THROW

The aim of this study is to clarify the differences between world elite and Japanese elite throwers in the discus throw by comparing their hip-shoulder and shoulder-arm separation angles. The performances of 12 male world elite discus throwers (the World group) and 12 male Japanese elite discus throwers (the National group) were analysed. The hip-shoulder and shoulder-arm separation through the throwing motion were greater in the World group than in the National group. In the World group, the hip-shoulder separation reached its local maximum at the middle of 2nd single support phase, and the shoulder-arm separation reached its local maximum around left-foot touchdown to the ground; whereas in the National group, the former reached its local maximum in the first half of 2nd single support phase, and the latter reached its local maximum in the middle of the delivery phase. Although the shoulder led hip in both the World and National groups, the shoulder led the arm in the National group and the arm led the shoulder in the World group at release. These results showed that the World group released the discus in front of the shoulder while utilising the kinematic-chain appropriately, while the National group released the discus with the arm still trailing behind the shoulder

短時間高強度運動における運動強度とエネルギー供給比率との関係： 個人内変動に着目して

This study investigated the relationship between exercise intensity and energy contribution in shortduration intensive exercise. Two competitive university sprinters performed 30-s pedaling tests at 4 high intensity levels, following a submaximal test to determine the energy contribution during the 30-s pedaling tests by using the linear regression between exercise power and O2 demand. The energy contribution in each subject was almost constant during the 30-s pedaling tests at the 4 high intensity levels. Furthermore, O2 uptake and peak blood lactate concentration increased with increasing O2 demand in each subject. These results suggest that the energy contribution during short-duration intensive exercise at different high intensity levels is almost constant and that aerobic and anaerobic energy increase with increasing exercise intensity in each individual

円盤投における高い初速度獲得のための動作要因間の因果関係

The purpose of this study was to investigate, using path analysis, causal relationships among motion factors for achieving a high release velocity in the male discus throw. The throwing motions of 61 male discus throwers were analyzed using three-dimensional motion analysis. Variables such as release velocity, velocities gained by each body segment, body segment velocity, body angle and angular velocity were obtained. The path model indicating the causal relationships among these factors was constructed by path analysis.　The main results were as follows:　Influences of velocities gained by each body segment on release velocity were largest for the arm, followed in order by the trunk and legs.　Motion factors such as weight shift, acquisition of the velocity of the center of gravity, sweeping the legs, rotations of the hip and shoulder, twisting and untwisting of the trunk, acquisition of the velocity of the right knee and extension of the left knee had direct or indirect influences on the velocities gained by each body segment.　Motion factors in the path model revealed causal relationships along the time sequence of the throwing motion. In addition, the path model in this study indicated the cause and effect structure of the throwing motion by which Japanese male discus throwers were able to achieve a high release velocity. The results of this study can be utilized for technical coaching of the discus throw based on causal relationships

ジャンプ運動における個人の反動動作特性を評価する方法の開発

The aim of this study was to examine the validity, reliability, and utility of a method for evaluating the characteristics of the counter movement jump. Fifty-two male track and field athletes (sprinters or decathletes) jumped from a 30-cm platform and consciously changed their counter movement times. This study determined the counter movement time required to achieve the highest jump.　The results are summarized as follows:　1. The waveform between the counter movement time and jumping height was an inverted U-shape.　2. It is normally accepted that the optimum counter movement time is determined via the jump test.　3. There was a significant correlation between the first test and the re-test in terms of the counter movement time.　4. Participants were classified into 5 groups based on their optimum counter movement times and highest jumping heights.　These results suggest that the newly developed jumping test discussed in this study is a valid method for evaluating the characteristics of counter movement