THE DIFFERENCES BETWEEN HORIZONTAL AND VERTICAL DIRECTION DURING A SINGLE-LEG REBOUND JUMP: OBTAINED USING THREE-DIMENSIONAL MOTION ANALYSIS

The purpose of this study was to clarify the differences between single-leg rebound jump for horizontal direction (HSJ) and vertical direction (VSJ) in terms of three-dimensional joint kinetics for the take-off leg focused on frontal plane movement. Eleven male track and field athletes were performed the HSJ and VSJ. Kinematics and kinetics data were recorded using Vicon T20 system (250 Hz) and force platforms (1000 Hz). In HSJ, as compared to VSJ, the joint kinetics characteristics are as follows: 1) the hip abduction torque and torque power around the adduction-abduction axis are larger; and 2) the trunk lateral flexion torque and torque power around the adduction-abduction axis are larger. Therefore, the hip adduction-abduction and trunk lateral flexion-extension movement plays an important role in a single-leg jump. Additionally, this is pronounced in HSJ as compared to VSJ

Characteristics of the Long Jump Take-off as the Novice Increases the Number of Steps in the Approach Run

AbstractThis study clarified factors affecting the increase in jump distance when the novice increased the number of steps in their approach run in the long jump, and discusses a training task designed to improve performance in the long jump. Twenty-eight male students who were novices in long jump and did not take part in any sport activity regularly participated in the study. They performed the long jump with run-ups of six and twelve strides. The take-off motions of the participants were captured with a high-speed digital camera (120 fps) for two-dimensional motion analysis. When students increased the number of steps in their approach run, the jump distance and approach velocity increased, horizontal deceleration during the take-off phase remained almost unchanged, and the vertical velocity at take-off and the contact time decreased. The change rate of the jump distance between six and twelve steps for the approach run had positive correlation with the change rates of the approach velocity and vertical velocity and negative correlation with the change rate of the contact time. In a previous study using athletes as participants, all athletes increased their jump distance as they increased the number of steps in their approach run. In the present study, however, many students did not increase their jump distance, and the change rate of the jump distance had a wide distribution. Therefore, we divided the students into groups according to whether the participant's change rate of the jump distance was lower or higher than the average change rate for all participants. Although both groups had increased horizontal velocity at touchdown for the lengthened run-up, participants in the low group did not increase their jump distance and their vertical velocity at take-off decreased. Additionally, in comparison with athletes, students had lower vertical velocity at take-off and horizontal deceleration during take-off. A novice should thus learn the proper technique of take-off to generate vertical velocity through horizontal deceleration

THE EFFECT OF INCREASING JUMP STEPS ON THE TAKE-OFF LEG IN BOUNDING

The purpose of this study was to clarify the effect of increasing jump steps in bounding in terms of three-dimensional joint kinetics for the take-off leg. Eleven male track and field athletes performed horizontal bounding from the standing posture. Kinematic and kinetic data were recorded using a Vicon T20 system (250 Hz) and force platforms (1,000 Hz). As jump steps increased, the joint kinetics characteristics are as follows: 1) ankle plantar flexion torque and knee extension torque and power increased, but hip extension torque and power did not increase; and 2) hip external torque and power (negative and positive) increased, particularly hip abduction torque and power. Therefore, in bounding initiated from the standing posture, ankle and knee joint kinetics from the sagittal plane and 3dimensional hip joint kinetics increased, particularly on hip adduction-abduction axis

DEVELOPMENT OF MULTISTEP DROP JUMP TEST BY USING DIFFERENT DROP HEIGHTS

We used different drop heights to evaluate the drop jump (DJ) test in elite athletes. Male jumpers (n=10) performed the test at 0.3, 0.6, 0.9, and 1.2 m. Jumping motions in the sagittal plane and the ground reaction force were recorded using a high-speed camera and force platform, respectively. The amount of negative work by 3 lower extremity joints increased with increased drop height of the DJ test, mainly at the hip joint. There were different performance patterns on the DJ test and lower extremity power output with an increased drop height according to individual characteristics of elite jumpers, compared with the average pattern. Jump performance was correlated with the DJ index at DJ1.2 and the decreased rate of the index from DJ0.3 to DJ1.2. Thus, to evaluate elite jumpers’ performance, various height ranges including a higher drop height should be used

COMPARISON OF PULL AND CATCH PHASES DURING CLEAN EXERCISESE

The purpose of this study was to identify differences in kinetic characteristics between the performed the PC at 30%, 60%, and 90% of one repetition maximum. Kinetic data were collected from recorded data by using a Vicon motion system and force platforms. In the comparison between the pull and catch phases, the kinetic characteristics of the catch phase were as follows: 1) The peak ground reaction force did not significantly differ according to load. 2) Ankle and knee kinetics showed large values. 3) The force and power in the ankle and knee did not significantly differ between the light load (30%) and heavy load (90%). Therefore, the importance of using PC in training not only for the pull movement but also for the catch movement

DEVELOPMENT OF A NEW ASSESSMENT METHOD FOR THE REBOUND JUMP TEST

We have proposed a new assessment method using joint kinetics and performance variables in the rebound jump (RJ) test. Twenty-seven male jumpers performed the RJ test. The Quick Motion Analysis System (jointly developed with DKH Inc.) was used to measure joint torque, power, and work of the three lower limb joints in real time, with high precision. High-performance jumpers had high performance values and showed a significantly large amount of joint work in the ankle and hip joints on the RJ test. Comparison of the work of the three lower limb joints confirmed a conflicting relationship between the hip and knee joints and that of the ankles, indicating that this new system is useful for evaluating joint kinetics of the three lower limb joints and may contribute greatly to the assessment of muscle strength and power

THE CHARACTERISTICS OF HITTING MOTION USING BATS HAVING DIFFERENT LENGTH AND MASS BUT EQUAL MOMENT OF INERTIA

The aim of this study was to investigate the characteristics of hitting motion when using training bats with altered length and mass. Four different long bats (LB) and four different weight bats (WB) that had the equal moment of inertia (MOI) were manufactured based on a normal bat (NB; 0.84 m, 0.90 kg). Eleven male collegiate baseball players performed tee batting with maximal effort. The hitting motion was analyzed using a VICON (250 Hz) to collect nine reflective markers fixed on the body and bat. Results indicated that the angular displacement of the trunk twist tended to be larger in LB with increasing MOI. And it was remarkable in subjects with smaller angular displacement of trunk twist in NB. Thus, compared to WB, LB may contribute to a larger angular displacement of trunk twist, particularly in players with smaller angular displacement of trunk twist in NB

THE COMPARISON TO THE CHARACTERISTICS OF THREE-DIMENSIONAL JOINT KINETICS BETWEEN SINGLE LEG AND DOUBLE LEG REBOUND JUMP

The purpose of this study was to clarify the differences between the SRJ and DRJ in terms of three-dimensional joint kinetics for the takeoff leg. Twenty male track and field athletes were performed repeated rebound jump with single leg (SRJ) and double leg (DRJ). Kinematics and kinetics data were recorded using Vicon T20 system (250 Hz) and force platforms (1000 Hz). When comparing a SRJ to a DRJ, the characteristics of the former are as follows: 1) the jump height by a single leg is significantly higher because of the larger hip joint work around the extension-flexion, especially on the abduction-adduction axes; 2) the hip extension and abduction torque is larger; and 3) in the SRJ, the hip abduction torque is larger than the hip extension torque. Therefore, the joint kinetics of the SRJ is characterized by the large hip abduction torque, in addition to the large hip extension torque

KINEMATICS OF THORAX AND PELVIS DURING MAXIMAL ACCELERATED SPRINTING

Changes in thorax and pelvis movements during acceleration phase of maximal sprinting, which relate to acceleration ability, are still unknown. This study aimed to clarify the changes in thorax and pelvis movements during maximal accelerated sprinting and its relation to better acceleration ability. Twelve sprinters performed a 60-m sprint, during which 3D kinematics of the sprinters were obtained. The same patterns of motions were maintained for thorax and pelvis respectively throughout the entire acceleration phase, although phase profiles of relative movements between thorax and pelvis in three planes differed. Moreover, results indicated that effective acceleration is characterised by suppressed trunk bend, delayed trunk rotation, and forward tilted pelvis in the middle acceleration section and suppressed trunk bend in the final acceleration section

EFFECTS OF STRETCH-SHORTENING CYCLE DURING TRUNK-TWIST EXERCISE USING DIFFERENT LOADS

The purpose of this study was to investigate the effects of stretch-shortening cyde (SSC) movement during bunk-twist and whether the effects change on increasing the loads by using a special trunk-twist machine. Twenty-one male college students performed trunktwist exercise with 3 loads. Participants performed this exercise for each load by using SSC and not using SSC (CON). Kinematic and kinetic data were recorded using Vimn system (250 Hz) and force platform (1,000 Hz). The following effects of SSC for this exercise were observed: (1) peak bar angular velocity was not potentiated by SSC, but SSC contributed to the acceleration of bar angular velocity and (2)for heavy loads, SSC did not affect mean angular velocity of the bar, upper trunk and pelvic rotation. Moreover, peak joint torque power of trunk-twist significantly decreased with heavy loads