CHARACTERISTICS OF THREE LOWER LIMB JOINT KIMETICS DURING THE REBOUND JUMP IN FEMALE ATHLETES

The aim of this study was to describe the lower limb muscle strength and power exertion characteristics of female athletes during the rebound jump (RJ) test. Forty-eight female soccer and basketball players performed the test, while the Quick Motion Analysis System was used to calculate joint kinetics (torque, power, and work of the three lower limb joints) in real time with high precision. A high correlation was found between the RJ index and contact time, jump height. In addition, a low correlation was found between jump height and contact time. However, the mechanical variables related to contact time and jump height were different. Therefore, for female athletes, the ability to shorten the contact time and the ability to obtain a jump height are considered independent abilities

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

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 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

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

EFFECTS OF MOVIE OBSERVATION AND MOTOR IMAGERY ON PERFORMANCE AND JOINT KINETICS DURING TAKE-OFF IN DROP JUMP

The aim of this study was to investigate the effects of movie observation and motor imagery intervention during the pre-set phase (prior to jumping off the platform), on drop jump (DJ) performance and the variables of lower leg kinetics. Three male jumpers performed the DJ under three different conditions (Normal, Movie, and Imagery) from a drop height of 0.3 m. The performance variables and joint kinetics were measured. The DJ performance tended to improve with the intervention of movie and imagery condition. Moreover, the negative ankle joint and positive hip joint kinetics variables (power and work) tended to improve with the intervention of movie and imagery condition. Therefore, it was suggested that movie observation and motor imagery intervention could improve DJ performance and the force exerted by lower leg, which affects performance

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

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

Association of multi-phase rates of force development during an isometric leg press with vertical jump performances.

PurposeThis study aimed to elucidate characteristics of explosive force-production capabilities represented by multi-phase rate of force developments (IRFDs) during isometric single-leg press (ISLP) through investigating relationships with countermovement (CMJ) and rebound continuous jump (RJ) performances.MethodsTwo-hundred-and-thirty male athletes performed ISLP, CMJ with an arm swing (CMJAS), and RJ with an arm swing (RJAS). IRFDs were measured during ISLP using a custom-built dynamometer, while CMJAS and RJAS were measured on force platforms. The IRFDs were obtained as rates of increase in force across 50 ms in the interval from the onset to 250 ms. Jump height (JH) was obtained from CMJAS, while RJAS provided JH, contact time (CT), and reactive strength index (RSI) values.ResultsAll IRFDs were correlated with CMJAS-JH (ρ = 0.20-0.45, p ≤ 0.003), RJAS-JH (ρ = 0.22-0.46, p ≤ 0.001), RJAS-RSI (ρ = 0.29-0.48, p ConclusionThe early phase (onset to 150 ms) IRFDs measured using ISLP enabled the assessment of multiple aspects of leg-extension strength characteristics that differ from maximal strength; these insights might be useful in the assessment of the athletes' leg-extension strength capabilities

A LONGITUDINAL INVESTIGATION ON DROP JUMP PERFORMANCE-FOCUSING ON BRAIN CONDITION DURING PRE-SET, STRETCH REFLEX AND JOINT KINETICS DURING TAKE-OFF

The purpose of this study was to investigate the change in drop jump (DJ) performance with a training process that focused on the state of the brain during the pre-set phase, the stretch reflex during the take-off phase, and the joint kinetics of lower extremities during take-off phase. Three male sprinters performed DJ from a drop height of 0.6 m. We measured variables for state of the brain during the pre-set phase, stretch reflex, and kinetics of lower extremities during take-off. The results revealed that the brain showed disinhibition during the pre-set phase, and stretch reflex facilitation, and an increase in force development of the ankle joint were observed during the take-off phase. Therefore, we propose that the mutual enhancement on component of performance in each phase may be effective in improving DJ performance during a training course