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

SPECIFICITY OF TORQUE PRODUCTION TO MUSCLE CONTRACTION AT HIP, KNEE AND ANKLE JOINTS

Ten male college students performed the simple strength test of the lower limb with using isokinetic dynamometer. The values of flexion and extension torques tended to be the largest at the hip and smallest at the ankle joint in both ECC and CON. However, the ratio of ECC/CON (%) was significantly greater at ankle joint compared with the hip and knee. These finding indicate that ankle joint produce torque more efficiently by ECC than by CON. Also, the correlation coefficients between the values of torques were not significant among three joints. These finding indicate that the ability of torque production is independent in each joint. These results suggest that the characteristics of torque production by the hip, knee and ankle joint vary considerably, reflecting their structural and functional properties

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

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 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

EFFECT OF LEG STIFFNESS DURING REBOUND JUMP ON SPRINT RUNNING KINEMATICS AND KINETICS

We investigated the relationship between stiffness in rebound jump (RJ) and kinematics and kinetics of the support- and swing-leg in sprint running (SP). We included 13 male track and field athletes performing maximal effort SP and RJ. During the support phase, kinematics, kinetic, and leg stiffness parameters were calculated using a force platform and data from a high-speed video camera that recorded movement in the sagittal plane. A significant correlation was observed between SP and RJ for stiffness (r = 0.683). In SP, stiffness was significantly correlated with contact time (r = -0.659), mean joint torque at the ankle (r = 0.703) and knee (r = -0.726) joints, CG (center of gravity) -toe distance (r = -0.818), and the swing-leg angle (r = -0.676) at touch down. Based on our results, kinematics and kinetics correlated with stiffness in SP are affected by RJ stiffness