[[alternative]]Reliability Of Selected Lower Limb Joint Kinetic Parameter

[[abstract]]In the past, many biomechanical studies were constrained by cost, time, and equipments. One of these factors can lead to poor research directly or indirectly. If researches are not sensitive to the statistical power, it may lead to support null hypothesis and claim the result is demonstrating by the treatments or conditions had the effect. The purpose of this study was to (1) find out every coefficient of variation (CV) of selected kinematic and kinetic parameters on lower limb joint of children during vertical jump (VJ) and standing long jump (SLJ). (2) determine the appropriate number of trials to establish a stable mean and reliability of selected kinetic parameters on lower limb joint of children during VJ and SLJ. Thirty primary school students were selected as subject( In VJ, N=14, age 12.1±0.8 years, height 153.1±6.9 cm ,weight 50.9±12.4 kg; In SLJ, N=16, age 11.4±0.5 years, height 143.7±11.9 cm ,weight 37.4±12.6 kg) to perform 25 trials of maximum VJ or SLJ. One Kistler force plate (600Hz) and one JVC digital camera (60Hz) were used to collect the data. The peak moment and power of lower limb joint were calculated by inverse dynamic method. Sequential estimation technique was used to determine the optimum number of trials. Based on the results of this study (1) In VJ, the most CV of kinetic parameters were bigger than kinematics’. ( not including the horizontal speed of center of gravity of takeoff ) And the kinetic parameter, power of hip joint, was the biggest. (2) In SLJ, the most CV of kinetic parameters were bigger than kinematics’. And the kinetic parameter, power of knee joint, was the biggest. (3) the best number of trials was suggested at least 13-trial for VJ and 14-trial for SLJ by Sequential estimation procedure. Therefore, in order to get a stable mean for kinetic variables, a multiple-trial protocol needed to be adopted.