HOW CAN WE TEACH STUDENT TO ESTIMATE VERTICAL JUMP HEIGHTS USING GROUND REACTION FORCE DATA

The purpose of this study was to estimate vertical jump heights using ground reaction force (GRF) data and to suggest one practical example of biomechanical theory application to a real human motion. Vertical jump heights of impulse and flight time method were statistically smaller than three-dimensional video method. The causes of height differences seemed mainly from the fact that impulse was used to move jumper into the horizontal direction as well as into the vertical direction. Other important factors for accurate height calculation are jumper's mass and threshold value of GRF data collection. Vertical jump height calculation with GRF data showed an example of practical application of biomechanical theory to human motion and demonstrated a way of GRF equipment use for effective biomechanical theory education

Effect of knee extensor fatigue level and sex on bilateral jump-landing

ObjectiveThe purpose of this study was to determine the effect of fatigue level and sex on the range of motions of the lower extremities and impulses during the jump-landing phase after performing bilateral fatiguing tasks.MethodsIn total, 41 healthy young adults volunteered for this study. Participants’ jump-landing trajectories were monitored using nine cameras, and ground reaction forces were measured using a force plate. Participants performed five maximal bilateral countermovement jumps as prefatiguing tasks. The fatiguing tasks consisted of maximal effort contractions of the knee extensor at 60°/s on a dynamometer until task failure, defined as the inability to reach 50% of the peak knee extension torque for three consecutive times. The post-task maximal bilateral jumps were immediately captured after the participants failed the fatiguing task. Participants were asked to perform this cycle again, performing the fatiguing contraction task until failure to reach 30% of the peak knee extension torque.Results and conclusionIt was found that the knee joint was more extended in the post-30% fatiguing task, which was due to the reduction of the flexion angle of the hip and knee joints in response to fatigue level. The impulses for both sexes were reduced at the severe fatigue level. Fatigability altered jump-landing kinematics, jump heights and impulses in response to fatigue level. The post-30% fatiguing task elicited more fatigue than the post-50% fatiguing task