CHANGES IN VERTICAL JUMP PERFORMANCE AS A RESULT OF ALTERING THE FORCE-TIME CURVE TO EXHIBIT A SMOOTH RISE TO PEAK FORCE

Abstract

INTRODUCTION Many individuals exhibit vertical jumping forcetime profiles that have multiple maxima. Based upon the discussions of Hochmuth (1984), the perfect force-time curve exhibited in a vertical jump, is one that exhibits an immediate rise to maximum force followed by a maintenance of maximum force for as long as possible until force application to the ground immediately ceases. Graphically, force with respect to time would resemble a square impulse. Physically this type of force production is impossible to generate by the human body. Pilot work examining force-time curves in vertical jumping indicated that some individuals generated smooth rises to a single maximum peak force. Continuing Hochmuth's argument, a smooth rise to a single peak force is most likely the best performance that one could exhibit. The exploratory question then becomes: Do smooth rises to peak force enhance performance? The purpose of this investigation was to examine the effects of altering existing force-time curves mathematically to produce a smooth rise to a single peak force. METHOD Smooth rises to peak force were attained by fitting a parabolic trajectory to the force record of 43 individuals. It was hypothesized that Effective Integration of the System (EIS) scores and vertical jump heights would improve as a result of fitting a parabolic rise to peak force. Variables with respect to time of jump, magnitude of maximum force, time of eccentric and concentric contractions were not altered. RESULTS AND CONCLUSIONS In every instance, EIS and vertical jump heights improved. EIS improved from 18.96% to 40.43% after creating a smooth rise to peak force. Vertical jump height improved from an average of 33.66cm to 50.08cm as a result of altering the forcetime profile. The result of manipulating force-time curves to exhibit a smooth rise to peak force resulted in improved performance (i.e., hypothetically) for all individuals (n=43). The prediction model for skillfulness also increased significantly E IS and vertical jump height following parabolic fitting. Admittedly, altering force-time curves to obtained a smooth rise to peak force does not offer significant insights into what to alter or how to alter movement in vertical jumping to elicit smooth rises to peak force. However, increased hypothetical performance measures certainly indicate that future investigations should examine other force-time patterns effects on performance and determine variables (e.g., in the kinematic record) that are conducive to assisting performers in producing smooth rises to maximum force application to the ground.