Vertical jump performance is an integral component to success in many athletic endeavors. Measurement of an athlete's jump prowess is typically accomplished with a Vertec (Sports Imports; Columbus, OH) which merely indicates the vertical height attained. However a recently created device calculates jump height from measurements collected as a person ascends, remains in the air, and lands on an instrumented platform. Before the new device can be used instead of a Vertec, the reliability of its jump heights in relation to the latter device must first be ascertained. Thus the purpose of this project is to assess the reliability of jump heights measured from the instrumented platform to those concurrently obtained from the Vertec. Subjects (n = 105) performed two separate jump trials. Preceded by a familiarization session, each trial consisted of a warm-up, followed by a series of vertical jumps performed with maximal effort. The instrumented device included a triangular-shaped platform and three load cells that measures forces associated with the vertical jump. Next to the instrumented platform was a Vertec, which is equipped with slap sticks separated by 1.27cm increments to provide simultaneous measurement of subject's performance. Thus with each jump, values derived from the instrumented platform were compared to those of the Vertec to assess the reliability of the former device. On-line data collection and software (Labview 8.0, Austin, TX) calculated subject's jump performance from the instrumented platform based on their takeoff, hang time, and landing. Reliability assessed platform vertical jump estimates from takeoff, hang time and landing to Vertec values. Intraclass correlation coefficients were used to determine reliability. With Vertec values as the criterion measure, intraclass correlation coefficients were as follows: takeoff = 0.90, hang time = 0.93 and landing = 0.67. Results suggest vertical jump estimates from takeoff and hang time, but not landing, serve as reliable measures from performance assessed from the Vertec. Apparently as subjects landed on the platform, impact forces reduced the reliability of height estimates derived from landing. In contrast, since subjects remained motionless at the start of jumps, this may have reduced the variability of the data and increased the reliability of measurements derived from takeoff on the platform. Future work should attempt to derive more reliable estimated from landing measurements, yet current results suggest the instrumented platform may be beneficial in the assessment of vertical jump performance.
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