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The authors investigated how changes in action capabilities affect estimation of affordances for another actor. Observers estimated maximum jumping-reach height for themselves and another actor. Half of the observers wore ankle weights that reduced their jumping ability. The ankle weights reduced estimates of maximum jumping-reach height that observers made for themselves and for the other actor, but only after observers had the opportunity to walk while wearing the weights. Changes in estimates closely matched changes in actual jumping-reach ability. Results confirm and extend recent investigations that indicate that perception of the spatial layout of surfaces in the environment is scaled to an observer's capacity to act, and they link that approach to another embodied cognition perspective that posits a link between one's own action capabilities and perception of the actions of other agents. Keywords: Action understanding; Affordance perception; Embodiment.

The purpose of the present study was to determine the number of familiarization sessions required to obtain an accurate measure of reliability associated with loaded vertical jump and 20-m sprint running performance. Ten physically active men attended 5 separate testing sessions over a 3-week period where they performed unloaded and loaded (10-kg extra load) countermovement (CMJ) and static (SJ) jumps, followed by straight-line 20-m sprints. Jump height was recorded for the vertical jumps using a jump mat, while the time for 10 m and 20 m was recorded during the sprints using photocells. The highest (jump conditions) and fastest (sprint) of 3 trials performed during each of the 5 testing sessions was used in the subsequent analysis. Familiarization was assessed using the scores obtained during the 5 separate testing sessions. Reliability was assessed by calculating intraclass correlation coefficients (ICCs) and coefficient of variation (CV). No significant differences were obtained between the testing sessions for any of the measures. ICCs ranged from 0.89 to 0.95, while CVs ranged from 1.9 to 2.6%. These results indicate that high levels of reliability can be achieved without the need for familiarization sessions when using loaded and unloaded CMJ and SJ and 20-m sprint performance with physically active men. KEY WORDS. vertical jump, sprinting, reproducibility, learning

This article examines the validity of a new athletic performance test. A discussion of the testing procedure, jump assessment, and retest reliability is presented.

This article examines the correct use of force plates to measure vertical jumping height, focusing on several areas in which errors can occur. Researchers present a model of jumping height measurement that considers body mass measurement, take-off point, integration frequency, and the determination of the start of movement.

To assess differences between the Vertec and the Just Jump Systems in measuring height of vertical jump, 248 boys and 232 girls between 7 and 11 years were required to perform four maximal countermovement vertical jumps. A maximum of the four trials recorded was the dependent variable. Each vertical jump was simultaneously evaluated by each measuring device and a paired t test indicated the systems were significantly different; however, the experimentwise difference of .93 in. has no practical value. The Just Jump System seems a viable alternative. Advantages and potential pitfalls regarding the use of each system are discussed.