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  • Author: Peter F. Vint x
  • Athletic Training, Therapy, and Rehabilitation x
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Peter F. Vint and Richard N. Hinrichs

Isometric knee extension force and average integrated EMG of the vastus lateralis muscle were obtained from 27 healthy subjects using a maximum effort, ramp and hold protocol. In each of the 125 total trials mat were included in the analysis, a 2-s plateau region was extracted and divided into two adjacent 1000-ms bins. Variability and reliability of bin-to-bin measurements of force and EMG were then evaluated across 14 different integration intervals ranging from 10 to 1000 ms. Statistical analyses of bin-to-bin variability measures demonstrated that integration intervals of 250 ms and longer significantly reduced variability and improved reliability of average integrated EMG values during maximum effort isometric exertions. Bin-to-bin EMG reliability increased from .728 at 10 ms to .991 at 1000 ms. Force parameters appeared less sensitive to changes in length of the integration interval. It was suggested that longer intervals might also improve the validity of the EMG-force relationship during maximum effort isometric exertions by reducing problems associated with electromechanical delay.

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Peter F. Vint and Richard N. Hinrichs

The purpose of this investigation was to quantify the differences between one- and two-foot vertical jumping performances. Fourteen subjects performed both jump styles with a four-step, self-paced approach. While overall jump and reach heights were similar between one-foot and two-foot jumps, the strategies employed to achieve these results were notably different. One-foot jumps benefited from an increased takeoff height that was largely attributable to the elevation of the free swinging leg. Further, it was suggested that the actions of this limb may have helped slow the rate of extension of the support leg during the propulsion phase. Greater flight heights were achieved during two-foot jumps, as expected, but the magnitude of this difference was only about 9 cm. It was suggested that factors associated with the development of muscular tension, vertical velocity at touchdown, and horizontal approach speed may have all contributed to the unexpectedly small differences in flight height between one-foot and two-foot jumping performances.

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Scott P. McLean, Michael J. Holthe, Peter F. Vint, Keith D. Beckett and Richard N. Hinrichs

Ten male collegiate swimmers (age = 20.2 ± 1.4 years, height = 184.6 ± 5.8 cm, mass = 82.9 ± 9.3 kg) performed 3 swimming relay step starts, which incorporated a one or two-step approach, and a no-step relay start. Time to 10 m was not significantly shorter between step and no-step starts. A double-step start increased horizontal takeoff velocity by 0.2 m/s. A single-step together start decreased vertical takeoff velocity by 0.2 m/s but increased takeoff height by 0.16 m. Subjects were more upright at takeoff by 4°, 2°, and 5° in the double-step, single-step apart, and single-step together starts, respectively, than in the no-step start. Entry angle was steeper by 2°, entry orientation was steeper by 3°, and entry vertical velocity was faster by 0.3 m/s in the single-step together start. Restricting step length by 50% had little effect on step starts with the exceptions that horizontal velocity was significantly reduced by 0.1 m/s in the double-step start and vertical takeoff velocity was increased by 0.2 m/s in the single-step together start. These data suggested that step starts offered some performance improvements over the no-step start, but these improvements were not widespread and, in the case of the double-step start, were dependent on the ability to take longer steps.