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Gregory C. Bogdanis, Athanasios Tsoukos, and Panagiotis Veligekas

Purpose:

To examine the acute effects of a conditioning plyometric exercise on long-jump performance during a simulated long-jump competition.

Methods:

Eight national-level track and field decathletes performed 6 long-jump attempts with a full approach run separated by 10-min recoveries. In the experimental condition subjects performed 3 rebound vertical jumps with maximal effort 3 min before the last 5 attempts, while the 1st attempt served as baseline. In the control condition the participants performed 6 long jumps without executing the conditioning exercise.

Results:

Compared with baseline, long-jump performance progressively increased only in the experimental condition, from 3.0%, or 17.5 cm, in the 3rd attempt (P = .046, d = 0.56), to 4.8%, or 28.2 cm, in the 6th attempt (P = .0001, d = 0.84). The improvement in long-jump performance was due to a gradual increase in vertical takeoff velocity from the 3rd (by 8.7%, P = .0001, d = 1.82) to the 6th jump (by 17.7%, P = .0001, d = 4.38). Horizontal-approach velocity, takeoff duration, and horizontal velocity at takeoff were similar at all long-jump attempts in both conditions (P = .80, P = .36, and P = .15, respectively).

Conclusions:

Long-jump performance progressively improved during a simulated competition when a plyometric conditioning exercise was executed 3 min before each attempt. This improvement was due to a progressive increase in vertical velocity of takeoff, while there was no effect on the horizontal velocity.

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Nicholas P. Linthorne

A mathematical model is presented of the takeoff phase in the pole vault for an athlete vaulting with a rigid pole. An expression is derived that gives the maximum height that the vaulter may grip on the pole in terms of the takeoff velocity, the takeoff angle, the athlete's vertical reach, and the depth of the takeoff box. Including the dependence of the vaulter's takeoff velocity on the takeoff angle reveals that there is an optimum takeoff angle that maximizes the vaulter's grip height. It is also shown that taller and faster vaulters are able to grip higher on the pole. The results of the investigation compare favorably with data for vaulters using bamboo and steel poles.

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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.

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Adrian Lees, Philip Graham-Smith, and Neil Fowler

This study was concerned with the measurement of performance variables from competitors in the men's long jump final of the World Student Games held in Sheffield, England, in July 1991. Several performances of 10 finalists were recorded on cine film at 100 Hz. Resulting sagittal plane kinematic data were obtained for the last stride, touchdown, and takeoff for a total of 27 jumps. It was confirmed that takeoff velocity was a function of touchdown velocity, and that there was an increase in vertical velocity at the expense of a reduction of horizontal velocity. It was concluded that there was evidence for mechanisms which may be termed mechanical, biomechanical, and muscular. The former relates to the generation of vertical velocity by the body pivoting over the base of support during the compression phase, and a lifting of the arms and free leg during the lift phase; the second is the elastic reutilization of energy; and the third is the contribution by concentric muscular contraction.

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George Vagenas and T. Blaine Hoshizaki

The sprint starts of 15 skilled sprinters were filmed and their sprinting times recorded while they were performing four 20-meter sprinting trials. They employed their natural hand-block spacings with alternative leg placements in the front starting block. The subjects were tested for dynamic strength on a force platform and their stronger leg was determined. Selected qualitative variables concerning certain perceived characteristics of lateral dominance and preferred leg for some basic motor skills were identified using a questionnaire. Significantly greater takeoff velocities and faster sprinting times were found when the stronger leg was placed in the front block. Previous empirical methods used in determining the best front leg in the start were found unreliable. Even some experienced sprinters fail to use their optimal leg in the forward position. Dynamic lower limb strength asymmetry was established as the key determinant in optimizing leg placement in the sprint start.

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James J. Dowling and Lydia Vamos

Subjects performed maximum vertical jumps on a force platform to reveal whether resulting force-time curves could identify characteristics of good performances. Instantaneous power-time curves were also derived from the force-time curves. Eighteen temporal and kinetic variables were calculated from the force- and power-time curves and were compared with the takeoff velocities and maximum heights via correlation and multiple regression. The large variability in the patterns of force application between the subjects made it difficult to identify important characteristics of a good performance. Maximum positive power was found to be an excellent single predictor of height, but the best three-predictor model, not including maximum power, could only explain 66.2% of the height variance. A high maximum force (> 2 body weights) was found to be necessary but not sufficient for a good performance. Some subjects had low jumps in spite of generating high peak forces, which indicated that the pattern of force application was more important than strength.

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Saied Jalal Aboodarda, Ashril Yusof, N.A. Abu Osman, Martin W. Thompson, and A. Halim Mokhtar

Purpose:

To identify the effect of additional elastic force on the kinetic and kinematic characteristics, as well as the magnitude of leg stiffness, during the performance of accentuated countermovement jumps (CMJs).

Methods:

Fifteen trained male subjects performed 3 types of CMJ including free CMJ (FCMJ; ie, body weight), ACMJ-20, and ACMJ-30 (ie, accentuated eccentric CMJ with downward tensile force equivalent to 20% and 30% body mass, respectively). A force platform synchronized with 6 high-speed infrared cameras was used to measure vertical ground-reaction force (VGRF) and displacement.

Results:

Using downward tensile force during the lowering phase of a CMJ and releasing the bands at the start of the concentric phase increased maximal concentric VGRF (6.34%), power output (23.21%), net impulse (16.65%), and jump height (9.52%) in ACMJ-30 compared with FCMJ (all P < .05). However, no significant difference was observed in the magnitude of leg stiffness between the 3 modes of jump. The results indicate that using downward recoil force of the elastic material during the eccentric phase of a CMJ could be an effective method to enhance jump performance by applying a greater eccentric loading on the parallel and series elastic components coupled with the release of stored elastic energy.

Conclusions:

The importance of this finding is related to the proposition that power output, net impulse, takeoff velocity, and jump height are the key parameters for successful athletic performance, and any training method that improves impulse and power production may improve sports performance, particularly in jumping aspects of sport.

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Christopher D. Ramos, Melvin Ramey, Rand R. Wilcox, and Jill L. McNitt-Gray

different example jumps. In Example A, the jumper has a horizontal takeoff velocity of 9.0 m/s and vertical takeoff velocity of 3.0 m/s, resulting in a horizontal displacement of 6.73 m. In Example B, the jumper has a smaller horizontal takeoff velocity of 8.5 m/s but greater vertical takeoff velocity of 3

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Athanasia Smirniotou, Flora Panteli, and Apostolos Theodorou

) horizontal (V x(TO) ) and vertical (V y(TO) ) center of mass velocity at takeoff prior to the hurdle, measured at the last instant of foot contact on the ground before takeoff; (b) the resultant takeoff velocity (V TO ) calculated by the horizontal and vertical velocities of the athlete’s center of mass at

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Conall F. Murtagh, Christopher Nulty, Jos Vanrenterghem, Andrew O’Boyle, Ryland Morgans, Barry Drust, and Robert M. Erskine

velocity 9 , 12 and RFD. 11 As the unilateral horizontal-forward CMJ requires greater takeoff velocities than unilateral vertical and unilateral medial CMJs, 3 a greater vastus lateralis θ p may reduce the quadriceps femoris contraction velocity and therefore reduce peak V-power during unilateral