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Drop jump

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Many have been the attempts to predict sprint performance based of different tests. In order to predict sprint performance, these tests should specifically assess the abilities that affect performance at given phases of the sprint. The aim of this study was to examine the relationship between the performances at acceleration (ACC), and maximal running (MAX) sprint phases, and jump selected variables [distance, GRF, velocity, power, and impulse, in absolute and relative terms (weight and height)]. Twenty two male sprinters, were assessed for five jump tests: Squat Jump (SJ), Counter Movement Jump (CMJ), Drop Jump (DJ), Repeated Vertical Jumps during ten seconds (vRJ10), and 5 horizontal jumps (5hJ). The best sprint predictors to ACC and MAX are an index between the horizontal distance and the 5 contact times from 5hJ. The results are favorable to the use of other variables beside distance jumped (GRF, velocity, power, and impulse) and also take in consideration the variable relative to body weight and height.

INTRODUCTION:

Success in sprinting events is determined by three major factors; (1) the athlete’s ability for fast acceleration, (2) the capacity to reach a high running velocity, and (3) the capability to maintain velocity against the onset of fatigue. The greater the level of force and the faster that force is applied to the ground in each stride, the better will be the sprint.

Many have been the attempts to predict sprint performance based of different tests that mostly evaluate strength and power abilities. In order to predict sprint performance. These tests should specifically assess (in terms of movement pattern, conditions of force production, muscle groups) those physical abilities that affect performance at given phases of the sprint: the start from the blocks, acceleration (ACC), and maximal running (MAX).

Jump tests are routinely used by coaches to monitor training progress in sprint athletes with distance jumped being usually the only measure that is taken into account [1, 2, 3, 4, 5, 6]. However, in a sport like sprint running, other variables beside distance jumped [ground reaction force (GRF), velocity at take off, power, and impulse, both taken in absolute magnitude or related to body dimensions (e.g. Weight and height)], can provide very useful data as predictors of performance and indicators of fitness level.

The aim of this study was to examine the relationship between the performance during two phases of the sprint running (ACC, MAX) and selected variables [distance, GRF, velocity, power, and impulse, in absolute and relative terms (weight and height)], from five different jump tests: Squat Jump (SJ), Counter Movement Jump (CMJ), Drop Jump (DJ), Repeated Vertical Jumps during ten seconds (vRJ10), and 5 horizontal jumps (5hJ).

Some authors have tried to find relationships between sprint (or sprint phases) and different kind of tests (to measure muscle strength). The different methodologies used on those studies have turned the comparisons very difficult mainly because of the different type of muscles actions used. We can find studies examining the relationships between: sprint and stretch-shortening cycle (SSC) tests (Mero et al., 1981; Nesser et al.1996; Kukolj et al. 1999; Hennessy and Kilty, 2001; Berthoin et al. 2001; Bret et al. 2002); sprint and isokinetic tests (Alexander, 1989; Guskiewicz et al.1993; Blazevich and Jenkins, 1998; Dowson et a. 1998); and sprint and isometric tests (Mero et al., 1981; Young et al.1995).

We can conclude that the goal of correlation studies to find the best strength predictors to a sprint run performance is difficult. It should be noted that correlations can only give associations (strong or weak) and not cause – effect.

Our option to choose the tests was related to the goal, validity and reliability of the tests. The squat jump (SJ) and LegPress has been described as a measure of leg explosiveness in concentric and isometric conditions The Isometric dynamometry is one of the most popular methods for assessing neuromuscular function in sport science as it permits the evaluation of both peak force and rate of force development.

The countermovement jump (CMJ) assessed leg power in long SSC, the drop jump (DJ) and the 5 horizontal steps (5hj) a measure of short SSC performance.Their external validity in athletic assessment is still a topic of debate (Wilson and Murphy, 1996). While some authors have found a significant correlation between isometric peak force or rate of force development and performance of sprinting (Mero et al., 1981; Young et al., 1995), others have failed to find a significant relationship between static measures of neuromuscular function and dynamic performance (Wilson et al.,1995; Kukolj et al., 1999). The aim of this study was to examine the relationships between the sprint run and the results obtained in common strength and power tests, which measure the capability to produce force in isometric, pure concentric and SSC contraction modes, to discriminate sprint capacity.

Values for times between 0-15m (ACC) and 45-55m (MAX), and distance, ground vertical force (GRF), power, and impulse, in absolute and relative terms (weight and height). Squat jump (SJ), counter movement jump (CMJ), drop jump (DJ), 10″ repeated jumps (RJ10), 5 horizontal jumps (5hJ) (mean ± SD, n=22).

Jump height; vertical ground reaction force (VertGRF); Body weight (BW); Time between 0-15m (ACC); Time between 40-50m (MAX); Average distance of 5 jumps (5hJ avgDist); Average distance of 5 jumps relative to subject height (5hJ avgDistRel); Average height of all jumps during 10 sec. (RJ AvgHeigth); Average relation between height and contact time of all jumps during 10 sec. (RJ H/cT Avg); Average impulse (= force x time) of all jumps during 10 sec. (RJ AvgImpulse); Average power (= force x velocity) of all jumps during 10 sec. (RJAvgPower1); Average mechanical power (= g2 × ft × 10″) / 4n (10″ – ft), ft = Sum of total flight time, n= number of jumps (Bosco, 1983) (RJAvgPower2); mgh / ct m = mass of subject (Kg), g = acceleration of gravity (9.81 m.s-2), h = height (9.81 x ft2)/8, ct = contact time prior to jump (RJAvgPower3).

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