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Herbert Hatze

The validity and reliability of the jumping ergometer method for evaluating performance in two-legged vertical countermovement and serial rebound jumps were investigated. The internal segmental and nonvertical energy flow components for drop jumps were also studied. The exact dynamic equations governing the jumping motion in three dimensions were derived and used together with the approximate relations of the jumping ergometer method to evaluate a total of 72 vertical jumps of different types executed by 22 subjects (15 males, 7 females), average age 24.59 years. The force-plate method was selected as a reference procedure, to which the jumping ergometer results were related. For countermovement jumps, the relative error for jumping height was 3.55% (±2.92%), and for average power per kilogram body mass during the propulsion phase it was 23.79% (±4.85%). For serial rebound jumps, the respective errors were 7.40% (±4.58%) and 5.09% (±4.48%). Internal and nonvertical energy flow components amounted to about 3% of the total. It was concluded that, because of a number of invalid assumptions, unpredictable errors, and contradictory performance requirements, the validity and reliability of the jumping ergometer method for evaluating certain aspects of athletic performance are highly questionable.

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Daniel Feeney, Steven J. Stanhope, Thomas W. Kaminski, Anthony Machi and Slobodan Jaric

The aims of the current study were to explore the pattern of the force–velocity (F–V) relationship of leg muscles, evaluate the reliability and concurrent validity of the obtained parameters, and explore the load associated changes in the muscle work and power output. Subjects performed maximum vertical countermovement jumps with a vest ranging 0–40% of their body mass. The ground reaction force and leg joint kinematics and kinetics were recorded. The data revealed a strong and approximately linear F–V relationship (individual correlation coefficients ranged from 0.78–0.93). The relationship slopes, F- and V-intercepts, and the calculated power were moderately to highly reliable (0.67 < ICC < 0.91), while the concurrent validity F- and V-intercepts, and power with respect to the directly measured values, was (on average) moderate. Despite that a load increase was associated with a decrease in both the countermovement depth and absolute power, the absolute work done increased, as well as the relative contribution of the knee work. The obtained findings generally suggest that the loaded vertical jumps could not only be developed into a routine method for testing the capacities of leg muscles, but also reveal the mechanisms of adaptation of multijoint movements to different loading conditions.

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Kyle Davis, Stephen Rossi, Jody Langdon and Jim McMillan

The purpose of the present investigation was to examine the relationship between jumping and sprinting among members of a regionally competitive club-level ultimate team. Twenty-two subjects (mean ± SD; 21.1±2.26 year) volunteered to participate in two testing sessions the week before the team’s regional tournament. Testing sessions included body-composition measurement, a 40-yard sprint (with a 10-yard split time recorded), a standing long jump (LJ) and a vertical jump (VJ). Pearson product-moment correlations revealed a significant negative correlation between LJ and 40-yard sprint time. Significant positive relationships were observed between VJ height and 10-yard power, VJ power and 10-yard power, VJ power and relative 10-yard power, relative VJ power and relative 10-yard power, BJ distance and 10-yard power, VJ height and 40-yard power, VJ power and 40-yard power, and relative VJ power and relative 40-yard power. BJ distance related significantly to 40-yard velocity, 40-yard power and 40-yard relative power. There appears to be a relationship between jumping ability and sprinting in this population, but more studies with this population are needed to confirm these results.

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Myosotis Massidda, Marco Scorcu and Carla M. Calò

Purpose:

The aim of the current study was to construct a genetic model with a new algorithm for predicting athletic-performance variability based on genetic variations.

Methods:

The influence of 6 polymorphisms (ACE, ACTN-3, BDKRB2, VDR-ApaI, VDR-BsmI, and VDR-FokI) on vertical jump was studied in top-level male Italian soccer players (n = 90). First, the authors calculated the traditional total genotype score and then determined the total weighting genotype score (TWGS), which accounts for the proportion of significant phenotypic variance predicted by the polymorphisms. Genomic DNA was extracted from saliva samples using a standard protocol. Genotyping was performed using polymerase chain reaction (PCR).

Results:

The results obtained from the new genetic model (TWGS) showed that only 3 polymorphisms entered the regression equation (ACTN-3, ACE, and BDKRB2), and these polymorphisms explained 17.68–24.24% of the verticaljump variance. With the weighting given to each polymorphism, it may be possible to identify a polygenic profile that more accurately explains, at least in part, the individual variance of athletic-performance traits.

Conclusions:

This model may be used to create individualized training programs based on a player’s genetic predispositions, as well as to identify athletes who need an adapted training routine to account for individual susceptibility to injury.

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Brian T. McCormick, James C. Hannon, Maria Newton, Barry Shultz, Nicole Detling and Warren B. Young

Plyometrics is a popular training modality for basketball players to improve power and change-of-direction speed. Most plyometric training has used sagittal-plane exercises, but improvements in change-of-direction speed have been greater in multidirection programs.

Purpose:

To determine the benefits of a 6-wk frontal-plane plyometric (FPP) training program compared with a 6-wk sagittal-plane plyometric (SPP) training program with regard to power and change-of-direction speed.

Methods:

Fourteen female varsity high school basketball players participated in the study. Multiple 2 × 2 repeated-measures ANOVAs were used to determine differences for the FPP and SPP groups from preintervention to postintervention on 4 tests of power and 2 tests of change-of-direction speed.

Results:

There was a group main effect for time in all 6 tests. There was a significant group × time interaction effect in 3 of the 6 tests. The SPP improved performance of the countermovement vertical jump more than the FPP, whereas the FPP improved performance of the lateral hop (left) and lateral-shuffle test (left) more than the SPP. The standing long jump, lateral hop (right), and lateral-shuffle test (right) did not show a significant interaction effect.

Conclusions:

These results suggest that basketball players should incorporate plyometric training in all planes to improve power and change-of-direction speed.

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Maarten F. Bobbert, Han Houdijk, Jos J. de Koning and Gert de Groot

To gain a better understanding of push-off mechanics in speed skating, forward simulations were performed with a model comprising four body segments and six muscles. We started with a simulated maximum height one-legged jump, obtained by optimization of muscle stimulation time histories. The simulated jump was very similar to one-legged jumps produced by a human, indicating that the model was realistic. We subsequently studied how performance was affected by introducing four conditions characteristic of speed skating: (a) We changed the initial position from that in jumping to that at the start of the push-off phase in skating. This change was accommodated by a delay in stimulation onset of the plantar flexors in the optimal solution. (b) The friction between foot and ground was reduced to zero. As a result, maximum jump height decreased by 1.2 cm and performance became more sensitive to errors in muscle stimulation. The reason is that without surface friction, the foot had to be prevented from slipping away, which constrained the solution space and reduced the tolerance to errors in stimulation. (c) We introduced the requirement to maintain the upper body in a more or less horizontal position. This change could be accommodated by a delay in stimulation onset of the hamstrings, which inevitably caused a reduction in maximum jump height by 11.6 cm. (d) We increased the effective foot length from 16.5 cm, representative of jumping, to 20.5 cm, representative of skating with klapskates. At the 20.5-cm foot length, rotation of the foot did not start during the buildup of plantar flexion moment as it did at smaller foot lengths, but was delayed until hip and knee extension moments decreased. This caused an unbalanced increase in segment angular velocities and muscle shortening velocities, leading to a decrease in muscle force and muscle work and a further decrease in maximum jump height by approximately 5 cm. Qualitatively, these findings help clarify why and how performance of speed skaters depends on the location of the hinge of their skate.

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Jenna M. Kraska, Michael W. Ramsey, G. Gregory Haff, Nate Fethke, William A. Sands, Margaret E. Stone and Michael H. Stone

Purpose:

To investigate the relationship between maximum strength and differences in jump height during weighted and unweighted (body weight) static (SJ) and countermovement jumps (CMJ).

Methods:

Sixty-three collegiate athletes (mean ± SD; age= 19.9 ± 1.3 y; body mass = 72.9 ± 19.6 kg; height = 172.8 ± 7.7 cm) performed two trials of the SJ and CMJ with 0 kg and 20 kg on a force plate; and two trials of mid-thigh isometric clean pulls in a custom rack over a force plate (1000-Hz sampling). Jump height (JH) was calculated from fight time. Force-time curve analyses determined the following: isometric peak force (IPF), isometric force (IF) at 50, 90, and 250 ms, and isometric rates of force development (IRFD). Absolute and allometric scaled forces, [absolute force/(body mass0.67)], were used in correlations.

Results:

IPF, IRFD, F50a, F50, F90, and F250 showed moderate/strong correlations with SJ and CMJ height percent decrease from 0 to 20 kg. IPFa and F250a showed weak/moderate correlations with percent height decrease. Comparing strongest (n = 6) to weakest (n = 6): t tests revealed that stronger athletes (IPFa) performed superior to weaker athletes.

Conclusion:

Data indicate the ability to produce higher peak and instantaneous forces and IRFD is related to JH and to smaller differences between weighted and unweighted jump heights. Stronger athletes jump higher and show smaller decrements in JH with load. A weighted jump may be a practical method of assessing relative strength levels.

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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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David Rodríguez-Osorio, Oliver Gonzalo-Skok and Fernando Pareja-Blanco

downward movement followed by a maximal effort vertical jump. In addition, they were instructed to land in an upright position and to bend the knees after landing. Three trials were completed with a 20-second rest between each trial. The mean of the 3 trials was then used for subsequent analyses. The

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Davide Ferioli, Andrea Bosio, Johann C. Bilsborough, Antonio La Torre, Michele Tornaghi and Ermanno Rampinini

measured using a vertical jump test and a repeated COD test and (2) relationships between TL with changes in neuromuscular physical performance during the same period. Methods Subjects A total of 12 PRO and 16 SEMIPRO male basketball players (age: 26.2 [6.5] and 23.6 [4.9] y, respectively) were recruited