The purpose of this study was to examine the effects of acute creatine-monohydrate supplementation on soccer-specific performance in young soccer players. Twenty young male soccer players (16.6 ± 1.9 years) participated in the study and were matched and allocated to 2 randomly assigned trials: ingesting creatine-monohydrate supplement (3 × 10-g doses) or placebo for 7 days. Before and after the supplementation protocol, each subject underwent a series of soccer-specific skill tests: dribble test, sprint-power test, endurance test, and vertical jump test. Specific dribble test times improved significantly in the creatine group (13.0 ± 1.5 vs. 10.2 ± 1.8 s; p < .05) after supplementation protocol. Sprint-power test times were significantly improved after creatine-monohydrate supplementation (2.7 ± 0.4 vs. 2.2 ± 0.5 s; p < .05) as well as vertical jump height (49.2 ± 5.9 vs. 55.1 ± 6.3 cm; p < .05) in creatine trial. Furthermore, dribble and power test times, along with vertical jump height, were superior in creatine versus placebo trial (p < .05) at post-supplementation performance. There were no changes in specific endurance test results within or between trials (p > .05). There were no between-trial differences in the placebo trial (p > .05). The main finding of the present study indicates that supplementation with creatine in young soccer players improved soccer-specific skill performance compared with ingestion of placebo.
Sergej M. Ostojic
Myosotis Massidda, Marco Scorcu and Carla M. Calò
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.
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).
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.
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.
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.
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.
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.
Jenna M. Kraska, Michael W. Ramsey, G. Gregory Haff, Nate Fethke, William A. Sands, Margaret E. Stone and Michael H. Stone
To investigate the relationship between maximum strength and differences in jump height during weighted and unweighted (body weight) static (SJ) and countermovement jumps (CMJ).
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.
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.
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.
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.
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.
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.
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.
These results suggest that basketball players should incorporate plyometric training in all planes to improve power and change-of-direction speed.
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
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
Juan A. Escobar Álvarez, Juan P. Fuentes García, Filipe A. Da Conceição and Pedro Jiménez-Reyes
N , Angioi MM , Nevill A , Twitchett E . Anthropometric factors affecting vertical jump height in ballet dancers . J Dance Med Sci . 2006 ; 10 ( 3–4 ): 106 – 110 . 11. Koutedakis Y . Fitness for dance . J Dance Med Sci . 2005 ; 9 ( 1 ): 5 – 6 . http