patterns that confound the relationships among the typically observed mechanical variables, such as the force, power output, and jump height. Specifically, an increase in the countermovement depth through the eccentric phase of natural countermovement jumps (CMJs) is associated not only with a slight
Kajetan J. Słomka, Slobodan Jaric, Grzegorz Sobota, Ryszard Litkowycz, Tomasz Skowronek, Marian Rzepko and Grzegorz Juras
Gavin L. Moir, Alberto Garcia and Gregory B. Dwyer
To investigate the intersession reliability of selected kinematic and kinetic variables during countermovement vertical jumps (CMJs).
Thirty-five men and 35 women performed CMJs on a force platform during four testing sessions each separated by 1 wk. Kinematic variables included time in the air (TIA), take-off velocity (TOV), total vertical displacement of the center of mass (TJH). and countermovement depth, whereas kinetic variables included positive impulse, negative impulse, vertical stiffness, and rates of force development. Systematic bias was assessed by calculating the 90% confidence interval of the change in the mean between consecutive testing sessions and between the first and final testing session for each variable. Coefficients of variation (CV) and intraclass correlation coefficients (ICC) were also calculated.
Systematic bias was observed only for peak rate of force development during the concentric phase of the movement. For TIA, TOV, and TJH, CV values ranged from 1.7% to 6.6%, with ICC values ranging from 0.82 to 0.97. The other variables showed greater variation (CV range: 1.7% to 39.9%; ICC range: 0.04 to 0.99). Only slight gender differences were found in the reliability statistics, and the reliability of most of the variables was diminished as the time between the testing sessions was increased.
Even though practitioners can expect good reliability for jump height measured from a force platform in men and women, other kinematic and kinetic variables often assessed during vertical jumps may not be reliable.
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.
Philip X. Fuchs, Andrea Fusco, Jeffrey W. Bell, Serge P. von Duvillard, Cristina Cortis and Herbert Wagner
Purpose: To determine the effect of in-season differential training on volleyball spike-jump technique and performance in elite-level female players. Methods: During the season, spike jumps of 12 elite female players (Austrian Volleyball League Women) were recorded by 13 Qualisys Oqus cameras (250 Hz) and an AMTI force plate (1000 Hz). First measurement was made at the beginning of the investigation. Two identical measurements were repeated after a first and a second interval. The first interval served as control phase. The second interval was comparable in length and regular program but included differential training (6 wk, 8 sessions of 15–20 min) as a modified warm-up. It addressed specific performance determinants. Analyses of variances were calculated for the 3 measurements and for the development during control and intervention phase. Results: Initial jump height (0.44 [0.09] m) changed by −4.5% during the control phase and +11.9% during the intervention (P < .001,
Blair Mills, Brad Mayo, Francisco Tavares and Matthew Driller
to eliminate the influence of arm swing. 12 Participants were then instructed to descend to a self-selected countermovement depth and to jump as high and quickly as possible. 13 The straight-line sprint tests were performed indoors on a synthetic running track. During each trial, participants were
John R. Harry, Leland A. Barker, Jeffrey D. Eggleston and Janet S. Dufek
landings separated by up to 1-minute rest as needed. Each trial began with the participants standing motionless with their arms at their side, and each foot was positioned on a force platform. Participants attempted to jump vertically as high as possible using a self-selected countermovement depth and arm
Talin Louder, Dennis Dolny and Eadric Bressel
the hips isolates performance to the lower-extremity, which was desired in this study. We did not standardize countermovement depth across participants; rather, we allowed for self-selected depth. The countermovement jump technique was demonstrated to all participants prior to data collection
John R. Harry, Max R. Paquette, Brian K. Schilling, Leland A. Barker, C. Roger James and Janet S. Dufek
participants were instructed to initiate the CMVJ using a self-selected countermovement depth and arm swing to ensure effort and/or performance was not compromised. 23 , 24 The participants then jumped vertically while reaching with 1 hand to strike the highest vane possible on the Vertec. The landing phase
Kym J. Williams, Dale W. Chapman, Elissa J. Phillips and Nick Ball
% (bodyweight) to 40% (loaded) of an athlete’s predicted 1RM at 10% increments performed in ascending order to provide a continual warm-up effect as load increased. 5 Athletes began each CMJ from an upright standing position and were instructed to use a self-selected countermovement depth to maintain constant
Niall Casserly, Ross Neville, Massimiliano Ditroilo and Adam Grainger
placed on the hips. Countermovement depth was self-selected by the player before jumping as high as possible with hips and feet extended throughout flight to prevent tucking of the knees. 21 Postjump, each participant received verbal feedback upon their performance. Players were familiar with the CMJ