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Kajetan J. Słomka, Slobodan Jaric, Grzegorz Sobota, Ryszard Litkowycz, Tomasz Skowronek, Marian Rzepko and Grzegorz Juras

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

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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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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

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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

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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

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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