Stretch-Shortening Cycle in Countermovement Jump: Exclusive Review of Force-Time Curve Variables in Eccentric and Concentric Phases

Abstract

Abstract:The importance of vertical jump in sport fields and rehabilitation is widely recognized.Furthermore, Force-Time variables of vertical jump are factors affecting jumping height. Exclusive review of each of this variables, in eccentric and concentric phases, can lead to a specific focus on them during jumping exercises. So, the aims of his study were to a) reviewing the relationship between force-time curve variables of eccentric and concentric phases with jump height and b) description of this variables in Iran national youth volleyball players society. This is an observational study. 12 elite volleyball player (Male, Iran national youth volleyball players, 17±0.7 years) have participated in this study. Correlation between Force-Time variables -included peak force (PF), relative peak force (RPP), peak power (PP), average power (AP), relative peak power (RPP), and Modified Reactive Strength Index (MRSI) -in eccentric and concentric phases and ultimate jump height has been studied. Results showed that the average power (r=0.7) and relative peak force (r=0.75) of concentric phase and MRSI (r=0.83) have significant correlation with ultimate jump height (JH). Relative peak power and average power of concentric phase can massively effect Jump Height in sports like volleyball, which vertical jump is an integral part of them. Focus on both of these factors, which has been studied in this research, in training programs, can improve athlete jump performance significantly.

Phase-Specific Predictors of Countermovement Jump Performance That Distinguish Good From Poor Jumpers

“…The definitions for the "concentric" or "propulsion" CMJ phases are generally consistent among studies, whereas definitions for the phases within the countermovement are much less consistent (1,13,27). Commonly, the countermovement portion of the CMJ has been deconstructed into unweighing (the entire time when the GRF reading is below body weight, i.e., negative COM acceleration) and braking or "eccentric" (time of downward COM deceleration) phases according to the total body COM kinematics (3,15,19,30,32,38). However, a recent study suggested that the countermovement be deconstructed into unloading, eccentric yielding, and eccentric braking phases (Figure 1) to better reflect the COM movement effects, while also including the predominant muscle actions driving changes in COM movement where appropriate (13).…”