Physical Performance Parameters

The stretch-shortening cycle (SSC) is a fundamental mechanism in explosive human movement, enabling musculotendinous units to store and release elastic energy, thereby allowing the body to produce higher forces and velocities with greater mechanical efficiency. Movements such as sprinting, jumping, hopping, and sudden changes of direction, which depend on rapid force application, are supported by an effective SSC. Because of this, identifying a simple and interpretable index of SSC function has long been a priority in both research and applied sport settings. The Reactive Strength Index (RSI), most commonly defined as the ratio of jump height to ground contact time, has become the most widely used metric for quantifying SSC performance. However, this ratio presents notable methodological limitations: it combines variables of incompatible dimensions and is insensitive to drop height, thereby ignoring the eccentric load imposed on the musculotendinous system. The Dynamic Rebound Index (DRI), recently proposed as a dimensionless and mechanically grounded alternative, is calculated as DRI = (box height + jump height) / (9.8 × ground contact time²). Despite its theoretical advantages, a direct comparison between the RSI and DRI remains unexplored in the literature, which justifies the relevance of the present study. This study aims to compare the RSI and the DRI in physically active adults of both sexes during the execution of the Drop Jump at four different drop heights (20, 30, 40, and 50 cm). The specific objectives are: (a) to characterize performance across the four height conditions; (b) to analyze differences between sexes in both indices; (c) to examine the effect of drop height on both indices; and (d) to explore the informative complementarity between the two indices.

This study aims to examine the acute effects of an elastic band warm-up on sprinting and vertical jump performance in female football players. A crossover design will be used across three separate sessions: (1) standardized warm-up (WU), (2) warm-up followed by elastic band activation (WU + EB), and (3) elastic band activation followed by the warm-up (EB + WU). Performance evaluations-including sprint time and vertical jump height and power-will be conducted at three time points during each session: baseline (before the warm-up), immediately after the warm-up intervention, and 10 minutes post-intervention. This structure will allow the study to compare the immediate and short-term effects of different warm-up sequences involving elastic bands on neuromuscular performance. The findings may help optimize warm-up strategies to enhance acute athletic performance in female football players.

The goal of this clinical trial is to assess the effects of an 8-week strength training program with elastic bands on several physical components in female football players at the U15, U19, and Senior levels. The main question it aims to answer is: Will a specific elastic band resistance training help improve some components of physical performance in female football players? Participants will perform a bi-weekly elastic band resistance training program lasting 20 minutes per session over 8 weeks. This program will be incorporated into their in-season regimen, with assessments conducted in the week prior (week 0) and after the intervention (week 9).