Optimal reactive strength index: Is it an accurate variable to optimize plyometric training effects on measures of physical fitness in young soccer players?

Ramirez-Campillo R., Cristian Álvarez, Felipe García Pinillos, Javier Sánchez, Yanci Javier, Daniel Castillo, Irineu Loturco, Helmi Chaabene, Jason Moran, Mikel Izquierdo

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Abstract

This study aimed to compare the effects of drop-jump training using a fixed drop-box height (i.e., 30-cm [FIXED]) versus an optimal drop-box height (i.e, 10-cm to 40-cm: generating an optimal [OPT] reactive strength index [RSI]) in youth soccer players’ physical fitness. Athletes were randomly allocated to a control-group (CG: n=24; age=13.7 years), a fixed drop-box height group (FIXED, n=25; age=13.9 years) or an optimal drop-box height group (OPT, n=24; age=13.1 years). Before and after 7 weeks of training, tests for the assessment of jumping (countermovement jump [CMJ], five multiple bounds [MB]), speed (20-m sprint time), change of direction (Illinois change of direction test [CODT]), strength (RSI and 5 maximal squat repetition test [5RM]), endurance (2.4 km time trial), and kicking ability (maximal kicking distance) were undertaken. Analyses revealed main effects of time for all dependent variables (p<0.001, d=0.24-0.72), except for 20-m sprint time. Analyses also revealed group×time interactions for CMJ (p<0.001, d=0.51), DJ (p<0.001, d=0.30), 20-m sprint time (p<0.001, d=0.25), CODT (p<0.001, d=0.22), and 5RM (p<0.01, d=0.16). Post-hoc analyses revealed increases for the FIXED group (CMJ: 7.4%, d=0.36; DJ: 19.2%, d=0.49; CODA: -3.1%, d=-0.21; 5RM: 10.5%, d=0.32) and the OPT group (CMJ: 16.7%, d=0.76; DJ: 36.1%, d=0.79; CODA: -4.4%, d=-0.34; 5RM: 18.1%, d=0.47). Post-hoc analyses also revealed increases for the OPT group in 20-m sprint time (-3.7%, d=0.27). Therefore, to maximize the effects of plyometric training, an OPT approach is recommended. However, using adequate fixed drop-box heights may provide a rational and practical alternative
Original languageEnglish
Pages (from-to)885-893
Number of pages9
JournalJournal of Strength and Conditioning Research
Volume32
Issue number4
Early online date30 Jan 2018
DOIs
Publication statusPublished - 1 Apr 2018

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R., R-C., Álvarez, C., García Pinillos, F., Sánchez, J., Javier, Y., Castillo, D., Loturco, I., Chaabene, H., Moran, J., & Izquierdo, M. (2018). Optimal reactive strength index: Is it an accurate variable to optimize plyometric training effects on measures of physical fitness in young soccer players? Journal of Strength and Conditioning Research, 32(4), 885-893. https://doi.org/10.1519/JSC.0000000000002467