TY  - JOUR
A1  - Ramirez-Campillo, Rodrigo
A1  - Alvarez, Cristian
A1  - Garcia-Pinillos, Felipe
A1  - Sanchez-Sanchez, Javier
A1  - Yanci, Javier
A1  - Castillo, Daniel
A1  - Loturco, Irineu
A1  - Chaabene, Helmi
A1  - Moran, Jason
A1  - Izquierdo, Mikel
T1  - Optimal reactive strength index
BT  - is it an accurate variable to optimize plyometric training effects on measures of physical fitness in young soccer players?
JF  - Journal of strength and conditioning research : the research journal of the NSCA
N2  - Ramirez-Campillo, R, Alvarez, C, García-Pinillos, F, Sanchez-Sanchez, J, Yanci, J, Castillo, D, Loturco, I, Chaabene, H, Moran, J, and Izquierdo, M. Optimal reactive strength index: is it an accurate variable to optimize plyometric training effects on measures of physical fitness in young soccer players? J Strength Cond Res 32(4): 885–893, 2018—This study aimed to compare the effects of drop-jump training using a fixed drop-box height (i.e., 30-cm [FIXED]) vs. an optimal (OPT) drop-box height (i.e., 10-cm to 40-cm: generating an OPT reactive strength index [RSI]) in youth soccer players' physical fitness. Athletes were randomly allocated to a control group (n = 24; age = 13.7 years), a fixed drop-box height group (FIXED, n = 25; age = 13.9 years), or an OPT 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], 5 multiple bounds), speed (20-m sprint time), change of direction ability (CODA [Illinois test]), strength {RSI and 5 maximal squat repetition test (5 repetition maximum [RM])}, 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), depth jump (DJ) (p < 0.001, d = 0.30), 20-m sprint time (p < 0.001, d = 0.25), CODA (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.
KW  - football
KW  - stretch-shortening cycle
KW  - maturity
KW  - training optimization
KW  - change of direction
KW  - jumping
Y1  - 2018
U6  - https://doi.org/10.1519/JSC.0000000000002467
SN  - 1064-8011
SN  - 1533-4287
VL  - 32
IS  - 4
SP  - 885
EP  - 893
PB  - Lippincott Williams & Wilkins
CY  - Philadelphia
ER  -