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; Alvarez, C; Garcia-Pinillos, F; Sanchez-Sanchez, J; Yanci, J; Castillo, D; Loturco, I; Chaabene, H; Moran, J; Izquierdo, M (J Strength Cond Res, 2018)