Modified Reactive Strength Index in Adolescent Athletes Competing in Different Sports and Its Relationship with Force Production

Abstract

The modified reactive strength index (RSImod) is used as a measurement of reactive strength and explosiveness. The main purpose of the current study was to assess RSImod in young athletes competing in various sports and to examine the relationship between RSImod and eccentric and concentric force and vertical displacement. Two-way ANOVA showed a significant main effect for sport group, but not for age group. Soccer (0.47±0.09 m/s) and basketball players (0.49±0.1 m/s) had significantly higher values than handball players (0.36±0.07 m/s) and rowers (0.35±0.07 m/s). Among the independent variables, average eccentric force had the strongest relationship with RSImod. In conclusion, RSImod differs between athletes from different sports, but not between athletes from different age groups in the examined age period. Also, RSImod is strongly associated mainly with the average eccentric force and secondarily with the average concentric force during the countermovement jump.