The reactive strength index (RSI) measures explosive power during depth jumps. The purpose of this study was to introduce a modification of the RSI (RSImod) that can be used to evaluate the explosive power of any vertical plyometric exercise, to assess its reliability, and evaluate the RSImod of a variety of plyometric exercises. Forty nine subjects performed 3 repetitions of 5 plyometric exercises including the countermovement jump, tuck jump, single leg jump, squat jump, and dumbbell countermovement jump. Data were analyzed using a two way ANOVA. Results reveal significant differences in RSImod between all plyometric exercises (P = 0.001). The RSImod was highly reliable for all of the plyometric exercises studied. The RSImod offers a reliable method of assessing the explosiveness developed during a variety of plyometric exercises.
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