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Int J Sports Physiol Perform. 2015 May;10(4):482-8. doi: 10.1123/ijspp.2014-0265. Epub 2014 Nov 13.

The intraday reliability of the Reactive Strength Index calculated from a drop jump in professional men's basketball.

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Centre for Exercise and Sport Science Research, Edith Cowan University, Joondalup, Western Australia.



To evaluate the reliability of the Reactive Strength Index (RSI) and jump-height (JH) performance from multiple drop heights in an elite population.


Thirteen professional basketball players (mean±SD age 25.8±3.5 y, height 1.96±0.07 m, mass 94.8±8.2 kg) completed 3 maximal drop-jump attempts onto a jump mat at 4 randomly assigned box heights and 3 countermovement-jump trials.


No statistical difference was observed between 3 trials for both the RSI and JH variable at all the tested drop heights. The RSI for drop-jump heights from 20 cm resulted in a coefficient of variation (CV)=3.1% and an intraclass correlation (ICC α)=.96, 40 cm resulted in a CV=3.0% and an ICC α=.95, and 50 cm resulted in a CV=2.1% and an ICC α=.99. The JH variable at the 40-cm drop-jump height resulted in the highest reliability CV=2.8% and an ICC α=.98.


When assessing the RSI the 20-, 40-, and 50-cm drop heights are recommended with this population. When assessing large groups it appears that only 1 trial is required when assessing the RSI variable from the 20, 40-, and 50-cm drop heights.

[Indexed for MEDLINE]

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