Reactive Strength Index
The reactive strength index (RSI) is a measure of lower-body reactive strength and elastic energy utilization, calculated as jump height divided by the contact time between landing from a drop and takeoff. Introduced by Bobbert and colleagues (1987), RSI quantifies the efficiency of the stretch-shortening cycle (SSC)—the ability to rapidly switch from eccentric (lengthening) to concentric (shortening) muscle contractions. High RSI indicates rapid, forceful engagement of muscles' elastic properties (tendons, contractile proteins) and is relevant in sports requiring rapid rebound (sprinting, jumping, rebounding). RSI is trainable and sensitive to plyometric training.
Source record
Citations copied verbatim from the method’s source record. No claim-level verification is inferred from them.
- Bobbert, M. F., Huijing, P. A., & van Ingen Schenau, G. J. (1987). Drop jumping. II. The influence of dropping height on the biomechanics of takeoff after landing. Medicine & Science in Sports & Exercise, 19(4), 339-346. · DOI 10.1249/00005768-198708000-00004
- Flanagan, E. P., & Comyns, T. M. (2008). The stretch-shortening cycle training in sport. Strength & Conditioning Journal, 30(6), 32-39. · URL
- Taube, W., Leukel, C., & Gollhofer, A. (2016). How neurons make us jump: the role of the motor cortex in stretch-shortening cycle movements. Exercise and Sport Sciences Reviews, 44(1), 4-11. · URL
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