The Reactive Strength Index (RSI = jump height ÷ contact time) is the standard field metric for assessing the stretch–shortening cycle (SSC) — the store-and-release elastic energy mechanism behind explosive movement. But RSI has real problems: it mixes incompatible units (producing m/s despite being treated as dimensionless), it ignores drop height entirely, and it rewards very short contact times even when almost no upward impulse is produced.

The Proposed Solution: DRI