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Infographic titled “Testing Rate of Force Development (RFD)” showing four methods: RSI (Reactive Strength Index = jump height ÷ contact time, reflects tendon elasticity and force speed, typical scores <2.5 low and elite 4.0+), Hopping Tests (repeated hops measure contact time and flight time to estimate leg stiffness, contact time 2.5–3.0 = average/good), Force Plate (directly measures the force–time curve to calculate RFD in milliseconds), and MyJump App (smartphone app that outputs RSI values to guide plyometric needs with ranges <2.5 low, 2.5–3.0 average, 3.0+ elite); footer reads testing methods guide targeted plyometric training → improved RFD → faster sprinting.

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