Rate of force development (RFD)

Rate of force development (RFD) is the change in muscle force per unit time (N/s), quantifying how rapidly maximal force can be expressed — a key component of muscular power distinct from peak force alone. Early-phase RFD (0–50 ms) reflects neural drive, motor unit synchronization, and Type II fiber recruitment; late-phase RFD (100–200 ms) is more influenced by muscle cross-sectional area and fiber composition. RFD declines with age more rapidly than maximal strength and is closely linked to fall-prevention capacity, functional power, and reactive balance, because most daily protective movements (catching a stumble, rising from a chair) occur within 100–200 ms. Power-focused and plyometric training preferentially improve RFD.