Rate of force developmentRFD

Rate of force development measures how fast force rises once a contraction begins, typically over the first hundred to two hundred milliseconds. Two people with the same maximal strength can have very different RFD, and in fast movements the quicker one wins because there simply is not time to reach peak force.

It matters because most athletic actions — a sprint step, a jump, a change of direction — last less time than it takes to develop maximum force. It is also relevant to falls in older adults, where the ability to react quickly enough to recover balance depends on it.

In practice it improves with explosive intent, plyometrics, jumps and light-to-moderate loads moved as fast as possible, alongside heavy strength work that raises the ceiling those fast efforts are drawn from.