RFD (Rate of Force Development)

RFD: what is it?

Producing maximum force takes something in the order of 300 milliseconds or more. A sprint ground contact lasts around 100 milliseconds, a jump take-off not much longer, and a stumble gives you even less. That mismatch is the entire reason RFD exists as a separate quality: in almost every real action, what limits the outcome is not how much force you can eventually produce but how much you have produced by the time the contact ends.

Early and late RFD

The force-time curve is usually split into windows, and they behave differently. Early RFD, in the first 50 to 100 milliseconds, is dominated by neural drive - how fast the nervous system can recruit and fire motor units - and it is what matters in sprinting and reactive jumping. Late RFD, from roughly 100 to 250 milliseconds and beyond, correlates more closely with maximal strength, because there is enough time for the force to approach the athlete's ceiling.

That split explains a common frustration. An athlete who gets much stronger and no faster has probably improved their late RFD and their maximum force while leaving early RFD untouched. Fixing that needs explosive intent and ballistic work, not more heavy sets.

The explosive strength deficit

A useful concept for coaches is the gap between the force an athlete can produce given unlimited time and the force they actually produce in the time available. A large gap means the athlete is strong but cannot access that strength quickly, and the priority is speed of expression. A small gap means they are already expressing most of what they have, and the priority is raising the ceiling with heavy work.

You do not need a force plate to make this call. If a client has a strong squat and a poor vertical jump, the gap is large. If both are modest, build strength first. If the jump is strong relative to the squat, more maximal strength will pay off.

Training it

Three levers, used together. Intent is the cheapest and most overlooked: instructing an athlete to move the bar as fast as possible on the concentric raises RFD even at moderate loads, without changing anything else in the programme. Ballistic movements - jumps, throws, Olympic lift derivatives - let force be expressed without a deceleration phase, which normal lifting always has. And plyometrics train the reactive, stretch-shortening component specifically.

Everything here is a quality-first prescription. Low reps, long rest, always fresh, and stopped the moment output drops. A fatigued RFD session trains the opposite of what it is meant to.

• Cue explosive intent on every concentric, even at moderate load.
• Program RFD work first in the session, after the warm-up.
• 1-5 reps per set with full recovery; stop the set when speed or height drops.
• Build a strength base first - there is a limit to how fast you can express force you do not have.

Measuring it in a normal gym

The reference method is a force plate, which gives the force-time curve directly. Most coaches do not have one, and do not need one. Countermovement jump height, a broad jump, a medicine ball throw distance, or bar velocity from a cheap velocity tracker all give a repeatable proxy that responds to the same training.

Track one of them weekly under identical conditions and read the trend. A rising number across a block means the RFD work is landing. A sudden drop is one of the more reliable everyday signals that fatigue has outrun recovery.