The signal arrives before the force

TL;DR

• Explosive power gets set upstream of the muscle: how fast your nervous system fires, not just how big or strong you are.
• Motor units fire above 100 pulses per second during explosive efforts, more than double the rate of a heavy grind, and that rate drops with age faster than strength does.
• The fix is training intent: brief, maximal-effort, high-speed contractions, done often and fresh, not more slow heavy reps.

Here is a fact that reorganizes how you should think about aging and training. When researchers put high-density EMG sensors on a muscle (basically a dense grid of electrodes that can eavesdrop on individual motor units, the bundles of a nerve plus the muscle fibers it controls) they can watch how fast those units fire. Each firing is a pulse of electrical command from the nervous system telling the muscle to contract. During a slow, maximal grind like a near-limit deadlift, motor units fire somewhere around 30 to 50 pulses per second. During a genuinely explosive effort (a jump, a hard throw, catching yourself after a trip) those same units can fire at over 100 pulses per second. More than double.

That gap matters more than it looks. It means rapid force expression is a separate neural quality, not just a faster version of strength. The evidence is clean: one study found that maximal motor unit discharge rate alone explained 71% of the between-person difference in how quickly people could produce force (their rate of force development, or RFD). Not muscle size. Not one-rep max. Firing rate. You can have plenty of muscle and a big lift and still be slow to deploy it, because the signal arrives late and thin. The force is there. The telegram summoning it is dawdling.

Why this is the aging story, not a footnote

The uncomfortable corollary is that this neural quality fades first. With age, power declines faster than maximal strength, and a good part of the reason is exactly this: rapid neural activation and peak discharge rate fall off. You can keep the muscle. You can keep a respectable amount of strength. And you can still quietly lose the ability to express force quickly, which is the ability that matters when your foot catches the edge of a rug. Stepping over an obstacle, throwing a hand out, reorganizing your feet in a tenth of a second: these are RFD problems, not strength problems. And the stakes compound. One-year mortality after a hip fracture runs somewhere between 22% and 58%. So the fast-firing system is not a nice-to-have for former athletes. It is a functional reserve you are supposed to defend on purpose after 40, because nobody defends it for you.

What training intent actually means

Here is the practical part, and it is less about new equipment than a new instruction to yourself. The nervous system learns to fire fast only when you ask it to fire fast. A heavy grinding lift, moved slowly because it is heavy, never demands those 100-pulse-per-second rates, so it does not fully train them. The trainable variable is intent: the deliberate attempt to accelerate as hard as possible, even against a moderate load. Coaching maximal bar speed on an identical weight measurably changes the power you produce, which means intent is something you can program, not just something you happen to have on a good day.

No single exercise builds this, because different tools impose different neural demands: heavy lifting, ballistic throws, plyometrics, Olympic-style lifts, short maximal sprints. The aim is varied exposure to high-intent contractions, each one forcing the system to recruit and fire as fast as it can. A useful entry point that costs almost nothing in fatigue is brief overcoming isometrics, pushing maximally against something immovable for a half-second to a second, with the intent to explode. These ballistic efforts train the pure rate-of-firing quality with minimal soreness. (One caveat: build a base of steadier max-effort isometric work over a few months before you layer in the ballistic versions.)

The programming principle that ties it together is stimulus-to-fatigue. This work is neurally loud but physically quiet: low reps, nowhere near failure, no eccentric wreckage the next day. That is a feature. It means you can put one explosive movement at the front of an otherwise ordinary strength or hypertrophy session (a jump, a med-ball throw, a fast first rep with real intent) and keep the fast-firing quality year-round without derailing anything else. Do it fresh, do it hard, keep it short. The whole point is that the signal has to arrive fast, and the only way to keep it fast is to keep practicing the speed of the message, not just the size of the muscle receiving it.