How long to rest between sets

Ask how long to rest between sets and you are handed a table. Thirty to ninety seconds for size. Two to five minutes for strength. Under a minute for circuits. The same table turns up on gym blogs, inside apps and under coaching videos, and it is worth knowing where the numbers came from.

They came largely from studies of a single session. Put a lifter under a bar, vary the rest, count the reps they manage that afternoon. Recommendations for how long to rest are mostly inferred from that kind of work, and how far it carries over to what happens across weeks of training is uncertain¹.

Which matters, because it is not the question you asked. You did not want to know how many reps you could get this afternoon. You wanted to know who was stronger in eight weeks.

What the training studies found

Grgic and colleagues gathered the studies that trained people for weeks at different rest intervals and measured their strength at the end. The review covers 23 studies and 491 people, and rates every one of them good or moderate quality¹.

Their conclusion is not the table. Strength goes up even on rests under a minute. Rests longer than two minutes are what it takes to get the most out of training once you are trained. If you are new to lifting, sixty to 120 seconds is enough¹.

Read that for what it does not say. It does not say a short rest wastes your session. It says the difference is small, that it shows up once you have enough training behind you for anything to be marginal, and that under a minute you are still getting stronger.

For size, the answer is smaller still

Rest has been argued about hardest around muscle size, on the theory that short rests keep the metabolic stress up. A Bayesian review pooled 9 studies carrying 19 measurements of muscle thickness and found the estimates for short and long rests overlapping almost entirely. What it could say was that something over sixty seconds is worth a small amount, and that past ninety seconds the evidence stops being clear in either direction².

A small benefit with wide uncertainty is the honest summary of this whole variable. It is not nothing. It is nowhere near the size of the difference between training and not training, or between finishing your sets and not finishing them.

Rest is the cheapest thing in the session to get roughly right and the most expensive one to obsess over.

What a short rest actually costs

Cut your rest and the first thing that happens is not a worse adaptation. It is fewer reps. Reviewing the acute work, de Salles and colleagues found that at loads between fifty and ninety per cent of a one repetition maximum, three to five minutes between sets allowed more repetitions across multiple sets³. You arrive at set three with less in you, you get eight where you got ten, and the work done in the session falls.

Which gives you a test that needs no research at all. Do your sets hold up? If set one is ten and set four is nine, your rest is doing its job. If set four is five, you are not resting, you are conditioning, which is a fine thing to train and a poor way to get strong.

It also explains why a trained lifter needs more of it. A stronger lifter moves a heavier absolute load and takes more out of themselves doing it, so the same clock buys them less recovery than it buys a beginner. The advice diverges because the people do.

How to pick a number, in the gym, today

1. Rest the heavy compound lifts longest. A set of squats takes far more out of you than a set of lateral raises and it takes longer to be ready to repeat. If you are going to spend rest anywhere, spend it here.
2. Let the last set decide, not the clock. The reason to rest longer is to arrive at the next set able to do the work. If you finished every set you were asked for, the rest was long enough. If your reps fell away, it was not.
3. Keep it the same week to week. Rest changes how many reps you get. Shorten it in week three and your reps drop, and you will read that as a bad week rather than as a shorter gap.
4. Take less on the small stuff without guilt. Forty five seconds on a cable movement is not a compromise you are making. It is most of the available benefit.

The thing the timer cannot tell you

None of this compared a session that varies rest by lift against one that uses a single number for everything. Grgic and colleagues say so outright: whether combining rest intervals of different durations by exercise and load would add anything is unclear¹.

So a plan that gives your squat two minutes and your cable curl forty five seconds is following a coach's judgment rather than a finding. It is a reasonable judgment. It is worth knowing that it is one.

Rest is not recovery. It is the gap that lets you repeat the set you already agreed to do. If the sets are getting done, the gap is right.

What Reckoner does with it

Every lift in a Reckoner session carries its own prescribed rest, longer on the heavy compound lifts than on the accessories, and the watch counts it down for you. Two things then happen that a timer on its own cannot do.

The first is that the rest you actually took is recorded beside the reps you actually did. So reps that fell away across the sets after a full rest and the same drop after forty seconds are not the same evidence, and the engine does not read them as the same evidence. One is a lift taking everything you have. The other is a rest problem, and it is named as one.

The second is what happens when a lift keeps coming back harder than it was asked to be. More rest is the first thing that lift is given. Before a rep comes off the target, before the sets move and before the load moves, the gap gets longer. That order is deliberate. Rest is the cheapest thing in the session to spend, and spending it first leaves your reps and your weight where you earned them.