How fast you lift each rep, and whether it matters

Lifting slow is often sold as a secret trick for more muscle. Lower the weight for a slow count of four, they say, and you'll grow faster. It's a reasonable-sounding idea. It's also not what the evidence shows.

What the research actually found

A systematic review with meta-analysis pulled together studies that compared different lifting speeds, both the lowering part of a rep and the lifting part, and checked what happened to muscle size. The finding was plain: resistance training tempo appears to have minimal overall effect on muscle hypertrophy, with any real differences only showing up in a few specific conditions.

That held up even when the researchers split the data by upper body versus lower body, and by whether people trained to failure or not. The differences they found were small at best. So if you've been worried that your reps are too fast or too slow, you can mostly stop worrying.

So what is worth paying attention to

Tempo being a non-issue doesn't mean technique doesn't matter at all. A narrative review on resistance training technique points out that technique covers more than speed. It also covers how far you move the weight and how well you control it, and those pieces do seem to carry more weight for muscle growth than tempo does.

One thing that does come with a trade-off is using momentum, like swinging your body to heave a dumbbell up during a curl. A study that had people do biceps curls and triceps pushdowns, one arm strict and one arm using swing, found that using momentum neither helped nor hurt muscle growth in the target muscle compared with strict form on the other arm. It did let people handle more weight, up to a quarter more load, but that extra load didn't translate into extra growth of the muscle being trained.

1. 1

   Pick a pace you can control Lower the weight in a way that doesn't feel like it's falling, and lift it without jerking. You don't need to count seconds.

2. 2

   Keep it the same set to set Using roughly the same speed each time makes it easier to tell if a weight is actually getting easier, which is what progression is built on.

3. 3

   Save the swing for when it's needed If you're using body momentum to finish a rep, the muscle you're trying to train is doing less of the work on that rep.

4. 4

   Don't chase a slow-rep gimmick Spending extra time under a very slow count doesn't buy you more muscle, it just makes the set take longer.

Speed of the rep isn't the lever that matters most, how far you move and how well you control it is.

Why this is good news

If tempo mattered a lot, every set would need a mental stopwatch running, counting down the lowering phase, pausing at the bottom, timing the lift. That's one more thing to think about on top of your reps, your rest and how hard the set feels. Since the evidence says tempo's effect is small, you can spend that attention somewhere it counts more, like finishing each set at the right effort and moving the weight through a full, controlled range.

This also means two people training the same exercise for the same muscle don't need to match each other's rep speed to both be making progress. One person's reps might look a beat faster than another's. As long as the weight is moving under control and the muscle is doing the work, both are fine.