Health Claims

If you're new to lifting weights, doing exercises where you lower the weight slowly (eccentric) might make your biceps grow bigger than exercises where you lift the weight up (concentric), after 8 weeks of training.

Correlational

Lifting weights slowly or quickly between half a second and 8 seconds per rep doesn’t seem to make a difference in how much your muscles grow — as long as you’re doing resistance training.

Correlational

How fast or slow you lift and lower weights probably doesn’t make much difference in how much muscle you build—unless there’s some special situation we haven’t figured out yet.

Descriptive

When people lift weights, changing how fast they lift or lower the weight, or whether they go all the way to exhaustion, doesn’t seem to make a big difference in muscle growth—any differences are tiny and not very clear.

Descriptive

Whether you lift weights slowly or quickly, you’re probably not going to build more muscle with one over the other — the difference is so tiny it doesn’t really matter in real life.

Quantitative

Whether you lift weights slowly or quickly, as long as everything else stays the same, you’ll likely build about the same amount of muscle—so how fast you move the weight might not matter much.

Correlational

We don’t have enough proof to say whether lifting weights slowly or quickly, or pushing down vs. lifting up, is better for building stronger or bigger thigh muscles in young, healthy guys after 12 weeks of working out.

Descriptive

If young, healthy guys lift weights for 12 weeks, their muscles get stronger at moderate speeds — like kicking or swinging — and they can generate 13% to 32% more force, no matter how they did the lifting.

Causal

If young, healthy guys do strength training for 12 weeks using different types of muscle contractions—whether slow or fast—they’ll get significantly stronger in their thigh muscles, no matter which style they pick.

Causal

How fast or slow you lift and lower weights probably doesn’t make much difference in how much muscle you build—but it might matter a little depending on whether you’re pushing down, pulling up, working a specific body part, or going all the way to exhaustion.

Descriptive

Lifting weights fast or slow doesn’t really make a difference in how much your muscles grow — the tiny difference you might see is so small it probably doesn’t matter.

Quantitative

Whether you lift weights slowly or quickly, you’re likely to gain about the same amount of muscle — the speed doesn’t seem to make a big difference.

Correlational

To figure out whether speeding up or slowing down the lifting vs. lowering part of a weight workout makes your muscles grow more, scientists need to test each part separately—not at the same time.

Mechanistic

When you first start lifting weights, you get stronger not because your muscles grow bigger right away, but because your brain gets better at telling your muscles when and how to contract.

Mechanistic

You can build muscle just as well lifting light weights as heavy ones — as long as you push yourself until you can’t do another rep.

Causal

When people lift weights without going all the way to exhaustion, using machines that force a set speed might make fast lifting look better—but that’s because those machines don’t act like real free weights or gym machines we usually use.

Descriptive

If you lift weights until you're really tired, it doesn't matter if you lift slowly or quickly—you'll still build about the same amount of muscle.

Descriptive

When people lift weights regularly, their muscles usually get about 5% bigger on average, no matter what kind of weight routine they follow.

Descriptive

Lifting weights really slowly with lighter weights doesn’t build as much muscle as lifting heavier weights at a normal speed—even if you push yourself to the limit in both cases.

Causal

If you lift and lower weights quickly or slowly, as long as you do both phases the same way, your muscles grow about the same amount—speed doesn’t make a big difference.

Descriptive

How fast or slow you lift and lower weights doesn’t matter as much for building muscle as how much weight you lift, how many reps you do, or how close you push yourself to failure.

Quantitative

Lifting weights fast or slow doesn’t make much difference in how much your muscles grow — the extra gain from going slow is practically nothing.

Quantitative

When you first start lifting weights, your muscles get stronger not just because they’re growing, but because your brain and nerves get better at telling your muscles when and how hard to contract.

Mechanistic

When people of any age do strength exercises multiple times in a row, their muscles fire more intensely for a short while—and that’s when they get a quick boost in strength.

Correlational