Health Claims

If you do lots of reps with lighter weights for six weeks, your body might make more of the non-muscle proteins inside your muscles than if you lift heavy weights with fewer reps — and this difference is pretty big.

Causal

If you lift heavy weights (80–85% of your max) instead of doing lots of lighter reps (60% of your max), your legs get stronger faster — after 6 weeks, you’ll likely gain 5–6 kg more in leg strength.

Causal

If you're a young man who already trains regularly, doing more sets with lighter weights for 6 weeks can make your thigh muscle grow a little bigger — but doing fewer sets with heavier weights won't make it grow at all.

Causal

Taking a one-week break from weightlifting won’t make your muscles grow bigger, even though some people think resting might help your muscles respond better to training again.

Causal

If you're a young person who regularly lifts weights, keeping up your workouts for 9 weeks might make you feel a little more mentally ready to train than if you took a full week off—but it's not a huge difference, and we're not sure if it really matters in real life.

Causal

If you take a one-week break from your heavy leg workouts, your leg strength and ability to keep going during exercises won’t drop in any meaningful way — at least not if you’re already trained.

Descriptive

If you take a one-week break from lifting weights—even if you’ve been training hard—you won’t lose or gain noticeable muscle in your legs, and taking short breaks like this won’t hurt or help your muscle growth.

Descriptive

If you take a one-week break from lifting weights halfway through a 9-week workout plan, you might lose a little bit of your strength gains in your legs, but your muscles won’t shrink any more than if you kept going, and your endurance and power won’t be affected.

Causal

For older people, lifting weights once or four times a week might not make much difference in how much stronger they get—but it could make a big difference in how much their muscles grow.

Quantitative

If older adults do not gain muscle from regular weight training, doing more sets and reps might help them finally start building muscle.

Causal

If you're an older adult who's already seeing some muscle growth from light weight training, doing more sets might help you build even more muscle—but the extra gain isn't big enough to be sure it's real and not just luck.

Causal

If older people don’t get stronger from doing just one or two sets of weight exercises, doing four sets might help them build more strength—but it doesn’t work as reliably as it does for making muscles bigger.

Causal

If you're an older adult who gets stronger with just a little bit of weight training, doing more sets won't make you any stronger than doing just one set.

Causal

If older people don’t get stronger from doing just one set of weight exercises, doing four sets instead might help them build more strength after training twice a week for 10 weeks.

Causal

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, they’ll likely grow bigger muscles in their thighs after 10 weeks of working out twice a week.

Causal

If you train one leg of an older adult with light weights and leave the other leg alone, scientists can tell whether that person’s muscles grow in response — and use that to figure out who benefits from this kind of training and who doesn’t.

Quantitative

If you're an older adult who gets stronger with just a little bit of weight training, doing more sets won't make you any stronger than doing just one set.

Causal

If you're an older adult who got stronger from light weight training, doing more sets might help you build even more muscle—but we're not as sure about this as we are for people who didn't respond to the light training at all.

Causal

If older people don’t get stronger with just one set of weight exercises, doing four sets instead might help them build more strength.

Causal

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, their thigh muscles will grow bigger — and this was measured with a detailed scan.

Causal

For older people lifting weights, doing just one set of exercises builds just as much strength as doing four sets—so more sets don’t necessarily mean stronger muscles.

Causal

Some older people’s muscles grow when they lift weights, and others don’t — this claim says that changing how many times you lift can tell the difference between those who grow and those who don’t, based on how much their thigh muscle size changes after just one set.

Causal

If you're an older adult who's already getting stronger from light weight training, doing even more weight training might help you build even more muscle—but not as much as it helps people who didn't respond to light training at all.

Causal

If older people don’t get stronger with light workouts, doing more sets of leg exercises might help them build more strength over 10 weeks.

Causal