Browse evidence-based analysis of health-related claims and assertions
People grow muscle at very different rates — but each person tends to grow their arms and legs similarly, no matter what weight they use. This means your genes and biology matter more than how heavy your weights are.
Causal
Your muscles make more protein when you start lifting weights, but after a few weeks, that boost fades — even if you keep lifting harder — no matter if you use heavy or light weights.
When people lift weights until they can't do another rep, their muscles grow about the same amount whether they use heavy or light weights — and how much they grow depends more on their own body than on how heavy the weights are.
Doing bicep curls with one arm makes that arm stronger for one-arm curls, but doesn’t make you stronger for two-arm curls or the other arm.
Training your right arm alone makes your right arm stronger, but doesn’t help your left arm get stronger — the benefit stays on the side you trained.
Training one arm at a time doesn’t make you stronger when lifting with both arms together — your total strength gain is the same as training both arms at once.
Whether you lift weights with one arm or both at the same time, your biceps grow about the same amount after 8 weeks of training.
Doing bicep curls one arm at a time makes your right arm stronger than doing them with both arms together, but doesn't make your biceps bigger than using both arms.
Older women who lift weights—even just one arm or leg at a time—gain muscle and fight off the natural muscle loss that comes with aging.
Training one arm or leg at a time helps older women build muscle just as well as training both at once—but it doesn’t help them use both sides together any better.
When older women try to push with both legs at once on a leg press or pull with both arms on a lat machine, they’re weaker than when using each side separately—but this doesn’t happen when they extend their knees.
Descriptive
Whether older women train one arm or leg at a time or both together, they both gain muscle—just as much as each other—and both are better than not training at all.
When older women train by pushing or pulling with both arms or legs at the same time, they get better at using both sides together, making their strength more efficient.
Training with squats or leg extensions didn’t make the upper or middle parts of your outer thigh muscle grow much — only the bottom part did, and only with squats.
Squats make the lower part of your outer thigh bigger, while leg extensions make your front thigh muscle bigger — your muscles grow in different spots depending on how you train them.
Whether you do squats or leg extensions for two months, you’ll get about equally stronger at doing leg extensions — the exercise you don’t do doesn’t hurt your progress on it.
If you're a woman new to lifting and do leg extensions twice a week for two months, your front thigh muscle (rectus femoris) will grow more all along its length than if you did squats.
If you're a woman new to lifting and do squats twice a week for two months, you'll get much stronger at squats and your outer thigh muscle near the knee will grow more than if you did leg extensions.
If you train one leg at a time, that leg gets much stronger than the other when tested alone — but if you train both legs together, both legs get stronger at the same rate, with no one leg getting ahead.
Even though people who trained one leg at a time ended up lifting heavier weights than those who trained both legs together, both groups ended up with the same muscle size and overall strength — so lifting heavier with one leg doesn’t automatically make you stronger overall.
Training one leg at a time makes it harder for both legs to work together at full power, while training both legs together makes them work better together — the way you train changes how your legs coordinate.
Whether you train one leg or both legs at once for 12 weeks, your legs get just as big and strong overall — the way you do the exercise doesn’t change how much muscle you build or how strong you become in general.
Doing leg extensions one leg at a time for 12 weeks makes each leg stronger and more active when tested alone, better than doing both legs together — even though both methods improve overall leg strength similarly.
Biscuits made with high-oleic sunflower oil or butter tasted good and had a nice texture, but the ones made with coconut and sunflower oil mix were liked the most by tasters.