Health Claims

If you're trying to build muscle with weight training, checking how your nerves talk to your muscles might help explain why some workouts work better than others.

Your brain's signals to your muscles might affect how much they grow when you lift weights — so how well your nervous system works could change how good your workout routine is at building muscle.

If you stretch or lift weights for 8 weeks, your chest muscle might grow a little, but that growth doesn’t explain much of why you get stronger—other factors are probably doing more of the work.

If you're someone who exercises regularly, doing chest workouts 3 times a week for 8 weeks might make your chest muscles about 10% stronger, but it won’t change how far you can move your shoulders.

If you stretch your chest muscles regularly for about 15 minutes, 4 times a week, for 8 weeks, you’ll likely get more shoulder flexibility—more than if you just did strength training.

Stretching your chest muscles for 15 minutes, 4 times a week for 8 weeks, might build muscle just as much as lifting weights — studies say it could increase muscle thickness by around 6%.

Stretching your chest muscles regularly might make them stronger—almost as much as lifting weights does—if you do it for 15 minutes, 4 times a week for two months.

Stretching mice's leg muscles didn't change the number of muscle repair cells, suggesting their muscles still grew without using more of these cells.

Stretching mouse leg muscles repeatedly seems to turn on a key switch inside the muscle cells that helps build new muscle protein.

Stretching mice passively over time might help reduce the activity of genes that break down muscle and block muscle growth, suggesting it could help protect against muscle loss.

Stretching mouse leg muscles regularly seems to turn on genes that help build muscle and repair muscle cells.

Stretching mouse leg muscles regularly for two weeks seemed to make the muscle fibers grow bigger, which could mean the muscles got stronger at a microscopic level.

Even if your muscles are growing inside, your body measurements like arm size or BMI might not change after 8 weeks of weight training.

If young guys lift weights for eight weeks—whether they go heavy or do more reps—they’ll likely build muscle in their upper body and back, and that can be seen with ultrasound scans.

Even if you're not gaining much muscle size, doing lots of light reps can still make you stronger in big lifts like bench and deadlift over 8 weeks.

Lifting heavy weights leads to bigger strength gains in big lifts like bench and squat than doing lots of light reps over 8 weeks.

If young guys lift heavy weights with fewer reps, they’ll likely build more chest and back muscle than if they lift lighter weights with more reps — at least over 8 weeks.

For people new to strength training, lifting light weights with restricted blood flow works just as well as lifting heavy weights for building muscle size over 6 weeks.

Doing light weight training with blood flow restriction doesn't change the space around muscle fibers any more than heavy weight training in regular active people — after six weeks, both seem to have the same effect.

When new people start lifting weights — whether with light weights and restricted blood flow or heavy weights — their muscle fibers grow evenly inside, keeping the same balance between the parts that contract and the rest. This means their muscles grow the usual way, not by just filling up with fluid.

For people who exercise casually but aren’t trained, doing light weightlifting with blood flow restriction helps grow fast-twitch muscle fibers almost as much as lifting heavy weights — and after 6 weeks, the difference between the two isn’t big enough to matter.

In rats with muscle soreness after exercise, two brain-chemical pathways team up to make muscles extra sensitive to pain, especially when certain pain-related proteins are present at low levels — and they both work through specific pain sensors in the nerves.

In rats, sore muscles after unusual exercise make a protein called NGF, which seems to cause pain sensitivity—blocking NGF quickly reduces soreness, and stopping another pain-related signal (bradykinin) also stops NGF from being made, suggesting it's part of the soreness chain reaction.

In rats, sore muscles after unusual exercise seem to start with a specific pain signal (called bradykinin) turning on right when the exercise happens. If you block that signal before exercise, the rats don’t get sore — but only if you block it early.