Browse evidence-based analysis of health-related claims and assertions
More reps don’t break your muscles more than heavy lifts — but they do make you more stressed and tired right after.
Causal
Doing many reps triggers a bigger stress and inflammation response in the body right after exercise than doing fewer heavy reps.
Both heavy lifting with few reps and light lifting with many reps cause muscle damage, but neither does it more than the other.
Doing lots of reps leaves your muscles weak for days, but doing fewer heavy reps doesn’t make you weak for long.
Doing a lot of reps with lighter weights right after each other makes your legs feel way more tired right after than doing fewer reps with heavier weights.
Just because changing your shoulder angle makes your biceps work harder during one workout doesn’t mean it will make your muscles bigger over time — this study didn’t test that.
Descriptive
When measuring muscle activity with electrodes during bicep curls, the results can be affected by how the muscle stretches and where the electrode sits — so the numbers aren’t always a perfect measure of effort.
Mechanistic
After a tough bicep workout, your muscles swell and show stress signs, but they bounce back fully by the next day — so these signs don’t tell you much about long-term growth.
Doing bicep curls with your arm stretched behind you makes the lower part of your bicep feel more strained right after the workout than doing them with your arm at your side.
Switching up your shoulder position during bicep curls makes your muscles fire more, even if you're lifting the same total weight.
Whether you change your shoulder angle or not during bicep curls, your muscles recover at the same speed over the next three days.
The middle part of your bicep gets a little more 'hazy' on ultrasound after a workout, but it clears up by the next day — and it doesn’t matter if you changed your shoulder angle.
When you do bicep curls with your shoulder stretched back, the lower part of your bicep shows more signs of stress on ultrasound right after the workout than when you keep your shoulder neutral.
After a tough bicep workout, your arm gets a little swollen, but it goes back to normal by the next day — and it doesn’t matter if you changed your shoulder angle during the workout.
Even when you change your shoulder position during bicep curls, you still lift the same total amount of weight — your total workout effort doesn’t go up or down.
Changing the angle of your shoulder while doing bicep curls makes your biceps work harder during the workout, even if you're lifting the same total weight.
Doing 14 sets vs. 21 sets doesn’t make your muscles look any different on ultrasound—even though you lifted more total weight in the 21-set version.
Correlational
Even after doing 21 sets of squats, you can still lift the same heavy weight two days later—your muscles bounce back fast.
You might feel like you got wrecked after a heavy workout, but your strength and muscle size don’t actually change—your brain is just telling you it was hard.
Even after a brutal leg workout, your muscles don’t get damaged or leak fluid in a way that shows up on ultrasound the next day.
After a really hard leg workout, you feel beat up the next day—but by the day after that, you’re back to feeling normal again.
No matter how many sets you do, your thigh muscles look the same on ultrasound before and up to three days after—so swelling isn’t worse with more work.
Doing more sets means you’re lifting more total weight—simple math, but important for tracking how hard you’re working.
Even after a super hard leg workout, your thighs don’t stay swollen for days—the puffiness goes away by the next day.