Browse evidence-based analysis of health-related claims and assertions
Most of the research on how much to lift and how often was done on young men who already train—so we don’t know if the same rules apply to women, older people, or beginners.
Descriptive
How much you lift in total each week matters more for results than whether you do it in 2 days or 5 days—unless you’re trying to get stronger, then frequency helps a bit.
Correlational
Training more often helps you get stronger, but doesn’t seem to help you get bigger muscles—so frequency matters more for strength than for size.
Muscle size and strength don’t respond the same way to more training—strength peaks faster, so adding more sets helps muscle growth longer than it helps strength.
Not all sets count the same—sets that directly target the muscle you're measuring matter more, and a method that gives partial credit to indirect sets works best for predicting results.
Quantitative
Spreading your workouts across more days per week can help you get stronger, but after a certain point, adding even more days doesn’t help much more.
Doing your workouts more often per week doesn’t seem to help you build more muscle, as long as the total amount of lifting stays the same.
Lifting more weights each week makes you stronger, but the extra strength you gain from each additional set gets smaller faster than the muscle gains do.
Doing more sets of weightlifting each week helps you build more muscle, but after a certain point, adding even more sets gives you less extra benefit.
When trained guys do lots of reps, they feel more tired, weaker longer, and more stressed than when they do fewer heavy reps — even though their muscles are damaged about the same.
Causal
Even after a tough workout, your body doesn’t show signs of widespread inflammation in the next few days.
One workout, whether heavy or high-rep, doesn’t change your testosterone levels in the hours after.
Your muscles don’t get bigger or smaller right after a single workout, no matter how hard or how many reps you do.
Pulling or squatting as hard as you can from a static position doesn’t get weaker after either type of heavy lifting session.
Lifting heavy weights just a few times doesn’t stress your body as much right after as doing lots of lighter reps.
More reps don’t break your muscles more than heavy lifts — but they do make you more stressed and tired right after.
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.
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.