If rats lift weights slowly for longer periods, they grow less muscle than if they lift quickly or at a medium pace—even if the total effort is the same—because how fast they move matters for muscle growth.

When rats do strength exercises with very slow, long reps, they don't push as hard as when they do faster reps—even if the total effort is the same—and that might be why their muscles don't grow as much.

When rats lift weights with different numbers of reps, their muscles show the same early biological changes no matter if they do few or many reps—and those early changes don’t tell us which workout will make muscles grow bigger over time.

Lifting weights slowly or quickly between half a second and 8 seconds per rep doesn’t seem to make a difference in how much your muscles grow — as long as you’re doing resistance training.

When rats do strength exercises for two weeks, their muscles don't get bigger or heavier, even though their muscle-building processes speed up. This might mean the muscles are just reorganizing themselves instead of growing in the short term.

Even the middle parts of your muscles grow more when you stretch them fully during workouts — it’s not just the ends that benefit from full range of motion.