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.

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 resistance is applied such that peak torque occurs at either the longest or shortest muscle length during a movement with identical total range of motion, muscle hypertrophy is not significantly different between conditions.

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.

When healthy young men lift weights until they're too tired to continue, their muscles grow about the same amount in both their arms and legs, no matter how heavy the weights are.

Your muscles don't grow while you're lifting weights—they grow later, while you rest, because that's when your body repairs tiny tears and builds more muscle tissue using the energy and nutrients you've eaten.