When beginners do arm curls and triceps exercises with a little swing to lift heavier weights, their arms grow just as much as when they do the movements slowly and strictly—even though they lift way more total weight with the swing.

Using momentum to help lift weights builds arm muscles just as well as lifting slowly and carefully for beginners doing bicep curls and triceps pushdowns over 8 weeks.

Whether you lift your arm weights slowly or with a little swing, your biceps and triceps both get noticeably bigger after eight weeks of training—your triceps grow even more than your biceps.

Even though people who swing weights use their whole body more, their upper arms don’t get any thicker than those who lift strictly—so the extra movement doesn’t help build more arm muscle.

People who swing the weights while doing arm exercises can lift a lot more total weight over time than those who do it slowly and strictly—even though both groups end up with the same size arms.

Doing bicep curls one arm at a time makes your right arm stronger than doing them with both arms together, but doesn't make your biceps bigger than using both arms.