Ever wonder why it’s easier to do a chin-up than a pull-up? They pretty much use all the same muscles, don’t they? The answer comes down to basic hand position!
While the muscles engaged largely remain the same, grip position changes the lines of pull on these muscles varying the amount of work they must do. For example a chin up gives the biceps brachii a better line of pull so they can’t help with the movement more taking some of the load off the latissimus dorsi.
The picture below shows all 3 grips; supinated (top) often called “underhand,” pronated (bottom) also known as “overhand,” and a neutral grip (right). If you’re wondering which grip is the best to use the answer, as usual, depends on what you’re trying to accomplish. If you want bigger forearms you may want to try high volume pronated curls. If you want to be able to do more pull ups, maybe try some heavy hammer curls with perfect form. So the best answer is to try different exercises with all 3!