Doing calf raises with your knees straight builds more of your main calf muscle than doing them with your knees bent. This happens because keeping your knees straight puts the muscle in a better position to handle more tension and stretch, leading to bigger growth.

Doing calf raises with your knees bent builds more of the deep calf muscle than doing them with straight legs. This happens because bending your knees changes how the calf muscles stretch and push, making the exercise more effective for that specific muscle.

Working your muscles while they are fully stretched builds more muscle than working them while they are shortened. This stretching advantage is especially noticeable in muscles that cross two joints, like the back of your lower leg, but doesn't seem to matter for muscles that only cross one joint.

Doing calf raises at the bottom part of the movement — where your calf is stretched — might build more calf muscle in young women than doing the full raise, according to this claim.

Doing calf raises through a shorter range of motion, when the muscle is more stretched, might build more calf muscle in young women compared to doing full up-and-down reps — especially in the inner part of the calf.

If young women do calf raises with their ankle stretched more, they might build more calf muscle than if they do the same move with a less stretched ankle — after 8 weeks, the stretched version led to almost twice as much muscle growth in one study.