Doing leg exercises with your knees bent or straight builds the deep calf muscle about the same amount over 12 weeks. This means your deep calf muscle doesn't really care whether your knee is bent or straight when you're lifting weights.

Doing calf raises with your knees straight or bent builds the deep calf muscle about the same amount. This happens because that specific muscle doesn't care as much about how stretched it is when you push off, unlike the outer calf muscle. So, you don't need to change your knee angle to get the best results for this muscle.

Doing calf raises while standing up with your knees straight builds more calf muscle than doing them while sitting down with your knees bent. Research shows that keeping your legs straight during the exercise leads to much bigger muscle growth over a few months.

Doing calf exercises while standing up builds more muscle in your lower legs than doing them while sitting down. Over three months, standing workouts can increase calf muscle size by about 10 to 12 percent, while sitting barely changes it at all.

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 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.