The outer part of your calf and the deeper calf muscle don’t grow better with either straight-knee or bent-knee calf raises — they respond similarly to both.

Doing calf raises with your knees straight (standing on toes) makes the inner part of your calf muscle grow more than doing them with your knees bent (seated), because the muscle is stretched more.

If you want to grow the inner part of your calf muscle, doing straight-leg calf raises might work better than seated ones.

For the outer calf and deep calf muscle, it doesn’t seem to matter much whether you do straight-leg or seated calf raises — both work about the same.

Pushing a heavy leg press machine makes the outer part of your thigh muscle grow more than doing leg extensions, because it puts more overall stress on that part of the muscle.

When young women want to strengthen their soleus muscle (the lower calf muscle), doing calf raises with bent knees works better than doing them with straight legs.