Hi! I am not Cathe and she may have something different to add to this but I thought I'd share a few pointers anyway. Are you keeping your weight in your heel (the heel of the front leg that is)? You should be pushing up through the heels when you lift your body. Also, make sure that your knee is lined up with your ankle on the down phase. If you are feeling the lunges in your calf muscle, my guess is that you are shifting your body weight to the front of your foot which would activate your calf muscle more. Otherwise, my only other thought would be that your calf muscles need to be strengthened more--they are working hard to stabilize your legs and maybe they are just not up to the challenge yet but with practice,they will catch up!