The calf response is likely not due to the front squats unless you were really tensing up your toes while in the hole. Your calf muscles are the hardest to develop in your body - period - but if you haven't worked 'em in a while, they're probably a tad angry. Enjoy it while it lasts - calf muscle response is hard to come by after a while. Make sure you stretch liberally - the spasming can last a while if you don't. Nice work thus far, WD. Like it!