Achilles Update: The Occasional Spasm

Over the past few days, I've noticed the calf muscle of my injured leg will occasionally spasm for a period of 2-3 seconds. This happens about three times a day and usually when my leg is not fully elevated. It's not overly painful. However, I am apprehensive of having my Achilles tendon move in the slightest; it causes me some concern when my calf muscle decides to complain about its living quarters (AKA, my fiberglass cast).

Is this normal? Should I be concerned?