Whenever I haven't walked for a while (like in the winter) and then I take my dog for a walk - I usually do 1.2miles in the morning, takes me approx. 20 minutes. Anyway, after about 3/4 of the way my thighs start totingle and get warm...what does that mean? Is it good or bad? Am I totally out of shape or are my muscles warming up? It normally stops after the second or third day. Anyone know???