just a silly curiousity question. i've been exercising regularly and pretty strenuously for a while now. i just was away for the last three days and really didnt do anything aerobic wise. today, i feel it in my joints - not sore or hurting - they feel kind of funny and lazy - not sure how else to describe it. was just curious if theres some scientific or chemical reason for this - any one have a clue what im talking about?