in the heat, it seems to me, it is so easy to get a pump, taking out trash, whatever you do. anytime that blood flows into a muscle and pumps it up, you lose some of that sharpness and detail. i've also heard in the cold, a greater portion of blood volume is concentrated in the core of the body to help keep vital organs warm and functioning properly, thus the extremities seem nice and ripped up..this is speculation mostly..but think about it, once you get that sick arm pump, the arm looks huge and massive, but less defined..its nice and warm.. when you first get out of bed in the morn. and throw up a bicep pose, the muscle is cold, yet looks real sharp..just my 2 cents..