Ok this may sound a little far fetched, but a veteran from my gym in the AAS field told me this...Lets say for instance it is 70 degrees F outside and you inject on that day. The next day it is either 10-15 degrees warmer or colder outside. He insists that this causes the "test flu" or at least the flu like symptoms to take effect and also insists that it will make the inject site incredibly sore for extended amounts of time. Anyone have any insight or thoughts on this?