Strength Training While Sick

In my desire to procrastinate on the homework assignment I have due at 11:59 tonight I decided I'd lift weights even though I'm slightly ill (sore throat, very very very little flemmy). After struggling slightly with my first exercise I found that I was able to handle significantly more weight/reps for every exercise (up 40lbs on bench press) and at the end of it I wasn't even close to as gassed as I normally am.

In the last 24 hours I've been eating regularly (okay confession: I had 2 slices of pizza last night) and haven't taken any medication.

I checked before hand and the majority of articles I found say its okay to exercise while ill; just don't over-do it. My question is whether anyone else is able to push themselves that much further while ill and if there is a scientific reason behind it. I'm also now wondering if the body rebuilds as quickly while the immune system is down or whether I'm going to have to wait a couple more days until I go at it again?