Good point on the carbonation. I also learned of its affects in college athletics, wrestling to be exact. It does have a significant affect on your aerobic performance. The reason you didn't notice is that football is a game played in explosive but short spurts(I played FB also), 3-10 seconds, then a break of 45-90secs. Try running a 10mile plus race sometime and you'll notice. If you dont hunt hard and consistent; as you pointed out; you wont notice the effects. on the other hand if you plan on hitting it hard and covering some miles, you will notice, especially if your not used to the altitude which is a killer anyway.