Dont do any in the gym, but do sport for at least an hour each day.
I do sports science in college so i either am playing some form of sport or coaching it nearly every day.
We also do fitness tests alot, and they are mainly aerobic.
Also, i have a team training session for rugby which is very demanding. A game also, so i do quite a bit of cal burning!
cant be to good for the mass...i try to keep the cals up, but it is hard.