I'm not talking about treadmill running or hitting up the elliptical, I'm talking about balls to the wall, push yourself until you can't stand or get lightheaded. I've been following some of Ross Enamait's GPP workouts lately but they all seem to be pretty similar. What does anyone else do for GPP work? I've played around with sandbags and would love to get my hands on a tractor tire to smash around and possibly flip also. Any good ideas?