For me any size gain hurts my cardio but especially in MMA .About three weeks after i start my cycle(test prop 300-500mg) my cardio starts going down ,but I dont have the best cardio in the world especially when grappling.Its not as bad in the stand up part of my training but it still has a negetive affect on me.On the other hand I have a freind that trains with me who is a cardio freak and he does 500mg test e a week and can roll for an hour at any pace.So if i you dont have really great cardio i would either do something like masteron or winny or just refrain from juice altogether but either way I would stay away from tren. Tap