Well, straight up boxing is hard but I would never try to be a triathlete. All my endurance is in the upper upper body. I haven’t even started running again since my aortic valve replacement last November. Being a fully trained boxer is a very demanding mix of punching, situps, sparring, jump rope and running. But I will stick to my shadowboxing it is getting me stronger very well and I could really pound a heavy bag right now, but that can wait til fall. You are a very disciplined mind for martial arts and martial spirit. Enjoy and punch to your heart’s content.