I think running is the single most important part of my training as a 200+lb guy. Running is an incredibly time efficient way to improve your cardio, maintain weight( which is 100% important to my overall grappling cardio and stamina), and teaches the mind to stay focused while the body is stressed. All while breaking you out of your comfort zone which helps you stay tough and improve. One thing that I like is that it takes me only about 30 min from start to finish for a running session ( from stretch to the run to shower). For jiu jistu I Have to drive 20 minutes, attend class for 1hr 15min. Then drive home and shower. All that adds up to about 2 hrs. That makes it a viable way to train every day, even days I wouldnt be able to make it to the gym. And my body cant take rolling 40 minutes every day. My joint hurt and end up with Injuries. But that isn't an excuse to not do anything that day to better yourself. Mixing up small portions of different styles of training and exercise is key to overall improvement.