I have always avoided cardiovascular exercise because of how uncomfortable it is and also because burning calories and/or weight loss has never been a fitness goal of mine, quite on the contrary, I'm always looking to gain a bit of weight, especially muscle. But after listening to talk about the importance of zone 4 and 5 training, I have been committing myself to running more and really getting my heart rate up. All I can say is, I have never felt better. My mind is clearer, my body feels more oxygenated, I feel less irritable, any stress I do have in my life I'm able to address it with more ease and patience, I have fewer digestive issues and am experiencing so many more benefits. I've noticed that there is a threshold point when doing cardio that you just need to push past, and after that, it is almost trance inducing and the feeling afterwards is so worth it.