JJ Virgin says too much cardio raises cortisol and causes muscle loss, leaving heavy runners with the same muscle as sedentary people. Resistance training does more: it builds strength, protects bone and brain, and improves heart health. If you pick one, pick weights.
Cardio alone can accelerate muscle loss. Now I'm talking about lots of cardio. When you're doing cardio, you're one of those cardio junkies. I know I was one back in the day that's doing loads and loads of cardio. I literally used to go for 2-hour runs in the evening after everything else. What's happening when you're doing that? You're raising cortisol, you're burning muscle. And in fact, what they've seen is that people who do loads of cardio without resistance training can actually end up with the same muscle mass as someone who's a couch a couch sitter, as someone who is sedentary. I'm not saying don't do cardio. I'm saying prioritize resistance training because actually if you had to pick one, you'd pick resistance training. Here's why. You'll get cardiovascular benefits from resistance training and the strength benefits and the brain benefits and the bone benefits. Whereas with the cardio, you're getting the cardiovascular, some of the brain, but you get bigger brain benefits from the resistance training.
