Why and When to Do Cardio

Two years ago I was doing a LOT of cardio. What? Why? Because I needed to be tough. Tough Mudder, tough. I needed to be ready for the 12-mile Tough Mudder race I did in Beaver Creek, Colorado, back in 2012. And I was. The course was brutal, starting at 8,500 feet in elevation and going up to 11,000 feet, but I finished in 2 hours and 45 minutes. A few months later my best friend and I did