Ignoring the clickbait article, HIIT (high intensity interval training) is incredible. I did this routine 3-4 times a week for a couple months: <a href="http:&#x2F;&#x2F;www.fitocracy.com&#x2F;knowledge&#x2F;dr-layne-nortons-best-damn-cardio-humanly-possible-in-15-minutes&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.fitocracy.com&#x2F;knowledge&#x2F;dr-layne-nortons-best-dam...</a> and got my resting heartrate down to 48 from the mid 60s. The best part? This was from just 45-60 minutes a week of fairly easy exercise (compared to running) on a bike machine.