Keep Your Body Wondering

Play with your work-to-rest ratios when doing intervals to keep your body guessing. When your body can't adapt to your plan, it's forced to work harder, so you're always working in your fat-burning capacity.

For example, run or pedal hard for 2 minutes, and then rest for 30 seconds. Go hard again for 2 minutes, and then rest for 1 minute. Extend your rest periods by 30 seconds until you reach 2 minutes, and then work your way back to 30-second rest periods, clipping 30 seconds at a time.