Slogging away on the treadmill to hit some magic number is a waste of time and energy since machines can only roughly estimate your metabolic rate, Vastola says. Ignore the red digits on the console and focus on intensity instead. If you work harder in shorter bursts, you’ll burn more calories even after your workout is over. Use a heart rate monitor (aim to stay between 75 to 85 percent of your max heart rate) or the rate of perceived exertion scale of 1 to 10 (strive for an 8 or 9 on high-intensity intervals) to determine if you're working hard enough.
