If you take a look around your gym, you probably won’t see a rainbow chart that spells out how hard you’re working out based on the number of times your heart beats in 10 seconds. And maybe that’s for the best.
Not everyone is the same age, gender or weight. And it’s these factors that count when you try to calculate how many calories you’re burning during that incredible spin class.
Your best bet is a heart rate monitor. Today’s models have a comfortable fit for under your shirt. Find one that keeps tracks of your weekly exercises. It will give you a big-picture idea of how many calories you burn in a week.