High-intensity interval training (HIIT) is all about burning calories through combining short bursts of high-intensity exercise and active recovery periods. The fluctuation between heavy exertion and recovery intervals improves both aerobic and anaerobic system development, strengthening your endurance and improving the amount of oxygen you can consume during a workout. But how do you know if your intervals are hitting the mark?

Your heart rate is the ideal metric to determine how much effort it takes to burn fat and improve your cardio, so wearing a heart rate monitor during your workout is a great way to maximize your results; it allows you to track your effort so you always know if you need to pick up the pace or slow down to get the most from your workout.

But a heart rate monitor is useless if you don’t know where your heart rate should be. To estimate your maximum age-related heart rate, subtract your age from 220. For example, a 50-year-old person’s maximum heart rate is 170 beats per minute (bpm), but a person who is 25 has a maximum heart rate of 195 bpm. Then, to calculate your optimal fat burning zone, multiply the maximum heart rate by 0.80. This, incidentally, is the infamous “Yellow Zone.”

HIIT classes that require a heart rate monitor color-code heart rate zones to make it easy to see your effort level at a glance. With heart rates of 0 to 61% and 62 to 71% respectively, the gray and blue zones are good active recovery zones for intermediate and advanced exercisers. The green zone is a good target for a sustained effort with a range of 72 to 81%. The yellow zone is typically the optimal fat burning zone with a range of 82 to 91% of your maximum heart rate. The red zone, which is 92 to 100% of your maximum heart rate, also burns calories, but it is not possible to work out at that intensity for a long time.

The World Health Organization & American College of Sports Medicine recommend that adults perform >150 minutes of moderate-intensity (blue and green zone) OR 75 minutes of vigorous-intensity (yellow and red zone) cardiorespiratory activity per week (or a combination of the two). The more physically fit you are, the more effort it takes to get your heart rate up. But all you have to do is keep your heart rate in the yellow zone, and you'll continue to get results.

Of course these zones are a generalization and work for most people. They are less accurate for athletes and for some older individuals; their maximum heart rates may go higher than what would be calculated. Unless there is a preexisting condition that becomes apparent or worsened during intense exercise, this is normal.

You can challenge yourself to stay in the yellow zone in any Success Studio North HIIT class. Our in-club display shows your color zones, heart rate, workout times, and MOVEs, in real time.

If you do not have a heart rate monitoring device, you can also track your heart rate by placing your index and middle fingers on your wrist and counting 30 seconds worth of heart beats. Then multiply by two to find beats per minute.

Your heart rate is the ideal metric to determine how much effort it takes to burn fat and improve your cardio. And the yellow zone is the infamous color that is the optimal fitness zone for caloric burn. But don’t get too hung up on heart rate in your workouts. It is useful to judge your effort, but if you’re doing a strength-based workout, your heart rate will not be as high as it would be in a cardio-based class. And keep in mind that although the optimal zone is yellow, you do burn calories in all the zones. However, the lower the zone, the longer you need to exercise to burn the same number of calories as a higher intensity level.

Are you ready to take the guesswork out of your cardio training to get targeted results so you can live the life you love fully? Book a Complimentary HIIT workout at Success Studio North or Success Studio Ivy to unveil the body you love.