Doing Too Much of This Popular Workout May Lower Your Metabolism and Mess With Your Blood Sugar

High intensity interval training (HIIT) workouts are becoming increasingly popular — especially since we’ve been working out at home so much these days. These exercises are known for being short bursts of vigorous activity (like burpees or several reps of sit-ups and lunges) followed by a resting period, then repeating that cycle a few times in a single session. As great as they are, not keeping track of how long you’re doing them for can actually do more harm to your body than good.

A recent study published in Cell Metabolism found that doing too many HIIT workouts in a week can reduce glucose tolerance and lower your metabolism. So all of the time and effort that you’re spending trying to stay healthy can end up negatively affecting your blood sugar and ability to burn off calories.

Researchers put this to the test by having a group of participants complete 36 minutes of HIIT over the course of the first week, 90 minutes in the second week, 152 minutes in the third week, and 53 minutes in the fourth week. They compared the participants’ metabolism and glucose tolerance at the end of each week to determine which amount of HIIT was most beneficial.

During the third week (the longest period of intense exercises) researchers noticed participants had a 40 percent decrease in their metabolism. The glucose tolerance levels also lowered between the beginning of the first week (the least amount of HIIT) and the end of the third week.

This challenges the idea that even one workout session should last one or two hours to be effective. It turns out, if you’re doing more than two hours of HIIT a week in total, it can even be too much.

That said, the researchers also found a sweet spot for getting the most out of HIIT workouts and maintaining an active lifestyle.

What is the recommended amount of HIIT?

This study concluded that 90 minutes of specifically doing HIIT each week was the best for improving the participants’ metabolism. Plus, this amount will give your body enough time to rest and recover without any annoying soreness lingering into the next day. This might sound like a short workout plan, especially after dividing it up throughout the week, but you can add in other non-HIIT workouts, like yoga, pilates, or walking, in-between if you want to get your blood pumping more often. Plus, it still goes a long way, burning 28 percent more body fat and significantly boosting your memory!

You can use a fitness tracker app on your phone or wear one around your wrist to keep an eye on your timing. Most options will also monitor your heart rate and the number of calories you’ve burned — which are all key for staying on top of your fitness goals. (Take a look at some of our favorite stylish and comfortable fitness watches!)

And there’s no need to go looking for a new exercise routine to try HIIT workouts. It can be as simple as picking up the pace for a few bursts when you’re going on an afternoon walk.

Just remember: Taking a “less is more” approach really works when it comes to this type of exercise!