Perhaps you’ve heard about the popular exercise trend, high-intensity interval training — commonly referred to as “HIIT.” But HIIT is much more than a mere workout trend! HIIT is an effective way to burn calories, in less time, working for core muscle groups. You can check out our post on types of core exercises.

Before you dive into an exercise routine, ask yourself what kind of results you want to see. Are you trying to lose weight and get a trimmer figure? Or perhaps get stronger and build your stamina? Or, are you looking for a holistic approach to improving your mental health? The good news is, HIIT can help you meet all of these goals. 

Is HIIT effective for weight loss?

Yes! Big time. HITT is so popular, in no small part, due to its ability to torch calories in a short amount of time. Many recent studies have determined that HIIT workouts are one of the most efficient ways to burn calories fast, even more so than steady-state cardio like running.

You continue burning calories for about 3 to 16 hours after a HIIT workout, due to a phenomenon called excess post-exercise oxygen consumption (EPOC). The more intense the workout, the greater your body’s oxygen debt is — as a result, you’re consuming oxygen at an elevated rate, which means you’re still expending energy and burning calories. HIIT’s effects on the EPOC stage are greater than that of running or cycling at a steady pace because the intensity of a HIIT workout raises your metabolic rate. 

In addition to consuming oxygen, your body uses energy replenishing its depleted resources (e.g. ATP, glycogen, lactate), reoxygenating the blood, returning to a normal temperature, and returning to a regular heart and breathing rate.

With that in mind, many experts agree that HIIT workouts are more efficient (in terms of calories per minute) at burning calories than other types of workouts. Check our post on HIIT exercises for obese people.

In fact, a 2015 study from the Journal of Strength and Conditioning Research found that HIIT workouts burned up to 25 to 30 percent more calories than a steady-state workout like running.

Combining your HIIT routine with a healthy diet will keep even more weight off.

Is HIIT effective for building muscle?

Let’s get one thing straight — if you’re trying to look like a bodybuilder, HIIT is not your best workout bet. It will, however, help you build lean muscle and make you stronger overall. According to exercise physiologist Aaron Karp, depending on your fitness level and genetics, you’ll see results in approximately four to six weeks or six to eight weeks of doing HIIT. He also emphasized that some forms of HIIT are more effective at building muscle than others. 

HIIT workouts that incorporate strength training moves, like lunges and push-ups, will help you build muscle if you consistently do them. Muscle soreness is the result of tiny tears that occur while you’re working them out. The body’s natural response is to rebuild and repair the fibers, resulting in bigger, stronger muscles. As you grow stronger, you can increase the difficulty of your HIIT routine by making the work period longer, or increasing the amount of weight you’re using. Don’t try to use too much weight, however — the fast-paced nature of HIIT doesn’t pair well with super heavyweights, and you risk injury if you’re not moving slow enough to focus on form.

How effective is HIIT for improving your stamina?

Because HIIT is such an intense anaerobic exercise, your body’s ability to consume oxygen will get faster over time, the more often you do HIIT. You’ll be able to see this as HIIT workouts become easier for you over time, and you’re not huffing and puffing as much. In more technical terms, HIIT has been shown to increase your VO2 max, which is the maximum rate of oxygen your body can use during exercise. The greater the VO2 max is, the greater your endurance, or stamina, is.

Although HIIT is an anaerobic workout, it can help improve your aerobic capacity as well. Studies have shown that incorporation of HIIT techniques into workout routines leads to improvement of one’s oxygen (O2) pulse, which is defined as “the ratio of oxygen consumption to heart rate and expresses the volume of oxygen ejected from the ventricles with each cardiac contraction.” As with the VO2 max, the greater the O2 pulse, the greater one’s aerobic capacity. In your HIIT journey, you’ll be able to continually increase your stamina by incrementally shortening your rest times as you get stronger.

Is HIIT good for your mental health?

Any type of exercise is good for your mental health, especially when you’re looking to destress. Stress can affect your body in many different ways, and exercise is a good way to confront it head-on. Doing a physical activity causes your body to produce endorphins, which are natural painkillers and the cause of the euphoric feeling you might feel after an intense workout.

But what about HIIT specifically? Short term, an exhilarating HIIT workout will leave you upbeat and hopefully less stressed out than you were before. There’s also research that shows HIIT’s effectiveness in improving mental health long term, as long as it’s a regular part of your routine. Scientists at UC Davis looked at the effects of high-intensity exercise on Major Depressive Disorder, with promising results.

They determined that doing intense exercise causes your body to produce glutamate and gamma-aminobutyric acid (GABA), which are often depleted in individuals with depression. Their research is preliminary but suggests that doing HIIT workouts may have longer-lasting results beyond the adrenaline rush you might experience during and after a session. Everyone’s mind operates differently, so we suggest you try this fun, high-energy workout for yourself and note any mental health improvement.

The bottom line is, HIIT workouts are effective if you put 110% of your effort into them, and if you do them consistently. One HIIT workout won’t yield immediate results, but if you do them a few times a week you’ll get closer to reaching your fitness goals.