No one has enough time these days, right? In a world where personal and professional commitments drag us in all directions, having some time to invest in yourself is a precious commodity. Perhaps that’s why high-intensity interval training (HIIT) has become such a phenomenon recently. After all, why spend an hour or more trudging through a traditional workout, when you can break a sweat fast and achieve just as much in half that period?
HIIT is a regime that involves short, intense bursts of high-intensity cardio and strength training offering a quick-fix solution: You will get fit fast. Of course, it's been around for a while, but it seems to have gained momentum ever since CrossFit took off. No doubt, the fast and furious workouts come with a lot of benefits, but as more and more science emerges studying the efficiency and dangers of the HIIT method, we’ve put together a quick guide to help you sort out if it’s right for you.
Pro: It’s Definitely Effective
The payoffs of pushing yourself with HIIT are plentiful. Studies have proven that these intense workouts can burn more calories in less time than traditional types of workouts—specifically steady-state exercise such as jogging. Other research proves HIIT to be significantly effective at reducing resting blood pressure, increasing VO2 max and—perhaps most importantly—reducing stubborn abdominal and subcutaneous (just under the skin) fat.
Pro: It’s Highly Adaptable
Although you can incorporate weights and machinery into your workout, no equipment is required for HIIT, so you can easily exercise at home or while traveling. For a beginner, that might mean push-ups, air punches and/or squats. While someone with advanced fitness levels might put together a set of burpees, box jumps, hills sprints and/or pull-ups.
Pro: It’s More Than Just Muscles
Giving it your all in a fast, intense workout isn’t exactly fun, but research suggests that working at a higher intensity releases more endorphins, producing more of a post-fitness high. Steve Tansey, head of research and development at Les Mills, suggests HIIT offers a sort of mental advantage, too. It encourages escapism, he says. When you’re forced to focus on your next breath, you’re not thinking about your problems anymore. There’s even a growing field of research that points to the potential positive impact HIIT can have on such afflictions as colon cancer and rheumatoid arthritis.
Con: Longer Recovery Time
When “high intensity” is in your workout’s name, you know it’s going to ask a lot of the human body. And this can result in a serious amount of post-workout soreness. Yes, the exercises are brief, but many people overexert themselves and run the risk of damaging muscles, leading to longer recovery times. This also makes it challenging to complete a HIIT workout every single day, so you will have to find alternate workout options in between to give your body the necessary break.
Con: High Risk of Injury
Just like with the recovery time, the increased stress on your body and quick, intense movement means your form may not be correct on some of the exercises. And that can lead to injuries both big and small. Overdoing any type of exercise can be hazardous, but with HIIT, it's important to be especially cautious. Recent research has shown that performing too much high-intensity exercise may undo the very benefits of being physically fit.
Con: Your Hormones Can Get Messed Up
While exercise is typically seen as a good stressor, it is still a stressor on the body. That means that it can significantly raise your cortisol levels. And while short-term spikes can help our body grow stronger, medical experts have found that too high an increase over longer periods can result in a number of unwanted side effects—everything from digestive issues and weight gain to trouble sleeping. Meanwhile, glycogen (the form of carbohydrates stored in your muscles and liver which our bodies use for fuel) gets replenished during rest. But if you don’t rest long enough between HIIT workouts, those stores will not get fully replenished. And low glycogen can make you feel both weaker and slower during your workouts.
* FYI: Most trainers, along with the American Council on Exercise, suggest at least one rest or low-intensity day in between your HIIT workouts. That means no more than two to three intense workouts a week.