Many of these hardcore, high-heart-rate fitness enthusiasts wouldn't dare walk on the treadmill for an hour. After all, in today's world, where time is money, why spend an hour burning calories when you could burn the same or more in 20 minutes?
That's the big sell for workouts involving high-intensity interval training (HIIT), a workout method that involves alternating bouts of vigorous effort with periods of slower-paced recovery. And fitness enthusiasts are HIIT-ing this trend hard (pun definitely intended).
But the growing trend on fitness-centered social media seems to point to the growing popularity of another attractive option for those who don't want to go quite so hard, but who don't want to go home either: low-intensity steady-state cardio (LISS).
What Is LISS?
Simply put, LISS involves elevating your heart rate with activity, but not letting it go beyond 50 percent of your maximum heart rate, and then keeping it there for an extended period of time (at least 30 minutes).
To estimate your maximum heart rate, subtract your age from 220. You can also use heartbeats per minute to measure intensity. Sports and conditioning coach Mike Robertson recommends keeping your BPM (beats per minute) between 120 and 150 for low-intensity exercise.
Some examples of LISS include going for a slow jog or a casual walk on flat terrain, riding a stationary bicycle at an easy pace of less than five miles per hour and at a low resistance, leisurely swimming and some forms of gentle yoga.
When you're doing LISS, you might break a light sweat, but not much more. Your breathing is fairly steady, and you can easily carry on a conversation with your friend on the neighboring treadmill.
However, keep in mind that intensity is relative. For a novice exerciser who's out of shape, a 30-minute walk could be a moderate- to high-intensity activity. For an athlete doing LISS on his rest day, a 45-minute jog might not take him out of the low-intensity cardio zone.
Why Is LISS So Popular?
LISS is nothing new; it just never had its own hashtag until now. In fact, in the '70s and '80s (way before Instagram and exercise selfies) steady-state cardio was all the rage. No one who wasn't an athlete was running sprints.
In some ways, the increasing popularity of LISS is a direct response to the emphasis on "all high-intensity, all the time" from the past two decades. People are slowing things down and becoming more mindful and gentle with their bodies. Plus, it's a lot less intimidating than jumping into a high-intensity boot camp class.
It's also a much more realistic approach to exercise for certain populations, such as beginners, people with injuries and those who aren't too crazy about working out in the first place — the same groups that have been shut out and turned off by the high-intensity craze.
The Benefits Of LISS
Anytime you do something active and get your heart rate up, you're doing something good for your body, both physically and mentally. Especially for people who work sedentary jobs — that's most of us — just getting up and going for a 30-minute walk on your lunch break can do wonders for your heart, lungs and state of mind.
For new exercisers just starting out on the path to fitness, LISS is a safe, effective way to build cardiovascular endurance and even muscle strength, says Nick Tumminello, owner of Performance University.
In fact, for beginners, LISS is really the only option to gain a solid fitness foundation. According to a December 2015 review of research published in the journal Sports Medicine - Open, low-intensity exercise results in better exercise adherence — meaning you're more likely to stick with a low-intensity cardio program — and has a lower risk of injury.
But even exercise enthusiasts and athletes benefit from LISS. You simply can't "go hard" all the time. If you do, you're setting yourself up for overtraining injuries. Tumminello says that steady-state cardio can basically provide active recovery time, which is great for letting your muscles heal while still doing a bit of activity.
LISS vs. HIIT
If your goal is fat loss, you're going to need more than LISS cardio a few times a week. The higher the intensity of your workout, the more calories you'll burn and the more fat you'll shed.
But for most of us, running at a steady pace of six miles per hour for an hour isn't going to happen on a regular basis. That's where HIIT comes in. With HIIT, you get your heart rate to skyrocket for between 30 seconds and four minutes, and then you get a period of recovery before the next round.
HIIT has also been shown to raise your metabolic rate, or the speed at which your body burns calories, both during and after exercise. This is called the EPOC effect, or excess post-exercise oxygen consumption, and health and fitness expert Pete McCall says HIIT is the best way to stimulate this effect.
The quickness with which HIIT improves performance and health parameters also can't be beat. Tumminello says that benefits from cardio, including burning fat and increasing your endurance, happen quicker during HIIT workouts.
A Happy Middle Ground?
Fitness trends tend to take an all-or-nothing approach, but getting in shape, losing weight, building strength and becoming healthier isn't black and white. Tumminello says you shouldn't treat HIIT and LISS as mutually exclusive and pit one against the other, as the two workout styles are complementary.
A well-rounded fitness program includes high-intensity days and low-intensity days. If cardio is all you do, try adding in one or two HIIT workouts a week, equally spaced between your lower-intensity workouts. If you strength train or do sport-specific training (which often qualifies as HIIT, depending on your training routine), balance your high-intensity workouts with rest days during which you do a long, slow LISS cardio workout.
On the other hand, if all you want to do is maintain a basic level of fitness, clear your head and chat with your friends on the treadmill: There's really no reason you ever need to go hard. Go at your own pace — even if it's really, really, really slow — and then go home.