What to Know About LISS Workouts and Why So Many People Are Doing Them

POPSUGAR Photography | Kat Borchart
POPSUGAR Photography | Kat Borchart

Are you in need of a break from a high-intensity cardio schedule? Maybe you've heard of LISS — a low-key style of cardio training and a fitness term that's been blowing up on social media. We chatted with Jake Peterson, a NASM-certified and Precision Nutrition-certified trainer, about the new fitness trend that's cropping up to figure out what exactly it is.

So, what is LISS?

LISS stands for Low-Intensity Sustained State — think marathon vs. sprint. Basically, any cardio- and aerobic-based activity that's performed at a low intensity but for a prolonged period (typically 30 to 60 minutes).

Is this a new type of fitness?

Not really. It's just trending thanks to some support from popular trainers. Peterson attributes its recent rise to the Australian trainer and Instagram star Kayla Itsines, who is a major supporter of LISS.

"This trend has made a comeback into recent fitness trends, but it has been used by bodybuilders and other aesthetic-based athletes for decades. As early as the late '60s and early '70s, it was a popular method used by bodybuilders to aid them in 'leaning out,' in combination with very low-carb diets," said Peterson.

What makes it so popular?

The reasons are varied, but each of them are enticing.

Active Rest and Recovery: LISS is ideal for an active rest or recovery day for those who have higher intensity workouts as a part of their everyday routine. The risk of injury is also significantly lower.

It's Not Intimidating: For those who are new to exercising and fitness, LISS is like a gateway to getting stronger and perfect for a first step on your fitness journey. Walking on a treadmill or going for a casual swim is much less intimidating than jumping into a bootcamp class. With more and more LISS activities, you can build strength and endurance to take on those higher intensity workouts.

The Lazy-Girl Concept: With low effort, you can get great results. Peterson noted that the recent uptick in LISS's popularity is partially due the desire to "lose weight while exerting the least amount of effort possible." It makes sense: the idea that you could get a leaner, trimmer body with just two hours of a slow walk on the treadmill each week is quite alluring.

What are some examples of LISS activities?

One of the great features of LISS is that you can do it in and outside of the gym. A brisk walk or a bike to work would constitute a good LISS activity, as well as using the rowing machine, elliptical, or stair machine at the gym. You could swim in a pool or in the ocean, surf or stand-up paddle, or kick up the incline on a treadmill. Check out some more steady-state cardio suggestions.

Does it actually work?

Short answer, yes. Peterson implements LISS when he works with clients — and it's part of his own training. However, just as you maintain a balanced diet, Peterson cautioned us to incorporate LISS into a balanced exercise schedule. "LISS training by itself will almost always lead to a negative yield in lean muscle mass and basal metabolic rate," said Peterson. "It's very effective at metabolizing fat for energy consumption by the body. However, it is horrible at accessing and breaking down stored fat."

So what does that mean? If you only do LISS training and LISS alone, your body will start to break down its own muscles as a source of fuel, "due to the much lower caloric requirements of burning muscle." You may thin out, but you'll lose strength.

How often can you do LISS?

If you're doing it correctly, all the time! Peterson recommends LISS to his clients who are in high-intensity training as an active recovery day and suggests doing a LISS activity after each training session to wind down, as it aids in the regeneration and conditioning of muscles.

When you're committing to LISS daily, Peterson recommends you to focus on your nutrition, as "adequate and proper nutrition — pre-, intra-, and post-workout — become much more important when training in this style."

As mentioned, the trick is to balance the low intensity with the high intensity; the combo of HIIT and LISS is the most effective approach for anyone trying to lose fat. "LISS training becomes very useful once it is performed after a workout session based on HIIT (high-intensity interval training)," said Peterson. "The HIIT style of training is great at breaking up the triglyceride bonds within more stubborn adipose tissue (the hard-to-burn fat), but it is not very effective at metabolizing it out."