How To Decide Between HIIT & LISS Workouts

Both HIIT and LISS styles of exercise are guaranteed to make you sweat. Beyond that, however, these two workout methods start to diverge. In fact, you could say that HIIT (high-intensity interval training) and LISS (low-intensity steady-state training) are on opposite ends of the fitness spectrum.

What sets HIIT and LISS apart, exactly? HIIT is a type of anaerobic exercise that alternates intense bursts of movement with brief periods of rest and recovery, says certified personal trainer Toshoya McEwan, BSHc Kin, CSEP-CPT. A HIIT workout typically includes circuits that are 45 seconds long followed by 15-second breaks, adds Samantha Deutchman, a NASM-certified personal trainer and co-founder of Yoga Strong. The goal is to work as hard as you can during those 45 seconds.

While HIIT routines often feature super-tough moves like burpees, air squats, lunges, and other bodyweight exercises, it’s possible to fit any type of movement into the HIIT format, including strength training, cycling, and even walking. “Beginners might want to start with a simple routine that alternates walking and running,” McEwan tells Bustle, while more experienced exercisers could increase the intensity by adding sprints or hills. As long as you get those intervals, you’re doing HIIT.

Then there’s LISS, which, while also a four-letter fitness acronym, is way more chill in comparison to HIIT. With LISS, you stick to one aerobic exercise and chug along at a moderate speed, whether that means walking, running, etc. “LISS can be performed using any type of cardio equipment, such as a treadmill, elliptical machine, rowing machine, or even by just walking at a steady pace,” McEwan says. “The key to LISS is that it should be performed for a prolonged period of time, typically longer than 30 to 40 minutes.” Read on below for more differences between HIIT vs. LISS.

The Benefits Of HIIT

All the benefits of HIIT stem from the highs and lows of the intervals. According to Deutchman, these ups and downs actually improve your heart and lung function by increasing your heart rate variability (the difference in time between each heartbeat) and resting heart rate. “The stimulus provided by the short bursts of intensity help your body adapt to a higher threshold so you can safely push your body to greater limits,” she says.

That’s why the rest periods also play a key role and are just as important as the work itself, Deutchman adds. “Taking breaks will not only help you stay injury-free, but it allows your body to recover so that you can maximize output during the work period,” she says. “When you rest between intervals, you allow your heart rate to return to normal so you can maintain your volume and repetitions in the next round.”

To take full advantage of the little break, you might walk in place, stand and stretch, or even sit down, all of which Deutchman says are great ways to conserve your energy before you spike your heart rate again with a fresh burst of burpees.

Because it’s quick and to the point, McEwan says HIIT can be done in a relatively short amount of time, which is why it’s a fave of gym-goers who don’t have much room in their calendars. It’s possible to start your HIIT circuits, get your heart rate up, sweat, and move on with your day in as little as 15 minutes — and still reap the health benefits.

That said, while you might largely equate HIIT to being cardio-based, it’s also a good choice for strength training, whether you’re doing bodyweight moves, bicep curls with a dumbbell, or getting in reps on a weight machine. Deutchman says the short rest periods help you build strength and muscle.

The Benefits Of LISS

Like any form of cardio exercise, LISS can help lower your risk of heart disease by improving your cardiovascular fitness, Deutchman says. Because it’s steady and ongoing, a LISS workout gets your heart pumping, increases your circulation, and helps improve your endurance.

LISS is also considered an ideal way to recover after other more strenuous types of exercise, according to Deutchman. If you just did HIIT the day before, it makes sense to follow up with LISS the next, since it’s steadier, slower, and more gentle on your body. A steady-state workout will help you recover by reducing the stress on your body and boosting circulation so that your muscles can heal, she adds.

Another perk of LISS is that it helps you relieve stress without putting too much extra stress on your body. While any type of workout is considered a “stressor”, Deutchman says LISS is less physically demanding and thus produces fewer stress hormones. And, thanks to the slow, steady-state movement, you get all the benefits of a runner’s high without pumping your body full of exercise-induced cortisol or adrenaline.

To put it simply, “LISS is a great way to increase your activity level without putting too much stress on your body,” McEwan says.

Should You Do HIIT Or LISS?

To figure out which style would be the best fit for your next workout, consider your goals, your fitness level — and your mood. “LISS is an excellent choice for a beginner or someone jump-starting their workout routine, as it’s less likely to lead to muscle soreness or injuries,” Deutchman says. It’s also perfect if you have 45 minutes or an hour to spend jogging on a treadmill and want to take your time.

Deutchman adds that LISS is ideal for folks who enjoy a “casual fitness atmosphere” because it allows you to move at your own pace. “LISS also allows you to multitask,” she says, “as many people listen to music, podcasts, or talk on the phone and watch TV simultaneously.” (Sounds like the perfect time to catch up on House of the Dragon, no?)

HIIT, on the other hand, might feel really good whenever you’re in the mood to burn off some energy or if you need to get your workout over with fast. These workouts are way more time efficient, McEwan says, but they do require a lot more energy.

HIIT is also appealing to athletes and to anyone who has a consistent workout routine. “Those with prior experience or clear-cut goals are more likely to enjoy the fast-paced style and variety of techniques used,” Deutchman notes. “Ultimately, it all comes down to your goals, mindset, and how you like to approach your workout regimen.”

Studies referenced:

Alansare, A. (2018). The Effects of High-Intensity Interval Training vs. Moderate-Intensity Continuous Training on Heart Rate Variability in Physically Inactive Adults. Int J Environ Res Public Health. doi: 10.3390/ijerph15071508.

Helgerud, J. (2007). Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. doi: 10.1249/mss.0b013e3180304570.

Hill, E.E. (2008). Exercise and circulating cortisol levels: the intensity threshold effect. J Endocrinol Invest. https://pubmed.ncbi.nlm.nih.gov/18787373/

Ketelhut, S. (2016). Influence of a high-intensity interval training session on peripheral and central blood pressure at rest and during stress testing in healthy individuals. Vasa. doi: 10.1024/0301-1526/a000560.

LaCroix, AZ. (1996). Does walking decrease the risk of cardiovascular disease hospitalizations and death in older adults? J Am Geriatr Soc. doi: 10.1111/j.1532-5415.1996.tb02425.x.

Patel, H. (2017). Aerobic vs anaerobic exercise training effects on the cardiovascular system. World J Cardiol. doi: 10.4330/wjc.v9.i2.134.

Sources:

Toshoya McEwan, BSHc Kin, CSEP-CPT, certified personal trainer

Samantha Deutchman, NASM-certified personal trainer, co-founder of Yoga Strong