Here's How Cardio & HIIT Affect Your Body Differently

Since both get your heart rate up and both leave you covered in sweat, you might not pay much attention to the differences between cardio and HIIT. But there is actually a lot that sets these two exercise modalities apart.

For a quick breakdown, cardio is an aerobic activity that elevates your heart rate for an extended period of time, says Sydney Miller, a trainer with Swerve Fitness, whereas HIIT (aka high-intensity interval training) is an anaerobic activity that alternates extremely tough bursts of exercise with short breaks.

“Many people associate HIIT training with specific exercises like burpees and mountain climbers,” Miller says. “While these can definitely be used within a HIIT workout, the definition refers more to the rhythm and style of the workout, rather than the exercises themselves.” You can do HIIT by alternating between walking and sprinting. You can mix up your HIIT with rounds of different plyometric moves, like plank jacks, jump squats, and skater lunges. You can even do HIIT-style walking by changing your speed and incline, as long as you get those intervals.

For an example of cardio, look no further than the classics. A long run, walk, or swim counts as cardio, Miller says, as well as more specialized workouts like cycling, dance cardio, and other movement-heavy fitness classes that aim to get your heart pumping — without all the ups and downs. Here, fitness pros break down everything to know about the differences between cardio. vs. HIIT.

The Benefits Of Cardio

Cardio is an aerobic exercise, which means it uses a lot of oxygen. “As you exercise, your body is breaking down glucose stores for energy with the help of oxygen,” Miller explains. And, of course, your heart rate goes up.

Typically, a good cardio workout will last anywhere from 30 to 90 minutes. The American Heart Association recommends getting 30 minutes of cardiovascular exercise five to seven days per week, so you can aim for 150 minutes total of moderate-intensity aerobic activity, 75 minutes of vigorous aerobic activity, or do a combo of both spread throughout the week.

According to Miller, regular cardio workouts are an effective way to reduce your risk of illnesses like heart disease, high blood pressure, and type two diabetes. It conditions your cardiovascular system, strengthens your muscles, controls your blood glucose levels, and improves your overall fitness.

A good heart rate-pumping sweat can also make you happy. “Physical activity in general boosts the production of feel-good neurotransmitters called endorphins,” Miller says. “It’s beneficial for both your physical and mental state.” To get the max benefits from your work, she recommends cardio-ing it up for at least 30 minutes for the endorphins to fully kick in.

Doing a gentle cardio workout is also an ideal way to recover from other forms of exercise, like weight training. “It increases blood flow to muscles, which can increase recovery and ultimately increase your body’s ability to utilize oxygen more efficiently,” says Marty Kretz, a trainer with Chuze Fitness. For that reason, it’s the go-to for anyone who wants to increase their endurance. (Hello, long runs.)

The Benefits Of HIIT

HIIT is an anaerobic exercise, which by design shouldn’t be sustained for long periods of time, Miller says. “Anaerobic means ‘without oxygen’ because the body experiences an oxygen deficit,” she adds, which is why it’s so important to take breaks between each burst of movement.

“After a warm-up, a typical HIIT workout roughly lasts somewhere between 10 to 30 minutes,” adds Kretz. “Your exercises or modalities could vary, but a HIIT workout can include cycling, running or power walking, rowing, and bodyweight exercises, to name a few.” Miller notes that the working intervals — where you really give it your all — should only last about 15 to 30 seconds, followed by 15 to 30 seconds of rest or active recovery. During that time can march in place, stretch or rest.

Like cardio, this workout style does great things for your heart and can lower your blood pressure. The other benefits depend on the types of exercise you do. “You could experience some muscle gain with HIIT-style workouts,” Kretz says. “Since HIIT is pretty versatile in its formatting, you could incorporate more of a strength or resistance-based training as the modality for their workout, like kettlebell swings, kettlebell thrusters, etc.”

HIIT also allows you to reach levels of intensity during your workout that might be tough to do during traditional cardio. Kretz offers that it would be much easier to full-out sprint (once properly warmed up) after a rest period than after jogging for a minute. “Because of this heightened intensity with HIIT, you also will increase your body’s ability to handle lactic acid, which will allow you to maintain higher intensities during regular cardio,” he says.

Cardio Vs. HIIT

“While both cardio and HIIT can achieve similar health goals, there are a few main differences,” says Kretz. “HIIT is meant to be a more condensed workout with rest periods programmed in so that you can reach levels of intensity that you cannot attain with traditional cardio.” Depending on your fitness or training goals, this may be a plus.

That said, HIIT is also much more stressful on the body than traditional cardio. Think of full-out springs versus a nice easy jog, Kretz says. Of course, regardless of the type you do, exercise is a form of stress on the body, which is why he suggests avoiding HIIT when you have other stressors in your life so that you don’t overdo it, injure yourself, or burn out.

That said, Kretz recommends doing whichever form of exercise you enjoy most. “Some people can’t stand traditional cardio and find it boring, but love the push and intensity of HIIT,” he says. “Others love the ability to ‘zone out’ and just run. I say try both and see what works best for you and what you enjoy the most. At the end of the day, the best form of exercise is the one that you will consistently do.”

Studies referenced:

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Amanat, S. (2020). Exercise and Type 2 Diabetes. Adv Exp Med Biol. doi: 10.1007/978-981-15-1792-1_6.

Dupuy, O. (2018). An Evidence-Based Approach for Choosing Post-exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation: A Systematic Review With Meta-Analysis. Frontiers in Physiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5932411/

Lin, TW. (2013) Exercise benefits brain function: the monoamine connection. Brain Sci. doi: 10.3390/brainsci3010039.

Mastorakos, G. (2005). Exercise and the stress system. Hormones (Athens). PMID: 16613809.

Nystoriak, MA. (2018). Cardiovascular Effects and Benefits of Exercise. Front Cardiovasc Med. doi: 10.3389/fcvm.2018.00135.

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

Radak, Z. (2013). Oxygen Consumption and Usage During Physical Exercise: The Balance Between Oxidative Stress and ROS-Dependent Adaptive Signaling. Antioxid Redox Signal. 2013 Apr 1; 18(10): 1208–1246. doi: 10.1089/ars.2011.4498

Stöggl, TL. (2017). High Intensity Interval Training Leads to Greater Improvements in Acute Heart Rate Recovery and Anaerobic Power as High Volume Low Intensity Training. Front Physiol. doi: 10.3389/fphys.2017.00562.

Sources:

Sydney Miller, trainer with Swerve Fitness

Marty Kretz, trainer and fitness manager at Chuze Fitness