What Really Happens to Your Body When You Do a HIIT Workout Every Day

Originally Published on January 1, 2021 Exercises and Workouts | By Rozalynn S. Frazier, CPT

It’s easy to become addicted to high-intensity interval training (HIIT) workouts. They’re short, and they melt fat and build muscle. Plus, they give you the ultimate exercise high that’ll leave you feeling like you ran a marathon and back. While it’s tempting to get into the HIIT habit every day, it’s not always the best idea for your body.

When you do HIIT, your body releases cortisol — the stress hormone — which “causes increased heart and breathing rate, pulse rate and blood pressure,” says Sherry A. Ross, MD, a board-certified obstetrician-gynecologist and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California. This makes it a good physical stressor because it activates your body’s fight-or-flight response without saddling you with health issues.

But if you do too much of it, HIIT can actually keep your cortisol levels sky-high when compounded with other life stressors (hello, COVID-19 pandemic). And that’s where you get into trouble because it puts your body in a chronic state of stress, which can lead to weight gain, heart disease and diabetes.

Whether you’re joining a group Zoom workout or doing a quick one on your own, here’s exactly what happens to your body when you do HIIT every day.

Your Heart Could Get Overworked

HIIT, at its essence, is a cardio workout, so it naturally increases your heart rate and the demand for oxygen in your blood.

“During HIIT, your heart works harder, meaning your blood pressure and heart rate increase at rates higher than low-intensity, steady-state exercises,” Satjit Bhusri, MD, founder of Upper East Side Cardiology, tells LIVESTRONG.com. “The higher cardiac output can result in increased arterial dilation,” which expands the blood vessels and increases blood flow.

This increased demand for oxygen during exercise, followed by rest, helps the heart become more efficient. So the heart not only does a better job of pumping blood, but it can pump ​more​ blood with each beat — all of which can decrease strain, and ultimately, lower blood pressure.

In addition, HIIT increases your energy and stamina levels, which are associated with a reduced risk of a heart attack, Dr. Bhusri says. In fact, HIIT is a great way to meet physical activity guidelines and decrease your risk of cardiovascular disease, according to a July 2019 article in the World Journal of Cardiology.

While HIIT can do great things for your heart, you want to avoid doing it every day. “The key is to do a variety of exercises and not do the same exercises every time,” Dr. Bhursi says.

If you have a heart condition, check with your doctor before you start a HIIT routine. You might have to adjust the intensity of your workout, he explains. Signs that you might be pushing yourself too hard during exercise include shortness of breath, chest pain and lightheadedness, according to Harvard Health Publishing. If you experience any of these symptoms, you should stop exercising and call your doctor.

Dr. Bhusri recommends using a heart rate monitor to help keep track of your exercise intensity. “Start exercising at a lower-intensity program and build up to higher intensities as you can tolerate it,” he says. | | | Next → |

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