Everything You Ever Wanted to Know About HIIT

With a short workout, high-intensity interval training (HIIT) can help you reach your health and fitness goals. Here’s how you can leverage HIIT into your routine.  

When you hear the words “high intensity” and “interval training,” your first instinct might be to shy away. And when you hear them being combined into one workout, you may find it even more intimidating. But it’s not as scary as it sounds!

High-intensity interval training (HIIT) is safe for people of all ages and fitness levels—and it does not require pushing yourself past your limit. It just means you’ll be working out at a higher intensity than what you’re used to. And you get to decide just how high you go in terms of intensity.  

What is HIIT?  

HIIT is a form of interval training that focuses on higher-intensity exercise, followed by short periods (intervals) of lower-intensity exercise. You’ll essentially repeat short bursts of working out hard from anywhere between 5 seconds and a few minutes. That’s the high-intensity interval. Then you’ll slow your intensity for the same duration or even a bit longer. This makes your “rest” periods active recovery periods, too.  

The high-intensity intervals in HIIT are considered vigorous. At this intensity, thanks to some huffing and puffing, it should be difficult to carry on a conversation. You’ll want to aim to get your heart rate to at least 80% of its maximum during these intervals.    

• To calculate your max heart rate yourself, just take your age and subtract it from 220. Another suggested way is to calculate your resting heart rate. You can do this with the heart rate reserve formula.    

HIIT training is typically shorter in duration—around 20 to 30 minutes. The workouts can even be as short as 10 minutes. Before you start a HIIT session, you should do a 5-minute warmup and end with 5 to 10 minutes of slower movements and stretching to cool down.    

The benefits of HIIT  

HIIT has been proven to be a safe option for both older adults and less active adults. It’s even safe for those with certain chronic conditions, such as obesity, heart disease, and type 2 diabetes. Research shows that HIIT can help:  

• Boost cardiovascular health 
• Lower blood pressure
• Improve insulin sensitivity
• Reduce blood sugar
• Encourage fat loss

How HIIT stands out from other types of exercise 

There are a number of reasons HIIT is so popular. 

• HIIT is versatile and adaptable. Similar to interval training and boot camps, you can tailor your HIIT workouts to your fitness level. This makes it a great option for beginners, older adults, sedentary adults, or those with chronic conditions. You can start by adding shorter and fewer intervals of high intensity into your aerobic routine. This may include your walk, jog, or strength training.
  
  Another perk? You can keep HIIT interesting with different exercises. Go for an outdoor run—or run indoors on a treadmill. You can dance. You can use bodyweight exercises or gym equipment. The options are endless. 

• HIIT is time efficient. You don’t have to spend hours working out to lose weight or improve your overall health. Shorter workouts do not mean less effective. Especially not when they are done right. As long as you keep the intensity level high and put in the work, you can achieve the same fitness and health benefits as other workouts—in a shorter amount of time, too.
  
  With HIIT, you can save time by doing a 20-minute workout instead of an hour-long workout. This can be useful if you are looking to squeeze a workout into a busy schedule. Plus, it is easier to maintain a high level of intensity for a short amount of time, like HIIT, than it is for a longer workout that is over 30 minutes.  

• HIIT helps you burn more calories. HIIT can help you lose weight—specifically, body fat. And you can burn more calories with HIIT than you would in a steady-state workout. Why? For hours after a HIIT workout, your metabolism stays elevated. This means that you not only burn calories during a HIIT workout, but you continue to burn them even after you wrap up your exercise. But remember that any activity is good for you; you don’t have to do HIIT to get the benefit.
  
  This is because of a process known as excess post-exercise oxygen consumption, or EPOC. Essentially, your body needs more oxygen after a HIIT workout to return to its normal resting state. So, your body keeps burning calories as it works to restore energy.    

How to add HIIT into your routine  

According to the U.S. Department of Health and Human Services, adults should aim for 150 minutes of moderate-intensity aerobic activity per week. As for vigorous intensity, you should aim for 75 minutes. A good target to aim for is 2 to 3 HIIT sessions a week. 

There are many ways to ramp up your current routine with HIIT. Start by choosing an aerobic exercise you enjoy. This might be cycling, dancing, stair climbing, or rowing. A good rule of thumb is to use a ratio of 1:1 for your HIIT intervals. You can do 3, 4, or 5 minutes of high intensity, followed by the same interval of low intensity. 

You may choose to work with a certified personal trainer. Or look for online and in-person fitness classes that weave HIIT into the mix. Here are 4 samples of HIIT sessions with different exercises:

• Tabata is a type of HIIT developed in the 1990s. It’s considered very high intensity. You can do this with a stationary bike. Start with an 8-minute warmup that increases gradually. For the Tabata cycles, you’ll do 20 seconds of high-intensity exercise, followed by 10 seconds of rest. Do this for 8 rounds. Wrap it up with an 8-minute stretching cooldown.

• Aquatic HIIT can be done in the pool. Start by treading water for a few minutes as a warmup. Swim one or 2 laps at a high intensity, moving as fast as you can. Then, swim one lap at a leisurely pace. Repeat this for 30 minutes.   
  
  
• Sprint interval training is a type of HIIT training specifically designed for running. Start with 10 minutes of brisk walking to warm up. Sprint for 30 seconds. Then walk or jog for 4 to 4.5 minutes. Repeat 3 to 5 times.

• Resistance-exercise HIIT. You can alternate bodyweight exercises such as high knees, side-step shuffle, jumping lunges, and squats. Start with a 10-minute dynamic warmup. This can include lunges, squats, and hip openers. You’ll do 60 seconds of high-intensity intervals, followed by 60 seconds of lower intensity. Repeat 10 times. This is a 20-minute HIIT exercise. 

Tips for safely integrating HIIT into a fitness routine 

Check with your doctor before starting HIIT, especially if you have any injuries or health conditions. Your workout should be adjusted based on this and your fitness level. If you’re someone who is both symptom-free and a regular exerciser, you may be able to start at low-to-moderate exercise intensity. Over time, you can increase the intensity and duration of your HIIT workout.

To safely integrate HIIT into a fitness routine, always start with a proper warmup. Listen to your body as you go. End each session with a cool-down and stretching. Also, be sure to space out each HIIT session by at least 48 hours. This recovery is crucial. It helps to restore your energy and repair muscle tissue. You can still work out the day after HIIT, but just do it at a low or moderate intensity.

With some effort, you can build a HIIT routine that works for you. Just go at your own pace and choose exercises that you enjoy. And remember, HIIT is flexible. You can adjust the intervals and intensity to suit your fitness. By staying consistent, you may even notice big changes in your health. So, if you’re looking to burn more calories and gain even more strength and endurance—all in about half the time—then consider giving HIIT a go. 

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This information is not intended to take the place of regular medical care or advice. Please check with your doctor before using this information or beginning any self-care program. Images used for this article do not depict any members of the Silver&Fit program.  

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This article was written by Stephanie Ruiz, edited by Jason Nielsen, and clinically reviewed by Jaynie Bjornaraa, PhD, MPH, PT, LAT, ATC, CSCS, CSPS, on August 28, 2025.  

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