Think of high-intensity interval training (HIIT) like baking: You need a precise amount of time in the oven as well as a cooling-off period. In workout terms, that means balancing intervals of work with rest.
The benefits of HIIT have been well studied and include improved endurance and heart health as well as decreased body fat percentage, according to an October 2016 review in the British Journal of Sports Medicine.
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"The primary goal of a HIIT workout is to perform at maximal effort with a specific exercise, followed by a predetermined rest break," says Grayson Wickham, DPT, certified strength and condition specialist, personal trainer and founder of Movement Vault.
The trick to getting the maximum benefit of a HIIT workout is finding the right work-to-rest ratio. If your work intervals are too long, you're not recovered enough for the next interval. Too much rest means you lose momentum and the after-burn benefits. Here's how to find the sweet spot in the work-to-rest ratio that works for your fitness level and goals.
Find the Ideal Work-to-Rest Ratio
One of the perks of a HIIT workout is that they are short, yet effective. In fact, the National Academy of Sports Medicine (NASM) says the exercise intervals do not need to go longer than 10 minutes to be effective. A typical 20-minute HIIT workout consists of a 5-minute warm-up, followed by 10 minutes of the exercise intervals and ending with a 5-minute cooldown. When you are starting out with HIIT, do 4 minutes of the intervals and then progress to 10 minutes.
Research has shed some light on pinpointing the right formula of work to rest for maximum benefits, but the right ratio for you depends on a few factors. "It really depends on your current fitness level, plus the workout and activity you're doing," says Mike Donavanik, CSCS, founder of Sweat Factor.
A Note About the Studies We Used
Because of the many variables surrounding HIIT workouts, including intensity level, work times and rest times, it is hard to pinpoint the exact right formula that works for every individual. We've used the best research available, but more needs to be done on this topic, including comparing several different interval times, different populations and a larger number of participants. Use the guidelines below as a starting point, and adjust them as needed.
If You're a Beginner
New to HIIT? Start with a 60-second exercise to 90-second rest ratio. A June 2022 study in BMC Geriatrics found this ratio improved cardiorespiratory fitness, blood pressure and cholesterol in older adults. The slightly longer rest should give your heart rate enough time to recover without dropping too much.
If You're at an Intermediate Level
When you're ready to challenge yourself more, decrease your rest time to have an equal work-to-rest ratio. A July 2013 study in PLOS One found the 60-second exercise to 60-second rest ratio showed cardiorespiratory improvement in men who have overweight or obesity. An October 2011 study in Medicine & Science in Sports & Exercise also found this 60-second exercise to 60-second rest ratio helped decrease your chances of developing insulin resistance and type 2 diabetes.
If You're Advanced
To push it up to the advanced level, you will have twice as much work as rest. Donavanik says to go for the 20-second exercise and 10-second rest ratio. Not only do you have less rest time, but you will do more rounds during your workout. This ratio is also referred to as Tabata training, per the NASM. Because it is so intense, the NASM recommends repeating your circuit 8 times in a row for a total of 4 minutes. You can add on more time as your endurance improves.
During the exercise intervals, you should be working out hard enough and long enough that you're breathless and unable to talk, according to the NASM. The rest periods need to be long enough to get your breathing is back under control before you jump back into the work interval. A good rule of thumb, according to the American Council on Exercise (ACE), is to rest long enough so you have caught your breath and could carry on a conversation. You can't rest too long, however, as you need your heart rate to stay up.
Consider Your Fitness Level and Workout Time
"If you're new to exercise, you'll typically need longer rest intervals as you're trying to gauge your body and understand how hard you can push it," Donavanik says. "As you start to get the hang of your body and what it can accomplish, you can start to push it harder during the work intervals and/or you can start lowering the amount of time during your rest intervals."
How do you know when it is time to switch levels from beginner to intermediate or advanced? Your body will give you cues. Start with the beginner ratios (60 seconds of work/90 seconds of rest), and as soon as you can do 10 minutes of the exercise intervals easily, it's time to move up to the next level.
If you want a more precise way to measure, Michael Julom, ACE-certified personal trainer and founder of ThisIsWhyImFit.com, offers this tip. "Wear a heart rate monitor. Whatever exercise-to-rest ratio will get you to the 85 percent or higher range for as long as possible is your own personal ideal timing." You can use our Target Heart Rate calculator to help determine yours.
Building a Workout With HIIT Interval Times
HIIT workouts are most suited to losing weight or improving endurance and overall conditioning. To recap, these are the work-to-rest ratios to start with when planning your workouts:
- Beginner interval: 60 seconds work and 90 seconds rest
- Intermediate interval: 60 seconds work with 60 seconds of rest
- Advanced interval: 20 seconds work with 10 seconds rest
It is important to always do a 5-minute warm-up and 5-minute cooldown. Start with 4 minutes of the exercise intervals and then work your way up to 10 minutes before progressing to the next level.
As far as what type of exercises to do during a HIIT workout, you can incorporate body-weight exercises such as jump squats, burpees or lunges — as well as using equipment or machines such as ropes, kettlebells and exercise bikes. These HIIT workouts are catered to your fitness level and needs.
Donavanik says 30 to 60 seconds of rest is ideal for weight loss or general conditioning, but he doesn't recommend going above 90 seconds.
"[The 60 seconds work/60 seconds rest ratio] is going to be the most efficient in regards to spiking your heart rate, keeping it spiked and creating an oxygen deficit during exercise," he says. "That essentially means your body needs more oxygen after your workout than it did before — meaning you'll be burning more calories after your workout (at rest) than you were prior to your workout."
Also, when determining how much rest you need, take into account the type of activity you are doing. "It really depends on what you're asking your body to do and how hard you're pushing your body during a given activity or workout," he says. For example, jumping lunges or high knees will require longer rest times than squats or crunches. "Typically, the harder or more demanding the activity, the more rest is needed."
In general, listen to your body and adjust your intervals accordingly. Once you hit your sweet spot, you'll feel it. You'll be working hard with just enough recovery to tackle the next interval.
- National Academy of Sports Medicine: "HIIT Workouts: Programming, Exercises, and Benefits"
- American Council on Exercise: "The Perfect HIIT Workout for 2020"
- The Physiological Society: "Longer Home-Based HIIT Intervals Elicit a Greater Improvement in Aerobic Capacity – a 6-Week Intervention Study"
- British Journal of Sports Medicine: "Effects of High-Intensity Interval Training on Cardiometabolic Health: A Systematic Review and Meta-Analysis of Intervention Studies"
- Frontiers in Sports and Active Living: "Short-Term, Equipment-Free High Intensity Interval Training Elicits Significant Improvements in Cardiorespiratory Fitness Irrespective of Supervision in Early Adulthood"
- BMC Geriatrics: "Equipment-Free, Unsupervised High Intensity Interval Training Elicits Significant Improvements in the Physiological Resilience of Older Adults"
- PLOS One: "Reducing the Intensity and Volume of Interval Training Diminishes Cardiovascular Adaptation but Not Mitochondrial Biogenesis in Overweight/Obese Men"
- Medicine & Science in Sports & Exercise: "Low-Volume Interval Training Improves Muscle Oxidative Capacity in Sedentary Adults"
- American Council on Exercise: "How to Use the ACE IFT Model to Design Effective HIIT Workouts"