Whether you’re starting a new diet, want to get in shape, or are training for a weightlifting competition, you’ve probably heard of the term, “HIIT”.
HIIT stands for high-intensity interval training. It’s one of the most efficient and effective ways to burn calories. But in today’s stressed out, multitasking society, faster isn’t always better.
As a health expert who previously worked for a HIIT-based fitness app, I saw firsthand what happens when you hit up too much HIIT.
So should you do HIIT every day? You should not do HIIT every day. Many health authorities rightfully recommend that you aim for about 30 minutes of cardio exercise per day to keep your body healthy. But, when it comes to an intense exercise like HIIT, doing it every day puts you at risk for injury, overtraining, mental burnout, and prevents your muscles from recovering and getting stronger.
Let’s turn up the intensity on searching through the scientific research to train our brains on the whys and hows of HIIT as well as 5 things to consider.
What is HIIT?
As the name describes, high-intensity interval training (HIIT) is done at a high level and strength, for brief periods of time. This is followed by a period of rest or easy recovery. HIIT is different than low-intensity steady-state (LIIS) cardio.
The intense exercise portion can last anywhere from 15 seconds to a few minutes. A typical HIIT workout has 5-8 exercises performed for 30-60 seconds each, alternating with 20-30 second rest periods.
The quick bursts of intense exercise are going as hard as you can, at 100% effort. Your body kicks into an anaerobic state, “deprived” of free oxygen. Your body relies on other energy storage such as stored glucose. This helps you burn fat and increases stamina.
The whole workout can be done in just 4 minutes for Tabata (more on this to come) and up to 30 minutes for longer rounds. The key to a productive HIIT workout is to do it as quickly as possible with little rest in between all while making sure to have good form.
Check out our article on Can HIIT Make You Sick?
Types of HIIT
Since HIIT workouts are generally characterized by intense bouts of fitness, followed by quick rest periods, a variety of workouts can apply.
The type of HIIT can include anything including biking, jumping, sprinting. Say you chose biking, in order to make it HIIT appropriate, you could sprint as fast as possible for about 30 seconds, then do a slow pace for a minute. This would count as one round which would then be completed 4 to 6 times in order to make one workout.
Tabata is one form of HIIT. It differs from other HIIT workouts because it’s the same exercise for four minutes. In comparison, HIIT workouts can include a variety of exercise movements.
As referenced in the Journal of Sports Science & Science Medicine, Tabata workouts are 20 seconds at max capacity, then rest for 10 seconds, then repeat the exercise another 20 seconds, then rest for 10 seconds. This goes for eight rounds or a total of four minutes.
Tabata is similar to metabolic resistance training.
Cardiovascular exercise, also known as aerobic fitness, is any form of exercise that elevates the heart rate and breathing rate. It differs from HIIT in terms of intensity and duration. Most cardio is slow and steady whereas HIIT is quick and intense.
Cardio exercise includes running, quick walking, biking, aerobic classes, dancing, or swimming.
Cardio and aerobic exercise are the same, they just refer to slightly different mechanisms. The term “cardio” refers to the process related to the heart, where “aerobic” refers to exercises that use oxygen.
Learn more here: Cardio vs. Aerobic vs. Anaerobic: Are they the same?
Since the intervals of HIIT are performed at max intensity, studies have shown that they can provide health benefits close to twice as much as moderate level exercise.
QUICK AND EFFECTIVE CALORIE BURN
Studies have shown that HIIT can burn 25-30% more calories than other forms of exercise such as running and biking. For this study, they tested a HIIT ratio of 20 seconds of full effort, followed by 40 seconds of rest.
Related Article: Can Hiit Be Done With Weights? (Yes, There Are 4 Rules)
LONG-LASTING CALORIE BURN
HIIT not only burns more calories during the activity, it also burns calories after the activity is done.
In one study, women participants completed six exercise sessions including aerobic exercise, HIIT, and resistance training. The participants were given carbohydrates and protein in order to measure how effectively their bodies burned the energy.
Related Article: How Does Cardio Burn Fat?
After exercise, resting energy expenditure (REE) and resting energy rates (RER) were analyzed right after the exercise, 30 minutes after exercise, and 60 minutes after exercise. On average, HIIT produced the greatest calorie burn post-exercise.
Related Article: Can You Do Too Much Cardio?
HIIT can improve your body measurements that are related to health, such as heart health and blood sugar.
Research shows that adults who are pre-hypertensive (at greater risk of developing high blood pressure) have improved resting blood pressure levels and C-reactive protein and inflammation, both of which have been linked to heart disease.
The study found that patients who did eight weeks of HIIT on a stationary bike had blood pressure decrease as much as traditional endurance training. Since the main barrier of exercise is time, HIIT can be a promising alternative.
A review also found that HIIT both reduces blood sugar and also improves insulin resistance more than continuous standard exercise. Regulated blood sugar will give you better energy levels, less cravings, and help prevent diseases such as diabetes.
Related Article: Should You Do Cardio On Rest Days?
General Fitness Recommendations
The American College of Sports Medicine (ACSM) created a position paper expressing the benefits of physical fitness in general including cardiorespiratory, resistance, flexibility, and neuromotor health. To get these benefits, activities should extend beyond activities of daily living, such as HIIT training.
ACSM recommends most adults engage in moderate-intensity cardiovascular exercise for at least 30 minutes per day for five days per week for a total of 150 minutes per week.
Vigorous-intensity training, such as HIIT, should be at least 20 minute per day for at least three days per week or 75 minutes per week. Or a combination of moderate and vigorous-intensity exercise.
Related Article: Sprinting On Treadmill vs Outside: Which One Is Better?
5 Things to Consider When Determining How & When You Do HIIT
HIIT is a highly effective workout, but it’s important to consider the risks that are associated. Since you’re working at your max capacity, it’s important to properly warm-up, focus on form, include different muscle groups, change it up, and give yourself a break.
According to Precision Nutrition, HIIT and intense physical activity puts your body in “crisis” mode and elevates stress hormones. This high intensity can help your body change and adapt, but it’s important not to push too hard.
1. DON’T DITCH THE WARM-UP
Adding just a few minutes of dynamic stretches or warm-up to your HIIT routine helps:
Enhances your performance
Gets you mentally ready to workout
Related Article: Beginner HIIT Treadmill Workout: Starting With HIIT Cardio
Especially when you’re strapped for time, it’s extremely tempting to pass the warm-up and jump right into the meat of your HIIT workout. But by warming up your muscles, you’re preparing them to do a better job, meaning you’ll get a better workout.
When you’re at rest, your muscles don’t get much blood flow because they don’t need it. This results in their temperature being lower and having less oxygen. They’re not ready to work.
It’s best to focus on the muscle group(s) that you’re going to train with dynamic stretching or movements. So say you’re going to do a HIIT workout focused on legs, warm up your legs. Easy enough, right?
Examples of dynamic warming-up include arm circles, lunge with a twist, lifting your knee to your chest, doing high kicks, or doing some light jogging.
For more, check out ACE Fitness
The most important reason to do a warm-up is to prevent injury during exercise.
Studies state that muscular injury is one of the major problems facing athletes, both in recreational and professional settings. In fact, injuries to skeletal muscle represent >30% of the injuries seen in sports medicine clinics.
Research shows that a warm-up helps prevent injury and should be included as part of a fitness routine. A warm-up and stretching protocol should be implemented prior to physical activity. The warm-up should occur within 15 minutes prior to the activity in order to receive the most benefit.
Related Article: Can You Do HIIT And Weight Training On The Same Day?
GETS YOU MENTALLY READY
A big part of a good workout is mental preparation and getting yourself pumped for what’s to come. If you’ve ever done a group exercise class or sport, you know that during the warm-up is when you “get your head in the game”.
Mentally preparing for your workout can also keep you more mindful during the upcoming workout. As a result you could have better technique, energy, and coordination, helping you push harder while staying safe.
Related Article: 30 Minute Full Body HIIT Workout: Total Body Resistance And Cardio
2. YOU’RE COMPROMISING FORM
During exercise, it’s extremely important to make sure you’re performing the exercises correctly. This will help you avoid injury as well as strengthen the muscles you intended to.
Think about those times you’ve seen someone squat but only a few inches, versus someone who squats deeply. Proper form also helps you reach your goals and gives you a better workout, while staying safe.
If you’re using weights in your HIIT workout, following proper form and technique becomes even more important. This is because weights put more stress on your muscles and joints then they’re used to handling. The same goes if you have high-impact using your body weight, such as jumping.
Good form also makes your workout more efficient. With bad technique, you’ll end up expending more energy than you need to.
A trusted app such as Fitbod can help guide you towards good exercise form with step-by-step instructional videos.
3. YOU’RE NEGLECTING STRENGTH TRAINING
Strength training is important for the health of your heart, balance, bones, and weight management. Strength training is designed to improve muscular fitness by exercising a specific muscle or muscle group.
It also helps you increase lean muscle mass, perfect for your muscle building or bodybuilding routine. If you’re a bodybuilder, HIIT can help with quick fat loss, giving you more pronounced muscle.
In order to keep the strength benefits while you incorporate HIIT into your routine, simply incorporate your own body weight or use equipment such as dumbells, resistance bands, or kettlebells.
If you’re a strength athlete you can add weights to at least half of the exercises in your HIIT workout. HIIT tends to be heavy on the legs, so aim to include a few exercises that focus on the upper body.
4. YOU’RE NOT MIXING IT UP
HIIT offers a lot of benefits in efficient time, so it’s easy to think that doing it over time will offer the same benefit. But just like any workout, it’s important to mix it up.
As explained in an American College of Sports Medicine article, it’s important to mix up the frequency, intensity, time, and type of exercise you do, also called the F.I.T.T. principle. It’s not only part of a successful fitness routine, but it’s also a good way to maintain a healthy weight.
Here’s an example of how you can mix up F.I.T.T. in HIIT:
Frequency: Start with one HIIT workout per week then increase to two.
Intensity: Start with just cardio, then add weights.
Time: Start with a total of 15 minutes, then increase to 20.
Type: Start with regular HIIT, then experiment with Tabata.
According to Mayo Clinic, doing HIIT once or twice a week at most, while mixing in less-intense activities on the other days will give your body time to recover and heal.
5. PUT REST TO THE TEST
Doing the exact same workout two or more days in a row doesn’t allow your muscles to have time to recover and get stronger. It can also cause your body and mind to grow tired or the same workout.
Rest and recovery are just as important as daily movement. When your muscles have time to repair and you get adequate sleep, it will help you reach your goals faster.
The important thing to consider is if your training routine includes specific muscle-groups. So say if you’re doing a workout that includes a lot of arm workouts, then the next day, switch it up and do legs instead.
If you’re doing a HIIT workout that covers multiple muscles, you can still move your body while practicing, called active recovery. As explained by the American Council on Exercise (ACE), the most important type of active recovery is general light physical activity.
Examples of active recovery include:
Talking a walk
Tossing a ball around
Going for an easy bike ride
A gentle yoga class
The goal is to get the blood flowing to your muscles and joints without exerting the muscles that you worked the previous day.
Find out if you’re doing too much cardio: Can Cardio Make You Fat? (5 Things to Consider)
To keep your body and mind healthy, exercise is essential. But due to today’s fast-paced life, you may struggle to add a proper fitness routine. HIIT is the perfect way to condense the benefits of activity into 30 minutes or less.
But when it comes to an intense exercise like HIIT, doing it every day, or for periods longer than 30 minutes can put you at risk for injury, overtraining, mental burnout, and prevent muscle recovery.
Your body is different than everybody else’s so tune into what feels like a challenge while not overexerting yourself. If you’re new to HIIT training, start with shorter periods of the high-intensity training and longer low-intensity times then work your way up.
High fives as you HITT your goals!
About The Author
Lisa is a registered dietitian nutritionist (RDN) with over 15 years of experience in nutrition, fitness, and mental health coaching and education. She studied Foods and Nutrition at San Diego State University and earned a Master of Science in Holistic Nutrition at Hawthorn University.
Having certifications and experience in group exercise, intuitive eating, coaching and psychotherapy, and digestive wellness, she’s enthusiastic about the relationship between the body and mind.
She’s dedicated to helping people understand how to implement healthy habit change, while gaining a deeper understanding of what makes them feel their personal best.