Whether your goal is to lose weight or get fit, cardio is an essential component to your workout program. Cardio is where you burn the most calories at one time, and cardio workouts strengthen your heart, lungs, and the muscles you're working.
Once upon a time, steady-state training was the norm. You'd head outside or hit the treadmill for a walk or run, and stay at about the same moderate intensity throughout the workout.
In recent years, that has changed. High intensity interval training (HIIT) is now popular. These workouts involve changing intensity—working harder for certain intervals—throughout the workout. These shorter, more intense workouts can give you more results in less time.
That sounds great, but is HIIT really better than steady-state cardio? Which one should you focus on if you're trying to lose weight and get fit? Can you actually enjoy your workouts if you're working at such a high intensity?
Basics of HIIT
HIIT involves pushing your body well out of its comfort zone for anywhere from five seconds to eight minutes, depending on the workout you're doing. The idea is to work at about 80% to 95% of your maximum heart rate if you're monitoring your target heart rate zones, or a level 9 to 10 on the perceived exertion chart, also known as your rate of perceived exertion (RPE).
Each work set is followed by a recovery period which can be shorter, the same duration, or longer than the work set. In this interval, you get your heart rate down to about a level 3 to 4 perceived exertion. You alternate work and rest intervals for 20 to 60 minutes total, depending on your fitness level, time constraints, and goals.
Pros and Cons of HIIT Training
Improved insulin sensitivity
Improved calorie after burn
Better for burning belly fat
Improved heart health
Can be uncomfortable
Not for beginners
Risk of injury
Risk of burnout or overtraining
Pros of HIIT Training
HIIT has a number of benefits, especially for people who already have some experience with exercise.
Some studies have shown that while steady state training taxes the aerobic system, HIIT workouts can stimulate both the aerobic and anaerobic systems. That means your body has more stamina and performs better in all your workouts, no matter what they are.
Improved Insulin Sensitivity
The more sensitive your body is to insulin, the less your body needs that insulin to lower blood glucose levels. In terms of exercise, that means your HIIT can help your exercising muscles use glucose for fuel more efficiently.
Improved Calorie After burn
One of the best benefits of HIIT is how many calories your body burns after your workout to get your system back to where it was before you exercised. This is also called post-exercise oxygen consumption (EPOC) or after burn. The harder you work during your workout, the longer it takes your body to get back to normal, meaning you'll burn more calories for an hour or more after your workout.
Burns Belly Fat
Research shows that HIIT may be more effective at reducing abdominal fat than other types of exercise.
Improved Heart Health
HIIT training can help lower blood pressure and improve your heart health.
Because you're working very hard, you get the benefits of training in less time than you would from slower, longer workout sessions. One study published in The Journal of Sports Science and Medicine showed that as few as three 10-minute HIIT sessions a week can make your body more efficient at delivering oxygen to your muscles as well as improving your metabolic health.
Cons of HIIT Training
HIIT training does have its disadvantages, and is not for everyone.
Can Be Uncomfortable
While you can modify the workouts to fit your fitness level, the idea is to get as far out of your comfort zone as you can. So these workouts are tough.
Not for Beginners
If you're coming from a completely sedentary lifestyle or returning to exercise after an injury, HIIT is probably not where you want to start. You should have a basic foundation of cardio training before trying HIIT. If you are in good health and active, you can modify if necessary.
Risk of Injury
High-intensity exercises like sprints, plyometrics, and jumps come with a risk of injury if your body isn't prepared for that kind of movement.
Risk of Burnout or Overtraining
Too much HIIT can be lead to burnout, an increased risk for dropping out of exercise.8 Experts recommend limiting HIIT workouts to one to two a week to avoid overtraining.
Basics of Steady-State Cardio Training
Steady state or moderate-intensity cardio is what many of us are used to. This involves exercising at a consistent speed and level of intensity for the entire workout. That would be at about level 4 to 5 on the perceived exertion scale. The idea is to work at a level where you can talk with maybe just a little difficulty.
Pros and Cons of Steady-State Training
Less stress on the cardiorespiratory system
Improved ability to use fat for fuel
Increases slow-twitch muscle fibers
Can be more enjoyable
Risk of overuse injury
Can be boring
Can cause weight-loss plateaus
Pros of Steady-State Training
Steady-state training also has plenty of benefits for your body.
Less Stress on the Cardiorespiratory System
Because you're working at a lower intensity, you can improve your endurance without putting as much stress on the heart and body as higher intensity exercise.
Longer, slower exercise helps build endurance in both your heart and your muscles.
Like HIIT, steady-state cardio makes your heart more efficient, getting oxygen to the muscles more quickly. Steady-state cardio also lowers blood pressure, reduces stress and anxiety and, along with a healthy diet, can help you lose weight.
Because you're putting less stress on your heart and body, you recover more quickly and can usually work out the next day without a problem.
Improved Ability to Use Fat
When you work at a lower intensity, fat is your main fuel source. Staying at that level allows you to save glycogen stores for higher intensity workouts. That doesn't necessarily mean you burn more fat, just that your body is better at using fat for fuel.
Increases Slow-Twitch Muscle Fibers
Slow twitch muscle fibers are more efficient at using oxygen to generate energy, so you can go for a longer period of time. This improves your aerobic metabolism, which is, essentially, how your body creates energy.
Part of the reason we stick with exercises is that, on some level, we like it, or at least we can tolerate it. It's much more comfortable to work at a lower level of intensity than it is higher intensity. Some exercisers may even quit after too much intense exercise just because it's so uncomfortable.
Cons of Steady-State Training
Naturally, there are disadvantages of steady-state training as well.
If you're trying to lose weight, you have to work out for longer periods of time if you want to burn enough calories.
Risk of Overuse Injuries
Doing the same motions over and over can lead to repetitive stress injuries15 unless you do plenty of cross training.
Not everyone is cut out for long, slow workouts, especially if the weather is bad and you have to get on a treadmill, stationary bike, or other cardio machine. That kind of workout can feel boring and tedious if you do it all the time.
Weight Loss Plateaus
Doing only steady-state cardio workouts without changing things up could lead to a plateau. You need to challenge your body with new and different activities so it can constantly change and grow stronger.
Should You Do HIIT or Steady State?
With all that in mind, which one is right for you? The answer really depends on your fitness level and goals more than anything else. And keep in mind that experts don't recommend doing HIIT more than twice to three times a week.
Try HIIT If...
You're an experienced exerciser comfortable with high intensity exercise.
You want to focus on losing weight and burning more calories during and after your workouts.
You want shorter workouts because of a busy lifestyle.
You want workouts that mix up different exercises and intensities to keep things interesting.
You want to build endurance quickly.
Stick With Steady-State If...
You are a beginner or are coming back from a long exercise break.
You can't do high-impact exercises or don't like working at very high intensities.
You are training for an endurance race, such as a half marathon or marathon (although you may do some high-intensity work depending on the training plan you're following).
You have been told to avoid high-intensity exercise by a doctor.