When most exercisers think about cardio, they tend to fixate on steady-paced workouts, like jogging, cycling, or hour-long group exercise classes. This type of cardio offers lots of benefits, including improved fitness and general health, but there is also a major disadvantage – workout duration.
With steady-paced cardio, other than minor incidental variations, your pace remains constant for the entire duration of your workout. Your heart rate will stay within your "aerobic training zone," which is 60-80% of your maximum. This means that steady-paced cardio workouts tend to be quite lengthy and only get longer as you get fitter.
Time is often in short supply, and many of us struggle to find time to exercise regularly. Steady-paced cardio workouts do nothing to fix this problem. Once you are reasonably fit, you'll probably need to work out for an hour or more to feel any real training affect. That's why a lot of group exercise attendees soon graduate to doing two classes back-to-back, and recreational runners often clock up 30 or more miles of training per week.
The good news is that there is an alternative to lengthy, laborious cardio workouts – interval training. Delivering comparable (and often superior) results in less time, interval training is a great way to work out, no matter what your fitness goals might be.
What is interval training?
Interval training is a blanket term for workouts that involve periods of activity alternated with periods of rest. For example, you could sprint for 30 seconds, walk for 90 seconds, and repeat ten times.
The actual work to rest ratios and number of repeats performed depend on a variety of factors, including your current level of fitness, your training aim, and the energy system you want to emphasise during your workout.
A lot of people mistakenly believe that interval training is only suitable for intermediate to advanced exercisers, but that's not actually true. In contrast, because interval training is infinitely customisable, even beginners can enjoy all the benefits that interval training can deliver. By manipulating the work to rest ratios, even a very unfit beginner can do forms of interval training.
The term interval training can be applied to a wide range of workouts. Almost any exercise modality can be used to create short, effective interval training sessions. For example, you can do bodyweight interval training sessions, treadmill interval training sessions, strength training interval sessions, or combine several different methods in the same workout. Interval training is as versatile as it is effective.
The advantages and benefits of interval training
Interval training offers a wide range of advantages and benefits over steady-paced cardio.
1. Shorter workouts
There is an old fitness adage that says you can train long, or you can train hard, but you can't do both. Interval training increases the intensity of your workout, which means you won't need to spend as much time working out.
Hour-long steady-paced cardio workouts are often the norm but, with interval training, you can have a productive workout in 30 minutes or less. This is especially attractive to anyone who wants to exercise regularly but doesn't have the time to commit to longer, steady-paced cardio workouts.
2. Burn more calories in less time
A large percentage of exercises work out for fat loss and weight management. While all types of exercise increase your metabolic rate and calorie expenditure, interval training burns more calories per minute.
Studies reveal (1) that interval training burns 25 to 30% more calories per minute than steady-paced cardio. While steady-paced cardio does use more fat for fuel, and interval training is more reliant on muscle glycogen, the actual source of those calories is not important. For weight loss, the total number of calories used is far more significant than their source.
More calories per minute of exercise mean that you can enjoy all the weight loss benefits of exercise without having to commit to marathon-duration workouts.
3. Improved aerobic fitness
Interval training is mostly anaerobic. That is to say, it uses the lactate and/or creatine phosphate energy systems and that energy is produced without the presence of oxygen. Your heart and lungs will still get a workout, but they do most of their work between intervals as you huff and puff to catch your breath.
Despite being anaerobic in nature, studies show (2) that interval training will also improve your aerobic fitness. It's important to note that the opposite is not the case – steady-paced cardio does very little for your anaerobic fitness. Interval training therefore delivers a great fitness twofer!
4. Increased post-exercise metabolic rate
Interval training not only uses more energy per minute compared to steady-paced cardio. It also triggers an "afterburn effect" that increases your calorific expenditure for as long as 24 hours after your workout is finished. This is called EPOC, which is short for excess post-exercise oxygen consumption.
According to studies (3), the afterburn effect means that you will burn an additional 14% of the number of calories used during your workout in the post-exercise period. This compares to 7% for regular cardio. The number of calories burned during EPOC isn't huge, but in the battle against the belly bulge, every little helps.
5. Preservation or increase in muscle mass
Steady-paced cardio workouts can lead to muscle loss, properly called atrophy. To make cardio easier, your body will shed small amounts of muscle mass. That's why long-distance runners are so slim – especially in the upper body.
While less muscle mass is good for endurance performance, there are more negatives than positives. For starters, it means that you'll be weaker and less physically able, which will make many everyday activities harder than they need to be. Muscle atrophy will also cause your metabolism to slow down, and that will hurt fat burning and weight loss.
Interval training puts more stress on your muscles than steady-paced cardio, especially when you perform bodyweight exercises and sprints. Your body operates on a "use it or lose it" principle, and if you expose your muscles to adequate stress, they are much less likely to atrophy. Studies suggest (4) that interval training can preserve or even increase muscle mass.
6. Effective for increasing insulin sensitivity and decreasing blood glucose levels
High blood glucose levels and increased insulin resistance can cause serious health problems. Elevated blood glucose increases your risk of developing type 2 diabetes, metabolic syndrome, and many other serious medical conditions.
The higher your blood glucose levels are, the more insulin your body will produce. This creates a perfect storm for fat storage and weight gain and also makes losing fat and weight much harder. Increased insulin sensitivity means that your body is better at removing glucose from your blood and ferrying it to your muscles and liver, where it can be used for energy.
Studies reveal (5) that interval training is more effective than steady-paced cardio for decreasing blood glucose levels and increasing insulin sensitivity.
7. Lower blood pressure and resting heart rate
High blood pressure, properly called hypertension, is often called the silent killer. There are no outward signs you have high blood pressure, but hypertension can wreak havoc on your heart, arteries, kidneys, and brain. It's a leading risk factor for coronary heart disease, heart attacks, and strokes.
Interval training has been revealed as an effective intervention for high blood pressure, not least because it lowers your resting heart rate. However, if you currently have high blood pressure, you should seek your doctor's permission before starting interval training.
Types of interval training
After reading that list of benefits, you should now be sold on interval training. The thing is, interval training means different things to different people. There are lots of ways to interpret and implement interval training.
The main types of interval training are:
1) Cardio interval training
As the name suggests, this interval training method uses the cardio training exercises that most people are familiar with, such as stationary bikes, treadmills, steppers, rowers, and ellipticals. You can also do cardio interval training in the great outdoors by going for a run or a bike ride.
Cardio interval training is effective for fat loss and fitness, but won't do much for your upper body conditioning, unless you do swimming intervals that is.
Example workouts include:
· Row 500 meters as fast as possible, row slowly for two minutes, and repeat five times.
· Run for two minutes, walk for one minute, and repeat seven times.
· Cycle fast for 60 seconds, pedal slow for 90 seconds, and repeat ten times.
Cardio intervals can be aerobic or anaerobic, which means they are suitable for all fitness levels and training goals. Anaerobic intervals are short, intense, and usually paired with longer rests. Aerobic intervals are longer, less intense, and usually paired with shorter rests.
2) High-intensity interval training
High-intensity interval training, HIIT for short, is a very popular form of interval training. Unlike cardio intervals, almost any exercise can be used as part of a HIIT workout. This means you can use HIIT to train your entire body, and not just your heart, lungs, and legs.
HIIT is ideal for exercisers who want to increase their fitness and overall conditioning in one, time-efficient workout.
With HIIT, you simply select a group of exercises, do each one for a predetermined number of reps or duration, and then rest briefly before moving onto the next. For example:
1. 20 air-squats
2. 15 push-ups
3. 30-second plank
4. 20 double-unders
5. 10 pull-ups
6. 15 box-jumps
With this type of interval training, you are only limited by the equipment you have available and your imagination. There are an infinite number of options and variations you can use to keep your workouts fresh, enjoyable, and productive.
3) Sprint interval training
Where HIIT is all about creating lots of fatigue and overloading your body with short rests, sprint interval training focuses more on achieving maximal training intensity. With sprint interval training, also known as SIT, you work periods are very brief, but your rests are longer.
· 6 x 30-second sprints at maximum intensity
· Passive or very low-intensity rest for 2-4 minutes after each sprint
HIIT and SIT provide similar benefits in terms of fitness and conditioning, but HIIT is superior for calorie burning. However, the brevity of SIT means that some exercisers may enjoy this type of training. It's especially useful for exercisers who feel "beaten up" after longer HIIT workouts.
Tabatas are an unusually short and brutal type of high-intensity interval training. Tabatas were invented by Japanese sports scientist Izumi Tabata who used this method to help already very fit Olympic speed skaters get even fitter.
What's so remarkable about Tabatas is that each session only lasts four minutes. Don't mistake this brevity for an easy workout; if you do Tabatas right, this will feel like the longest four minutes of your life!
To try Tabatas for yourself, choose an exercise (Izumi Tabata used a stationary bike) and go as hard as you can for 20 seconds. Enjoy a very brief 10-second rest and then repeat. Do eight sets to total four minutes. Where some pacing is necessary with HIIT, with Tabatas you must go all out on each set.
Tabatas aren't for everyone. But, if your time is short and you don't mind working very hard, this interval training workout may be right for you.
Interval training considerations
Because it is so flexible, and there are numerous interpretations, most exercisers can participate in interval training and enjoy all the benefits this time-efficient workout method can provide. However, there are some things that you should consider before trying this workout method.
Warm-up before you start – interval training is intense and puts a lot of strain on your muscles, joints, heart, and lungs. Make sure your body is prepared for what is to come by spending a few minutes warming up before you start. Not only will this make your workout more comfortable and enjoyable, but it will also reduce your risk of injury.
Learn to differentiate between pain and PAIN – interval training causes lactic acid to build up in your muscles, and that can cause burning and pain. This is nothing to worry about and causes no permanent damage. In contrast, pulled muscles and joint injuries cause real PAIN, and you should not work through this type of discomfort.
If you ignore the PAIN caused by injury, you could cause serious damage to your body and may have to miss several weeks of training while you wait to heal. Learn to differentiate between the pain caused by fatigue and the PAIN of injury. It's okay to push through the former, but you should never ignore the latter.
Always use proper exercise technique – there are two ways to perform any exercise, the right way and the wrong way. The right way is safe, keeps the stress on your working muscle and off your joints, and presents the lowest risk of injury. The right way could lead to acute or chronic injury, and also makes the exercise less effective.
Make sure you do every exercise in your interval training workout with the best possible technique. Be aware that your technique can breakdown as you get tired, so be prepared to modify your workouts according to how you feel. For example, you might start out doing full push-ups, but then switch to kneeling push-ups as your workout progresses and are unable to maintain proper exercise form.
Cooldown afterward – the last thing you'll probably feel like doing after interval training is more exercise. But, just a few more minutes could help ward off muscle soreness and speed up your recovery. Don't just stop the second you complete your last set. Instead, do a few minutes of light cardio and then stretch the muscles you have just been training.
Yes, this will add an extra 5-10 minutes to your workout but could also mean you recover sooner and suffer less post-workout muscle pain.
Energy and time are two of your most valuable commodities. Don't waste them on long, inefficient workouts! Instead, invest them wisely and include interval training in your workouts. With interval training, your workouts are shorter, and yet they will produce the same (or even better) results than longer workouts.
As an added benefit, there are dozens of ways you can adopt and implement interval training. As well as being more productive, your workouts need never be boring.
There is nothing inherently wrong with steady-paced cardio, but it is not the be-all-and-end-all of exercise. Interval training is every bit as beneficial but takes much less time.
If you don't have time for long workouts, or the very idea of another hour-long exercise class or run fills you with dread, give interval training a try. You will love the results!