Cardio is a type of physical activity that increases heart rate. It usually involves repetitive movements of the major muscle groups in the arms and legs, and it has historically been associated with endurance exercise. When many people think of cardio they imagine long runs on a treadmill. Recently, another type of cardio exercise, known as interval training, has gained popularity. What kind of cardio should you do, and how often? Read on to find out.
How Does Cardio Exercise Improve Your Body?
Most people should be including some type of cardio exercise into their training routine. Cardio exercise is very important for health and fitness, and regular cardio exercise has a number of benefits including increased cardiovascular fitness and performance, decreased body weight and body fat, decreased risk of cardiovascular and metabolic disease, improved mood and cognitive function, and many others. Both interval training and continuous cardio exercise can produce those benefits.
What’s the Difference Between Interval Training and Continuous Cardio
There are a lot of specific interval training protocols and a lot of different names for this kind of training, including “interval training”, “sprint interval training”, “high intensity interval training”, “aerobic interval training”, etc. Technically, each of those are slightly different, but for the sake of simplicity, I’m going to use the term “interval training” and define it as: alternating periods of high intensity exercise with low intensity recovery or rest periods, repeated for a number of repetitions. Generally, the high intensity and rest periods last anywhere from 6 seconds to 4 minutes and the whole workout lasts between 10 and 25 minutes. In contrast, continuous aerobic training (also known as steady-state cardio) is generally considered to be moderate intensity endurance activity lasting 30 minutes or more.
Which One is Better?
These days, the popular answer seems to be that interval training is superior to continuous cardio. I don’t agree with that. Continuous cardio has gotten a lot of bad press lately, with many people claiming that it’s ineffective for weight loss or that it will prevent you from putting on muscle (or even make you lose muscle). None of those things are true for the average recreational exerciser.
A common argument used to convince people to give up continuous cardio and turn to intervals instead is to compare the physique of a sprinter to a marathon runner. The premise is that if you do intervals, like sprinters do in their training, you’ll develop the body of a sprinter. If you do long distance running, you’ll look like a marathon runner. That’s bad logic and I want to debunk that argument right now.
The first obvious problem with the argument is the idea that if you just do a certain kind of training you’ll automatically develop a certain body type. That’s not how it works. Your genetics plays a big part in how your body looks and how it responds to training. That actually explains why each of these guys became the type of athletes they are. Elite strength and power athletes are generally people who are genetically predisposed to putting on muscle mass, and they often end up competing in strength or power sports (like Roxroy Cato, the track athlete above). Elite endurance athletes are generally people who are predisposed to be good at distance-based sports, and often end up competing in endurance events (like Stephen Kiprotich, the marathon runner). Those guys don’t look the way they do just because they sprint or run for distance.
Second, strength and power athletes do a lot of training specifically to add strength and size, which contributes a lot to the way they look. Endurance athletes don’t usually do that kind of strength training because putting on extra muscle mass would just mean more weight they have to carry for long distances, which would probably decrease their performance.
Third, the people usually used to illustrate this argument are elite athletes, in the top 1% of the world in their sports. Even if you trained with the volume and intensity that those athletes do (which is very unlikely), you’re probably not going to develop the body of an elite sprinter or marathon runner. It’s like saying: “I don’t want to look like Arnold Schwarzenegger did in his competition days, so I better not lift weights.” As if it’s easy to get a body like that and anyone could do it if they just pick up some dumbbells.
You’re not going to look like a sprinter or marathon runner because of the type of cardio you choose to do, so don’t use that faulty argument to make your training decisions. What will happen if you exercise regularly, whether it’s with intervals or continuous cardio (or any other type of exercise), is that you’ll get fitter, healthier, and improve your body composition.
Another common argument for intervals over continuous cardio is that interval training produces a greater “afterburn” effect than continuous cardio. That afterburn effect is called Excess Post-Exercise Oxygen Consumption (EPOC), and it means that your body continues to use extra energy after you finish exercising. The argument is that interval training burns more calories after your training, so if you want to create a negative energy balance (which is necessary for losing weight), interval training is better.
It turns out that the EPOC effect is much smaller than these claims make it sound, and studies have shown that when energy expenditure is measured for several hours after a training session, intervals and continuous cardio burn about the same amount of post-exercise calories, although interval training produces that effect in less time.
So back to our question: which type of cardio is better? My honest answer is… it depends. It depends on your goals, your current fitness level, your preferences, your lifestyle, and your ability to push yourself. There is no “best” type of cardio (or any other exercise), and anyone who tells you otherwise either doesn’t know what they’re talking about or is trying to sell you something. Both interval training and continuous cardio are good for you, and they provide similar benefits in terms of health, fitness, and body composition.
Pros of interval training:
- Time efficient. Most interval training protocols last a total of 10 to 25 minutes.
- Can be more varied than continuous cardio. Intervals can be structured in many different ways, which is good for people who like a lot of variety in their training.
Cons of interval training:
- Must be done at very high intensity to get benefits. Since training volume is so low, the intensity has to be very high for intervals to be effective. It can be very difficult to push yourself to the necessary intensity.
- Very taxing on the body, requires longer recovery time and entails an increased injury risk. Working at such a high intensity puts a lot of strain on the muscles, joints, and cardiovascular system.
Pros of continuous cardio:
- Less strenuous than intervals. The lower intensity of continuous cardio is easier on the body, so you need less recovery time and continuous cardio can be performed more often.
- Can be meditative. Some people enjoy the repetitive motion of continuous cardio. They find this type of exercise relaxing and it may allow them time to think and reflect (I’m one of these people).
Cons of continuous cardio:
- Time consuming. It’s usually recommended that continuous cardio be performed for about 30-45 minutes, several times per week. Some people do their cardio for much longer than that.
- May be boring or monotonous. Some people like the repetitive nature of continuous cardio, and others find it to be boring.
So Which Should You Do?
First, consider your starting fitness level. If you haven’t done much cardio before, you should start by building a base of endurance before starting interval training. Interval training is very strenuous and you can get hurt if your body isn’t prepared to handle the stress and intensity. If you don’t have a base of aerobic capacity, you also probably won’t be able to achieve the high intensity needed to get benefits from intervals.
Next, think about your goals. If you want to complete a half-marathon, you’ll have to do some continuous cardio. In that case, I would do mostly long distance running and also some intervals. If you want to be a better sprinter, you should be sprinting. I recommend short intervals with long rest periods to improve sprint performance. If you want to lose weight or increase your general health and fitness, both interval training and continuous cardio will help.
Since continuous cardio and interval training provide similar body composition, health, and fitness benefits, you might want to base your decision on your lifestyle and preferences. If you don’t have time for prolonged exercise or if you find continuous cardio boring, do intervals. If you enjoy continuous cardio and have time to do longer sessions, do continuous cardio. If you want the best of both worlds, do some interval sessions and some continuous sessions.
Apart from enjoying one type of cardio over the other, or having one type fit your lifestyle better, you may also find that your body responds better to intervals or continuous cardio. As with any exercise, make sure you’re tracking your performance and evaluating how your training is working for you, and pay attention to how you feel during and after your sessions. If you find that one or the other is better for you (you’re able to progress quickly or you feel better during or afterwards), emphasize that type of cardio in your training.
How To Do Continuous Cardio
I want to make an important distinction, one that I hope will clear up some of the confusion about continuous cardio. I think one reason that people fail to get results from steady state cardio (this also applies to other types of exercise) is that they don’t work hard enough. Walk through any gym’s cardio machine area and you’ll see people on treadmills barely breaking a sweat, leisurely watching tv, or talking on their phones.
When I recommend continuous cardio, I’m not talking about plodding along on a treadmill or spinning your wheels aimlessly on a bike for a certain amount of time or distance and then calling it a day. That kind of cardio is ineffective, and if you perform your cardio that way you probably won’t get results. Like strength training, you need to push yourself and progressively increase the difficulty of the exercise over time to force your body to adapt. Just as your muscles will get bigger and stronger with progressive resistance exercise, your cardiovascular and metabolic systems will get stronger and more efficient with progressive cardio exercise. Intensity is key here, just like it is with resistance exercise.
Work your way up to being able to run continuously for 20-30 minutes by running for as long as you can, then walking until you’re ready to run again. Keep track of how long you run and walk for (there are a lot of apps that can help you do that) and try to increase each running period and decrease each walking period by about 30 seconds every session until you can go for 30 minutes without stopping.
If running isn’t your thing, you can cycle, use an elliptical machine, or row. Or, if you want more variety, you can mix it up between those types of cardio. Make sure you keep track of your performance in each one and try to go a little bit harder each time.
Once you can do 30 minutes straight, you can continue to increase your time, or start increasing your speed. I prefer to focus on increasing speed rather than distance or time because it works well for most people and it keeps sessions relatively short. I recommend working on improving your pace over 30 minutes for 6-8 weeks, then work on gradually increasing your distance or time if you want.
For best results, try to do continuous cardio 2-3 times per week. You can do more sessions than that if you want, but I would recommend no more than 5 sessions per week to make sure you are recovering properly.
How To Do Intervals
Effort is especially important in interval training. Since the volume associated with interval training is so low (usually only about 4-10 minutes of hard exercise, and a total session time of about 10-25 minutes), you really have to perform each interval at a very high intensity to get benefits from it. You should be going as hard as you possibly can for the entire interval, then resting or reducing the intensity until it’s time to start the next all-out interval.
The great thing about intervals is that there are so many ways to structure them, and as long as you’re pushing yourself as hard as possible during your sessions, you should get the benefits.
If you want to increase a certain aspect of sports performance or emphasize a certain energy system with intervals, you need to get more specific about your sprint and rest times. Here’s a good article to get your started on that from the National Strength and Conditioning Association, but for general health, fitness, and body composition benefits, I wouldn’t worry too much about those details. You can alter your interval and rest periods pretty much any way you want, as long as you push yourself in each interval. Choose an interval duration which allows you to maintain a high intensity for the entire interval period. When first starting intervals, shorter maximal sprints may be more appropriate than longer ones since you’re less likely to be able to maintain a high exercise intensity over several minutes.
For short, maximal sprints (30 seconds or less), rest time should be longer than sprint time: a good starting point is to rest for 2-4 times longer than your sprint.
For longer intervals (1 minute or more), rest time should be equal to high-intensity time.
Here are some examples:
- 8 x 1 minute hard, 1 minute rest
- 10 x 30 seconds hard, 90 seconds rest
- 20 x 10 seconds hard, 40 seconds rest
- Interval pyramid: Start with 30 seconds as hard as you can, then 30 seconds rest. Then do 1 minute as hard as you can, then 1 minute rest. Next, do 2 minutes as hard as you can, then 2 minutes rest, then back to 1 minute hard, 1 minute rest, and 30 seconds hard, 30 seconds rest. Do that sequence twice.
Limit your interval training no more than once per week when starting out. Even when you get more experienced, you shouldn’t do more than 2 or 3 interval sessions per week to make sure you can recover properly.
How to Use Both Intervals and Continuous Cardio
For most people who want to improve their general health, fitness, or body composition, I recommend a program that includes continuous cardio, interval training, and resistance training. Do each type of training in a separate session, if you have time, so you can really focus on your movement and performance and give a maximum effort in each exercise.
If you want to save time by combining different types of training in one session, I would recommend combining resistance training and continuous cardio in one session, completing all your resistance exercises first and then doing continuous cardio. You can also combine intervals and continuous cardio in one session, performing your intervals first and then finishing with continuous cardio. I wouldn’t do resistance training and intervals in the same session, since they’re both very strenuous and if you push yourself (as you should) in one type of training, you probably won’t have the energy to give a maximal effort in the other.
There are a couple of ways you can structure your training to include both intervals and continuous cardio: You can do one interval session and 2 continuous cardio sessions per week, or you can alternate a few weeks of intervals with a few weeks of continuous cardio.
Remember, the best workout is the one that you can perform over time, that you enjoy, and that works for you. No matter what kind of cardio you choose to do, make sure you train consistently and aim to progressively increase your performance, and you’ll get results.