When most people think of cardio they begrudgingly picture themselves logging hours on the treadmill or stationary bike. Rarely does cardio produce excitement or passion. More often, people hate it, cut their workouts short, or simply don’t do prescribed cardio.
Case in point, according to surveys, less than 30 percent of Americans are doing regular cardio. Which begs the question, is there an alternative that people will like more and be willing to do?
One possible solution is interval training. Interval training is when you do short bursts of activity interspersed with rest. The most obvious example is sprinting, but more moderate options can also be effective. For example, alternating walking briskly on an incline with easy walking for a total of 30 minutes can significantly improve physical fitness (1).
In fact, the great thing about interval training is that it gives you all the traditional health benefits of cardio, but in much less time. It’s also effective for reducing body fat, which traditional cardio is woefully ineffective for (2).
But wait! Doesn’t everyone need to do cardio to develop an aerobic base? Aren’t there benefits you can only get from doing long-duration exercise?
Actually, just about every benefit you can get from cardio, applies to interval training when matched for work performed. In many cases interval training is more effective. In order to give you the BEST information to design your workout plan, this article will review the research comparing traditional cardio with intervals and give you pros and cons of each to help you determine which will give you the greatest outcome.
SHARED BENEFITS OF CARDIO & INTERVALS
First, let’s look at the shared benefits you can get from cardio and intervals.
#1: Both will improve cardiovascular efficiency.
One of the greatest benefits of conditioning exercise is improved efficiency of the heart. Both intervals and cardio cause adaptations that lead to a lower resting heart rate, while allowing the heart to pump more blood with each beat.
This means that more oxygenated blood reaches your brain and muscles, but with less effort. Additionally, you have increases in the density and number of capillaries that carry blood to the muscles, making oxygen delivery more efficient. You also get an increase in the mitochondria energy factories in the cell so that your body is better able to burn calories to power work.
#2: Both will build your aerobic base.
Coaches talk about the primacy of cardio for building an aerobic base. What does this mean?
There are three different ways your body produces energy. One of them is your aerobic system, which you rely on for everything from walking on the beach to running 3 miles. In order for you to go from being sedentary to start working out, your body must undergo certain aerobic adaptations in order to be able to deliver oxygen, blood, and nutrients to keep up with the increased rate of activity. This is your aerobic base.
Athletes who have achieved a certain threshold of aerobic fitness are able to recover faster during strength training or when competing in sports. This threshold can be achieved by either traditional cardio or intervals, but the benefit of intervals is that it doesn’t interfere with the strength and power adaptations necessary for peak athletic performance.
On the other hand, things are a little different if you’re completely new to exercise and are overweight. In this situation, it makes sense to start with slow and steady cardio if you prefer. However, very quickly, your body will adapt and you’ll need to increase the overload on your body to ensure continued adaptations and fully develop your aerobic base. This can be done by increasing your pace and going longer or you can try short and sweet intervals in which you increase intensity for a short burst.
#3: Both will increase fat burning, but intervals may have a greater effect.
Both cardio and intervals will increase the body’s ability to burn body fat by a couple of different mechanisms. First, you get an increase in fat burning enzymes. Second, greater blood flow to the muscle allows muscle to use stored fat instead of stored carbs (glycogen) for energy. Third, your body comes more sensitive to hormones that increase fat burning.
It should be noted that although both cardio and interval forms of conditioning improve fat burning, intervals may have a greater effect. Additionally, in certain populations such as individuals with diabetes or who are overweight, only intervals produce an increase in fat burning. Aerobic exercise may not be effective.
PROS & CONS OF TRADITIONAL CARDIO
Hopefully, you’re on board that some form of conditioning is worth the effort. Now lets look at the unique pros and cons of traditional cardio.
Pro #1: Some people enjoy it.
Certain people have a passion for running, cycling, walking, etc. It gives them time to think and de-stress, and there’s no need to watch the clock or push too hard. These people tend to be “high-responders,” which is a term used for individual who have a genetic makeup that is designed for endurance activity. They adapt quickly and their bodies become highly efficient machines at pumping oxygen to their muscles.
Pro #2: Can be a social activity.
Because traditional cardio is done at a moderate pace that allows you to talk throughout, it is conducive to socializing, which can make it more fun and improve adherence. The key point is to make sure the quality of your workout doesn’t devolve due to the social aspect. Duration and intensity are the most important factors for getting adaptations and measurable results from your efforts.
Pro #3: Reduces muscle soreness and improves recovery.
One of the best ways to reduce muscle soreness, either from intense weight training or the rigors of life, is to perform exercise that taps into the aerobic system, getting more blood, oxygen, and nutrients to the muscle. Traditional cardio has been shown to significantly reduce intense muscle soreness (known as DOMS).
Con #1: May increase appetite.
Ever finish a cardio workout and find you have a voracious appetite? Maybe you fantasize about your post-workout meal during your workout. Although more research is needed, there is some evidence that cardio triggers elevations in hormones that make you hungry, increasing appetite so that you eat more. This tends to make efforts to reduce body fat futile and may lead to disordered eating or excessive exercise when people find they aren’t getting results.
Con #2: May lead to compensation and fat gain.
“Compensation” is a phenomenon that occurs when people exercise and then eat more calories as a reward. They may also be less active in daily life, reducing the amount of energy burned daily. Compensators don’t lose body fat from exercise and they tend to gain it. For example, one study found that 69 percent of women who did 30 minutes of cardio 3 times a week gained body fat due to compensation (3). The average gain was about a pound, but some women increased body fat by 25 pounds.
Con #3: May lead to muscle loss.
Most people believe that all forms of exercise improve muscle mass. Unless you continually increase your training intensity, or do regular weight training workouts, this is not so. Over the long-term, doing cardio as your sole form of exercise leads to the loss of lean muscle mass (4). This reduces the amount of calories burned by the body at rest and puts people at risk of pain, dysfunction, and increased diabetes risk.
PROS AND CONS OF INTERVALS
Consider these pros and cons of interval training in deciding which type of exercise will give you the most powerful outcomes.
Pro #1: Lose body fat.
Probably the biggest way that interval training trumps traditional cardio is that it leads to reductions in body fat. For example, a 15-week cycle training program that had subjects do 8 second intervals with 12 seconds rest resulted in a 6 pound loss of body fat, whereas a work-matched cardio program produced no change in body fat percentage (5). Why is interval training superior? Researchers explain it by the fact that intervals trigger protein synthesis (see #3 below) and leads to a greater post-workout energy burn (see #4 below).
Pro #2: Save time.
Not only does interval training lead to greater fat loss than traditional cardio, but it allows you to see body composition FASTER and with LESS training time. Naturally, this is great for giving you a mental boost and fitting workouts into a busy schedule.
Repeatedly studies show that more fat loss is achieved with interval programs that use 20 to 25 minutes of training time compared to cardio workouts that last 45 minutes to an hour. A classic example is a 1994 study that found that the lucky participants who did 15 weeks of intervals (15 sprints for 30 seconds each) lost 9 times more body fat than a cardio training group that exercised for 20 weeks (6).
Pro #3: Triggers protein synthesis, maintaining muscle.
The true power of exercise for producing fat loss is in its ability to build muscle because this increases your total net calorie burn over the course of a day, everyday.
Besides strength training, interval workouts are the only way to achieve this. With traditional cardio, you lose muscle over the long-term because it’s catabolic. Plus, it trains efficiency, which is the opposite of what needs to happen if you want to stay lean without progressively eating fewer calories as your metabolic rate goes down.
Pro #4: Triggers greater EPOC.
Previously, we mentioned that traditional cardio trains the aerobic energy system, but there are two additional ways the body produces energy for exercise. Interval training taps into these pathways, which triggers a large metabolic disturbance in the body. This means that the body is using energy at a very high rate, which translates into a major boost in calories burned.
Known as post-exercise oxygen consumption (EPOC) because the body uses oxygen at an accelerated rate, a 2006 review showed that interval protocols reliably produce higher EPOC values than traditional cardio because the trained muscle cells must restore physiological factors in the cells, which translates to a lot of energy expenditure.
Con #1: Can be mentally challenging.
The one possible drawback to interval training is that it can be mentally challenging to push yourself through the interval portion of your workout. The upside is that the total exercise time is much shorter than with cardio. Plus, many people find intervals are less boring than cardio and they enjoy feeling powerful from the intense bursts of effort. Finally, the fact that the hard work you are doing will improve a leaner body composition is often enough to keep you coming back for more.
How To Get Started With Interval
Hopefully, you’re ready to include interval training in your exercise program. The big question is how start?
If you’re overweight and just beginning to work out, you can’t go wrong with walking intervals. These are typically done two ways. You can alternate brisk and easy walking or alternate walking on a flat surface with an incline. Try starting with 3-minute intervals interspersed with 3 minutes rest for a total of 20 to 30 minutes. Progress by shortening the rest interval down to as little as 30 seconds. You could also use the same approach with a bike or other cardio machine.
This approach is also appropriate for elderly individuals who are new to exercise. In fact, it’s been tested in a number of studies in Japan and found to produce dramatic body composition and quality of life benefits.
If you’re already active, you can start with more intense running or cycling intervals. For example, a protocol that has been verified by research is 20 minutes of resisted cycling intervals of 8 seconds interspersed with 12 seconds of rest in which you cycle at a slow pace. The intervals are short, which makes the workout go by in no time.
Another option that has produced significant fat loss in both men and women is the Wingate protocol, which on a bike, on the track, or a treadmill. In one study, subjects used a self-propelled Woodway treadmill that mimicked the motion of pushing a sled. They would run all-out for 30 seconds and then do a passive recovery for 3 minutes.
If your primary goal is to improve aerobic capacity to compete in an endurance event, try longer intervals. Do intervals of 2 minutes with a 1:1 rest ratio and a moderately high intensity.
Hill intervals are another great way to apply overload and mix up workouts. If body composition is your goal, try 200-meter hill sprints. If you’re more focused on improving aerobic capacity and endurance, extend your hill run to 400 to 500 meters. Your rest interval is an easy walk or job down the hill.
For athletes who want to improve conditioning, try a descending distance protocol: On a track or treadmill, do 400 meters followed by 4 minutes rest, 300 meters, followed by 3 minutes rest, 200 meters followed by 2 minutes rest, and then 100 meters.
Another option to boost power is shuttle sprints of 4 X 50 meters, repeated 4 to 6 times with 2 minutes rest between sets.
Final Words: Don’t be scared to experiment with different protocols. The key to success with interval training is to match your protocol to your fitness levels and goals.