Can't find time for exercise? Forget this old excuse. More and more recent evidence, including new and recent research, indicates that even a short workout that includes high-intensity parts may accelerate physical fitness and has the potential to reduce the waistline.

In the new study, Kyle Sevits, a physiologist in the field of physical activity, a graduate of "Colorado State" University, together with his team, proved that a 2.5-minute workout on an exercise bike, performed at full strength, may burn up to 220 calories!

Of course, this does not mean that you will be able to perform all your physical exercise in a few seconds, but you can certainly divide these 2.5 minutes into five 30-second episodes, in which you will train on the exercise bike with all your strength, when between training sessions, you will rest for 4 minutes while pedaling only lightly. Thus, in less than 25 minutes, you will burn more calories than you would burn in 30 minutes of moderate riding.

"You will burn a lot of calories in a short amount of time," says Sevits, "Most of the calories will be burned during the 2.5 minutes of intense activity, while during the rest intervals, you will burn very few calories."

He also points to additional advantages inherent in such interval training, including the development of increased insulin sensitivity and glucose tolerance, which are extremely important for general health.

"A study like this may encourage people to get in shape and burn more calories," says Heather Gillespie, MD, a sports medicine specialist at the UCLA Medical Center in Santa Monica (a city in the southwestern United States), who was not involved in the study. "This is a very small, but very promising study that provides further proof of the many benefits of interval training."

Training outside the gym

For the purpose of the study, Sevits and his colleagues recruited ten healthy men around the age of 25. For 3 days, the recruits prepared for the study by sticking to a strict diet based on their calorie intake, so the researchers could make sure they didn't eat too much or too little. After that, they were taken to the laboratory for testing.

The rooms where they spent the next two days were equipped with equipment that allowed the researchers to measure the number of calories that each of the study participants managed to burn during their stay there. They stuck to the same diet, sitting in front of the computer or watching movies, and one of the days, they had to exercise.  

Their interval training worked as follows:

The workout begins with a 2-minute warm-up, followed by 30 seconds of intense training in which everyone must pedal as fast and hard as they can, against high resistance. After that comes four minutes of leisurely pedaling, then again - powerful pedaling for half a minute.

The study participants performed five intense workouts in which they pushed themselves to the limits of their ability, and each of them burned approximately 220 calories thanks to this.

Previous studies in the field have proven that this kind of interval training contributes to the heart, among healthy people as well as among those suffering from heart disease. But while the health benefits of such interval training have been well established, its effect on calories, according to the authors, was far from clear. This study provided preliminary evidence that this type of exercise may be beneficial in maintaining a healthy weight and has the potential to aid in shedding excess pounds.

Try this at home too, but with a little caution

According to Gillespie, interval training comes with some caveats, like any other physical exercise. "Everyone is different from the other," she says, "and therefore, it is very important that everyone be aware of their limits. I want people to motivate themselves, but equally I want to prevent them from harm."

She points out that interval training on an exercise bike is considered low-impact, which means it's easier on the joints. Extra caution should be taken with higher impact training, such as running, especially if the trainees are overweight or obese.

She also warns that the entire workout should not be compressed into a few minutes. "You will not be able to withstand such intense training for 2.5 minutes, therefore, the minutes of rest are just as important as the minutes of training," she notes. "If you only want, you can use the four minutes of rest even to check your email."  

When it comes to reaping the benefits of interval training, the trainees face a number of significant obstacles, according to Sevits.

"The biggest barriers are the inherent difficulty in this type of training, and the commitment to perform it," says Sevits. According to him, working with a personal trainer who will encourage the trainees to push themselves properly, may be extremely effective. "This type of personal training can be extremely stimulating," he says.

According to him, beginners should enter the field of interval training in a balanced and calculated way. "First, build your endurance and confidence, and your comfort on whatever type of exercise equipment you choose. Only after that, you can push yourself forward and incorporate a few minutes of powerful and intense training into your usual 30-minute workout."

And if you find yourself struggling for an all-out workout for the required 30 seconds, don't overexert yourself.

"In reality, there is a full continuum of benefits waiting for you as you approach the limit of your ability," says Sevits.

The study was presented in Westminster, Colorado, at a joint meeting between the American Physiological Society, the American College of Sports Medicine and the Canadian Society for Exercise Physiology.

These findings were presented at a medical conference, and should be considered preliminary, since they have not yet passed the "peer review" process, during which external experts examine the information before it is published in a medical journal.