Written by Danielle Scheinman, MPH, CHES
July 7, 2013
One of today’s biggest exercise trends? Interval training. But what is the big hype about it? There are many adaptations that the body makes when put under the stresses of intense exercise followed by lighter exercise repeatedly.
The biggest change that occurs in the body is the improvement of one’s VO2 max – the largest amount of oxygen the muscles can utilize during intense exercise. The importance of this is to decrease the strain on working muscles by making them more efficient. The greater the amount of oxygen that the muscle can extract from the blood at one time, the less blood needs to circulate. And therefore, the less the body needs to work in order to supply oxygen to working muscles. As a result of this adaptation, the body is able to perform higher amounts of exercise with greater ease because there is a large pool of oxygen to fuel muscle activity.
So now maybe you’re asking: I breathe oxygen, I love oxygen, but why do my muscles need oxygen? Well, oxygen is one of the primary components for creating energy in the muscle. And, of course, without energy the muscle will not have the ability to contract. Now you can see the significance of efficiency in the muscle.
All right, back to the details of interval training. The basic idea is that you introduce your body to bouts of high intensity exercise that you can only maintain for a short period of time. This is followed by a recovery phase to let your body rest. For example, one might run for thirty seconds and then walk for a minute before repeating this set. Untrained athletes are told to follow the work to rest ratio of either 1:2 or 1:3. This means that for every one bout of strenuous exercise, you are to complete two bouts of recovery activity (30 sec work: 1 min recovery)
When first starting this type of a training program, you might not be able to complete very many sets of intervals. However, as the body adapts and the work feels easier, there are two different ways to challenge the body again. One option is to try and increase the number of intervals you can complete. The second way to increase the difficulty is by changing the intensity of the interval. If you started by alternating between jogging and walking, now try running and walking. Want to keep the same speed? Add an incline during the work phase. Do not feel limited to running. You can also use intervals on the bicycle and treadmill by varying speed or resistance. Eventually, an ideal work to rest ratio is 1:1, with one-minute intervals.
A result of this exercise is also enhanced endurance. This is due to the multitude of intervals that ultimately take a long time to complete, and are also more draining because of the constant speed changes. Ultimately, when you try and complete a longer run at a more leisurely pace, it will seem easier because the body is not working as heard to recover from high intensity exercise. The last, and most immediate benefit of interval training is “afterburn.” This term refers to the continual burning of calories once an interval workout is complete. A similar effect can be seen through any high intensity workout; however, interval training is a more assured way to attain “afterburn.” During such a training program, body temperature and circulating hormone concentrations, such as epinephrine, are significantly higher, resulting in arousal and higher heart rate. The longer these symptoms are maintained, the longer the body will be working to reestablish normalized levels, and therefore will burn more calories.
What is so great about interval training is the ability to fit in an exhaustive workout in a short amount of time. Because the body is working to it’s potential with only a slight recovery time it does not take very long to become fatigued. On the other hand, this also means that you should not be performing this type of exercise every day in order to allow the body to completely repair itself. Implementing this exercise once or twice a week is more than adequate.
Example 1:
1 minute walk at 3.5mph
1 minute run at 6.5 mph
1 minute walk at 3.5 mph
1 minute run at 6.5 mph
Example 2:
Bicycle for 45 seconds at a normal pace
“Sprint” for 15 seconds
Pedal normally for 45 seconds
“Sprint” for 15 seconds
Example 3:
Complete one minute at the automatic settings on the elliptical
1 minute at two resistance levels higher
1 minute at the original settings
1 minute at three resistance levels higher
1 minute at original settings
1 minute at four resistance levels higher
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