The How and Why Of Interval Training

Interval training is a form of cardio that relies on increasing the exercise difficulty for brief periods of time while you workout.  Most people might be familiar with the name but they’re not familiar with the details.

Benefits

The benefits of interval training are increased performance and increased calorie burn.  The higher difficulty intervals cause your heart to beat faster and your body to spend more energy.  This energy expenditure is maintained even when you slow down for a few minutes.  Thus, your body spends energy as though it’s running at a high speed while you rest.  This is similar in concept to the post workout energy burn where your body is still spending calories as though the workout is continuing while you’re in the recovery and rest stage.

For example, if you’re running at 5.0mph, which is a pretty slow pace, your body might be burning 400 calories an hour.  Now you increase that speed to 6.5mph and your calorie burn goes up to 800 calories per hour.  You maintain 6.5mph for a minute and then go back down to 5.0mph.  Well, your calorie burn doesn’t immediately go back down to 400.  In fact, it stays up near 800 for a few minutes before your body realizes that it’s no longer needed.  At that point you can do another high speed interval.  The result is a high calorie burn even though you spent most of your run at a relatively low speed.

The other benefit of interval training is increased performance.  By increasing difficulty for brief periods of time, you make your body adjust to this increased demand.  The result, is an increased ability to handle greater demand.  This is similar to using a very high weight for one rep and then switching back to your normal weights.  The normal weight will seem easy because your body is adjusting to the strain and demand of the very high weight.

For example, if you normally run at 5.0mph, you might find it difficult to increase that speed to 5.5mph.  However, if you increase the speed to 6.5mph for 1 minute, you might find that decreasing it back down to 5.5mph feels quite good.  Where before 5.5mph seemed impossible, it now seems positively restful.

How To Interval Train

The how to of interval training is pretty easy.  Just exercise at your normal speed for a few minutes.  Now increase that speed for a minute or so and then drop it back down.  There are no hard and fast rules about how much you should increase the speed and for how long.  You need to pick a time and speed high enough to challenge you but not high enough to force you to stop or slow down to a slower pace then usual.  For example, I usually run at 6.5mph.  When I do intervals, I will spend every 5th minute running at 7mph.  That’s high enough to really challenge me, but it’s not too high which means I can go back to 6.5mph afterwards and keep running for another 4 minutes until my next 7mph interval.  If I had to slow down to less than 6.5mph after my interval then I’m probably speeding up too much during that 1 minute.

By the way, interval training isn’t just for running.  You can do it with any cardio activity.  When I swim, I do 9 laps of at a relatively moderate pace and then 1 lap at a really fast pace that leaves me out of breath and in need of rest.  I get that rest during the next 9 laps of moderate pace and then I’m ready for another fast lap.

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By the way, the other side benefit of intervals is that it makes your exercise time go by much faster.  You’re so busy getting ready for the next interval that you don’t even notice how long you’ve been working out.

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