Is that all you need to get in shape? In a recent study from Colorado State University and the University of Colorado, it was shown that in just 2.5 minutes of intense exercise, an extra 200 calories are burned during that day. (for you science people that like to see the study). http://www.eurekalert.org/pub_releases/2012-10/aps-moh101112.php
Notice I didn't say during the actual exercise. Over the course of the day, the uptick in metabolism is accounting for that calorie burn.
In this study, participants sprinted on a bike for 30 seconds at an all out effort with a 4 minute recovery. They did this 5 times. Essentially a typical interval training workout. What researchers discovered was that the participants burned an extra 200 calories on those workout days.
An extra 200 calories from just 2.5 minutes of hardcore work? Seems like a good trade off to me.
Now what I don't want you to do is go overboard and say "if 2.5 minutes is good, then 60 minutes must be even better.". When it comes to intervals, intensity and rest are essential. The sprint part needs to be all out, and if you reach a point where that is no longer possible, then what's the point of continuing?
A safe place to start is doing 5-10 intervals for 30 seconds with enough recovery where your heart rate and breathing rate come down. This ensures that you can give a max effort on the next interval.
An even better way to do interval training is by monitoring your heart rate. To do this we need to look at the following formula.
Target Heart Rate = ((max HR − resting HR) × %Intensity) + resting HR
(max HR being 220-AGE)
So for someone looking to do intervals over 85% of their max, we'll look at a 30 year old with resting HR of 60.
THR= ((220-30)-60)* .85 + 60.
So in this example HR should get to 170 to be an effective interval.
As for the rest period, HR should reach below 50% of max. Therefore based on the same formula the THR is 125.
Just another way of doing this workout. Try plugging in your own numbers. Just be sure to take your resting HR as soon as you wake up in the morning. That's when it's at it's lowest.
We used to chart that number over the course of a cross country season to see how our body adapted to training. As the season progressed, the more efficient our bodies got at handling the training, and our resting HR would come down.
Give this a try and if you need help with the formula, leave a comment and I'll help in anyway I can. I even have a few beginner interval workouts to try on your own.