If you are like me at the gym, you get bored easily.  Even when listening to Boom Boom Pow on my Ipod and watching the guy in the corner to see how much he can bench press before he passes out. I run for 20 minutes and only burn 225 calories (I know, not the fastest 2 miles in the world).  This routine was getting old for me.  I had heard a lot about interval training and how it can maximize time in gym and decided to try it.
What is it you ask, well, interval training is simply alternating bursts of intense activity with intervals of lighter activity.  It really is not as complicated as you think. It’s all a matter of speeding up and slowing down throughout your workout.  Whether you’re a novice exerciser or you’ve been working out  for years, interval training can help you mix up your workout routine.
Consider the benefits:

You’ll burn more calories. The more vigorously you exercise, the more calories you’ll burn — even if you increase intensity for just a few minutes at a time.
You’ll improve your aerobic capacity. As your cardiovascular fitness improves, you’ll be able to exercise longer or with more intensity.
You’ll keep boredom at bay. Turning up your intensity in short intervals can add variety to your exercise routine, and you will forget all about the guy bench pressing in the corner.
You can use interval training workouts any way you want - running, cycling, swimming, on elliptical trainers, even walking if you alternate a speed walk and slow walk.  There is no single accepted formula for the ratio between intense activity and lighter activity, but some guidelines apply. The high-intensity phase should be long and strenuous enough that a person is out of breath and recovery periods should not last long enough for their pulse to return to its resting rate.
Here is an example of a workout
1. 3 - 5 minutes warm-up
2. 30 seconds high intensity, 1 minute low intensity
3. 45 seconds high intensity, 1 minute low intensity
4. 60 seconds high intensity, 1 minute low intensity
5. 90 seconds high intensity, 1 minute low intensity
6. 60 seconds high intensity, 1 minute low intensity
7. 45 seconds high intensity, 1 minute low intensity
8. 30 seconds high intensity
9. 3 - 5 minutes cooldown

-Amanda Reichert, M.Ed., CHES