Interval Training

Yesterday I did my 3 mile run at the gym on the treadmill.  My father goes to the gym a lot as well and we got into a conversation about interval training.  His dietician told him that intervals help burn fat faster and is an overall better workout.  I personally try to avoid walking when going for a run (it is called a run after all!).  So I decided to give it a try.  Here's what I did, which came out to be 3.1 miles:

7.5 min @ 5.8 mph
2.5 min @ 4.0 mph
7.5 min @ 5.9 mph
2.5 min @ 4.0 mph
5.0 min @ 6.0 mph
2.5 min @ 4.0 mph
6.0 min @ 5.8 mph
1.5 min @ 4.0 mph (cool down)

It sounds easier than it is.  When I got off that treadmill I was beat.  Granted, this was only my second running workout since Christmas Eve, but I felt that I had an intense workout.  And really, I walked 7.5 min of the whole 35 minute workout and I still got in 3.1 miles.  Since I felt that I got an even better workout than if I had just gone for a 3 mile run outside, I decided to do a little research on interval training.  Here's what I found:

"It's not as complicated as you might think. Interval training is simply alternating bursts of intense activity with intervals of lighter activity."

This next quote explains the basis for the claim that interval training can burn more fat:

"Interval training works both the aerobic and the anaerobic system. During the high intensity effort, the anaerobic system uses the energy stored in the muscles (glycogen) for short bursts of activity. Anaerobic metabolism works without oxygen. The by-product is lactic acid, which is related to the burning sensation felt in the muscles during high intensity efforts. During the high intensity interval, lactic acid builds and the athlete enters oxygen debt. During the recovery phase the heart and lungs work together to "pay back" this oxygen debt and break down the lactic acid. It is in this phase that the aerobic system is in control, using oxygen to convert stored carbohydrates into energy."

More or less, the alternating between fast and slow forces your body to let your heart rate to go up and down.  For runner, interval training is a great way to improve overall times as well.  To do that you have to use the intervals and as time goes by you cut down the times of the slower segments until you can eventually do the whole time or distance at the faster pace.  The key here is that the faster segments need to be at a faster pace than you normally run for this to be effective.  Interval training also has a special name in the running world: Fartlek.  You heard me right: Fartlek.  I just like saying it.  Anyway, if anyone knows where that name came from, would you please let me know?  Oddly enough, I saw this word on one of the training plans I found for half-marathons and I didn't know what it meant so I picked a plan that didn't have that word on it.  Just after doing some reasearch did I stumble across it again.

If you would like to read more on your own, here are some interesting articles I found:
IntervalTraining.net
About.Com
The Mayo Clinic

Since I have two 3 mile runs per week on my training plan and one longer run, I plan to do one of the 3 mile runs as I would normally do it, and the other with intervals to work on speed.  I plan to use the longer run for endurance and just go at a pace that is comfortable so that I am able to finish.

Have you tried interval training?  Do you find it helps?  Any tips?