The Training Crucible

Runner's World's latest issue features an article on speedwork focusing on fartleks. For those unfamiliar with the term fartlek, it is Swedish for "speed play."  The basic concept is to alternate between periods of fast and slower run. 
Here's how it works:
1. Run at your average pace.
2. Either pick a specific point in front of you, or a specific amount of time at which you are going to pick up the pace. While the increase doesn't need to be a sprint, it should be 30-40 seconds faster than your average pace.
3. After you reach your distance or time goal, slow back down to your previous pace. Continue running at this pace until you are ready to run fast again.
4. Repeat.

I think the best way to do this type of workout is to have a specific total run time or distance planned.  In order to get the speed work benefit of this workout you also have to be disciplined about picking up the pace.  Don't cheat yourself on this workout.  Sure, there are times when this could be the easiest workout of the week becasue of the slower pace, but you need to push the pace in order to improve.
In order to help me track those periods of increased pace I use a watch with a lap function (my Garmin 205). 
There are a couple of things I would recommend you track when you do your fartlek workouts:
1. What was your pace your pace during the periods of when you were running faster?
2. How long were your recovery periods? 
3. What was the total run time?
4. What was your total distance?

By tracking these parts of your workout you can make some great comparsions between your workouts.
I'm currently working on a spreadsheet that will help me track and compare my workouts. Once I get it ready, I'll make it available for anyone who is interested, just look for an updated post.