found this great article courtesy of www.active.com:
Fartlek training can boost your running speed, endurance
Chicago Daily Herald
Q. I have been running for about three years. I really love it and would like to begin improving my speed and distance. What are your recommendations for doing this safely and effectively?
A. One word: Fartlek.
Funny word, great training tool. Fartlek training -- the word means "speed-play" in Swedish -- has been around for about 50 years and is very effective in increasing a runner's speed and endurance.
Personally, I swear by this method, and generally bring it into my training a month or so before a race. Or, I'll integrate it into my regular training to improve my personal training time.
Basically, Fartlek involves varying your pace throughout your run. In other words, you integrate intense sprints into your workout, followed by a recovery run or slow jog slightly below your normal running pace.
For example, if you are a beginner, you might include five short sprints -- that's every 6 or 7 minutes -- over the duration of a 45-minute run. As your fitness level improves, you can increase it to 10 sprints. I usually run 4 to 5 minutes followed by a 30-second sprint.
You need to keep in mind that this is a pretty advanced form of training that requires discipline and running experience. You must be willing to really kick up the pace of your run for a brief period -- about 30 seconds -- in order to make the intervals work effectively.
It's also a good idea to check with your doctor before beginning this training method. Being fit doesn't make one immune to potential risks.
Here is a suggestion for an intermediate program for a Fartlek session:
As you head out for your regular run (or if you are using your treadmill), keep up the same pace for about 5 to 10 minutes. Then, kick up your pace for about 30 seconds, going as fast as you can. After 30 seconds, bring your pace back to normal until your breathing is no longer labored.
The idea here is that each time you kick up your speed, you are putting stress on your cardiovascular system, which allows your system to improve its threshold. Thus, you will be increasing both speed and endurance.
If you decide to introduce Fartlek to your regular training, just remember: Listen to your body and avoid doing too much too soon.
You can use hills for your sprint work as an effective means to elevate your heart rate and work on strength, speed and endurance.
You have to be your own coach, so push yourself to make sure you're putting out the necessary effort.
Nicki Anderson is a certified personal trainer, author and owner of Reality Fitness in Naperville. For information, visit www.realityfitness.com.