Who Fartleked?

I ran a fartlek run the other night. It felt great. What is a fartlek run?  A fartlek run is when you have speed spurts during your run at an irregular interval.  This means, after I warmed up for a mile, I would run as fast to a certain and then slow down. Then when I felt ready again, I would repeat. 

This is different than intervals.  In interval training, you are picking up your pace at regular intervals. For example, when I used to run intervals on the treadmill, I would do 30 seconds at 9.0 miles per hour followed by 90 seconds at 7.0 miles per hour and then repeat 10 times. 

With Fartlek running, I would pick a random spot like a light post and then pick up my pace until I arrived at a lamppost.  Then I would repeat as I felt.  The night I went out, it was a little warm than I expected, but I still tried this.  I warmed up for about 1.25 miles and then picked up my pace and slowed back down for about 2.5 miles. Then I cooled down for the last 1.25 miles.

This felt great.  It changed up my routine.  The route I would run felt like a new route. I was so focused on when to start and stop that the run seemed faster.  Also, the run was harder than previous runs I have had recently. 

Do you have ever use fartlek or interval training?