Fartlek - a speed workout of varying speeds and lengths ranging from walking to sprinting. This is speed work, but it is much more enjoyable than interval training. It is Swedish for speed play. Some of my high school freshman track team members will remember this workout. Mr. Hern with his whistle. He would have us run the parking lot (since we didn't have a track yet) and sprint when he blew one whistle. Jog when he blew two whistles. Sometimes it was fun. Sometimes you wanted him to choke on that whistle.
Yesterday, I went out for a fartlek run. I jogged a 1 mile warmup and made quick work of a stretch routine. I darted down the road in my new Asics for their first speed workout. They performed nicely. I did have one or two steps when I was really moving fast where my foot slid a little. I don't think that is bad considering my run was a few thousand steps. My fast parts of the fartlek were around 5 minute pace, but I couldn't keep that up for very long. Maybe 100 - 300 meters at most. I did some walking and mostly jogging between speed portions.
During the speed sessions, I felt like I was floating on the sidewalks. I was going close to all out, but very relaxed. My arms were barely moving while my legs were just powering my body forward. I think my center of gravity moved just up an inch or so from normal and that is how I got that sensation of floating. It made easy work for my legs, but it was really hard cardio to keep up.