As fun to run as it is to say, a fartlek workout is a kind of informal interval session and a great way to incorporate speedwork into your routine when you want a change from the track. “Fartlek” is Swedish for “speed play” and consists of bursts of speed in the middle of a training run. After warming up, run at an easy training pace, throwing in bursts of speed for various distances throughout the run. Vary the speed and times of the speed sections, from as short as 15 seconds to as long as two or three minutes. Between these bursts, allow yourself enough recovery time to match roughly 2/3 of the effort time. The recovery pace, though, should be faster than the recovery jog you might do during intervals on the track; keep it moving at an easy training pace.
Tip of the day compliments of Cool Running