CoachFrom the Coach guide
Speed play.
Faster and easier running, mixed by feel.
What it is for
Fartlek is Swedish for speed play. You mix faster and easier running by feel, without fixed distances.
How to run it
Pick a landmark and run faster to it. Then jog easy until you recover. Repeat for the time the plan gives.
Why plans use it
It trains changes of pace with less pressure than timed intervals. Coach uses this coaching practice to vary the effort without fixed splits.
Not the same as
Intervals: fixed lengths and fixed rests.