Thresh4
Fartlek: Warm-up, then 5 x 2 minutes Fartlek with 2 minutes recovery. Fartlek runs are done as an effort interval followed by a recovery interval. The recovery interval is done as an easy run, at a pace similar to your base or aerobic runs. Let your heart rate rise to zones 3 to 4 for the effort intervals, and drop to 1 to 2 for the recovery. Cool-down.