In a fartlek run, is there a minimum duration of faster intervals?
A fartlek is a continuous run that includes harder efforts, with easy running between them. The number of intervals depends on what you are trying to get out of the session and also the event you are training for. A more endurance-based fartlek may involve fewer but longer intervals – you might only do four or five intervals, with each one lasting four or five minutes. In contrast, a speedier fartlek might involve up to 10 intervals, each lasting around a minute.
You could also mix and match, whereby you start with longer, slower efforts and progress to shorter, faster efforts (see below for an example). Finally, for a completely free-form fartlek, you can just put in surges as you feel, perhaps using specific landmarks on your running route.
Structured fartlek workout
Why do it: This workout builds endurance and speed. The intervals get shorter, so try to increase your perceived exertion and run slightly faster with each one. This session also encourages you to find speed when you’re tired.
How to do it:
10-minute steady warm-up
5-minute effort (90 secs steady)
4-minute effort (90 secs steady)
3-minute effort (5:30 mins steady for longer mid-workout recovery)
2-minute effort (90 secs steady)
90-second effort (90 secs steady)
60-second effort (90 secs steady)
30-second effort (60 secs steady)
10-minute easy warm-down