Despite its intriguing Swedish name, fartlek is actually very simple. It involves a continuous run in which periods of faster running are interspersed with periods of easy or moderate-paced running, rather than periods of complete rest, as with classic interval training.
This form of unstructured speedwork allows for plenty of flexibility. For instance, you can use time as the measurement for fartlek sessions: runing one minute at a faster effort, then three minutes at an easy effort. Alternatively, you can use distance – here, try running faster for half a mile, say, then easy for another half a mile. Or you can get truly creative and make it up as you go along: run to the next tree, jog to the next lampost. The possibilities are endless.
How are fartlek sessions different to other speed workouts?
Tempo runs should feel ‘comfortably hard’. Unlike fartlek sessions, tempo sessions are run at a consistent pace and at a level of effort that you could sustain for an hour – this is typically about 20 to 45 seconds per mile slower than your 5K race pace. (To figure this out, use our training pace calculator.) In terms of perceived level of effort, tempo runs are a 7 or 8 out of 10.
Intervals, meanwhile, are short, intense efforts followed by equal or slightly longer periods of recovery, which might involve slow jogging or stopping completely. A typical interval workout might be 8 x 400m at 5K pace, with recoveries lasting the duration of each repetition.