Fartlek training involves running at different speeds for intervals, but that’s kind of where the rules end. Much like HIIT, it’s up to you to decide how you break up your work/rest pattern.

“It’s about varying the intensity at which you train,” explains Kerry. “Unlike a 5k, in which you try to maintain a low tempo pace for a continuous run, in fartlek training there’s going to be short bursts of speed.”

For example, you might run for two minutes at a steady pace, and then pick up the speed for three minutes, and repeat for the duration of your session. Although the period of faster running can be a sprint, it doesn’t have to be, and if you do want to go super-fast, Kerry advises reducing the amount of time you spend working on speed. “You could try sprinting for 30 metres and walking for 100m,” she suggests.

Fartlek training: this interval running style is the easy way to improve your run