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One-Hour Workout: Mailbox Fartlek Run Intervals

Use this run session to boost your aerobic endurance and speed—while having some fartlek fun at the same time.

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We’re reaching that time of the season when it’s totally understandable if you’re looking for a way of mixing up your workouts and adding some variety to your training. Look no further than this run session, which involves a blend of intensity, effort, and pacing. You’ll also want to make sure you choose the right neighborhood to do it in, as (after the warm-up) this mailbox fartlek involves running hard between mailboxes—different, but fun!

The warm-up should start out incredibly easy—even walking for the opening minutes if you desire—as you slowly bring up your heart rate and breathing rate. Approach the warm-up as three blocks of five minutes, gradually increasing effort every five minutes. You’ll then have another five minutes of pick-ups, which should be 20-30 second accelerations, designed to get you ready for the harder efforts later on in this workout.

The main set is a fun one: You have 30 minutes of fartlek running here, which is dependent on mailboxes—so pick your route carefully! Run hard to one mailbox, then run easy for the next two. Run hard for the next two, then run easy for one. Continue with this pattern or switch it up if you prefer, going hard for three, easy for one, or hard for one and easy for two. The beauty of this workout is you can push as hard as you feel, but it’s definitely important to “polarize” the hard and easy efforts, that is, make the hard, hard—and the easy, very easy. Try to also keep the pace consistent for these respective efforts, too. For example, if you’re running 7:30 minute/mile pace for the hard efforts at the start of this workout, the goal is to be running the same pace at the end.

This mailbox fartlek workout also inadvertently forces you to pay attention to your surroundings, which is something that not all triathletes do when they’re super focused on training.

Enjoy a relaxed 10-minute cooldown, where you really bring your heart rate down and kickstart the recovery process.

Mailbox Fartlek


15 minutes very easy, gradually building pace, starting out as 5/10 RPE (rate of perceived exertion) for the first 5 minutes, then 6/10 for the next 5, then 7/10 for the final 5

5 minutes of pick-ups (5 x 20-30 seconds of accelerations with 30 seconds jog recovery)

Main set

30 minutes of mailbox run intervals, fartlek style. Pick a route where you can run hard and easy between mailboxes. Start out running hard to one mailbox (think 8-9/10 RPE) and then run easy (4-5/10 RPE) for two. Run hard for two, then easy for one. Continue with this pattern or mix it up however you see fit. The goal is to hit higher intensities, recover just enough, and then run hard again.


10 minutes relaxed, easy running