Use this run session to boost your aerobic endurance and speed–and all in under an hour.

This is a seemingly gentle run workout that packs a punch at the end, so approach this building block run with body and mind fresh enough to run well. The 10-minute warm-up should be extremely easy, nothing more than 5 out of 10 RPE (rate of perceived exertion), and don’t be afraid to start out by walking in the opening minutes. Once well warmed up, hit the first 10-minute interval, building effort through the first 5 minutes and then holding Ironman pace for the second 5 minutes. If you’re not an Ironman racer, think of this as 7.5-8/10 RPE. Run relaxed and easy for 5 minutes, before repeating this 10-minute interval, aiming to hold the same/similar pace as the first one. Follow it up with another easy 5 minutes of relaxed running. The final 5-minute interval is the one that could sting: Aim to hit this running at least 15 seconds per mile faster than those earlier 10-minute pieces. If you feel good here, go for it! This is a great workout for boosting aerobic endurance and peppering in some top-end speed at the end, just when you’re starting to fatigue. Enjoy it!

Warm-up

10 minutes very easy, gradually building pace, nothing more than 5/10 RPE

Building Block Run Main set

10 minutes build to Ironman pace (7.5-8/10 RPE)
5 minutes easy
10 minutes build to Ironman pace, aiming to hold the same/similar pace as the first interval
5 minutes easy
5 minutes running 15 seconds per mile pace faster than the first and second intervals. Push it if you feel good.

Cooldown

10 minutes relaxed, easy running