I did a lot of investigation a few years ago about what science had to say about the “perfect interval workout” for endurance athletes.

All things pointed towards spending the most amount of time at high intensities, duh. But how one picks interval duration, intensity and number of replicates is much harder.

What I found was you want to first do an incremental exercise test to determine the maximal aerobic power (MAP) you can produce. Use a testing protocol like Conconi or the MAP. This stepwise test is just like a VO2max test but the step lengths are longer to reduce the contribution from the anaerobic systems.

Then the next day when recovered test how long you can hold the MAP. We will call this sustainable duration of MAP (SDMAP).

For the next month do intervals at MAP for 60% of SDMAP, recover until HR hits ~65%MHR and repeat until you can no longer hold the power for the prescribed duration.

That is the key, because the whole program is based at maximizing high intensity volume you must repeat these until you really can’t perform up to snuff. Otherwise do all intervals to failure (get sick, hit maxhr, crash).

The nice thing with these is that it’s not really the hardest you can go, and it’s only 60% of how long you can go, so they don’t hurt right? LOL

Once you are able to do more reps, retest.

You can do this without a power meter, just not as well.

Too complicated?