Finding My AeT

AeT, or Aerobic endurance threshold, is the point at which your body begins to open the anaerobic pathways. Knowing, and training below your AeT is critical to building aerobic and muscular endurance – enabling you to run, or bike, or swim longer and faster, and process fuel more efficiently. Lots of people have lots of research and opinions around AeT and heart rate zone training – Hadd, Joe Friel, and others, and have shown great results. It is somewhat counterintuitive: in order to get faster, you need to train slower – training at or below your AeT, which is typically the top of Zone 1, or 70% of your max heart rate. Most people train solidly in Zone 3, all the time. With consistent training at AeT, your AeT doesn't change, but you are able to increase your speed at that same heart rate.

There's actually a LOT to be gained from smart training, and training at AeT. Most triathlon training, in fact, focuses on zone training. So now that we're working with Jill, it's time to do a little better than guesstimate my heart rate zones.

For most people, figuring out heart rate zones is pretty straightforward with the use of a formula. But not for me. Why? Because I have a freakishly low heart rate. And I do mean freakish. Sure, my resting heart rate is low, but that's not really all that interesting. It's my max heart rate that is low – that makes things interesting. Most zones are built off of max, so really figuring out what mine is, is important.

Well, the 10K race this past weekend got us pretty close to that number. Jill's been crunching some numbers, and came up with a set of ranges for my zones, including a hypothesis about my AeT. Today's run was all about testing that hypothesis, to determine if we had the number about right.

The test consisted of an hour treadmill run. Based on my heart rates & pacing from the 10K, Jill suggested the following: warm up 10 minutes at 5.0 mph, then run the remaining 50 minutes at 6.0 mph, and see where my heart rate ends up at the end. Okay – no problem. But wow – 5.0 mph – S L O W….

Well, for the first 10 minutes I barely cracked 100 bpm (see, I told you my heart rate was freakishly low..). Then over the course of the subsequent 50 minutes, my heart rate floated around and between about 107 bpm up to about 116 bpm. Which, according to Jill, is just about right. She'd pegged my AeT at 113 bpm – roughly equivalent with 10 minute miles.

Which is all to say that I'm going to be spending a lot of time over the next several months leading up to IM CdA running a lot slower than I'm accustomed.

Guess I better charge my iPod.