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# How to destroy aerobic capacity
- URL: https://www.scottsemple.com/how-to-destroy-aerobic-capacity/
- Published: 2018-03-17T08:14:09.000Z
- Updated: 2025-05-03T18:58:45.000Z
- Author: Scott Semple

I’ve had a high ~~an~~aerobic threshold for the past several years. Six weeks ago, I followed some bad advice and did way too much intensity for my fiber type. I almost blew up. I had one race during that period, and I finished several minutes behind my usual cohort. (Several minutes is a lot.)

Now I’m struggling to finish the race season and looking at a lot of repair work to get back to where I was. My aerobic threshold heart rate is usually between 180-185 bpm. Today, it’s down to \~170.

## —

> “There’s not a lot you can do to make an athlete better in the last month before a race. But there’s a lot you can do to make them worse.”  
> \~ [Renato Canova](https://en.wikipedia.org/wiki/Renato%5FCanova?ref=scottsemple.com) (paraphrased) 

A difference of ten to fifteen beats per minute may not sound like much. But my skimo race pace is in the high-180s. Racing for two hours at \~188 is a very different experience with an AeT of \~170 than with an AeT of \~183\. Races feel a lot harder and, afterward, recovery takes a lot longer.

**Stupid is as stupid does**

I have two principal interests: training and investing. I hired a coach so that I could be more effective and end the frustration of a split focus.

The coach was from a different school of thought, but based on his resume, I was sure the differences would be small. He’s had significant success with many athletes at a very high level. I assumed there would be some common ground, and that I’d learn a lot. Despite some early warning signs, I [emptied my cup](http://wiki.c2.com/?EmptyYourCup&ref=scottsemple.com).

I felt fantastic for two weeks. It was a lot more intensity, but it seemed to be working.

But then I started to slow down. I could no longer match the paces that I had hit in the first few workouts. I told my coach that the workouts were feeling harder. I was having trouble completing them, and my pace was slowing.

I received no response. Nothing changed in my workout prescriptions. He cut-and-pasted workouts from one week to the next.

Generic programming was not what I signed up for.

> “If you are not getting daily feedback, then you are not getting coaching. You’re getting a training plan applied to you.” 

I disregarded the warning signs, insecure about my knowledge in the shadow of his. I knew better than to do so much intensity, but I didn’t have the confidence to say so.

Now I know better.

**Stay the course**

To make matters worse, the start of this season was perfect. Last summer, I tried several new training ideas that I responded to really well. I went into the winter feeling quite strong.

In early December, a spot lactate test was one of the best I had ever had. Rather than \~2 mM in the low 180s, I was at only 1.8\. The day after that spot test, I had a new race experience, feeling stronger and stronger as the race went on. [Except for some tactical errors](https://www.scottsemple.com/do-it-before-youre-ready/), the race was perfect.

Now I’m faced with one more race, low confidence, and the demoralizing prospect of rebuilding what I’ve lost.

**The road ahead**

The good news is that wasting over $1,000 may turn out to be the best training money I’ve ever spent.

I realized that I know more about training than I thought. I know what works, what doesn’t, and why that’s the case. I know what my weaknesses are, and I know how to fix them.

It’s just going to take another season to do so…

## —

![Image of intensity distribution for the entire season, before a good race, and before a bad race](https://i0.wp.com/scottsemple.com/wp/wp-content/uploads/2018/03/Intensity-Breakdown.png?ssl=1)

Intensity Distribution: A) all season, including races (so intensity in training is overstated); B) before the good race; and C) before the bad race. Intensity above aerobic threshold (AeT) increased from 4.11% (for the good race) to 9.73% (for the bad race), more than doubling. Speed work (Zone 9) decreased from 0.45% to 0.00%.

NOTE: The zone system I use is unusual but effective. It’s based on the work of Renato Canova and has two big advantages: 1) it uses aerobic threshold as the reference intensity, not maximum heart rate; and 2) it emphasizes much more polarization of intensity than more traditional systems. The lower six zones do not directly correspond to a generic zone breakdown, but zones 7, 8, and 9 do correspond to the traditional zones of 3, 4, and 5, respectively.