When I introduced an allowance to our oldest son, I used three jars: Spend, Give, and Save. The three jars represented three big-picture elements of managing money. After describing the first two, I got to the one that I was most excited about, the Save jar.

“And with this jar,” I said with glee. “This money you keep forever.”

“FOREVER…?” my son said, horrified. “But I don’t want to save forever…” His 5-year-old face fell. He looked dejected.

It was my fault. I did a bad job of explaining the concept. And for young kids, the idea of building toward self-perpetuating wealth is too hard to grasp.

But for adults, the advantages of building and maintaining wealth should be obvious. Watching the first few dollars add up is a long, slow slog, but it’s worth it in the end.

And building aerobic capacity works the same way.

Building aerobic capacity is saving. Using capacity is spending.

Michael Phelps’ coach Bob Bowman uses a capacity versus utilization model. The idea comes from Jan Olbrecht. In any training session, you can either build capacity or use it, but not both.

You can “save” your aerobic money by building up mitochondria. Or you can “spend” your money by using it up.

So when can you spend everything you’ve saved?

How many people do you know that spent their way to wealth?

You can blow your bankroll whenever you want to be poor. Or if delayed gratification is too much of a challenge. When you no longer care about being as fit and fast as you can be, then aerobic capacity doesn’t matter anymore. Spend at will.

But who wants to be poor?1

If you don’t want to spend it all, how much can you spend?

Let’s jump back to the wealth example. Based on the historical annual gains of the S&P 500 index, a sustainable withdrawal rate is only 3-4%. So on a nest egg of a million dollars, you can only take out $30-$40,000 per year. That’s not a lot, is it?

The good news for your fitness is that you can make bigger withdrawals on aerobic capacity. The bad news for your ego is that it’s not bigger by much.

  • For events of 90 minutes or more, high-intensity training shouldn’t exceed 5% of training time. So in a 10-hour week, you’d want to keep the minutes of high-intensity training to 30 minutes or less. In a 500-hour year, high intensity should be 25 hours or less.
  • For shorter events, you can stretch the high-intensity up to 10% of training time.2

So a good rule of thumb is 3-6 minutes of intensity per hour of aerobic capacity training (applied on a weekly or longer basis).

So most of my training will be slow forever?

No. There’s good news after all!

The more “savings” you have the more “spending” you can do.

A deca-millionaire can spend ten times as much as a millionaire and still maintain her wealth. The ratio is the same for both–3 to 4%–but the deca-millionaire has ten times the disposable income. Saving is tedious when it starts, but more and more gratifying as the amounts get bigger.

The same is true for aerobic capacity. It’s slow to start, speeds up, and gets fun when it’s fast.

How does aerobic capacity work get faster?

Building aerobic capacity happens in two stages; one short, one long:

  1. In the first phase, the athlete’s aerobic threshold heart rate will start to rise. The the sugar/fat fuel mix improves. And then the aerobic threshold heart rate gets closer to the anaerobic. How fast it changes depends on three things:
  1. In the second phase, the aerobic and anaerobic threshold speeds rise and converge.

With the right training, the first phase can happen in weeks or months. The second can persist for years.

So get saving.

“The best time to plant a tree was 20 years ago. The second best time is today.”

At the start, aerobic capacity training is tedious and slow. And it can be lonely. With all your friends chasing KOMs and getting weaker, it can be hard to hold back and get stronger.

When I started proper endurance training, I was always the slow guy. I was way off the back with almost everyone I went out with.

After years of proper training, what I used to think was hard is a pace that I can maintain all day. I don’t have the genetics to be world-class, but the gains I’ve made have transformed my experience. As my performance has improved, my days in the mountains have expanded. I have a wider menu of terrain to choose from.

It was a long road, but it was worth it.


  1. Some may argue that religious mystics are quite happy being poor, but that’s only in the material sense. I don’t see a difference between a monk and a millionaire. The monk is other-supported, living off the generosity of others. The millionaire is self-supported, living within his means (which has to be a small part of his net worth). Both are wealthy in their own way. 
  2. The “80:20 rule” is common when it comes to recommended volumes of low- and high-intensity training. That ratio comes from a “session goal” approach to quantifying training time. It counts intensity by the goal of a session rather than the actual minutes of low- or high-intensity. So if you had two high-intensity workouts in ten, that would qualify as an 80:20 split for a session goal approach. But that doesn’t reveal the actual training ratio. In a world-class program, minutes of high-intensity are a much smaller proportion.