Big muscles or athletic endurance?

You may think there's a tradeoff. You can't have both.

But it doesn't really matter, unless you are aspiring to compete in the Olympics.

Here's a snippet of Peter Attia's article.

As a single fiber gets larger, it cannot sustain the same relative aerobic capacity that it could at a smaller size. With a lower surface-area-to-volume ratio, the distance between the cell membrane and the central areas of the cell becomes larger and the same number of capillaries must support larger demands. Together, these challenges mean that it becomes progressively more difficult to suffuse the cell with nutrients. Conversely, a cell operating at maximum aerobic capacity will not be able to increase its size too much or the mitochondria inside will start losing easy access to nutrients and oxygen.

But this is our consolation:

A consistent, measurable ceiling limits the size and concurrent oxidative capacity of individual muscle fibers, and for elite athletes, this ceiling may indeed have important implications for training decisions. For instance, it might mean that an Olympic marathon runner may not be simultaneously competitive as a professional bodybuilder and vice versa.

But for the rest of us, we can have our cake and eat it, too. Below the elite end of the spectrum, we can safely assume that our muscle fibers have plenty of room for improving in both size and oxidative capacity. We can continue to engage in a mix of endurance training and resistance training without having to choose between these two modalities—both of which are vital for long-term health and physical function.

There you have it. You can have both.