In last week’s newsletter I talked about the effects of double threshold training on my performance. In short I went over exactly what workouts I did, how I did them, the rest that I took, and what it did to both my lactate threshold and blood lactates at the same intensities as 6 weeks prior. Long story short, it worked.

This week on the podcast I was lucky enough to have Dr.Jake Hudgins, who has a PhD in exercise physiology, as well as Justin Rinaldi, whose episode I am editing and posting soon. Both podcasts were awesome and I thoroughly enjoyed them. In fact, I debated doing an entire newsletter on the podcast that I did with Justin, but I think I’m going to save it for another time.

In terms of the conversation with Jake, he’s an expert on power measurement and using modern tech to do so is really cool. We also got into all the tech they’re using at Brooks to measure these elite athletes.

That conversation actually leads pretty well into today’s newsletter because I’m going to talk about building what I call a “metabolic profile.” I don’t know if this has been talked about before or if someone has already used this term, but here we go.

Before I get into how we actually build the profile, let’s quickly go through what those three systems are.

Let’s start with the first one: the ATP-PCR system. This system is incredibly fast, lasts up to about 15 seconds in duration, and can produce energy far faster than any metabolic process. The downside is that it has a very, very low capacity. Type II fibers are particularly relevant here, and this system is really important for power and speed athletes.

The second process is called glycolysis. Glycolysis itself does not require oxygen, but what happens to pyruvate afterward depends on the metabolic conditions. Pyruvate can ultimately enter the mitochondria and contribute to oxidative metabolism, or lactate production can increase when glycolytic flux exceeds the rate at which pyruvate can be oxidized.

This metabolic process becomes especially important during hard efforts lasting somewhere around a couple of minutes, so you can think about something like the 800-meter run. When ATP consumption is very high, so too is ATP production, and the breakdown of ATP itself also produces hydrogen ions. As these accumulate, they contribute to the metabolic environment associated with fatigue.

And then finally we have oxidative phosphorylation. This is basically where you take the products that started with the breakdown of carbohydrate and ultimately generate a bunch of what we call reducing equivalents, including NADH. These donate electrons to the electron transport chain, which helps produce a proton gradient that your mitochondria can use to produce ATP.

This is a whole lecture in a basic bio class, so I’m really dumbing it down.

Now, obviously none of these systems simply turns on when another one turns off. They’re all contributing simultaneously. What changes is how much each contributes depending on the intensity and duration of what you’re doing. That’s where this becomes useful for runners.

Functionally, we can get information about these systems using different tests:

We can use all three of these to create what I call your metabolic profile.

But most runners aren’t going into a lab and getting their VO2 max, VLamax, Wingate power, lactate threshold, and running economy tested.

So how do we practically do this?

Instead of directly measuring every metabolic system, we can use race performances across very different durations as practical proxies. They’re obviously not perfect measures of any single metabolic pathway because every race uses all three systems, but the relative strengths and weaknesses across those distances can still tell us a lot.

We can estimate your speed from something like your 400 m dash time or maybe even just what you’d run in a few 200s. This is a good starting place for distance runners, as few of them know their actual 100 m dash, flying 30, or other metrics like that.

The next piece of the puzzle that I usually ask for is someone’s 800 time or their mile time. The reason I ask about the 800 is because this event has a very large anaerobic contribution and tells me, relative to their sprint time and distance-based times, where they fall on the spectrum.

Finally, I’ll ask for either their 5K time, 10K time, or half marathon time. This is probably the best proxy of their aerobic profile out of these race performances.

I know I said that the oxidative phosphorylation system can be measured with one’s VO2 max, but on this end of the spectrum we’re really interested in more than just VO2 max. Running economy, lactate threshold, fractional utilization, and durability all influence how much of that aerobic capacity you can actually use during a race. This builds out the final component of your aerobic profile, though it doesn’t necessarily fit perfectly in with the other metabolic processes because these are secondary characteristics that influence performance rather than separate energy systems themselves.

So now we have performances at the short, middle, and long ends of the spectrum.

Long story short, we can plot your performances across these events using the 2.2 rule which states that your 400 should be 2.2 times faster than your 800 and your 800 is 2.2 times faster than your mile. We can then use some simple rules of thumb to see where you fall on the spectrum.

For example, your threshold pace should often be somewhere around 60 to 70 seconds per mile slower than your mile pace. Something like your 10K pace may also sit somewhere around your actual lactate threshold depending on your ability and how long the race takes you.

And I mean actual lactate threshold, not what you think your lactate threshold is. Side note: there’s a lot of confusion here because people don’t actually measure lactate threshold. They simply approximate it from workouts that they do or what feels like threshold, but what feels like threshold may not actually be your lactate threshold.

If we find that these relationships don’t hold true, then we can start to ask whether you’re more of an aerobic or anaerobic runner.

For example, I talked to two very fast milers today: Riley Witt and his friend Grant Bradley.

Riley ran 3:59 in the mile. Grant ran 3:59 in the mile. Riley is a 1:45 800 runner and can rip 200s in 23 to 22 seconds. Grant, however, is on the complete opposite side of the spectrum. He’s an aerobic beast. His threshold is probably somewhere around 4:40 to 4:45 per mile when he’s in shape, but he cannot break 50 or 51 seconds in a 400. He said that he couldn’t rip a 200 faster than 25-mid.

Despite breaking 4:00 in the mile, Grant lacks speed. If he could just improve some of his leg speed, he might have run 3:55 or 3:53 or faster in the mile. I truly believe that. And this is exactly why I like looking at the entire profile instead of just someone’s mile time.

Two athletes can run almost exactly the same performance while getting there with completely different strengths. This is actually the perfect case study for somebody’s metabolic profile, and you can think of it in another way as being either speed- or endurance-based, albeit using actual data to ground your reasoning.

Another way to do this is to look at a pacing chart. Jack Daniels has a lot of these and they basically follow the same trend. Instead of looking at one race in isolation, you’re looking at how performances should theoretically relate across distances.

For example, if somebody runs a 4:20 mile, or about 65 seconds a lap, you can estimate what their performance might look like as the distance increases. If their actual 3K, 3200, 5K, or 10K performance is substantially better or worse than that expected relationship, that tells you something about the shape of their profile.

This matters because it helps us determine where you’re deficient.

If you’re somebody who has incredible leg speed like Riley, then improving the aerobic side of the profile may give you more room to improve your mile. Conversely, if you’re someone like Grant who wants to get better at the mile, it’s very obvious that improving leg speed could be an important piece of the puzzle.

Even though it’s going to feel like you’re working extra hard for seemingly milliseconds off your 100-meter dash, this can improve your sprint speed reserve, or how fast your race pace is relative to your maximal sprint speed.

For example, if two athletes both run the mile at the same speed but one athlete has a much higher maximal sprint speed, that athlete is running the mile at a lower percentage of their maximal speed. That’s the basic idea behind speed reserve. This doesn’t mean improving your 100-meter time automatically makes you a faster miler, but it does mean that improving it may change how demanding a given submaximal speed is from a neuromuscular and mechanical perspective.

In summary, we can use many of these rules of thumb, along with your performances, to create a snapshot of where you sit relative to other normative data for people of a similar talent level.

If we see that you’re falling off on one end of the spectrum or the other, then we probably work that part of the system and see if it can improve performance back up toward the rest of the normative data.

If we retest after doing that and we still find that you’re skewed in one direction or the other, then chances are you’re probably truly more gifted at the other end of the spectrum. You may need to make a decision about how you want to approach your training, as you might be getting diminishing returns by investing in that other metabolic system. And importantly, this doesn’t mean you just hammer your weakness year-round.

This is where a good coach will help determine exactly what you need, at which point of the season you need it, and when it’s totally fine to make these investments because you don’t have a race coming up and you have time on your side.

Hopefully you find this helpful. Go ahead and give it a try with your own training and let me know if it works or what you find.

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