This article is purely theoretical. Some readers will think that the theory is obvious on its face, and others will think that it’s wrong. The joy of talking about training theory at the intersection of science and anecdote is that there are too many physiological metrics to track, and too many variable responses to interventions, so the resulting conclusions fall somewhere on the spectrum between fundamental truth and biased bullshit. Throughout, I’ll try to check my biases and acknowledge the unknowns.
You know I’m nervous about writing an article when the first paragraph is undercutting myself with disclaimers. To be fully real with you: I am unsure on this one.
This article tries to articulate an unexpected observation that now forms a cornerstone of my coaching approach, but I have too much self-doubt to ignore my biases. It’s like looking at a diagram of constellations in the night sky. The diagram might say: “This is the mighty hunter, pursuing the courageous bear.” And all I can think is: “Actually, you are pointing at 4 dots and the vague outline of a penis.”
So remember, as I try to break this down, I’m describing a scene with a mighty hunter, but I’m painfully aware it might just be dots and a phallus.
Here it is, distilled down to 3 sentences:
- Output at VO2 max while climbing (measured via grade-adjusted pace) may have a high predictive value for athlete progression and regression over time, particularly with age.
- The metric likely is a proxy variable for limitations of mechanical output that are faced by some athletes from the start of their running journeys, and confronted by all athletes with age.
- Constant reinforcement of the metric may improve performance at all effort levels, including long ultras, and can seem to reverse the athletic decline process in some cases.
That’s it. To paraphrase The Lion King: Simba, let me tell you something that my father told me. Look at the stars. YOU SEE WHATEVER YOU WANT TO SEE.
Observations From Athlete Training
Let’s have some fun with training theory, reverse-engineering why I think this conclusion is significant and may be overlooked. When my co-coach/wife Megan and I started coaching (we talk about this topic more on episode 114 of our podcast), we began as acolytes to coaches like Renato Canova and Jack Daniels who excelled with Olympic-level athletes on the road and track.
We added some wrinkles here and there based on data we saw along the way, which seemed to especially manifest themselves with athletes that might not have Olympic-level VO2 maxes, whether due to genetics or age (VO2 max measures peak oxygen utilization during exercise, has a strong genetic component, declines with age, and is not highly trainable). You have probably seen me write about a lot of those wrinkles: plenty of fast strides, a higher proportion of short yet controlled intervals, and the heavy use of hill intervals year-round.
But Megan and I both kept hitting the same stumbling block: athletes over age 40 just didn’t respond as well as we would like.
So we tried something new. With sub-ultra trail runner Mark Tatum and a few other athletes, we moved almost every workout into the hills, with an astounding number of power hill strides, and at least one session most weeks with short hill intervals. Mark and some others had breakthroughs, seemingly giving a big middle finger to the aging process. For Mark, a few years of training later, it led to an overall win at the Dipsea Race.
That made sense with aging athletes. Hills reduce impact forces and may increase muscle recruitment/mechanical demand (2017 review article in Sports Medicine), and short intervals may counteract natural VO2 max reductions, so they are great for the aging athlete. I’ve written about that before, as have others. It was nothing new, although maybe the approach was more committed to the bit.
But then something fascinating happened. A few younger athletes that we coached also seemed to have issues where traditional speedwork didn’t lead to the expected adaptations. Maybe it was repeated injury cycles without clear explanations, or maybe it was just an unexplained performance reduction. So we tried a similar intervention. While results varied, the hill emphasis had a substantial effect size on results in our team, including preceding a couple national championships.
Now we were intrigued. Is it just the specificity of hills for trail running? Possibly, but we saw similar improvements in some road runners. Could it be an improvement in the VO2 max variable? That’s doubtful, since there’s little evidence that it can increase much in trained athletes. Lower injury rates? That likely plays a big role, but later we started to see similar results in athletes who rarely got injured. Or, to summarize: The hunter, or a random association of dots?
As we started to incorporate short hills more for all of our athletes, with all different backgrounds, we started to hone in on one primary explanation: the unique neuromuscular and biomechanical demands of mechanical output in running.
Here, mechanical output is shorthand for how aerobic processes interact with the musculoskeletal, biomechanical, and neuromuscular systems to create speed. A thorough explanation of mechanical power output is in this 2018 article in the Journal of Biomechanics, but just think of it as how each stride transmits force, rather than as conveying everything that goes with the technical term. For our purposes, effort level at VO2 max does not refer to the specific physiological measure, but is a general shorthand for high-yet-controlled outputs.
We have seen that if an athlete can improve their output around VO2 max on hills, they can counteract – even reverse – part of the athletic aging process at all distances. The reason that the short hills should lead to more broad-ranging development is that athletes accumulate lots of aerobic work over time, and those lower-level aerobic gains accumulate.
There is nothing new about this concept. For example, Norwegian training principles are so hot right now. Most of the focus is on the high volume of threshold work. But if you look closely at some of the sample weeks, you’ll sometimes see a day full of short, fast hills (and that’s for young, immensely talented athletes). Similar concepts were rumored to be included in the training of Jake Wightman, World Champion in the 1500 meters. Whether it’s Lydiard-based systems from the 1960s and 1970s, Canova-inspired hill sprints, or hybrid approaches, once you start looking, you’ll see these elements all over, even for athletes that seem to have almost no genetic or age limitations.
Possible Physiological Explanation
Okay, let’s go back to first principles. VO2 max peaks at a young age, and it isn’t highly trainable. So how do athletes keep getting faster if their peak oxygen intake is staying flat or declining?
The answer is that their output at VO2 max improves, usually measured as velocity at VO2 max, even as the denominator doesn’t improve. The prototypical example is Paula Radcliffe (see this 2006 study in the International Journal of Sports Science & Coaching), whose VO2 max actually decreased from when she was a champion junior athlete, but her running economy (the amount of energy she used to run fast) improved by 15 percent. Those running economy improvements likely come from some mix of lower-level aerobic development leading to more efficient cellular processes of fatigue management, neuromuscular/biomechanical efficiency, and mechanical output. I’m not concerned with how much oxygen an athlete can consume, but what they do with the oxygen they have.
Running economy can be measured across multiple intensity levels. At the intense end of the spectrum, you have velocity at VO2 max (think 10ish minute effort, with variance). More toward the middle is critical velocity or velocity at lactate threshold (~30- to 60-minute effort). At the easier end of the spectrum is velocity at aerobic threshold (2-3+ hours, depending on the athlete). With age, vVO2 goes down first (often in an athlete’s mid-20s), followed by vLT (30s or later), then vAeT (which can stay higher for a long time due to the aerobic component). That makes intuitive sense–athletes move up in distance with age by necessity as VO2 max and mechanical output go down, while long-term aerobic development is ongoing.
Side note: there are 10 statements in the preceding paragraphs that are controversial in exercise physiology. Sorry about that. If there’s anything I learned from eating a lot of cereal as a kid, it’s that if you spot them all and mail proof of purchase to General Mills, they might send a free toy!
Back to it. Our theory is that focusing too heavily on the aerobic side of the running economy equations misses out on the mechanical power side. Yes, VO2 max will decrease with time. But based on what we have seen, the mechanical output associated with VO2 max doesn’t need to decrease much at all. And it can even go up very far into an athletic journey!
Why is that significant for an athlete competing in longer races? Think back to the experienced 60-year old athlete who progresses a bunch with short hill intervals. Their VO2 max number likely can’t change much at that point of their athletic journeys, but we think that their mechanical output can. And because mechanical power is a strong performance indicator at all efforts in aging athletes, it doesn’t matter that the short hills are non-specific to their race distances. It’s the highest-yield stimulus for output, and it pushes back the strongest against the inertia of aging, so they get faster at everything.
If you’re 50+, I think that you can take that to the bank. Focus on mechanical output/strength alongside aerobic development, and you’ll be rich as hell. Now, let’s dive into a more speculative investment.
The hardest logical leap is to take these principles and apply them to younger athletes. Why might they progress even when they aren’t limited by mechanical output in the same way?
Our theory: they are limited in that same way, just to a less clear extent. In fact, most of us have some mechanical limitations that are semi-independent of traditional aerobic development.
Talented, elite athletes are the origin point for many training theories, and most of those athletes have few limits associated with vVO2–that’s why they’re elite in the first place. So they can focus more heavily on the aerobic-input components of speed, plus specific training for their events. But for most of us, mechanical power at the top-end of aerobic capacity is a limiter from when we are young, and it only gets worse with time.
That’s one reason we strongly encourage athletes to eat enough, always. Running is a power sport, even if it doesn’t always feel that way. And that may add another explanation of why athletes who restrict food almost never improve over time.
Since mechanical output is the true theorized limiter, it may be better to do many of the sessions targeting it on uphills. Flat intervals are fantastic and important at times, but many athletes end up not having the biomechanical and neuromuscular efficiency to translate their aerobic ability into the same output. In our data, an athlete who is not extremely fast (in a road/track sense) will often have a faster grade-adjusted pace on a 2-minute hill interval than pace on a 2-minute flat interval, often by 20-30 seconds per mile. Combined with the higher muscular demand and lower injury risk, output around VO2 max seems to be optimized on hills.
A quick disclaimer: we could easily be confusing cause-and-effect here. Perhaps it’s all driven by reduced injury rates and lower soreness levels, creating more consistency over time (or any other explanation you can think of). Going backwards from outcome to mechanism is problematic for 99 reasons, and for the strength of this theory, each and every one of them is a bitch.
But the practical takeaway is this: we have seen that if an athlete can improve their output around VO2 max on hills, they can counteract – even reverse – part of the athletic aging process at all distances. The reason that the short hills should lead to more broad-ranging development is that athletes accumulate lots of aerobic work over time, and those lower-level aerobic gains accumulate.
The aerobic system can continue to improve, but for many athletes, it runs into a ceiling that we think is often set by mechanical output. If you raise that ceiling, there can be a positive feedback cycle where improved mechanical output allows the improving aerobic system to translate to better running economy, which improves mechanical output more, and so on.
The Big Takeaway
Don’t let your mechanical output be too strong of a limiter, no matter what training approach you use. For us, that involves three main elements.
First, athletes do hill strides year-round to encourage max power development. That can be as simple as 2 sessions of 4-6 by 20-30 second fast hills in the 2nd half of runs each week, or adding hill strides after a flat workout. Or it can be bigger, dedicated sessions like in the Norwegian training sample weeks. Flat strides can also work for this purpose, particularly for advanced athletes.
Second, athletes periodically do moderately hard hill intervals, as often as weekly for aging or injury-prone athletes, and as little as every 6 weeks in durable track or road athletes (with other sessions being on flat or rolling terrain). Our usual guideline is 12-20 minutes of total intervals, with each interval being 3 minutes or less with run down recovery between them. Simple go-to examples are 16-20 x 45 seconds, 8 x 90 seconds, 6 x 2 minutes, or 5 x 3 minutes, though you can get creative with it based on what’s the most fun for you. Mix up the gradient, with the sweet spot being 8%, but it’s cool to have fun with steeper or shallower grades, too.
And remember: this is just one element of our training theory, and our training theory is a grain of sand on the beach of training theories that are out there for free on the internet. Even for us, it interacts with hundreds of other concepts. Listen to your body and do what works for you. Ignore this if you disagree. Send all of your complaints to General Mills.
But don’t accept that getting weaker is a foregone conclusion. Aging is inevitable. If you zoom out far enough, slowing down is inevitable, too. But slowing down is not inevitable tomorrow or next year. And I think there’s a strong argument that it’s not inevitable 5 or 10 years from now either. What do we say to getting weaker and slower? Not today. Then we do some hills and punch inevitability in the freaking face.
David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. With Megan Roche, M.D., he hosts the Some Work, All Play podcast on running (and other things), and you can find more of their work (AND PLAY) on their Patreon page starting at $5 a month.