Your brain plays a bigger role in endurance than you think
Eight years ago, journalist Alex Hutchinson published his popular book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance, built around one deceptively simple question: when an athlete "hits the wall," is it their muscles failing, or their brain deciding they've had enough?
That question became personal for me long before I started thinking about it through the lens of new neuroscience. I read Endure, and the chapter on perceived effort stuck with me ever since: the idea that how an effort feels can matter as much as what's actually happening in your muscles, heart, or VO2 max. If the effort feels harder than expected, pace can drop. If it feels easier, there's sometimes more gear than you thought you had.
That same question shaped my MSc thesis, where I looked at how to design real-time wearables for long-distance runners and built a Garmin watch app to explore it. As Hutchinson lays out, it's widely agreed that the brain plays a critical role in performance, but the open question is how. Now, new 2026 research gives us another fascinating piece of that puzzle.
Brain neurons programming endurance capacity?
Researchers co-led by UT Southwestern, the University of Pennsylvania, and The Jackson Laboratory identified a cluster of neurons in the ventromedial hypothalamus (VMH) that became more active with repeated exercise in mice. Across three weeks of training, the activity of these neurons changed alongside improvements in the animals' endurance.
When the researchers artificially stimulated these neurons, the mice continued to show endurance improvements. When the neurons were silenced, the benefits of training were greatly reduced, even though the mice continued to perform the same workouts.
That finding suggests that the brain is not simply observing the adaptations happening in the muscles and cardiovascular system. In mice, at least, specific brain circuits appear to participate in how the body adapts to repeated exercise (Kindel et al., 2026).
What Hutchinson was already circling
This is where the 2026 research connects directly back to Endure and to a debate Hutchinson spent an entire book trying to referee. The debate questions whether endurance is limited primarily by what the body can physically produce, or by how the brain regulates and interprets the effort.
Tim Noakes: the brain as bodyguard
In the late 1990s, South African sports scientist Tim Noakes proposed the "central governor" theory: exhaustion isn't your muscles or heart running out of capacity; it's your brain deliberately holding effort back, well before real physiological failure. In his model, the brain acts almost like a dimmer switch, recruiting less muscle as fatigue builds, not because the muscle can't do more, but because the brain won't let it, to protect you from catastrophic damage. It was a genuinely radical claim at the time, since the accepted wisdom was that VO2 max was the hard ceiling on effort.
Samuele Marcora: it's not your legs, it's your head
Hutchinson gives equal space to the counter-argument from exercise physiologist Samuele Marcora, whose "psychobiological model" reframes the same wall in different terms. For Marcora, there's no unconscious governor quietly protecting you from harm, only perceived effort and motivation. As Marcora himself has put it, "endurance performance is directly determined exclusively by psychological factors," with training and fitness affecting performance only indirectly, by changing how hard the effort feels. He argues that the limit is generated centrally rather than read off the body.
The two approaches disagree about the mechanism, and this particular new research doesn't resolve that debate. But it does add something important to the picture: there are identifiable brain circuits that change with exercise and appear to influence how endurance adaptations develop.
A personal note: chasing the same question
As a long-time marathoner, I immediately saw the value of learning to understand my perception of effort, both in training and when racing. Understanding what my true 10 out of 10 effort actually feels like has helped me dig a little deeper into my own performance limits, too.
Mental, not a physical block
When my legs stopped working about 200 metres before the finish of the Tallinn marathon in 2023, and I had to crawl the last stretch, it wasn't from a lack of carbs or sodium. I'd taken plenty of both. It wasn't hitting the wall either, as my splits stayed pretty even all the way to the 42nd kilometre.
I still don't know exactly what caused those final 200 metres to lose control over my feet. I believe it was my central nervous system, worn down from holding my absolute limit for so long, desperate to reach the finish and claim my bronze at the Estonian Championship. Because it felt hard. And because I wanted it to be over before it actually was.
The powerful habit of self-reflection on how it feels
Even today, fitness wearables and apps track a wide range of physiological data, but not really how an effort feels to the runner. As a coach, I see it all too often: new runners who think their zone 4 heart rate reflects their true easy run. It doesn't. They just don't know what easy is actually supposed to feel like. Yet.
At KULG, we aim to promote the simple habit of self-reflection to learn about the athlete’s effort perceptions. Adding context to the training log about what’s going on in your life can help reveal patterns that physiological data alone might miss. Subjective data is still data.
Learning to recognise your own effort levels is therefore a skill, not just a subjective opinion. A useful starting point is simply to ask yourself after training: How hard did that actually feel, from 1 to 10? Not what did my watch say. Not what pace did I run. How did it feel?
How does this apply to run coaching?
Respect the brain's role in adaptation
If central nervous system fatigue can block endurance gains at the neural level for humans as well, recovery becomes a major limiter when done wrong. Recovery and adaptation may involve more than muscles simply repairing themselves.
Build recovery and deload weeks into training, and pay attention when an athlete repeatedly reports that familiar efforts feel harder than they normally do. That subjective change may be one of the first signals that something in the overall system has changed.
Train the perception of effort, not just the legs
Perceived effort isn't something runners should try to ignore. It is something they can learn to understand.
Sessions at different intensities, controlled long runs, race simulations, and simply paying attention to how different efforts feel can help athletes build a more accurate internal scale.
The goal isn't to become better at tolerating pain for its own sake but to become better at recognising the difference between an effort that is appropriately challenging and one that is unnecessarily hard.
Further reading
Kindel et al. (2026) — Exercise-induced activation of ventromedial hypothalamic SF1 neurons mediates improvements in endurance — Neuron
Alex Hutchinson (2018) — Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance
