[mental] The Central Governor: does your brain referee your fatigue?

Created on October 23, 2025

2025   ·   trail   endurance   fatigue   mental   physiology   Noakes   RPE   perception   science   ·   trail   science

“When everything starts hurting and your brain is begging you to pull over, is the engine really out of gas? Are you running on reserve? And if you are, how big is that reserve?”

I keep hearing things about this. On Instagram posts, YouTube videos, post-race conversations. “It’s all in your head.” “You have 40% left in the tank.” “The mind gives up before the body does.” But I rarely know what these ideas actually rest on, or whether any science supports them.

So I did what I always do: I went looking in the literature. I started reading the early models that try to explain how the mind handles effort, and I checked whether they match, or don’t, what we actually experience out on the trail.

This article sits deliberately at the boundary between theory and practice. It does not prescribe what you should do. It does not offer recipes. It tries to shed light on how some ideas about mental toughness were built, and on what they truly explain when we talk about effort, fatigue, and self-regulation.

Today’s topic: Noakes’ central governor theory.

Fair warning: this is one theory among several, and it has been extensively questioned and supplemented by more recent, more precise models.

When fatigue was mostly about muscles

For a long time, fatigue was framed in a fairly simple way: you stop because the body cannot go on.

Less fuel available, more metabolic disorder, a progressive collapse of muscular capacity. In this framework, the decision to stop is not even a decision. It is a consequence.

This model explains part of the picture. Obviously. But when you dig into the scientific literature, a gap shows up quickly.

Neurophysiology research has shown that at the point of voluntary exhaustion, neuromuscular capacity is not fully depleted. Even under severe fatigue, it remains possible to recruit additional motor units through external electrical stimulation, indicating a residual functional capacity (Gandevia, 2001).

And here is something every runner knows: with 500 meters to go before the finish line, the pain somehow vanishes and you can sprint like a rabbit. Coincidence? Probably not.

It is from observations like these that a different perspective on fatigue started to take shape.

The central governor hypothesis: regulate before you break

Between 1997 and 2000, exercise physiologist Timothy Noakes proposed what he called the central governor theory, starting from a straightforward observation: in many endurance situations, the decision to stop does not correspond to a total physiological failure.

In a synthesis paper published in 2000, Noakes suggested that fatigue might not only result from peripheral exhaustion, but also act as a central regulatory mechanism designed to protect the organism.

In this framework, the brain would continuously integrate:

  • physiological signals (core temperature, neuromuscular status, fuel availability);
  • contextual information (remaining effort duration, environment);
  • past experience and expectations.

Based on this integration, it would adjust exercise behavior (pace, engagement, perceived exertion) in order to avoid a situation deemed too costly or potentially dangerous for homeostasis (Noakes, 2000; Noakes, 2012).

A key feature of this model is its anticipatory nature. The brain would not simply react to the body’s current state. It would try to anticipate the future trajectory of the effort. This helps explain well-documented phenomena in endurance, such as early pacing and the ability to produce a final acceleration despite advanced fatigue (Abbiss & Laursen, 2005).

One important clarification: the central governor remains a debated hypothesis, not a localized neurophysiological mechanism with a known anatomical address. But it has profoundly influenced the way fatigue is understood, by placing central regulation and subjective experience at the heart of the discussion.

What this theory does not say

The central governor theory is sometimes invoked to support the idea that there exists a large hidden energy reserve, and that you just need enough willpower to access it.

On this point, the scientific literature is far more cautious.

What the data show is that voluntary cessation of effort frequently occurs before total physiological depletion, and that a residual functional margin does exist (Gandevia, 2001; Enoka & Duchateau, 2016).

But this margin:

  • is not fixed,
  • cannot be simply quantified,
  • and is not independent of context.

The pacing strategies observed in endurance events, as well as the possibility of an end spurt, are incompatible with the idea of a linear depletion down to zero (Abbiss & Laursen, 2005).

So we are not talking about a hidden battery. We are talking about a dynamic balance between physiological constraints and central regulation.

Perceived exertion: the real tipping point

As you go deeper into the literature, one concept becomes central: perceived exertion.

It is what translates, at any given moment, the overall cost of continuing. What “holding on” actually represents, right here, right now.

This perception has been studied for decades through the RPE (Rating of Perceived Exertion), developed by Gunnar Borg (1970). Far from being a simple subjective indicator, RPE:

  • increases predictably with intensity and duration;
  • is strongly associated with the decision to slow down or stop;
  • can vary at comparable physiological load.

Two objectively similar efforts can therefore be experienced very differently.

If you use a sports watch, you have probably encountered RPE already: it is the 1-to-10 score you give after each session. That number feeds into training load calculations, notably through Foster’s method.

When the mind changes the feeling, not the physiology

In the now-classic study by Marcora et al. (2009), subjects first perform a cognitively demanding task designed to induce mental fatigue, then ride a bike to exhaustion at 80% of their maximum power.

The result is clear: performance drops. Time to exhaustion is shorter.

The striking part is that the standard physiological responses measured during exercise (heart rate, ventilation, gas exchange) show no major difference between conditions. What does change is perceived exertion: RPE rises faster, and the subject reaches maximal perceived effort earlier (Marcora et al., 2009).

These findings have since been confirmed and synthesized in several reviews converging on the same interpretation: mental fatigue does not directly impair peripheral physiological capacity, but increases the perceived cost of effort, reducing tolerance (Pageaux & Lepers, 2016; Van Cutsem et al., 2017).

This shows that fatigue cannot be reduced to a question of muscles or energy stores alone. It also depends on the perception of effort, on tolerance to perceived cost, and on the regulatory mechanisms involved.

What I take away for endurance

I clearly do not see the central governor theory as a definitive explanation.

It has been criticized, supplemented by other models, notably the psychobiological model of fatigue, which places more emphasis on conscious perception of effort and motivation.

But it has one essential merit: it forces us to take the role of subjective experience seriously in effort management. This seems obvious today, since we are used to answering “How was your session?” and giving an RPE between 1 and 10. But this practice is a direct consequence of the research carried out by Noakes, Foster, and many others.

In trail running (and in all endurance sports, really), lasting a long time is not about ignoring fatigue. It is more about negotiating with it, interpreting the signals correctly, and maintaining a form of lucidity when the effort becomes costly.

To wrap up

So, this central governor?

The theory suggests that not everything is “in the head.” But feeling “done” does not necessarily mean being depleted. It more likely means that the effort has reached a threshold of perceptual tolerance.

This threshold is neither magical nor universal. It depends on context, on experience, on the attention you pay to the effort, on your mental state at the time.

From there, one question becomes hard to avoid: is it possible to push this threshold back?

And if so, what exactly are we talking about when we say “push back”? Better tolerate discomfort? Better interpret the signals? Better regulate the effort? Something else entirely?

These are the questions I want to explore in upcoming articles. Not to convince myself that I can always go further, but to understand under which conditions this limit moves, and under which conditions maybe it should not.

References

Clicking on the DOI links should take you directly to the paper.

  • Borg, G. (1970). Perceived exertion as an indicator of somatic stress. Scandinavian Journal of Rehabilitation Medicine, 2(2), 92-98.
  • Noakes, T. D. (2000). Physiological models to understand exercise fatigue and the adaptations that predict or enhance athletic performance. Scand. J. Med. Sci. Sports, 10(3), 123-145. DOI: 10.1034/j.1600-0838.2000.010003123.x
  • Noakes, T. D. (2012). Fatigue is a brain-derived emotion that regulates the exercise behavior to ensure the protection of whole body homeostasis. Frontiers in Physiology, 3:82. DOI: 10.3389/fphys.2012.00082
  • Abbiss, C. R., & Laursen, P. B. (2005). Models to explain fatigue during prolonged endurance cycling. Sports Medicine, 35(10), 865-898. DOI: 10.2165/00007256-200535100-00004
  • Marcora, S. M., Staiano, W., & Manning, V. (2009). Mental fatigue impairs physical performance in humans. J. Appl. Physiol., 106(3), 857-864. DOI: 10.1152/japplphysiol.91324.2008
  • Pageaux, B., & Lepers, R. (2016). Fatigue induced by physical and mental exertion increases perception of effort and impairs subsequent endurance performance. Frontiers in Physiology, 7, 587. DOI: 10.3389/fphys.2016.00587
  • Van Cutsem, J., Marcora, S., De Pauw, K., et al. (2017). The effects of mental fatigue on physical performance: A systematic review. Sports Medicine, 47(8), 1569-1588. DOI: 10.1007/s40279-017-0692-2
  • Gandevia, S. C. (2001). Spinal and supraspinal factors in human muscle fatigue. Physiological Reviews, 81(4), 1725-1789. DOI: 10.1152/physrev.00015.2001
  • Enoka, R. M., & Duchateau, J. (2016). Translating fatigue to human performance. Medicine and Science in Sports and Exercise, 48(11), 2228-2238. DOI: 10.1249/MSS.0000000000000929

Disclaimer: I am a research engineer, not a sports physiologist. What you read here is the logbook of a curious trail runner who enjoys digging into the science behind his data. Not a lecture, not medical advice. The references are there so you can check for yourself.