Book Summary: Endure by Alex Hutchinson

A book summary of the key lessons from Endure: Mind, Body and the Curiously Elastic Limits of Human Performance by Alex Hutchinson, along with informal notes and quotations.

The Book in a Nutshell

The book explores the long-running endurance debate, which has taken us from a physiological understanding towards a new frontier of psychological research. Hutchinson presents a detailed account of the research, putting forward the view that we can train our brains as well as our bodies to improve our endurance levels.

Book Summary: The Key Lessons

#1: Endurance is psychobiological. The psychology and physiology of endurance are inextricably linked. Tasks that last more than a dozen or so seconds inevitably require conscious and unconscious decisions about when to push and when not to.

#2: The law of perceived effort. According to Samuele Marcora’s psychobiological theory, perceived effort is the final arbiter for what goes on in the rest of the body. Physical cues, like dehydration and tired muscles, contribute to this perceived effort along with a wide range of psychological factors.

#3: Brain training and brain doping. Brain training, such as exercises to induce mental fatigue and mindfulness, may enhance performance by altering the brain’s perception of effort.

#4: No pain, no gain. Endurance athletes tend to have a higher pain threshold, which can be trained through regular high-intensity workouts.

#5: Myths and misconceptions on water and fuel. Thirst, not dehydration, increases your sense of perceived effort and causes you to slow down.

Book Notes: The Key Lessons in Detail

The below book notes outline the key lessons I took away from reading Endure in more detail. These notes by no means provide complete coverage of the wide-ranging breadth of research in the book. They are instead intended to consolidate the key ideas and serve as an introduction to decide whether the full book is worth further attention.

Lesson #1: Endurance is psychobiological

For many years, academics studied endurance in the context of our physiology. Early studies progressed towards an understanding of VO2 max (or maximum oxygen uptake) and lactate threshold as physical gauges of endurance.

But physiologists have found that the will to endure can’t reliably be tied to any single physiological variable. Instead, endurance seems to be a more complex function of physiological and psychological factors.

The fact that so few die from overexertion tells us that the brain plays a critical regulatory role.

“Knowing (or believing) that your ultimate limits are all in your head doesn’t make them any less real in the heat of a race. And it doesn’t mean you can simply decide to change them.”

Bottom line: the psychology and physiology of endurance are inextricably linked. Tasks that last more than a dozen or so seconds require conscious and unconscious decisions about when to push and when not to.

Lesson #2: The law of perceived effort

In the late 1990s, Tim Noakes put forward a new perspective, which continues to be the subject of much debate. Its basic premise is that the brain alone sets and enforces the physical limits we encounter in endurance activities. In short, the brain is seen to act as a “central governor”.

The “central governor” theory has two key assumptions:

  1. The limits we confront in exercise are imposed in advance by our brains (known as anticipatory regulation).
  2. The brain imposes these limits by controlling how much muscle is used at different effort levels.

The so-called “end sprints” of athletes and their pacing patterns seem to add some weight to this idea. Developmental psychology studies even show that our pacing patterns change with age, where we are more likely to anticipate our energy needs.

An alternative perspective is Samuele Marcora’s “psychobiological model”. This theory takes a similar but subtly different view: that perceived effort is the final arbiter for what goes on in the rest of the body. All the usual physical cues, like dehydration and tired muscles, contribute to this perceived effort (or “effort dial”) along with a wide range of psychological factors.

Marcora’s perspective appears to be supported by studies that have shown that participants who completed mental exercises before physical exercise had lower physical endurance. In other words, their perceived effort increased and their endurance decreased. A similar argument can be made for incentives, which have been shown to affect endurance on time-to-exertion studies.

Lesson #3: Brain training and brain doping

The implied conclusion from these theories:

“Anything that moves the “effort dial” in your head up or down will affect your endurance, even if it has no effect on your muscles or heart or VO2 max.”

If this perspective is correct, the question turns to whether training the brain could improve physical endurance.

One key research area looks at how we might acclimatise the brain to mental fatigue and therefore reduce perceived effort. Initial research shows promise for endurance athletes and even soldiers.

Another important area is reaction to negative stimuli. Mindfulness programmes offer some promise in improving response to negative stimuli and, in turn, performance. Similarly, positive self-talk has been shown to favourably impact endurance.

“Just like a smile of a frown, the words in your head have the power to influence the very feelings they’re supposed to reflect.”

Some researchers are taking this even further. One of the most intriguing techniques literally targets specific brain regions with a small electric current. Transcranial direct current stimulation (tDCS) alters the sensitivity of neurons after 10-20 minutes of exposure in a targeted region.

Research has shown such techniques to have a real effect in learning, depression and fighting addiction. While the research on the effects on physical endurance is more mixed, the field raises the real possibility of a “brain doping” debate in sport.

Lesson #4: No pain, no gain

Research also suggests that endurance athletes tend to have a higher pain threshold. What’s more, regular physical training, especially high-intensity workouts, increase pain tolerance.

“Simply getting fit doesn’t magically increase your pain tolerance; how you get fit matters: you have to suffer.”

Interestingly, removing pain doesn’t seem to have the dramatic effects on endurance that one might expect. In studies, participants given pain-eliminating drugs like Fentanyl tended to be incapable of pacing themselves, starting overzealously and facing the physical toll as muscle overrode mind later.

Temperature can also inhibit or enhance endurance. When exposed to hot conditions for high-intensity exercise, it typically takes 2 weeks for our bodies to adapt. Researchers have found that reducing body heat (e.g. by drinking a cold drink) may increase endurance.

But it’s also a question of perception. One study found that rigging a thermometer to display a falsely low temperature was associated with faster speeds of cyclists in a heat chamber.

As Hutchinson notes, in reality, most of us self-adjust performance long before the dangerous effects of heat kick in:

“Heat doesn’t act like a light switch that flicks your muscles off; in most real-world situations, it’s a dimmer switch, controlled by the brain for your own protection.”

Trained athletes seem to push further toward their heat limit, but motivational self-talk can also increase these limits.

Lesson #5: Myths and misconceptions on water and fuel

While the dangers of severe dehydration are well-established, results of endurance races tend to be the opposite of what you might expect: the fastest finishers tend to be the most dehydrated.

To understand this, we need to understand the mechanisms of thirst.

Contrary to popular belief, our bodies don’t monitor fluid levels; they monitor “plasma osmolality”, which is the concentration of electrolytes in the blood. We should therefore draw a distinction between dehydration and thirst and voluntary dehydration.

In fact, studies have found that switching the focus to avoiding thirst, rather than avoiding dehydration, is an important strategy for higher performance.

Perception of quenching thirst also plays a critical role. Studies have shown that the mere act of swallowing fluids can fight thirst and improve performance, even if these are negligible quantities.

“Thirst, not dehydration, increases your sense of perceived effort and in turn causes you to slow down.”

As for food, there has been a considerable amount of debate around fat-based and carbohydrate-based diets for endurance, but the truth is somewhere between and context dependent.

Carbohydrates tend to dominate in intense exercise, with glycogen in our muscles being a good predictor of muscular endurance. Meanwhile, high-fat diets seem to increase our bodies’ ability to burn fat but stunt our bodies’ ability to use carbohydrates.

“Given the complementary strengths and weaknesses of the two options – carbohydrate as a fast fuel with limited storage capability, fat as an inexhaustible but rate-limited alternative – it makes sense to aim to maximise both fuel pathways.”

Again, perception also seems to play an important role. Research has found that a mere swish of a sports drink can impact performance, without it actually entering the bloodstream.

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