Thoughts on the curiously elastic limits of performance

By Konstantinos Apostolou

I’m approaching the finish line when, just 30 seconds before crossing, I hear the race staff saying on the handheld radio: “The third is coming.” Only in the last 50 metres do I realise that I’m on the podium.

I’m crossing the finish line. My girlfriend is waiting for me there. She grabs me by the head, staring at me with wide eyes. “Wow, baby. I didn’t know you were that good.”

I smile, exhausted. “Neither do I.”

In the Foreword of Alex Hutchinson’s book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance, Malcolm Gladwell describes having a few mysteriously great races – performances far better than his training or past results should have allowed; performances which closely mirror the author’s experience. These incidents led both men to realise that expectations, perceptions and the brain’s interpretation of effort can both unlock and limit performance. Gladwell’s confusion becomes the question Hutchinson spends the book answering: Why can humans sometimes perform far beyond what their bodies “should” allow? This question stayed with me for days after my first-ever trail-running race, and this book was where I found some answers.

Endure is an exceptional book that explores what truly limits human endurance, showing that it isn’t just muscles, lungs, or oxygen, but the brain’s role in deciding when we stop. Blending science, storytelling, and sports history, Hutchinson examines pain, fatigue, heat, thirst, belief, and mental toughness to explain how mind and body interact to set (and sometimes stretch) our performance limits, suggesting that these limits are more flexible – and more mental – than we think.

The author problematises the traditional physiological, body-as-machine model, which treats the body as a mechanical engine constrained by hard limits such as VO2max (the maximum rate of oxygen consumption attainable during physical exertion), muscle fatigue, lactate buildup, fuel depletion, heat, and dehydration, and assumes that once these limits are reached, the system automatically fails, like an overheated motor.

In contrast, contemporary scholarship proposes a perception-based approach in which the brain acts as a regulator, treating physical responses as protective signals rather than failures. Thus, performance is also shaped by perceived effort, expectations, motivation, beliefs and context, as the brain continuously adjusts its output to prevent damage. Accordingly, quitting occurs before physical limits are reached because the brain decides the cost is too high.

Reading Endure helped me realise that my performance that day was not determined solely by my (above-average) VO2max, but also by my brain’s perception of effort, my expectations and my motivation.

Yet even with this insight, I found myself grappling with lingering questions: how do I pace myself when I don’t truly know my limits? My sore, lactate-filled legs and the HRV metrics from my Garmin fitness tracker in the days after the race were clear physical signals that my performance had been a stretch. But rather than providing guidance for future races, this effort left me even more puzzled. How should I pace myself next time? How can I know exactly how much effort to put in? How is it even possible to spend my fuel evenly across a course when I have no idea what the true capacity of my tank is?

In his novel Once a Runner, John L Parker Jr. accurately narrates how pacing is perceived by a runner: “A runner is a miser, spending the pennies of his energy with great stinginess, constantly wanting to know how much he has spent and how much longer he will be expected to pay. He wants to be broke at precisely the moment he no longer needs his coin.”

I had that on my mind before setting foot on the starting line of the Kambos Mountain Race on January 25. However, a rational evaluation of my running capital and an efficient strategy for spending my endurance currency proved impossible.

As the race began, I became captivated by chasing down the leading pack, and before I knew it, I was diving deep into the uncharted waters of my endurance. By the end of the first kilometre, I had passed three runners who clearly overestimated their abilities and were already gasping on the uphill. “What if I end up like them in the next couple of kilometres?” I thought. Nevertheless, I refused to be discouraged and kept pushing up the demanding uphill that spanned the opening four kilometres. The race covered an 11km course with 830 metres of elevation gain, half of which came in these opening kilometres. The route followed a scenic loop through pine forests and rocky hills before returning to Kambos village.

By the halfway point, I had passed four or five more runners and felt strong enough to chase a curly-haired runner about 100–200 metres ahead. I caught up to him and spent the rest of the course paced by this fellow runner, Fabien, a kind Frenchman I met along the way, with whom I exchanged company and encouragement.

With care and great sportsmanship, we alternated the lead: I let Fabien take the uphill, where his steady, rigorous ascent shone, and he gave me room to lead on the downhill, where my aggressive descent took over. Around the 8th kilometre, I asked how many runners were ahead. “Five or six,” he said light-heartedly. “OK,” I said to myself, “that’s it, stick with Fabien, you don’t have enough energy to chase them down, you cannot even see them.”.

But… “There he is,” Fabien told me, pointing surprisingly towards a guy a few metres ahead on a steep uphill. “Let’s go”.

My competitiveness flared, and I was fuelled by an urge to catch him. Approaching the 10th kilometre, the climb intensified – it was thankfully the final uphill challenge of the course. The runner ahead seemed drained. I passed him and asked how he was doing, but it seemed we didn’t share a common language. Nevertheless, I kept pushing, overcoming what seemed to be an endless uphill struggle.

I was finally into the last kilometre – a sweet, steep downhill. I was descending at a frenetic pace in an all-out effort to finish the race in the best possible time. I landed, spent, in a fig tree field at the entrance of the village. Yet, the exhausted runner I had just passed seemed reborn, somehow reclaiming the lead in these final moments. Perhaps he, too, was experiencing his breakthrough race day. I was nevertheless deeply satisfied. Crossing the line, I learned to my surprise that I had finished third (almost second). Fabien’s unintentional misinformation had left me with a podium finish I hadn’t expected – a perfect, unexpected reward.

Days later, I keep returning to the same question: Why did I push myself beyond what my body “should” have allowed? What motivated me to break through what I thought were my limits? Was it the innocent ignorance of a beginner in trail running races? The impulse of an inexperienced runner, driven forward by the pace of the leaders? Was it the goat I spotted on the way to the village – a lucky omen? Or the naively optimistic promise I made to my girlfriend before the race that I would be back in an hour and a half? (I made it in 1:29:07.)

Regardless, this race wasn’t just about testing my endurance and physical limits – it also came with stunning views, a new friend, blistered feet, delicious palouze, and a beautifully organised event I can’t wait to return to next year.