Why humans are optimised for endurance running, not speed

Other animals have us beat over short distances, but in an interspecies Olympic ultramarathon, Homo sapiens would likely take all the medals

Roger Bannister hits the tape to become the first person to run a sub-four-minute mile, on 6 May 1954 in Oxford, England.

Roger Bannister’s four-minute mile, while a remarkable human milestone, is noteworthy from a comparative physiology standpoint only for its mediocrity. A seminal paper by AV Hill on biomechanics illustrates the point with a table of maximum speeds across the animal kingdom – humans are outperformed by almost every animal on the list, including the wild donkey, the ostrich and the elephant. We just about beat the black rhinoceros, while the cheetah would complete the mile in about a minute.

Carrying on past the mile and further still, past the marathon, we begin to fare a little better in comparative terms only when we enter the realm of the ultramarathon. The UltraTrail du Mont Blanc (UTMB) is perhaps the most iconic trail race in the world, winding 166km around the Mont Blanc massif, taking in more than an Everest’s worth of cumulative climbing as it rises over Alpine passes on its way from Chamonix in France to Switzerland, down into Italy and back to the finish line in Chamonix. In 2017, 29 runners completed the course in under 24 hours. If there were ever an interspecies Olympic games with a UTMB-like event, Homo sapiens would likely take all the medals.

Moving further along the spectrum, a recent paper in the journal Frontiers in Physiology studied athletes in a 690km foot race in Alaska – the Yukon Arctic Ultra, or YAU. The key findings from this remarkable race relate to the sympathetic and parasympathetic wings of the nervous system, which are, in a sense, mirror images of each other. In a relaxed state, parasympathetic (or vagal) tone dominates, while conversely, a state of emergency activates sympathetic pathways, causing heart rate to increase and blood to be diverted from the gut to skeletal muscles. The two systems are usually in balance, although it’s hardly surprising that YAU athletes experienced increased sympathetic drive even before the beginning of their race.

A woman trail-runs in the mountains above Chamonix, France.
A woman trail-runs in the mountains above Chamonix, France. Photograph: Alamy

Once underway, however, it was the balance between the two systems that distinguished finishers from nonfinishers. Even at the first checkpoint (kilometre 277), loss of vagal tone, as recorded by analysis of electrocardiogram data, was greater in nonfinishers. Clearly, stress levels were high in both groups, but finishers were better able to claw back a degree of parasympathetic control. Vagal tone was even found to start on a trajectory towards recovery before the end of the race in the case of finishers. Overall, a recovery of vagal tone, however partial, was vital for allowing the body just enough physiological relaxation to get through the 268 hours that were needed, on average, to complete the course.

In terms of the biomechanics of survival, different species have undergone different selection pressures. Fatigue-resistant, slow-twitch muscle fibres are inherently more economical than fast-twitch muscle fibres. Many studies point to our origins as a persistence hunter: unable to outsprint a deer, but capable of pursuing it for one or two days until the animal collapses from exhaustion, just as the Tarahumara Indians in Mexico still do. A recent paper in the journal Nature notes that the distribution of fast versus slow muscle fibres in different animals reflects opposing pressures in an evolutionary arms race. On the one hand there is a need for speed and fast-twitch muscles, to avoid a sprinting cheetah; on the other, there is a need for endurance and slow-twitch muscles, to engage in persistence hunting. All this has a knock-on effect on brain evolution, as the hazards of hunting (such as the risk of dehydration and increased exposure to sun as well as to other predators) provide strong selection pressure for increased intelligence, group cooperation and precise communication.

But biomechanics isn’t everything. Before Reinhold Messner climbed Everest without bottled oxygen in 1978, most physiologists believed his project was not only doomed to failure but also potentially lethal. When he proved the medics wrong, they reasoned that his feat was likely explained by extraordinary physiology. They were particularly interested in studying his VO2 max, which is a measure of maximal aerobic capacity, measured in millilitres of oxygen used in one minute per kilogram of body weight (ml/kg/min). Publishing their work in the Journal of Applied Physiology, researchers found that Messner had “rather normal” physiological features. His VO2 max was 49 ml/kg/min, a distinctly underwhelming value – Marit Bjørgen, the Norwegian skier and winner of the most medals at the 2018 Winter Olympics, recorded a VO2 max of 72. It is striking however that the authors felt it necessary to add that Messner was characterised by “an obsessive need to be the first and the best”.

Psychology inevitably weaves through physiology. An increasing number of studies are looking at the ways athletes transition from states of mental and physical depletion through to states of perseverance and even euphoria. One hypothesis that has been proposed to account for altered states of consciousness such as the timelessness and peacefulness frequently reported in endurance sports is “transient hypofrontality”. Extreme movement requires enormous amounts of neural computation.

Why are Kenyans the best distance runners?

This is best exemplified by the fact that while AI conquered the world of chess quite some time ago, it is a long way from creating a two-legged robot that might compete with a human at a hundred-mile mountain race. The list of brain structures needed for running is impressively long; it includes the primary and secondary motor cortices, the basal ganglia, the motor thalamus and the cerebellum, to name just a few. Facing such a computational load, the transient hypofrontality hypothesis proposes that the brain shifts finite resources away from nonessential areas as it prioritises motor function. The prefrontal cortex, our centre of high-level analytical thinking, is placed, not quite offline, but into a state of hypoactivity. Both depression and obsessive-compulsive disorder [11] have been shown to be linked with hyperactivity in the prefrontal cortex. Might it be possible that the “high” of endurance sports comes partly from disconnecting or zooming out from processes that dissect and analyse the world in fine detail, and in some cases too-fine detail? This levelling out of emotional and conceptual thinking was noted by Friedrich Nietzsche, who was hardly renowned for his athletic ability but astute nonetheless in his observation that “a few hours mountain climbing make of a rogue and a saint two fairly equal creatures”.

Tendai Buddhists have perhaps taken endurance to its ultimate conclusion with the practice of kaihogyo, which incorporates 1,000 days of marathons on a route around Mount Hiei in Japan. The 46 monks who have completed this ritual in the modern era are thought to have reached enlightenment. As for motivation, traditionally, kaihogyo practitioners are pledged to kill themselves if they are not able to finish the course, which is why they are obliged to carry a hemp rope and a dagger as they go about their practice.


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