Nepalese Sherpas have a physiology that uses oxygen more efficiently than those used to the atmosphere at sea level.
This is the finding of a new study that investigated high-altitude adaptation in mountain populations.
The research involved taking muscle samples from mountaineers at 5,300m altitude and even putting them on an exercise bike at Mt Everest Base Camp.
The Sherpas owe this ability to an advantageous genetic mutation that gives them a unique metabolism.
It has long been a puzzle that Sherpas can cope with the low-oxygen atmosphere present high in the Himalayas far better than those visiting the region.
Mountaineers trekking to the area can adapt to the low oxygen by increasing the number of red cells in their blood, increasing its oxygen-carrying capacity.
In contrast, Sherpas actually have thinner blood, with less haemoglobin and a reduced capacity for oxygen (although this does have the advantage that the blood flows more easily and puts less strain on the heart).
“This shows that it’s not how much oxygen you’ve got, it’s what you do with it that counts,” concludes Cambridge University’s Prof Andrew Murray, the senior author on the new study.
“Sherpas are extraordinary performers, especially on the high Himalayan peaks. So, there’s something really unusual about their physiology,” he told the BBC World Service’s Science In Action programme.