Sherpas scale Everest using 'superhuman' energy efficiency

Nepalese mountain guides or Sherpas are extremely efficient at producing energy to power their bodies when oxygen is scarce, making them "superhuman" mountain climbers of the Himalayas, new study suggests.
The findings could help develop new ways of treating hypoxia or lack of oxygen in patients, researchers said.
"Sherpas have spent thousands of years living at high altitudes, so it should be unsurprising that they have adapted to become more efficient at using oxygen and generating energy," said Andrew Murray from the University of Cambridge in the UK.
"When those of us from lower-lying countries spend time at high altitude, our bodies adapt to some extent to become more 'Sherpa-like', but we are no match for their efficiency," said Murray.

Mountain climbers are often exposed to low levels of oxygen, particularly at high altitudes.
Scientists have known for some time that people have different responses to high altitudes.

While most climbers require additional oxygen to scale Mount Everest, whose peak is 8,848 metres above sea level, a handful of climbers have managed to do so without.
Sherpas, an ethnic group from the mountain regions of Nepal, are able to live at high altitude with no apparent consequences to their health.
As a result, many act as guides to support expeditions in the Himalayas, and two Sherpas are known to have reached the summit of Everest an incredible 21 times.

Previous studies have suggested differences between Sherpas and people living in non-high altitude areas, known collectively as 'lowlanders', including fewer red blood cells in Sherpas at altitude, but higher levels of nitric oxide, a chemical that opens up blood vessels and keeps blood flowing.
Evidence suggests that the first humans were present on the Tibetan Plateau around 30,000 years ago, with the first permanent settlers appearing between 6,000-9,000 years ago.
This raises the possibility that they have evolved to adapt to the extreme environment, researchers said.
"Sherpas have evolved to become superhuman mountain climbers, extremely efficient at producing the energy to power their bodies even when oxygen is scarce," researchers wrote in the study published in the journal PNAS.

This is supported by recent DNA studies, which have found clear genetic differences between Sherpa and Tibetan populations on the one hand and lowlanders on the other.
Some of these differences were in their mitochondrial DNA - the genetic code that programmes mitochondria, the body's 'batteries' that generate our energy, researchers said.
To understand the biological differences between the Sherpas and lowlanders, researchers followed two groups as they made a gradual ascent up to Everest Base Camp at an elevation of 5,300 metres.
The lowlanders group comprised 10 investigators selected to operate the Everest Base Camp laboratory.
They took samples, including blood and muscle biopsies, in London to give a baseline measurement, then again when they first arrived at Base Camp and a third time after two months at Base Camp.

These samples were compared with those taken from 15 Sherpas, all of whom were living in relatively low-lying areas, rather than being the 'elite' high altitude climbers.
The Sherpas' baseline measurements were taken at Kathmandu, Nepal.
The researchers found that even at baseline, the Sherpas' mitochondria were more efficient at using oxygen to produce ATP, the energy that powers our bodies.
As predicted from genetic differences, they also found lower levels of fat oxidation in the Sherpas.
"Although lack of oxygen might be viewed as an occupational hazard for mountain climbers, for people in intensive care units it can be life threatening," said Professor Mike Grocott, from the University of Southampton.

"By understanding how Sherpas are able to survive with low levels of oxygen, we can get clues to help us identify those at greatest risk in ICUs and inform the development of better treatments to help in their recovery," Grocott said.