Here's how altitude influences bone growth

  Washington D.C. [USA]: An international team of scientists has found that high altitude and the limited available energy can affect the growth of long bones in Himalayan populations.

High altitude is difficult as the terrain is physically challenging and most importantly, oxygen levels are lower which means that conversion of food into energy in an individual's body is not very easy and leads to relatively limited energy available for growth.

By measuring the limbs of people of similar ancestry from high altitude and low altitude regions, the team found that those living at high altitude had significantly shorter lower arm segments. However, compared to people living at low altitude, the length of the upper arm and hand were relatively the same.

According to lead author Stephanie Payne of the Department of Archaeology, University of Cambridge, "Our findings are really interesting as they show that the human body prioritises which segments to grow when there is limited energy available for growth, such as at high altitude."

He added, "This comes at the expense of other segments, for example, the lower arm. The body may prioritise full growth of the hand because it is essential for manual dexterity, whilst the length of the upper arm is particularly important for strength."

However, there are many challenges associated with conducting research at high altitude. In addition, to undertake the so-called 'most dangerous flight in the world' from Kathmandu to Lukla airport, a two-day trek at c. 3500m above sea level left Payne, a National Geographic young explorer, suffering from altitude sickness.

"We used Namche Bazaar on the Everest Trail as our base to conduct the study with the local population. It was an incredible experience with yaks carrying our anthropometric equipment through the mountain passes," said Payne.

Whilst this pattern of differential limb segment growth is interesting, scientists are still uncertain of the biological mechanism behind it.
The study is published in the journal Royal Society Open Science.