'We found approximately six to 10 percent more aerobic muscle fibres in bar-headed geese compared to low altitude birds. There were also more capillaries -- the body's smallest blood vessels -- surrounding these fibres in bar-headed geese,' said Scott.

He said they also found that the geese's mitochondria -- the cell's power sources -- are distributed closer to the cell membrane and therefore closer to capillaries.

'These traits allow oxygen to be carried and diffused more effectively to the flight muscles,' said Scott, who has previously found that bar-headed geese are fine-tuned for flying high as they breathe more when oxygen is scarce than most other animals do.

The study, which has been published in 'Proceedings of the Royal Society B: Biological Sciences' this week, will allow scientists to better understand the limitations of human physiology and find ways to exceed them, the university statement said.