Fig 1. Altitude ascent profile of participants from plain to plateau.

All subjects ascended to 3700 m (Lhasa in Tibet) in 2.5 hours by plane from 500 m (Chengdu in Sichuan province). After they acclimatized at 3700 m for a week, the subjects traveled by motorcar and arrived in Yangbajing (in Tibet, at 4400 m) within 3 hours; they in Yangbajing for 7 days. For all participants, the starting data collection point was in Chengdu (500 m), the second data collection point was in Lhasa (3700 m) within 24 h of arrival, and the third data collection was on the 7^th day in Yangbajing (4400 m).