Annually, thousands of air travellers visit high altitude destinations to enjoy hiking tours to attractions in surrounding areas. However, many of them are not adequately trained, not sufficiently acclimatized and/or may suffer from pre-existing diseases. To prevent adverse health effects and unpleasant experiences at high altitude, simple submaximal exercise testing at low altitude for the prediction of exercise tolerance at high altitude would be helpful. Therefore, 40 healthy males and females performed submaximal exercise tests at low (600 m) and high altitude (3500 m). We demonstrate that exercise tolerance during acute exposure to high altitude can be predicted by the individual heart rate response to submaximal exercise assessed at low altitude.