In low oxygen environments, such as altitude, some adults may become ill and suffer from acute mountain sickness. Further, all adults will find that exercising becomes much more difficult when compared with exercise at lower altitudes (e.g. sea-level). The purpose of this investigation is to study the effects of two drugs that may help people adjust to high-altitude quickly, prevent them from becoming ill and improve their exercise performance. The drugs are Methazolamide and Aminophylline.