An exercise with oxygen therapy (EWOT) apparatus for rejuvenating oxygen- depleted cell tissue and simulating high altitude oxygen conditions. The EWOT apparatus includes a first cylindrical bladder for providing oxygen -enriched air and a second bladder for providing lower-purity hypoxic air. The first bladder is retained within an open, lightweight rectangular-shaped frame having vertical frame members. An air supply source provides the oxygen-enriched and hypoxic air to the first and second bladders, respectively. A control switch, which can be manually and/or programmed to automatically operate, selectively delivers the oxygen-enriched and/or hypoxic air to a breathing mask worn by a user while exercising on exercise equipment. The first bladder includes a plurality of weights which provide a positive pressure to the air therein. The cylindrical first bladder is attached to the vertical frame members with slidable rings and expands and collapses in a vertical direction when being filled or during use, respectively.