A 35-year-old, active duty Army officer presented for a screening physical exam before entering special training for HALO (High Altitude Low Opening) parachute qualification. This training involves jumping from aircraft at extreme altitudes with deployment of the parachute at relatively low altitudes (free fall). At the time of this evaluation he was assigned to a special operations airborne unit on active jump status. Careful review of his recent exercise history revealed a gradual decrease in endurance over the past several years, which he felt was due to decreased training intensity. His exercise consisted of running 3 to 4 miles four times a week and physical fitness training with his military unit three times a week. He continued to achieve high scores on the Army Physical Readiness Test.