Two swims (1993 and 1994) are described which led to post-swim orthostatic intolerance and one episode of syncope in a 50/51-yr-old well-trained and experienced marathon swimmer. The swims of 33 km and 38 km took 12 h 30 s and 17 h 35 min, respectively. Water temperature in each swim was above 23 degrees C and rectal core-temperature stayed above 37.0 degrees C. Air temperatures differed, ranging from 23 degrees to 37 degrees C and 15 degrees to 21 degrees C, respectively. Regular fluid consumption totalled approximately 5.0 and 6.0 1, respectively. Fifteen minutes after completing the 1993 swim, the swimmer experienced orthostatic intolerance and fainted at the lakeside; hospital tests revealed an elevated creatine phosphokinase (CK) of 521 U.l-1. The 1994 swim was abandoned due to severe muscle cramps and CK was found to be markedly elevated at 909 U.l-1. Orthostatic intolerance was recorded in both cases; however, no cardiac abnormalities were found. After overnight rest and intravenous saline infusions of 3.0 and 1.5 l, respectively, the orthostatic intolerance was relieved. Based on previous descriptions of exercise-associated collapse in marathon runners, the swimmer's orthostatic intolerance and syncope are attributed to blood pooling in his legs due to inactivation of the venous muscle pump on completion of the swim.
