The effect of swimming on patients with ischemic heart disease.

Swimming is frequently recommended for cardiac rehabilitation, but little is known of its physiologic consequences in ischemic heart disease. Eight males who had had a myocardial infarction 8-17 months before the study were exercised to exhaustion or angina with 10 W/min-1 ramp on a cycle ergometer in sitting and supine positions. Oxygen uptake (VO2) was continuously measured to monitor the physiologic power requirement. All eight patients were taking beta blockers and four were taking digoxin. During sitting cycling, angina occurred in four and ST depression in five; during supine cycling, angina occurred in five and ST depression in six. VO2 was then measured while they swam at their own comfortable speed (mean 0.43 m/sec-1) in a swimming flume at water temperatures of 25.5 degrees C and 18 degrees C. In six, the water speed was gradually increased until they were limited by symptoms. Comfortable swimming at 25.5 degrees C was 87% (1.28 1/min-1) and at 18 degrees C 89% (1.30 1/min-1) of sitting peak VO2, while heart rates were 92% and 91% respectively. The mean peak VO2 and heart rate did not differ significantly between bicycle and swim tests (peak VO2 sitting 1.49 +/- 0.23, supine 1.42 +/- 0.24, 25.5 degrees C 1.60 +/- 0.17, 18 degrees C 1.52 +/- 0.19 1/min-1). Only two patients reported angina while swimming in warm water and one in cold water, although ST depression occurred in six in both swims. The subjective comfort and large muscle groups involved make swimming a good exercise, but the high relative energy cost and failure to identify ischemic symptoms indicate caution in cardiac patients, especially if their swimming skills are poor.