Postexercise Peril

To the Editor.— Dimsdale et al attempt to make a quantum leap between the laboratory and the real world with little supporting evidence. They demonstrate approximately a 50% increase in norepinephrine levels and less than 30% increase in epinephrine levels from peak effort to the immediate postexercise period in ten healthy men. They suggest that these elevations provide "a possible mechanism for the increased risk of cardiac arrhythmias and ischemia during the cool-down period after strenuous exercise." Although the ECG was apparently monitored throughout the test, no mention of ectopic activity prevalence or time of occurrence is given—the crucial data needed to test their hypothesis. In a prior study from one of the authors, ventricular ectopic beats occurred 2.5 times more frequently during exercise than during recovery in a large sample of apparently normal subjects.¹ This is the same reference given to support the statement that serious cardiac events