Editor,—Rinaldi et alperformed an important study, demonstrating for the first time in patients with coronary disease that protection against postexercise “stunning” occurs in association with the warm-up effect when exercise tests are separated by 30 minutes.1 Cumulative stunning occurs when tests are separated by 60 minutes. Moreover, previous reports have failed to demonstrate persistent impairment ofglobal left ventricular function, even using radionuclide ventriculography.2 The study illustrates the difficulty of applying concepts defined in highly instrumented animal preparations to a rather less controllable human model. The warm-up effect in angina is a complex phenomenon and probably represents an interplay of protective mechanisms including a short term training effect and improved myocardial perfusion via collaterals, …