Abstract: Isometric exercise(IE) is an essential component of daily living activities.Lack of IE may result in deconditioning of IE capacity.IE has not been used in cardiac rehabilitation because of poor understanding in cardiovascular response to IE and the Valsalva Maneuver associated with IE.Eingteen healthy young subjects aged 23.7 yrs on average was studied by administration of beta blocker and antagonist of opioids during IE.The result demonstrated that the regulation of cardiovasular response during IE is attributed to both sympathetic system and opioids activity.Twenty patients with coronary artery disease (CAD) were also studied during brief maximal IE,sustained maximal IE and dynamic exercise(DE).The patients included 13 cases with more than one vessel lesions and 7 post myocardial infarction and/or angina.Ten age matched apparent healthy subjects were examined as the control group.The result showed that IE without the Valsalva Maneuver in patients with CAD might increase coronary artery perfusion by enhancing diastolic pressure and prolonging diastolic period,which had no harmful effect on CAD.Hemodynamic responses and cardiac function were weaker during IE than DE.The intensity of the responses to IE was correlated to the central command but not to the absolute work load.It is concluded that significant release of endogenous opioids due to strong central command during IE,especially perceived maximal sustained IE,may help to attenuate activity of sympathetic system,thus reducing risk of exercise in patients with CAD.

Key words: Isometric exercise(IE), coronary artery disease(CAD), rehabilitation