Exercise and myocardial tolerance to ischaemia-reperfusion

It is well established that both short-term (1-5 days) and long-term (weeks to months) high intensity exercise (i.e. 70-75% VO_2max) provides cardioprotection against ischaemia-reperfusion injury. However, it is unclear if moderate intensity exercise will also provide cardioprotection. Aim: Therefore, these experiments compared the protective effects of moderate vs. high intensity exercise in providing defense against ischaemia-reperfusion injury. Methods: Male Sprague-Dawley rats were randomly assigned to one of three-experimental groups: (1) sedentary (control); (2) moderate intensity treadmill exercise (60 min day^-1 at ∼55% VO2_max); or (3) high intensity treadmill exercise (60 min day^-1 at ∼75% VO2_max). Hearts were exposed to 20 min of global ischaemia followed by 30 min reperfusion in an isolated working heart preparation. Results: Compared with sedentary rats, both moderate and high intensity exercised rats maintained a higher (P < 0.05) percentage of pre-ischaemia cardiac output and cardiac work (cardiac output x systolic blood pressure) during reperfusion. No differences in the percent recovery of cardiac output and heart work existed (P > 0.05) between the two exercise groups. Conclusions: These data reveal that both moderate and high intensity exercise training provide equivalent protection against ischaemia-reperfusion injury.