Time-course of changes in cardiac function during recovery after acute exercise.

Exercise-induced cardiac dysfunction (EICD) has been observed immediately following exhaustive exercise in trained individuals, but limited and conflicting data are available regarding EICD in a previously untrained population days after an exhaustive exercise bout. The purpose of this study was to examine the effects of a single bout of acute exercise on cardiac function during the 72 h after exercise and identify potential contributing mechanisms. After completing an acute exercise bout on a motorized treadmill (25 m/min, 5% grade, 60 min), rats were sacrificed immediately, 24 h, 48 h, or 72 h after the exercise bout. At the scheduled time of sacrifice, hearts were isolated and perfused for determination of ex vivo cardiac function, and examined for malondialdehyde (MDA), a lipid peroxidation index, and antioxidant potential (AOP). During the 48 h post exercise, left ventricular developed pressure decreased by 30%, dP/dtmax declined by 37%, and dP/dtmin showed a 34% decrease (p<0.05). By 72 h, cardiac function had returned to control levels. MDA was increased immediately after the exercise bout and at the 24 and 48 h intervals (p<0.05). Conversely, AOP progressively decreased at the 24 and 48 h intervals. As with cardiac function, MDA and AOP had returned to control levels by 72 h post-exercise. These data indicate that a single bout of prolonged, moderately intense exercise performed by previously sedentary rats impaired cardiac function for up to 48 h. This decrement in cardiac function was associated with increased lipid peroxidation and decreased antioxidant potential.