Haram PM, Adams V, Kemi OJ, Brubakk AO, Hambrecht R, Ellingsen O, Wisloff U
Eur J Cardiovasc Prev Rehabil. 2006;13:585-591.
Background
Regular exercise training has emerged as a powerful tool to improve endothelium-dependent vasorelaxation. However, little is known about the magnitude of change and the permanence of exercise-induced adaptations in endothelial function.
Design.
Rats were randomized to either 6 weeks of regular exercise or 1 bout of exercise. Rats were then killed 0, 6, 12, 24, 48, 96, or 192 hours postexercise, and vascular responsiveness to acetylcholine was determined.
Methods.
Endothelium-dependent dilation was assessed by exposure to accumulating doses of acetylcholine in ring segments of the abdominal aorta from female Sprague-Dawley rats that either exercised regularly for 6 weeks or performed a single bout of exercise.
Results.
A single exercise session improved endothelium-dependent vasodilatation for approximately 48 hours. Six weeks of regular exercise induced a significantly larger improvement that lasted for approximately 192 hours. Sensitivity to acetylcholine was 2-fold higher in chronically trained animals than in those exposed to a single bout of exercise. The decay after a single bout of exercise was approximately 8-fold faster than that after 6 weeks of training.
Conclusion.
The present data extend our concept of exercise-induced adaptation of endothelium-dependent vasodilatation in 2 regards: (1) a single bout of exercise improves endothelium-dependent dilation for approximately 2 days, with peak effect after 12 to 24 hours, and (2) regular exercise further improves adaptation and increases the sensitivity to acetylcholine approximately 4-fold, which slowly returns to sedentary levels within a week of detraining.
Comment.
Although this is an animal study, this information begins to clarify our notion of the time course of training adaptations. The chronic changes that we often attribute to exercise training over many weeks to months of exercise may, in fact, often be changes that occur subsequent to single exercise sessions. These changes are termed "subacute" (an uncommon term in the literature) effects of exercise-that is, they occur subsequent to a single bout of exercise. It seems as though these effects may have great importance in the prevention of coronary artery disease and other chronic diseases. This study examines both single bouts of relatively high intensity (80-90% Max VO2) exercise and endurance training. Endothelial function was improved for 24 to 48 hours after a single bout and also improved after chronic exercise training of 6 weeks. This provides further support for both the importance of these subacute effects of exercise and for daily exercise and activity as a preventive measure for coronary artery disease and chronic disease.
JR