Exercise Helps After MI, If You Stick To It
By Kristina Fiore, Staff Writer, MedPage Today
Published: March 16, 2009
Reviewed by Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine.
§ Explain to interested patients that aerobic exercise and resistance training improved endothelial function in myocardial infarction patients, but benefits disappeared a month after exercise was stopped.
MONTREUX, Switzerland, March 16 -- All types of exercise improve blood vessel function after myocardial infarction, but benefits disappear after patients stop training, researchers here said.
Flow-mediated dilation significantly increased in patients who did aerobic exercise, resistance training, or a combination of both, compared with those who did no exercise at all.
But after a month without any physical activity, endothelial function returned to baseline levels, Margherita Vona, M.D., of Clinique Valmont-Genolier, and colleagues reported in Circulation: Journal of the American Heart Association.
"Our data confirm that one month of detraining is sufficient for both resistance and aerobic training to lose all positive effects on endothelial function," the researchers said. "These data imply that good, long-term adherence to training programs is necessary to maintain vascular benefits on endothelial dysfunction."
Exercise training for patients with coronary artery disease is generally thought to improve endothelial function, although controversy exists over the type and level of exercise that's most beneficial.
So the researchers conducted a controlled trial of 209 patients referred to a cardiac rehabilitation program after MI between March 31, 2003, and March 31, 2005.
The participants were randomized to aerobic training, resistance training, both combined, or no exercise for four weeks.
Flow-mediated dilation significantly improved in those who participated in all three exercise regimes (P<0.01). It also improved in patients who did not exercise, but to a much lesser extent (P<0.05).
At baseline, flow-mediated dilation was about 4%, but after exercise, it increased to about 10% in all three exercise groups, whereas in those who didn't exercise, it only increased to about 5%.
"These findings provide evidence of the important contribution of exercise to the improvement of endothelial function," the researchers said, noting that all three types of exercise appear to work.
"This should be an additional reason to encourage patients to carry out several types of physical activity to avoid exercise boredom and promote better long-term adherence to exercise programs," Dr. Vona said.
Patients who exercised also had a decrease in endothelial dysfunction as measured by the von Willebrand factor level. After exercise training the levels decreased by 16% (P=0.01) similarly in groups 1, 2, and 3 but remained unchanged in the control group, who did not exercise.
After a month of not exercising at all, flow-mediated dilation was significantly lower for those who exercised than it was at the end of the training period.
"Long-term adherence to training programs is necessary to maintain vascular benefits on endothelial function," Dr. Vona said.
The researchers aren't sure of the mechanism by which exercise improves endothelial function, but noted that it increases shear stress, which is a strong physiological stimulus for the release of nitric oxide.
"The mechanism is likely to involve a chronic increase in nitric oxide bioavailability mediated by an increase in the expression of nitric oxide synthase," the researchers said, "and by an increase in antioxidant enzymatic activity."
Primary source: Circulation: Journal of the American Heart Association
Vona M, et al "Effects of different types of exercise training followed by detraining on endothelium-dependent dilation in patients with recent myocardial infarction" Circulation 2009; DOI: 10.1161/CIRCULATIONAHA.108.821736.