High-Intensity Exercise Better At Improving Metabolic Syndrome

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In a small study, short, vigorous exercise appeared to reduce metabolic risk factors better than longer spells of moderate intensity exercise according to a report in Circulation: Journal of the American Heart Association.

Forty-six percent of metabolic syndrome patients who participated in a 4-month, intense aerobic interval training (AIT) program had fewer metabolic syndrome risk factors compared to 37 percent of patients following a moderate training plan.

Metabolic syndrome — estimated to affect 24 percent of the U.S. adult population — is a clustering of metabolic risk factors that increase your vulnerability to coronary heart disease, stroke, peripheral vascular diseases and other diseases related to plaque build-ups in artery walls. As defined by the World Health Organization, the risk factors include type 2 diabetes, obesity (body-mass index of 30 or greater), abdominal obesity, high triglycerides, low high-density lipoprotein (HDL) cholesterol, high blood pressure, insulin resistance, glucose intolerance and microalbuminuria.

To determine what kind of exercise works best against the metabolic syndrome, researchers divided 32 patients (average age 52) into three groups. One group used a high-intensity aerobic-interval training for four months. Another used a less-intense regimen called “moderate continuous-training” (CME). Another did not exercise.

“The current study suggests that exercise in general and AIT in particular is partly or fully able to reverse metabolic syndrome, suggesting that this may be a promising treatment strategy,” said Arnt Erik Tjonna, M.Sc., lead author of the study and a doctoral candidate in clinical medicine at the Norwegian University of Science and Technology in Trondheim, Norway. “Guidelines calling for 30 minutes of exercise of moderate intensity may be too general for this population.”

Patients in both exercise groups lost roughly the same weight and waist circumference. Thus, AIT’s ability to cause patients’ hearts to beat faster — and thus absorb and use oxygen — seems to be why patients in this group became healthier than those in the CME group, researchers said.

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Patients in the AIT group increased their ability to absorb oxygen by 35 percent, while those in the CME increased their ability to absorb oxygen by only 16 percent.

“To get good results in maximal oxygen intake, we have to train the heart, because the heart’s pumping capacity seems to be the limiting factor when we talk about maximal oxygen intake in these patients,” Tjonna said. “AIT trained the heart muscles the most and made them pump more oxygen.”

This group also outperform the CME group in several other key measures, including endothelial function, blood pressure, insulin sensitivity, fasting glucose, HDL cholesterol and mitochondrial biogenesis (the ability of cells to produce fuel for work).

Given the small number of patients studied, a larger study is needed before formally changing guidelines about how to manage the metabolic syndrome through exercise, he said.

The American Heart Association and other health organizations recommend that patients with the metabolic syndrome undertake moderate-intensity physical activity, at least 30 minutes on most days of the week. But this study challenges those recommendations.

Barry Franklin, Ph.D., an American Heart Association spokesperson and an author of the association’s physical activity guidelines, noted that several recent epidemiological and clinical studies now suggest that if the total energy expenditure of exercise is held constant, exercise performed at a vigorous intensity appears to convey greater cardioprotective benefits than exercise of a moderate intensity.

“However, these added benefits must be weighed against the potential for increased musculoskeletal and cardiovascular complications as well as reduced compliance,” said Franklin, co- and director of the William Beaumont Hospital Cardiac Rehab and Exercise Laboratories in Royal Oak, Michigan. “Accordingly, when previously sedentary individuals can comfortably exercise at a moderate intensity, they should consider the goal of more vigorous exercise, provided that it is sustainable and can be achieved without adverse signs or symptoms.”

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