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Medium to Vigorous Exercise Improves Cardiac Function in Type 2 Diabetes

Posted: Wednesday, August 26, 2009

While an exercise program generally leads to improvements in metabolic function in patients with Type 2 diabetes, it only improves myocardial function when activity is at least moderate to vigorous, according to a new study.

Dr. Thomas H. Marwick, of the University of Queensland School of Medicine, Brisbane, Australia, and colleagues write, "Heart failure has an important association with Type 2 diabetes mellitus, although coronary artery disease is responsible for much of the cardiovascular burden of this disease.… One potential mediator of this phenomenon is subclinical myocardial dysfunction, which is present in the absence of left ventricular (LV) hypertrophy at rest and during exercise."

Small studies have suggested that pharmaceutical interventions aimed at improving glycemic control may reverse myocardial dysfunction in these patients. While exercise training has been shown to improve myocardial function in an animal model of Type 2 diabetes, this has not yet been assessed in humans, the authors note.

In a randomized controlled trial, the researchers assigned 223 patients free of occult coronary artery disease between the ages of 18 and 75 years to exercise training (n = 111) or usual care (n = 112).

Patients in the exercise intervention group completed a 4-week supervised, gym-based training program. This was followed by home-based training with regular telephone exercise counseling. The program "aimed to achieve a minimum of 150 minutes of at least moderate exercise each week from a combination of aerobic and resistance training."

Complete follow-up data were available for 176 patients, of whom 88 were in the exercise group and 88 in the usual care group. Main outcome measures included tissue Doppler-derived myocardial velocities, strain-rate and strain, echocardiography measures, body composition, glycated hemoglobin (HbA1c), maximum oxygen consumption (VO2max), and physical activity.

Patients in the intervention group spent significantly more time in vigorous activity than control-group patients (p < 0.001). No differences were observed in overall changes in myocardial function between the groups. Patients in the intervention group did have improvements in waist circumference, fat mass, glucose, HbA1c, insulin sensitivity, VO2max, and 6-minute walk distance.

Results of post-hoc analysis showed that patients who had the greatest increases in both moderate and vigorous activity had significantly improved myocardial tissue velocity, HbA1c, and cardiorespiratory fitness.

"Further, there was an increased systolic deformation (myocardial strain rate) in intervention patients who had the greatest increases in moderate activity compared to controls," Dr. Marwick and colleagues explain. "Intervention patients who had greater increases in moderate or vigorous activity showed significant improvements in HbA1c and diastolic blood pressure, respectively."

The findings "highlight the importance of including both moderate and vigorous activity in exercise prescription for these patients," the authors conclude.

Source: Diabetes In Control: Heart 2009;95:1343-1349.