Influence of Exercise Therapy on Insulin Resistance in Patients With Heart Failure

• Background and study aims During the last decades, the prevalence of (pre)diabetes but also of chronic heart failure (CHF) has increased dramatically. Somehow, both conditions are linked, but the mechanisms involved have not been completely clarified yet. It is clear that the presence of (pre)diabetes in CHF patients affects morbidity and mortality. Although feasibility, safety and beneficial effects of exercise training in CHF are generally acknowledged, its effects on insulin resistance are not well understood. Therefore, the presented study aims to investigate the effect of ET on insulin resistance and the possible link with cardiac function, exercise tolerance, muscle strength and body composition in CHF patients.
• What does the study involve?

A randomized controlled study (n=30) will be performed over a period of 12 weeks. Following study inclusion, baseline measurements will be performed in 1 week. They include:

• a maximal exercise test on a bicycle ergometer to assess exercise tolerance,
• two oral glucose tolerance tests to assess fasting and post-exercise insulin resistance,
• a venous blood sample to determine HbA1c, blood lipids, BNP,
• a muscle strength measurement on a isokinetic dynamometer,
• assessment of body composition via dual energy x-ray absorptiometry,
• cardiac echography,
• questionnaires to assess health-related quality of life,
• a questionnaire (IPAQ) and a pedometer (3 days) to assess physical activity. Following baseline measurements, subjects will be randomized to a control group (CON, n=10) and an exercise intervention group (EX, n=20), matching for gender and reduced/preserved ejection fraction and glucose tolerance. Hereafter, CON will receive usual care and will be advised to maintain their normal lifestyle, EX subjects will be enrolled in a 12-week training program. Following 6 (MID) and 12 (POST) weeks of exercise training including progressive training load adaptations, baseline measurements will be repeated in all patients.
• What are the possible benefits and risks of participating?

• Benefits: patients receive a free training program with personal and professional supervision. After completing the study, they receive a report with personal results and evaluation of training effects.
• Risks: the usual risks of exercise tolerance testing and exercise training in a CHF population are limited because training sessions are held in the supervised conditions of the Jessa hospital and because training characteristics are according to guidelines of the European Society of Cardiology. Exposure to x-rays during body composition assessment is very low, almost negligible.

Inclusion criteria

• diagnosis of chronic heart failure for at least 6 months
• clinically stable (not hospitalized) for more than 3 months prior to the onset of the study
• optimal medical therapy.

Exclusion criteria

• any contra-indication for exercise therapy,
• glucose lowering medical therapy,
• active lifestyle with regular physical activity.