Metabolic Effects of Aerobic Training and Resistance Training in Type 2 Diabetic Subjects

Abstract

OBJECTIVEdTo assess differences between the effects of aerobic and resistance training on HbA 1c (primary outcome) and several metabolic risk factors in subjects with type 2 diabetes, and to identify predictors of exercise-induced metabolic improvement. RESEARCH DESIGN AND METHODSdType 2 diabetic patients (n = 40) were randomly assigned to aerobic training or resistance training. Before and after 4 months of intervention , metabolic phenotypes (including HbA 1c , glucose clamp-measured insulin sensitivity, and oral glucose tolerance test-assessed b-cell function), body composition by dual-energy X-ray absorptiometry, visceral (VAT) and subcutaneous (SAT) adipose tissue by magnetic resonance imaging, cardiorespiratory fitness, and muscular strength were measured. RESULTSdAfter training, increase in peak oxygen consumption (VO 2peak) was greater in the aerobic group (time-by-group interaction P = 0.045), whereas increase in strength was greater in the resistance group (time-by-group interaction P , 0.0001). HbA 1c was similarly reduced in both groups (20.40% [95% CI 20.61 to 20.18] vs. 20.35% [20.59 to 20.10], respectively). Total and truncal fat, VAT, and SAT were also similarly reduced in both groups, whereas insulin sensitivity and lean limb mass were similarly increased. b-Cell function showed no significant changes. In multivariate analyses, improvement in HbA 1c after training was independently predicted by baseline HbA 1c and by changes in VO 2peak and truncal fat. CONCLUSIONSdResistance training, similarly to aerobic training, improves metabolic features and insulin sensitivity and reduces abdominal fat in type 2 diabetic patients. Changes after training in VO 2peak and truncal fat may be primary determinants of exercise-induced metabolic improvement. Diabetes Care 35:676-682, 2012 R ecent data suggest that both aerobic and resistance training may exert beneficial effects on glucose control in subjects with type 2 diabetes (1,2). However, it remains unclear if the extent of improvement and the mechanisms underlying the metabolic effects of these exercise protocols are similar. Two recent comparison studies reported similar HbA 1c reductions after aerobic or resistance training (3,4). However, the extent of HbA 1c changes in other studies using either type of exercise varied considerably (2), and therefore the results cannot be considered conclusive. The most direct determinants of glucose control are b-cell function and insulin sensitivity. In particular, most of the benefit of regular exercise on glucose control in these subjects is attributed to attenuation of insulin resistance. However, only a few studies have accurately assessed, by the gold-standard glucose clamp technique, the effects of aerobic training on insulin sensitivity in diabetic patients (5-8), and only one small study assessed the effects of resistance training (9). In contrast, little attention has been devoted to the potential effects of physical training on insulin secretion , with controversial results (10,11). The amelioration of insulin resistance brought about by physical training may be due to changes in a number of potential factors, including, but not limited to, body fat mass, fat distribution, lean mass, and maximal aerobic performance. The role played by these factors is still unsettled. Answering this question is of great interest and could help in programming more appropriate exercise training protocols in diabetic subjects. We carried out the RAED2 (Resistance Versus Aerobic Exercise in Type 2 Diabetes) trial to assess what differences and similarities exist between the effects of aerobic and resistance training in diabetic subjects, and which of these are the main determinants of the exercise-induced improvement of glucose control. To answer these questions, the effects of these exercise protocols on body fat, body composition, insulin sensitivity, b-cell function, aerobic performance, and strength measures were carefully assessed. RESEARCH DESIGN AND METHODS Subjects Type 2 diabetic patients (n = 40) were enrolled from the Diabetic Outpatient Clinic of the City Hospital of Verona. Participants were recruited between September