Effects of Long-Term Exercise Interventions on Glycaemic Control in Type 1 and Type 2 Diabetes: a Systematic Review

Aim: Physical activity is one of the cornerstones in the prevention and management of diabetes mellitus, but the effects of different training forms on metabolic control still remain unclear. The aims of this review are to summarize the recommendations of 5 selected diabetes associations and to systematically review the effects of long-term supervised exercise interventions without calorie-restriction on glycemic control in people with type 1 and 2 diabetes focusing on resistance, endurance and combined training consisting of both endurance and resistance training. Methods: Literature searches were performed using MEDLINE for articles published between January 1, 2000 and March 17, 2015. Of 76 articles retrieved, 15 randomized and controlled studies met the inclusion criteria and allowed for examining the effect of exercise training in type 1 and 2 diabetes. Results: Diabetes associations recommend volume-focused exercise in their guidelines. In our analysis, all 3 training forms have the potential to improve the glycemic control, as assessed by HbA_1c (absolute changes in HbA_1c ranging from -0.1% to -1.1% (-1.1 to -12 mmol/mol) in resistance training, from -0.2% to -1.6% (-2.2 to -17.5 mmol/mol) in endurance training and from +0.1% to -1.5% (+1.1 to -16.4 mmol/mol) in combined training, respectively). Conclusions: There is evidence that combined exercise training may improve glycemic control to a greater extent than single forms of exercise, especially under moderate-intensive training conditions with equal training durations. In addition, intensity of training appears to be an important determinant of the degree of metabolic improvement. Nonetheless, it is still unknown to what extent exercise effects glycemic homeostasis.