The Role of Aerobic Training Variables Progression on Glycemic Control of Patients with Type 2 Diabetes: a Systematic Review with Meta-analysis

BACKGROUND: Aerobic training (AT) improves glycemic control in patients with type 2 diabetes. However, the role of the progression of training variables remains unclear. The objective of this review was to analyze the effects of progressive AT (PAT) and non-progressive AT (NPAT) on glycated hemoglobin (HbA1c) in patients with type 2 diabetes. METHODS: Data sources used were PubMed, Cochrane Central, Embase, SPORTDiscus, and LILACS. Studies that evaluated the effect of at least 12 weeks of PAT and NPAT compared to a control condition on HbA1c levels in type 2 diabetes patients were eligible for analysis. Two independent reviewers screened the search results, extracted the data, and assessed the risk of bias. Effect sizes (ESs) were calculated using the standardized mean difference in HbA1c levels between the intervention and control groups using a random-effect model. RESULTS: Of 5848 articles retrieved, 24 randomized clinical trials (825 participants) were included. Among the included studies, 92% reported to have performed a randomization process, 8% presented allocation concealment, 21% reported blinding of outcome assessment, and 38% reported complete outcome data. AT reduced HbA1c levels by 0.65% (ES: − 1.037; 95% confidence interval [CI]: − 1.386, − 0.688; p < 0.001). The reduction in HbA1c induced by PAT was 0.84% (ES: − 1.478; 95% CI − 2.197, − 0.759; p < 0.001), and NPAT was 0.45% (ES: − 0.920; 95% CI − 1.329, − 0.512; p < 0.001). Subgroup analysis of the different forms of progression showed a reduction in HbA1c levels of 0.94% (ES: − 1.967; 95% CI − 3.783, − 0.151; p = 0.034) with progression in volume, 0.41% (ES: − 1.277; 95% CI − 2.499, − 0.056; p = 0.040) with progression in intensity, and 1.27% (ES: − 1.422; 95% CI − 2.544, − 0.300; p = 0.013) with progression in both volume and intensity. Subgroup analysis of the different modalities of AT showed a reduction of 0.69% (ES: − 1.078; 95% CI − 1.817, − 0.340; p = 0.004) with walking and/or running and of 1.12% (ES: − 2.614; 95% CI − 4.206, − 1.022; p = 0.001) with mixed protocols while progressive training was adopted. In non-progressive protocols, a significant HbA1c reduction was only found with walking and/or running (− 0.43%; ES: − 1.292; 95% CI − 1.856, − 0.72; p < 0.001). CONCLUSION: The effect of PAT on glycemic control was greater than that of NPAT, especially when volume and intensity were progressively incremented throughout the interventions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s40798-019-0194-z) contains supplementary material, which is available to authorized users.