Background.
Guidelines for the prevention of type 2 diabetes suggest exercise can be accumulated in bouts of 10 minutes or more, however it is unclear whether this is as beneficial as a single exercise bout for glycaemic control.
Methods.
A systematic literature search was conducted in seven databases on 31 October 2016. Results were limited to peer-reviewed studies with humans aged 19 to 64 years. Studies were excluded if participants were diagnosed with a chronic disease and where participants were meeting or exceeding current exercise guidelines. Studies shorter than six weeks duration or that combined aerobic exercise interventions with interventions such as resistance exercise or nutrition were excluded. Studies not evaluating glycaemic control (HbA1c) were excluded. Meta-analyses were conducted using RevMan 5 software. Standard mean difference (SMD) with 95% CI were used to calculate effect size on post-intervention outcome measures using random effects models.
Results.
No studies that assessed HbA1c were identified comparing accumulated exercise with a single exercise bout or with a no-exercise control. Six studies comparing a single bout of exercise with no exercise were included in the review, with five included in meta-analyses producing a low-moderate quality of evidence. A single bout of exercise produced a small favourable effect for HbA1c in comparison to no-exercise (5 studies, 182 participants, SMD -0.18: 95%; CI -0.49 to -0.13).
Conclusions.
There is no evidence available that allows a determination of the effects of accumulating exercise in short bouts on glycaemic control as recommended in the guidelines. There is a lack of quality evidence available to determine the efficacy of a single bout of exercise for glycaemic control as a preventative measure; however, a single bout of continuous aerobic exercise might be beneficial for improving glycaemic control in individuals at risk of developing type 2 diabetes.