Effect of aerobic exercise intensity on glycemic control in type 2 diabetes: a meta-analysis of head-to-head randomized trials
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To conduct a meta-analysis of head-to-head trials comparing aerobic exercise training of different intensities on glycemic control in type 2 diabetes.
Databases, including MEDLINE and EMBASE, were searched up to January 2016. Randomized trials of at least 12 weeks in duration that compared two exercise interventions of different intensities were identified. Two reviewers independently extracted data from eligible trials. Using fixed effect model, weighted mean differences (WMD) between different exercise intensities were calculated for changes in glycated hemoglobin (HbA1c) and secondary outcomes, such as fasting glucose and fasting insulin.
Eight studies with a total of 235 participants were eligible. The exercise interventions lasted from 12 weeks to 6 months. The prescribed exercise intensities varied among studies. Four studies utilized vigorous exercise intensities for short durations by performing interval training. Overall, higher-intensity exercise resulted in a greater reduction in HbA1c compared to lower-intensity exercise (WMD = −0.22 %; 95 % confidence interval [−0.38, −0.06]; or −2.4 mmol/mol [−4.15, −0.66], I 2 = 0). Adherence to exercise and proportion of dropouts did not differ within trials. No adverse events were reported in these small trials with selected inclusion criteria.
Although our meta-analysis had a limited sample size, increasing exercise intensity safely accentuated reductions in HbA1c in some people with type 2 diabetes. Different approaches have been used to increase exercise intensity (i.e., some used interval training, whereas others used higher-intensity continuous exercise). However, at this time, it is unclear which form, if any, leads to the most favorable results.
KeywordsSystematic review HbA1c HOMA of insulin resistance Physical activity intensity
The authors would like to thank Drs. Hansen, Manders, and Karstoft for sharing change-from-baseline standard deviations from their studies. We would also like to thank Linda Slater for performing the computerized literature searches. This study was supported by the University of Alberta, Faculty of Physical Education and Recreation, Physical Activity and Diabetes Laboratory.
Compliance with ethical standards
Conflict of interest
Dr. Terada and Dr. Boulé have received funding and equipment from Medtronic of Canada for projects unrelated to this article. Dr. Terada and Dr. Boulé are the authors of one of the articles included in this meta-analysis.
All procedures performed in the study by Terada et al. were in accordance with the ethical standards of the University of Alberta Research Ethics Board and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Human and animal rights
This article does not contain any studies with human participants or animals performed by any of the authors, with the exception of the eligible and previously published study by Terada et al. .
All of the eligible articles included in the meta-analysis stated that they had obtained informed consent from participants.
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