The Best Exercise Modality and Dose to Reduce Glycosylated Hemoglobin in Patients with Type 2 Diabetes: A Systematic Review with Pairwise, Network, and Dose–Response Meta-Analyses

Background Persistently elevated glycosylated hemoglobin (HbA1c) is associated with a higher risk of long-term vascular complications. Objective We evaluated the effect of different exercise modalities and doses on HbA1c levels in patients with type 2 diabetes. Methods A systematic search for randomized controlled trials involving exercise interventions in patients with type 2 diabetes was conducted across seven electronic databases, encompassing data from their inception up to October 2023. Two independent reviewers assessed the quality of the literature. Pairwise, network, and dose–response meta-analyses using the random-effects model were conducted to analyze the effect of exercise on HbA1c levels. Results A total of 85 randomized controlled trials with 5535 participants were included. The network meta-analysis showed that high-intensity interval training (HIIT) has the highest ranked (MD = − 0.78% [− 8.50 mmol/mol]; 95% CrI: − 1.04, − 0.51), followed by combined aerobic and resistance exercise (CE) (MD = − 0.54% [− 5.90 mmol/mol]; 95% CrI: − 0.69, − 0.40), yoga (MD = − 0.45% [− 4.92 mmol/mol]; 95% CrI: − 0.77, − 0.13), and continuous aerobic exercise (CAE) (MD = − 0.42% [− 4.58 mmol/mol]; 95% CrI: − 0.54, − 0.30). In addition, a significant improvement in HbA1c levels can be observed when the total exercise dose reaches 840 metabolic equivalent of tasks-min/week. Conclusions There was low-quality evidence that HIIT, CE, yoga, and CAE may be effective treatment modalities for improving HbA1c in patients with type 2 diabetes, and there was no significant difference in efficacy. Moreover, a non-linear dose–response relationship was found for total exercise and HbA1c levels. Future research should further investigate the specific effects of different exercise doses on HbA1c levels in patients with type 2 diabetes and provide a more personalized exercise prescription.