The effect of exercise characteristics on HbA1c and other cardiovascular risk factors in adults with type 2 diabetes: a systematic review and meta-analysis of randomised controlled trials

Abstract

Background: Exercise is a first-line therapy in adults with type 2 diabetes, yet its optimal characteristics remain unclear. Moreover, most meta-analyses focus on glycated haemoglobin (HbA1c), providing limited insight into the concomitant effects of these exercise programmes on the overall cardiovascular risk profile. Methods: A systematic review and meta-analysis was conducted. Nine electronic databases were searched from inception to January 2025 for randomised controlled trials evaluating the effects of exercise on HbA1c and concomitantly reported cardiovascular risk factors in adults with type 2 diabetes. Outcomes were pooled using random-effects models and analysed by exercise type. Subgroup analyses were performed to explore optimal exercise characteristics for improving HbA1c. Results: One hundred randomised controlled trials (7195 participants, 136 interventions) were included. All exercise types significantly improved HbA1c, with the largest reductions observed for combined training (–0.74%, 95%CI [-0.91; -0.57], n=38) and high-intensity interval training (HIIT) (-0.71%, 95%CI [-1.07; -0.35], n=13), followed by continuous aerobic training (CAT) (-0.62%, 95%CI [-0.84; -0.41], n=57) and resistance training (-0.36%, 95%CI [-0.51; -0.20], n=38). Supervised interventions and those prescribing a weekly volume of 150–210 minutes were consistently the most effective. Analyses of concomitantly reported cardiovascular risk factors showed improvements in VO₂peak with CAT, combined training and HIIT (+2.77 to +4.19 ml/kg/min) and in muscle strength with resistance and combined training (SMD: +0.44 to +0.66). All modalities reduced fasting plasma glucose (–0.60 to –1.13 mmol/L), LDL cholesterol (–0.18 to –0.31 mmol/L) and systolic blood pressure (–1.24 to –4.15 mmHg), while improvements in body fat were observed only after CAT, combined training and HIIT (SMD: –0.36 to –0.59). Conclusions: All types of exercise significantly improved HbA1c, with combined training producing the largest reduction. Moreover, each modality provides distinct advantages for other cardiovascular risk factors, with combined training offering the broadest benefits and HIIT serving as a time-efficient alternative. Tailoring exercise programmes based on the patient’s individual risk profile, and adjusting exercise types accordingly, may help optimise outcomes.