Effect of resistance training on HbA1c and other cardiovascular risk factors in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

Abstract

Introduction: Obesity, hypertension, hyperlipidemia, and other cardiovascular risk factors are commonly clustered in patients with diabetes type II (T2DM). As a result, patients with T2DM are at increased cardiovascular (CV) risk. Exercise therapy is recommended in the prevention and management of patients with T2DM. In the last decade, dynamic resistance training has attracted more interest as an exercise therapy in the management of patients with diabetes. Though, the primary outcome in these intervention trials has mostly been glycated hemoglobin (HbA1c). Given the high prevalence of other CV risk factors in patients with T2DM, knowledge on the impact of dynamic resistance training on the overall CV risk profile of these patients is important. Purpose: To perform a systematic review with meta-analysis to investigate the effects of resistance training on HbA1c and other traditional cardiovascular risk factors in patients with T2DM. Methods and analyses: A systematic search was conducted in the electronic databases MEDLINE, Embase, SPORTdiscus and PEDro from the earliest date available until the first of September 2021 to identify peer reviewed randomized controlled trials investigating the effect of resistance training on HbA1C in adults with T2DM. Primary outcome was HbA1C. Secondary outcomes included traditional CV risk factors (i.e. blood pressure, blood lipids, body composition) and physical fitness (muscle strength, exercise capacity). Effect sizes were calculated using random effect models. Data are reported as weighted mean and 95% confidence limits. Results: Fourteen trials could be included in the meta-analysis. Resistance training was found to significantly reduce HbA1c [-0.35 % (95% CL -0.61 to -0.11)], systolic blood pressure [-4.6 mmHg (95%CL -8.7 to -0.39)], diastolic blood pressure -2.25 (95%CL -4.45 to -0.048)) and body fat (-0 0.038). Muscle strength was significantly improved in the three studies reporting this outcome. Other cardiovascular risk factors including fasting plasma glucose, high-density-lipoprotein, low-density-lipoprotein, triglycerides and peak oxygen uptake capacity (VO2 peak) remained unchanged after resistance training in patients with T2DM. Conclusion: The available data suggests that resistance training can exert favorable effects on HbA1C but also on blood pressure, body composition and muscle strength of patients with type 2 diabetes. Further research is needed to determine the impact of different resistance training characteristics such as volume, frequency and type of training on the overall CV risk profile of patients with type 2 diabetes.