A meta-analysis evaluating the effects of walking (duration at least 8 weeks) on glycemic control in type 2 diabetes patients included 20 RCTs (866 participants). Walking significantly decreased HbA1c by 0.50% (95% CI -0.78% to -0.21%). Supervised walking was associated with a pronounced decrease in HbA1c (WMD -0.58%, 95% CI -0.93% to -0.23%), whereas non-supervised walking was not. Further subgroup analysis suggested non-supervised walking using motivational strategies is also effective in decreasing HbA1c (WMD -0.53%, 95% CI -1.05% to -0.02%). For other cardiovascular risk factors, walking significantly reduced body mass index (BMI) and lowered diastolic blood pressure (DBP), but non-significantly lowered systolic blood pressure (SBP), or changed high-density or low-density lipoprotein cholesterol levels.
Another meta-analysis assessing associations of structured exercise training (aerobic, resistance, or both) in type 2 diabetes included 47 RCTs with 8538 patients. Structured exercise decreased HbA1c (-0.67%, 95% CI -0.84% to -0.49%; 23 trials) compared with control. Declines in HbA1c compared with control were -0.73% (95% CI -1.06% to -0.40%) in structured aerobic exercise; -0.57% (95% CI -1.14% to -0.01%) in structured resistance training; and -0.51% (95% CI -0.79% to -0.23%) in both combined. Structured exercise durations of more than 150 minutes per week were associated with HbA1c reductions of 0.89%, while structured exercise durations of 150 minutes or less per week were associated with HbA1c reductions of 0.36%. Combined physical activity advice and dietary advice was associated with decreased HbA1c (-0.58%; 95% CI -0.74% to -0.43%) as compared with control. Physical activity advice alone was not associated with HbA1c changes.
A Cochrane review included 14 studies with a total of 377 subjects. Compared with the control, the exercise intervention significantly improved glycaemic control as indicated by a decrease in glycated haemoglobin levels of 0.6% (–0.6 % HbA1c, 95% CI –0.9 to –0.3). The exercise intervention significantly increased insulin response (131 AUC, 95% CI 20 to 242) (one trial), and decreased plasma triglycerides (–0.25 mmol/l, 95% CI –0.48 to –0.02). No significant difference was found between groups in quality of life (one trial), plasma cholesterol or blood pressure. The decrease of HbA1c was achieved over relatively short periods of time (the shortest studies were of eight weeks duration, and there were only two studies with an intervention of six months or more).
A randomized controlled trial comparing the effects of different exercise forms in patients with type 2 diabetes included 251 adults aged 39 to 70 years. The participants were randomized to either aerobic training (treadmill or bicycle ergometer), resistance training (different weight machines), or both types of exercise. A sedentary control group was included. Exercise training was performed 3 times weekly for 22 weeks. The absolute change in the hemoglobin A1c as compared with the control group was –0.51 percentage point (95% CI –0.87 to –0.14) in the aerobic training group and –0.38 percentage point (95% CI –0.72 to –0.22) in the resistance training group. Combined exercise training resulted in an additional change in the hemoglobin A1c value of –0.46 percentage point (95% CI –0.83 to –0.09) compared with aerobic training alone and –0.59 percentage point (95% CI –0.95 to –0.23) compared with resistance training alone. Changes in blood pressure and lipid values did not statistically significantly differ among groups. Adverse events were more common in the exercise groups. The participants were not blinded, and the total duration of exercise was greater in the combined exercise training group than in the aerobic and resistance training groups.