Significant Dose–Response between Exercise Adherence and Hemoglobin A1c Change

INTRODUCTIONThe Diabetes Aerobic and Resistance Exercise trial found that aerobic training and resistance training alone each reduced hemoglobin A1c (HbA1c) compared with nonexercising controls, and combined aerobic and resistance training caused greater HbA1c reduction than either training type alone. Our objective was to determine whether a dose–response relationship existed between frequency of exercise training and HbA1c change, and whether this varied by exercise modality or participant characteristics. METHODSPost hoc analysis of data from 185 Diabetes Aerobic and Resistance Exercise trial participants with type 2 diabetes randomized to aerobic, resistance or combined training thrice weekly. Dose–response relationships between adherence (percent of prescribed training sessions completed) and HbA1c change were assessed with linear regression. RESULTSMedian overall adherence was 84.9% (interquartile range, 74.4%–93.6%). Higher exercise adherence was associated with greater HbA1c reduction; a 20% increase in adherence (e.g., an additional two sessions per month) was associated with a 0.15% (2 mmol·mol) decrease in HbA1c (β = −0.0076, R = −0.170, P = 0.021). Significant dose–response relationships were identified for aerobic (β = −0.0142, R = −0.313, P = 0.016) and combined training (β = −0.0109, R = −0.259, P = 0.041), but not resistance training (β = 0.0068, R = 0.153, P = 0.233). Dose–response relationships in all training groups combined were significant in subgroups younger than 55 yr (β = −0.0113, R = −0.286, P = 0.005), males (β = −0.0123, R = −0.234, P = 0.010), and baseline HbA1c ≥7.5% (58 mmol·mol) (β = −0.013, R = −0.263, P = 0.011). CONCLUSIONSThere was a dose–response relationship between adherence to prescribed exercise and HbA1c reduction suggesting that glycemic control is improved more in individuals with type 2 diabetes with a higher training volume. Dose–response relationships existed for aerobic and combined training but not resistance training. These findings support aerobic and combined exercise prescriptions outlined in clinical practice guidelines.