Associations between physical fitness and HbA1c in type 2 diabetes mellitus

Abstract

Aim/hypothesis: In people with type 2 diabetes, exercise improves glucose control (as reflected in HbA1c) and physical fitness, but it is not clear to what extent these exercise-induced improvements are correlated with one another. We hypothesised that reductions in HbA1c would be related: (1) to increases in aerobic fitness and strength respectively in patients performing aerobic training or resistance training; and (2) to changes in strength and aerobic fitness in patients performing aerobic and resistance training. Methods: We randomly allocated 251 type 2 diabetes patients to aerobic, resistance, or aerobic plus resistance training, or to a sedentary control group. Peak oxygen consumption (V̇O2peak), workload, treadmill time and ventilatory threshold measurements from maximal treadmill exercise testing were measured at baseline and 6 months. Muscular strength was measured as the maximum weight that could be lifted eight times on the leg press, bench press and seated row exercises. Results: With aerobic training, significant associations were found between changes in both V̇O 2peak (p=0.040) and workload (p=0.022), and changes in HbA 1c. With combined training, improvements in V̇O2peak (p=0.008), workload (p=0.034) and ventilatory threshold (p=0.003) were significantly associated with changes in HbA1c. Increases in strength on the seated row (p=0.006) and in mid-thigh muscle cross-sectional area (p=0.030) were significantly associated with changes in HbA1c after resistance exercise, whereas the association between increases in muscle cross-sectional area and HbA1c in participants doing aerobic plus resistance exercise (p= 0.059) was of borderline significance. Conclusions/interpretation: There appears to be a link between changes in fitness and HbA1c. The improvements in cardiorespiratory fitness with aerobic training may be a better predictor of changes in HbA1c than improvements in strength. © Springer-Verlag 2010.