Individuals with type 2 diabetes (T2D) who complete a higher volume of exercise training exhibit more improved glycemic control compared with individuals who exercise less frequently, according to a study published in Medicine & Science in Sports & Exercise.
In addition to improving glycemic control, exercise can induce modest weight loss, improve insulin sensitivity, and modify cardiovascular risk factors, including blood pressure and triglycerides in the T2D population.
The American Diabetes Association recommends individuals with T2D complete a minimum of 150 minutes of aerobic physical activity per week, at least 2 weekly sessions of resistance exercise training, and minimize sedentary time.
“Although clinical practice guidelines recommend exercise, the majority of individuals with T2D are not achieving the physical activity recommendations in these guidelines,” the researchers said. One study looking at US physical activity levels found only 41.1% of individuals with T2D met aerobic exercise recommendations compared with 12.4% for resistance training.
The Diabetes Aerobic and Resistance Trial (DARE) has shown aerobic and resistance training alone can reduce hemoglobin A1C (A1C) levels, while combined training leads to a greater reduction than either type in isolation. However, the trial did not determine whether a dose-response relationship exists between frequency of exercise and A1C change.
To better understand this relationship, and to see whether it varies by exercise modality or participant characteristics, the researchers conducted a post hoc analysis of data from 185 trial participants.
Patients were randomized to aerobic, resistance, or combined exercise training programs, which took place 3 times a week for 6 months. Adherence to training interventions was assessed via participant-completed logs filled out in real time. Personal trainers also provided direct individual supervision twice weekly during the run-in period, weekly for the first 4 weeks of the intervention, and biweekly for the remainder of the intervention.
The researchers used simple linear regression to assess the significance of the dose-response relationship between adherence to exercise intervention and change in A1C from baseline to the end of the 6 months.
Participants had a mean (SD) age of 54 (7.2) years and 36% were female. The mean baseline A1C was 7.69% (61 mmol·mol−1) (SD, 0.87% [10 mmol·mol−1]).
- Median (interquartile range [IQR]) overall adherence was 84.9% (IQR, 74.4%-93.6%)
- Higher exercise adherence was associated with greater A1C reduction; a 20% increase in adherence (eg, an additional 2 sessions per month) was associated with a 0.15% (2 mmol·mol−1) decrease in A1C (β = −0.0076; R = −0.170; P = .021)
- Significant dose-response relationships were identified for aerobic (β = −0.0142; R = −0.313; P = .016) and combined training (β = −0.0109; R = −0.259; P = .041), but not resistance training (β = 0.0068; R = 0.153; P = .233)
- Dose-response relationships in all training groups combined were significant in subgroups younger than 55 years (β = −0.0113; R = −0.286; P = .005), males (β = −0.0123; R = −0.234; P = .010), and baseline A1C ≥7.5% (58 mmol·mol−1) (β = −0.013; R = −0.263; P = .011)
No further benefits in terms of A1C reduction were identified with more than 2 sessions of resistance training per week, suggesting this may be an adequate volume of resistance exercise for patients. “The difference we observed between aerobic and resistance exercise training could be explained by the variable effect of these exercise modalities on insulin sensitivity,” the researchers hypothesized.
In addition, although the dose-response relationship was not statistically significant in populations not identified in stratified analyses, exercise is still important in these subgroups. In the original DARE trial, patients with an A1C <7.5% randomized to any exercise intervention had greater A1C reductions than controls.
When it comes to sex differences, the investigators speculate higher testosterone levels in males may facilitate changes in muscle that increase glucose disposal, but future studies are warranted.
“These results suggest that an increased volume of aerobic or combined aerobic and resistance exercise is associated with greater improvement in glycemic control,” the researchers concluded. “Our findings support clinical practice guideline recommendations for aerobic and combined exercise prescriptions.”
Benham JL, Booth JE, Dunbar MJ, et al. Significant dose-response between exercise adherence and hemoglobin A1c change. Med Sci Sports Exerc. 2020;52(9):1960-1965. doi:10.1249/MSS.0000000000002339