This “dose–response” relationship between exercise and reductions in A1c held firm for those who did aerobic training or a mixture of aerobic and resistance exercises (combined), but not for those who only did resistance exercises, say Ronald J. Sigal, MD, and colleagues in their article published in the September issue of Medicine & Science in Sports & Exercise.
The findings “suggest that an increased volume of aerobic or combined aerobic and resistance exercise is associated with greater improvement in glycemic control,” say Sigal, a professor in the division of endocrinology and metabolism at the University of Calgary, Alberta, Canada, and colleagues.
In addition, the results “support aerobic and combined exercise prescriptions outlined in clinical practice guidelines…such as those published by the American Diabetes Association (Diabetes Care. 2016;39:2065-2079),” they note.
Sigal was also a coauthor of the ADA position statement on exercise, physical activity, and diabetes.
Those Who Exercised the Most Saw Biggest Drop in A1c
In the new report, Sigal and coauthors note they are “unaware of previous studies exploring the relationship between adherence to prescribed exercise and change in glycemic control in patients with type 2 diabetes.”
The analysis used data collected from the DARE (Diabetes Aerobic and Resistance Exercise) trial, which randomized 251 patients with type 2 diabetes to a 6-month supervised exercise program or their usual habits (the latter were used as sedentary controls). The original DARE results showed that each of the three tested modes of supervised exercise — exclusively aerobic, exclusively resistance training, or a combination of both — resulted in a significant drop in average A1c level compared with controls (Ann Int Med. 2007;147:357-369).
This original study did not subdivide patients in the intervention groups by level of adherence to their exercise prescription.
The new analysis focused on the 185 patients randomized to one of the three exercise arms, and tracked adherence by both self-recorded logs from patients and reports from the trainers who ran the exercise sessions.
The patients were an average of 54 years old, and slightly more than a third were women. Median A1c at baseline was about 7.7%. Median overall adherence to their exercise regimen was about 86% and was roughly similar in the three exercise subgroups.
The exercise prescription consisted of a 60-minute session (including warm-up and cool-down) three times weekly.
Those who did the most exercise saw the biggest improvements in A1c: a 20% increase in adherence (which correlated with an additional two sessions per month) was associated with a 0.15% decrease in A1c (P = .021)
When analyzed by type of exercise, both the subgroup that performed aerobic exercise only and the subgroup that did both aerobic and resistance exercise showed significant correlations with reductions in A1c. There was no significant association with A1c for the patients who only did resistance training.
Further subgroup analyses showed that significant relationships between exercise adherence and reduced glycemia were seen only in patients younger than 55 years old, men, and those with a baseline A1c ≥ 7.5%.
The researchers caution that the low number of patients in their analysis limits the statistical power and thereby interpretation of the findings, as does the post-hoc nature of the analysis.
DARE received no commercial funding. The authors have reported no relevant financial relationships.
Med Sci Sports Exerc. 2020;52:1960-1965. Abstract