Spotlight on resistance training

Four recent studies looked at the effects of resistance training in patients with diabetes.

An analysis of the Health Professionals Follow-up Study, published by Diabetes Care on Nov. 21, focused on weight training in men with (n=2,588) or without (n=31,140) type 2 diabetes. With up to 26 years of follow-up, the study found that in men without diabetes, weight training for less than an hour or between an hour and 149 minutes per week was associated with a 14% and 8% reduction in mortality risk, respectively, after adjustment for aerobic activity. In men who developed diabetes, weight training before diagnosis was associated with a 32% and 27% reduction in mortality, respectively, also after adjustment for aerobic activity. In neither group was weight training for more time associated with benefit. There was a trend toward lower mortality being associated with weight training initiated after diabetes diagnosis, but it was not statistically significant. “Our findings support the current physical activity guideline for type 2 diabetes, which encourages 2–3 days/week of resistance training and provide new evidence for the benefits of long-term weight training (pre- and post-diagnosis) for long-term survival in adults with type 2 diabetes,” the authors said.

A Canadian trial, published by the Journal of Clinical Endocrinology and Metabolism on Dec. 2, randomized patients with type 1 diabetes to resistance exercise (n=71) or control (n=60) for 22 weeks. All patients were already aerobically active, underwent a run-in period where their diabetes treatment was optimized, and received free gym memberships. The intervention group was assigned to resistance training three times per week, three sets of eight repetitions of seven exercises, supervised by a trainer at the beginning and at regular intervals. The study found that HbA1c level declined slightly in both groups, with no significant difference between them. The resistance training group did have greater decreases in waist circumference and increases in muscular strength. “These findings suggest that the addition of resistance exercise to already aerobically active adults who already have fair to good glycemic management should not be expected to further optimize glycemia or reduce daily insulin needs, in spite of improving strength and body composition,” the authors said.

Another trial, published by the International Journal of Environmental Research and Public Health on Nov. 15, randomized 40 patients in Taiwan who were age 50 years or older and had type 2 diabetes and possible sarcopenia (based on calf circumference and grip strength) to resistance exercises or control. The intervention group was taught to perform exercises for the upper and lower extremities using sandbags (0.5 kg at the beginning, increasing to 1 kg after a month) three times per week for 12 weeks. The study found that HbA1c levels decreased significantly in both the intervention and control groups, but significantly more in the intervention group. The intervention group also improved on the five times sit-to-stand test and calf circumference, while the control group had reductions in these measures. Lipid levels and grip strength were not significantly affected. The authors noted that no safety concerns were identified, suggesting that the approach “can be used for elderly diabetic patients with poor physical fitness to increase muscle strength.”

Finally, a systematic review and meta-analysis, published by Diabetes/Metabolism Research and Reviews on Nov. 24, compiled 106 randomized controlled trials of exercise for type 2 diabetes. It found evidence of low to moderate certainty that supervised aerobic/resistance exercise improved glycemic control, body weight, blood pressure, and blood lipid profiles compared with no exercise. Supervised exercise appeared more effective than unsupervised, with the review finding that unsupervised aerobic/resistance exercise did not have a significant effect on HbA1c level, although the combination of the two kinds of exercise was more effective than unsupervised aerobic exercise alone. The authors found limited evidence supporting the benefits of flexibility or balance exercises. The authors concluded that their results showed significant benefit to exercise in patients with type 2 diabetes without complications, “and the magnitude of the benefit varies depending on the type of exercise and the outcome of interest.”