Resistance Training Benefits Type 2 Diabetics

Miriam E. Tucker

March 13, 2013

Improvements in body composition with progressive resistance exercise led to better glucose control and less insulin resistance among older type 2 diabetes patients, but the same phenomenon was not seen with low-resistance "sham" exercise, researchers found.

The results, from the Graded Resistance Exercise and Type 2 Diabetes in Older Adults (GREAT2DO) study were published online March 8 in Diabetes Care by Yorgi Mavros, a PhD candidate and postgraduate teaching fellow at the University of Sydney, Australia, and colleagues.

"We have shown that progressive resistance training can reduce [glycated hemoglobin (HbA1c)] and insulin resistance through increasing skeletal muscle mass and/or reducing fat mass. This means that you can see improvements in metabolic health without weight loss with this mode of exercise," Mr. Mavros told Medscape Medical News.

He added, "We saw improvements in metabolic health similar to those seen with the addition of a second diabetic medication [with] progressive resistance training."

Current guidelines from the American Diabetes Association, the American College of Sports Medicine, and the federal government all advise a combination of aerobic and resistance training for optimal health benefit.

A previous randomized, controlled clinical trial of 262 patients with type 2 diabetes showed that the combination of both aerobic and resistance training, but not either one alone, improved HbA1c levels (JAMA. 2010;304:2253-2262).

That study's author, Timothy S. Church, MD, the John S. McIlHenny Endowed Chair in Health Wisdom Professor at Pennington Medical Research Center, Baton Rouge, Louisiana, told Medscape Medical News, "I like to think of them as 2 different pills. Aerobic training is kind of like one pill, and resistance training is another pill. They're different mechanisms, and together they're synergistic." However, he stressed that the current evidence base for aerobic exercise is still far greater than that for resistance training. "If you've got to pick one, it's not even an argument. Aerobic is going to get it done."

Metabolic Parameters Improved Only in High-Intensity Training

In the current paper, Mr. Mavros and colleagues report data from the first year of GREAT2DO, in which 103 adults with type 2 diabetes older than 60 years of age were randomized to 3 days per week of either supervised, high-intensity progressive resistance training (PRT) exercises — weight training with repetitions — or sham exercise, which involved the same equipment but was low in intensity, slow, and not progressive.

Among the 86 patients who were assessed at 12 months, mid-thigh cross-sectional area increased significantly among the PRT patients compared with the sham-exercise group (P < .01).

But contrary to the authors' hypothesis, there were no differences between the PRT and sham-exercise groups in body weight changes, skeletal muscle mass, fat mass, or visceral adipose tissue. Both groups similarly lost fat mass and improved mid-thigh muscle attenuation (P < .0001).

Despite these similar changes in body composition between the 2 groups, metabolic parameters were improved only in the PRT group and not the sham-exercise group.

"Both increases in skeletal muscle mass and reductions in visceral adipose tissue achieved through high-intensity PRT improved insulin resistance and glucose homeostasis in this cohort of older adults with type 2 diabetes. Notably, increased skeletal muscle mass or decreased visceral adipose tissue and intramyocellular lipid accumulation achieved without anabolic exercise did not have the same metabolic benefit," the authors observe.

"Future investigations should be directed toward understanding the heterogeneity in body composition adaptations to anabolic exercise…and to developing strategies to maximize these beneficial changes to improve metabolic health and future disease risk in this vulnerable cohort."

Clinical Implications: Use Resistance Training as 'Baby Steps'

The HbA1c reduction seen with PRT is similar in magnitude to that of adding a sulfonylurea to metformin therapy, Mr. Mavros and colleagues note.

Mr. Mavros told Medscape Medical News that although combined aerobic and resistance training is ideal and should be encouraged, a unique advantage to progressive resistance training is its ability to increase muscle mass, which aerobic exercise such as walking can't do.

And, particularly in older adults, the presence of other chronic diseases such as osteoarthritis and peripheral vascular disease can make aerobic exercise difficult to adhere to; weight lifting offers a mode of exercise for people who would otherwise find aerobic exercise difficult.

Dr. Church agrees, adding that obesity also makes aerobic exercise difficult for many with type 2 diabetes. "We find you can almost use resistance training as an entry-level activity… I like to call it the baby step."

One additional consideration with resistance training, unlike walking, is that it requires instruction, but YMCAs around the country are increasingly offering this for those who don't have access to personal trainers or gyms, he noted.

Dr. Church questioned, however, the current paper's conclusion that only body composition changes mediated through PRT would improve metabolic parameters, noting that his data suggest such improvements occur with increased muscle and reduced fat, regardless of the mechanism.

Nevertheless, both investigators agree that physicians should increase their focus on exercise as an effective treatment for patients with type 2 diabetes.

Referring to resistance training in particular, Mr. Mavros said, "The challenge for physicians is to incorporate this potent form of treatment into the mainstream of their medical care of type 2 diabetes for life."

Dr. Church said he has seen a shift in thinking. "Physicians are finally starting to get comfortable talking about diet, exercise, and resistance training. We didn't get any of this in medical school… To me, this [study] is more evidence toward the optimal program being both aerobic and resistance."

 

The GREAT2DO study was funded by a grant from the National Health and Medical Research Council (NHMRC) and grants from the Australian Diabetes Society and Diabetes Australia. Mr. Mavros was supported by the Australian Postgraduate Award Scholarship and a University of Sydney International Postgraduate Research Scholarship. The authors have disclosed no relevant financial relationships. Dr. Church said he has numerous disclosures with regard to pharmaceutical companies, but nothing relevant to this topic.

Diabetes Care . Published online March 8. Abstract

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