By Karl Minges, M.P.H., and David Dunstan, Ph.D.
Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies
Karl Minges is a doctoral student at Yale University Graduate School of Arts & Sciences. His research
interests broadly relate to diabetes and cardiovascular disease and the role of health behaviors in preventing
overweight/obesity. Mr. Minges completed the present work with the support of a U.S. Fulbright Scholarship
administered by the Australian-American Fulbright Commission.
Professor Dunstan is an Australian Research Council Future Fellow and heads the Physical Activity Laboratory at the Baker IDI Heart and Diabetes Institute in Melbourne, Australia. He is an ACSM member whose research focuses on the role of physical activity and sedentary behavior in the prevention and management of chronic diseases.
This commentary presents perspectives from Mr. Minges and Dr. Dunstan’s relative to issues central to their cross-sectional study that appears in the February 2013 issue of ACSM’s Medicine and Science in Sports and Exercise® (MSSE).
Increasing rates of type 2 diabetes (T2D) have global public health implications; furthermore, about 1 in 3 adults are afflicted with the precursor to T2D – impaired glucose metabolism (IGM). Thus, they are at risk of developing T2D and associated cardiovascular complications.
Participation in regular physical activity has a key role in managing insulin resistance in those who have T2D and in preventing the development of T2D in those with IGM. Traditionally, engagement in aerobic activity has been the exercise modality championed for the prevention and management of T2D. However, there is a plethora of studies to show that strength training (ST) – resistance exercise – not only leads to improved glycemic control, but also provides a means to maintain functional capacity and prevent and manage other health impairments. Indeed, several leading organizations, including ACSM, endorse ST exercise as an integral component of adults’ daily physical activity – recommending a frequency of ST of at least twice per week for those with and without T2D. Further, Braith and Stewart, in their 2006 research review, have suggested that training objectives may be accomplished in about 40 minutes of ST per week.
However, epidemiological questions on ST are germane, particularly about the extent to which these guidelines are met at a population level, and whether they are associated with a reduced risk of IGM. Our recently published study in MSSE examined population prevalence of meeting the guideline on ST activity (both frequency and duration) and associations of achieving the guideline with IGM, in a large national population-based sample of adults without clinically diagnosed diabetes.
We examined data on 5,831 Australian adults from the 2004-2005 AusDiab study, in which self-reported ST and anthropometric measures were available and an oral glucose tolerance test was performed. Frequency of ST was categorized as = 2 times/week (meeting guidelines); 1 time/week; and, <1 times/week. Duration was also categorized into three groups: = 40 minutes/week (meeting guidelines); 10 – 39 minutes/week; and, < 10 minutes/week. Relationships with having IGM, which includes impaired glucose tolerance, impaired fasting glycemia, or undiagnosed T2D, were examined. Analyses were also stratified by either meeting both of the ST frequency and duration criteria, or not doing so. Multiple logistic regressions examined associations with IGM of self-reported ST frequency and duration.
We found that those who achieved these ST guidelines – either for frequency or for duration — were at reduced risk of IGM, after controlling for the main known confounding factors. No additional benefit was apparent for meeting both recommended guidelines. Interestingly, those participating in even a modest amount of ST – as little as once/week or for 10-39 minutes/week – were at reduced risk of IGM. These findings support the importance of emphasizing ST activity at a frequency of at least once per week within public health recommendations on physical activity and as part of population-based and high-risk diabetes prevention strategies.