Title: Muscle-Strengthening and Conditioning Activities and Risk of Type 2 Diabetes: A Prospective Study in Two Cohorts of US Women
Authors: Grøntved, A et al
Date: January, 2014
Journal: PLoS Med
Impact Factor: 4.32
Why they did it?
Type 2 diabetes (T2DM) is a condition where there is too much glucose (sugar) in the blood (e.g. hyperglycemia). If untreated, T2DM can lead to increased risk of increased risk of heart disease and stroke, reduce the life expectancy of people with T2DM by about 10 years compared to people without T2DM. Regular aerobic physical activity (PA) (brisk walking and jogging) has been shown to prevent T2DM. Strength training (ST) has also been shown to reduce the complications associated with T2DM. However, ST and T2DM research has only been conducted among those who already have T2DM. It is currently unknown whether ST prevents T2DM. The aim of this study was to examine the longitudinal effects of ST among a large population sample of women.
How they did it?
This prospective study used combined data from two famous U.S. studies (1) Nurses' Health Study and (2) Nurses' Health Study II (www.channing.harvard.edu/nhs/). In brief, this study involved over 100,000 women, aged 24-55 years, who were followed up from 1976 to 2000-1. Over the study period, questionnaires were sent to the women every two years to update their information on disease status and major lifestyles, such as weight, smoking history, and physical activity. The physical activity assessments examined average weekly time spent in; (1) aerobic physical activities (e.g. brisk walking, running, bicycling) or (2) strength training (e.g. free weights, weight machines). For comparisons, the time spent in combinations of these activities was grouped into: none, 1-29, 30-59, 60-150 and >150 minutes/week. Self-reported incidence of T2DM was also recorded.
What they found?
Over the study period, a total of 3,491 participants developed T2DM. The key finding was that, when compared to women who did no PA-ST, those who did >150 minutes/week PA-ST had a 40% lower risk of developing T2DM. Importantly, the combination of PA-ST was more effective in reducing T2DM risk, when compared to either PA or ST, alone. These results remained significant after accounting for confounding factors such as age, education, smoking, alcohol consumption, body weight and poor diet. In a sub-analysis, the largest protective effect was observed among those who did PA >150 minutes/week and ST >60 minutes/week (70% lower T2DM risk).
Ok, what does this mean to me?
This study is among the first to show that among a large population sample of women, PA-ST were effective in preventing T2DM. The most important finding was that PA and ST were most protective of T2DM incidence when combined. Limitations of this study were that all data was collected by self-administered questionnaires, which may have resulted in over reporting of PA and ST. Nevertheless, these data highlight the role of regular combining PA and ST to prevent T2DM.