Research published in the March issue of Medicine & Science in Sports & Exercise found that individuals who did any amount of strength training on a weekly basis had a 40 to 70 percent reduced risk of developing heart attack, stroke, or death related to heart disease compared with individuals who did no strength training (independent of how much aerobic exercise people did). And in a related study — published online ahead of print this month in Mayo Clinic Proceedings — researchers reported that having moderate muscle strength reduced type 2 diabetes risk by 32 percent, independent of individuals’ cardiovascular fitness levels. Both studies analyzed data that came from the Aerobics Center Longitudinal Study conducted at the Cooper Clinic in Dallas (an ongoing cohort of the study is now called the Cooper Center Longitudinal Study). “It is well-known that aerobic exercise is good for the heart and prevents heart attack or stroke,” says DC (Duck-Chul) Lee, PhD, associate professor of kinesiology at Iowa State University in Ames — who was a co-author of both studies. “However, there is still limited evidence to show if resistance exercise is good for the heart. Our findings suggest that resistance exercise alone, such as weight lifting, may be good enough to reduce the risk of developing cardiovascular diseases. ” Dr. Lee and his collaborators found that the benefits of strength exercises were independent of running, walking, or other aerobic activity. Even a small amount of strength training per week appears to be linked to a benefit in terms of reducing risk of heart problems, specifically, Lee says. People in the Medicine & Science in Sports & Exercise study who reported doing strength training just once per week (for any amount of time) had this lower risk compared with people who didn’t do strength training at all. He adds that it doesn’t matter what type of exercise you do — resistance exercise (aka “strength or weight training”) refers to any exercise that increases resistance on your muscles. “My muscle doesn’t know the difference if I’m digging in the yard, carrying heavy shopping bags, or lifting a dumbbell,” he says.
Study Data Suggests Any Amount of Strength Training Likely to Lead to Heart Benefits
For the study that looked at cardiovascular disease morbidity and mortality, researchers analyzed data from 12,591 adults between the ages of 18 and 89 who had received at least two clinical exams between 1987 and 2006 at the Cooper Clinic and were part of the Cooper Center Longitudinal Study. Using a medical history questionnaire, participants self-reported their resistance exercise and aerobic activity. Compared with those who did no strength training, those who performed resistance exercises one to three times a week for a cumulative total of up to 59 minutes experienced the 40 to 70 percent decreased risk of heart attack, stroke, or death related to heart disease. Putting in over an hour, or more than four times a week, however, did not seem to lower heart disease or diabetes risks any further than those who did less weekly strength training (but was still advantageous over not doing any strength training at all). “It’s not entirely clear why higher strength and/or high amounts of resistance training did not protect against diabetes and cardiovascular disease,” says Angelique Brellenthin, PhD, a postdoc research associate in kinesiology at Iowa State University, who was a co-author of the diabetes study. The study authors note that high-intensity resistance training may play a role in heart disease by contributing to arterial stiffness. But currently there’s not enough evidence to show that there should necessarily be an upper limit to the recommendation for weekly strength training, Brellenthin says — particularly when you consider a wide range of potential health outcomes like osteoporosis and frailty. For the study that looked at incidence of type 2 diabetes, the researchers followed a smaller subset of individuals from the same Cooper Clinic dataset. This one included 4,681 people who did not have diabetes at the start of the study. Participants underwent muscular strength tests and maximal treadmill exercise tests when they enrolled in the study. Of that group, 229 developed type 2 diabetes over an average follow-up period of eight years. The data showed that people who had moderate muscle strength at the beginning of the study had a 32 percent reduced risk of developing diabetes over the follow-up period. More research will be needed to determine the optimal target amount of strength training linked to the most benefit in terms of reducing risk of heart disease and diabetes. The bottom line you should know, Brellenthin says: “Doing some strength training — whatever you can fit in your schedule — likely provides benefits.”
The Data Doesn’t Mean You Can Skip the Cardio. We Know Aerobic Exercise Is Important, Too, Experts Say
Results also showed that participants who were regularly doing strength training (as noted above) were getting these heart disease and diabetes prevention benefits whether or not they met the guidelines established by the Centers for Disease Control and Prevention (which recommend that adults do at least 150 minutes of moderate or 75 minutes of vigorous aerobic activity per week). Sarah Samaan, MD, a cardiologist with Baylor Scott & White Legacy Heart Center in Plano, Texas, cautions, however, that resistance training should not take the place of aerobic exercise. “The two should be considered complementary,” she says. “Aerobic exercise has been found to lower the risk of heart disease, stroke, and dementia, and to improve memory and overall well-being.” Dr. Samaan notes that adding resistance exercise to aerobic activity has previously been found to be particularly beneficial for type 2 diabetes patients. “Resistance exercise may be particularly beneficial for weight loss. Decreasing abdominal fat, which is the more dangerous and inflammatory type of fat, is another beneficial effect of exercise that can lower risk for diabetes and heart disease,” Samaan says. It’s important to note that both studies are correlational. They show relationships between strength training and risk of heart disease or diabetes, but alone this data is not enough evidence to prove strength training definitively causes these outcomes (other factors could be at play). “We would like to next conduct a randomized controlled trial directly comparing aerobic and resistance exercise on chronic disease risk factors like blood pressure, lipids [blood fats], and glucose [blood sugar],” Brellenthin explains. That data would help researchers understand the mechanisms in the body that underlie these findings. Meanwhile, Samaan echoes the same message as Brellenthin: People should be exercising regularly. “The majority of Americans do not do regular physical exercise; and undoubtedly this contributes to our high rates of obesity, diabetes, hypertension, and heart disease,” Samaan says. RELATED: How to Find and Stick to an Exercise Routine
