Lifting weights — even for less than an hour a week — is associated with a reduced risk of having a heart attack or stroke, according to a study by Iowa State University researchers.

That benefit appears to be independent of how much time people spend doing aerobic activities, such as running, walking and biking, the study also found.

These findings underscore the importance of including some kind of regular resistance exercises — ones that strengthen muscles — in our physical activity routines. They also support the U.S. government’s recently updated “Physical Activity Guidelines,” which recommend that adults engage in muscle-strengthening activity, such as lifting weights or doing push-ups, at least two days each week.

“People may think they need to spend a lot of time lifting weights, but just two sets of bench presses that take less than five minutes could be effective,” says Duck-Chul Lee, the study’s senior author and an associate professor of kinesiology at Iowa State University, in a released statement.

The research was published earlier this month in the journal Medicine & Science in Sports & Exercise.

Study details

As background information in the study points out, most previous research on muscle strengthening has focused on its positive effects on bone health, physical function and older people’s quality of life. Few studies have looked at whether muscle strengthening has an impact on the risk of cardiovascular disease, such as heart attacks and strokes, or on premature death. Those that have investigated that topic have produced inconsistent results.

For the current study, Lee and his colleagues used data collected between 1987 and 2006 from almost 13,000 adults (mean age: 47) participating in the ongoing Aerobics Center Longitudinal Study, which began in 1970 to investigate the relationship between physical fitness and cardiovascular health. The participants had received at least two comprehensive medical checkups at the Cooper Clinic in Dallas, Texas. They had also filled out questionnaires about their health-related behaviors, including how often they did resistance exercises (either using free weights or weight-training machines) and/or aerobic activities weekly.

During the period of the study, 205 of the participants experienced cardiovascular events, such as heart attacks or strokes, and 276 of them died from those or other causes.

When the researchers looked at the relationship between those outcomes and the participants’ exercise habits, they found that people who had reported doing resistance exercises for one to three times a week for a total of up to 60 minutes were 40 to 70 percent less likely to have had a cardiovascular event or to have died from any cause during the study period. That association held even if the participants did not meet the minimum recommended guidelines for weekly aerobic exercise.

Interestingly, the study found that people reaped no significant added benefit when they did resistance exercises for four or more times a week or for more than 120 minutes a week. The reason for this finding is unknown, but Lee and his colleagues point out that high-intensity resistance training is associated with an increased risk of arterial stiffness, which can lead to heart attack and stroke.

Findings are not definitive

This study comes with several important caveats. Most notably, it was observational, so it can show only a correlation, not a direct cause-and-effect relationship, between resistance exercises and a lower risk of heart attack, stroke and premature death. Other factors might also explain the results, including one obvious one: The people in the study who engaged in resistance exercises may have been healthier to start with than those who did not.

Another limitation is that the participants self-reported how often they exercised. People tend to overestimate their leisure-time physical activity on questionnaires (and that may be especially true of men when it comes to weightlifting, Lee and his colleagues point out).

Still, the study’s findings support other research on this topic. One study involving middle-aged and older men found, for example, that weight-resistance training for at least 30 minutes a week was associated with a 23 percent reduced risk of coronary heart disease. And data from the ongoing Women’s Health Study have revealed similar benefits for middle-aged and older women who do strength training for up to an hour a week.

‘The million-dollar question’

As Lee points out, the results of all this research are “encouraging.”

“But will people make weightlifting part of their lifestyle? Will they do it and stick with it?” he asked. “That’s the million-dollar question.”

Part of the problem is that many of us think we must have access to a gym — with its free weights and weight machines — to do resistance exercises. But there are other ways to keep our muscles strong.

“Lifting any weight that increases resistance on your muscles is the key,” said Lee. “My muscle doesn’t know the difference if I’m digging in the yard, carrying heavy shopping bags or lifting a dumbbell.”

“Muscle is the power plant to burn calories,” he added. “Building muscles helps move your joints and bones, but also there are metabolic benefits. I don’t think this is well appreciated. If you build muscle, even if you’re not aerobically active, you burn more energy because you have more muscle. This also helps prevent obesity and provide long-term benefits on various health outcomes.”

FMI: You’ll find an abstract of the study on the Medicine & Science in Sports & Exercise website. For tips on how to incorporate muscle-strengthening exercises into your weekly activities, you can start with the National Institute on Aging’s website. It offers a set of exercises that people can do at home. Some require light weights and a resistance band, but others can be done without any extra equipment. Of course, if you have health issues or concerns, you should talk with your doctor before starting any exercise program.