The ability to do a lot of pushups may be a sign not only of strength but also of good heart health, a new study suggests.

The study tested the stamina of middle-aged male firefighters. It found that those who could do more than 40 pushups in a row had a 96 percent lower risk of being diagnosed with heart disease or experiencing other heart problems over a 10-year period, as compared with those men who could do fewer than 10 push-ups.

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However, because the study looked at only male firefighters, who have very active jobs, it's unclear if the findings apply to average Joes. [9 New Ways to Keep Your Heart Healthy]

But the findings suggest that "pushup capacity could be an easy, no-cost method to help assess cardiovascular disease risk," study lead author Justin Yang, an occupational medicine resident at the Harvard T.H. Chan School of Public Health in Boston, said in a statement.

The study was published Feb. 15 in the journal JAMA Network Open.

A simple test

Physicians know that being physically fit is linked with better heart health. But it can be difficult for doctors to accurately assess a person's fitness level during a routine visit. Doctors sometimes use "treadmill tests" to evaluate a person's fitness level. In these evaluations, people run on a treadmill until their heart rate reaches a certain level. But the tests are time-consuming and require expensive equipment, so they aren't done routinely.

The new study tested whether a simple exercise like a pushup could provide clues to heart health. To find out, researchers examined records from more than 1,100 Indiana firefighters (with an average age of 39) who underwent a pushup test at the beginning of the study. The participants were then followed for a decade to see if they experienced a cardiovascular event, such as a diagnosis of coronary artery disease, heart failure or cardiac arrest.

During the study period, 37 cardiovascular events were found among the study participants, but only one cardiovascular event occurred among the men who completed more than 40 pushups.

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Those who could do 11 or more pushups had a lower risk of cardiovascular events, compared with those who could do 10 or fewer, the study found. And men who could do more than 40 pushups had the largest reduction in risk.

However, the researchers cautioned that pushup capacity is not necessarily an "independent predictor" of heart disease risk. That is, there may be other factors tied to heart disease risk that are also related to how many pushups an individual can do. Such factors could include a person's age, body mass index (BMI) and aerobic fitness level. But, in general, pushup capacity could be an indicator of overall fitness, the researchers said.

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"This study emphasizes the importance of physical fitness on health and why clinicians should assess fitness" during doctors' visits, study senior author Stefanos Kales, a professor in the Department of Environmental Health at Harvard T.H. Chan School, said in the statement.

More research is now needed to examine the link between pushup ability and heart disease in the general population, including among women and less-active men, the researchers noted in their paper.

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Originally published on Live Science.