Everyone knows that joining a gym is a quote-unquote good idea. Now, a new study looks at exactly how much of a benefit fitness club-goers have over the rest of us when it comes to getting regular exercise—and its results may convince you to restart that stalled membership.
To put some research behind this commonly held belief, Iowa State University scientists recruited 405 relatively healthy adults, half of whom had belonged to a gym for at least 30 days, and half who had not been members for at least least three months. All participants had their resting blood pressure, heart rate, and body mass index measured, and completed questionnaires about their time spent exercising, sitting, and doing various lifestyle activities each week.
The researchers then analyzed those responses to determine which participants met the national recommended guidelines for physical activity: 150 minutes of moderate or 75 minutes of vigorous aerobic activity each week, including at least two days of weight lifting or other muscle-strengthening activities.
The difference between groups was “pretty dramatic and surprising,” says corresponding author Duck-chul Lee, an assistant professor of kinesiology. While non-members only exercised an average of 137 minutes a week, those who belonged to a gym logged an average of 484 minutes a week. Only 18% of non-members met the guidelines for both physical activity and strength training, compared to 75% of members.
Overall, the researchers calculated, a gym membership was related to 14 times higher odds of meeting weekly physical activity guidelines. The results were similar in both men and women, and were adjusted for health issues like high cholesterol, arthritis, and asthma.
Not only did gym members exercise more; they also had better cardiovascular measures and were less likely to be obese. Gym-goers—especially those who had kept a membership for a year or more—tended to have lower resting heart rates, higher cardiorespiratory fitness, and smaller waist circumferences than their non-member peers.
Before their analysis, Lee and his co-authors suspected that gym members may be more sedentary in their time outside the gym than non-members. “We thought maybe they’d be more tired, or be satisfied they’d done enough for the day,” he says.
But they didn’t find that to be the case, either. “Physical activity outside of the gym was the same for both groups,” he says, “For non-members, joining a gym really may increase overall activity levels.”
Because of the study’s cross-sectional design, Lee says, it’s also possible that people who are more active are simply more likely to join a gym. And while the study took place in a city with lots of health-club options, he notes, people living in more rural areas may find it more difficult to attend a gym regularly.
And, of course, you do have to show up. “It’s true that some people with a gym membership do not go regularly, just as some people who don’t have memberships still go out and run or bike and still meet the guidelines,” Lee says. For this study, some measurements were taken at the gyms themselves, assuring that memberships were in use.
But Lee says the study supports the idea that joining a gym can help people who aren’t getting enough exercise on their own. Only half of Americans get the recommended amount of aerobic activity, the study reports, and only about 20% meet the guidelines for strength training.
“At the gym you can use the weights or the resistance machines,” Lee says. “In real-life, there aren’t a lot of day-to-day activities that improve muscle.” (The researchers did not ask participants if they had weights or other fitness equipment at home.)
The researchers report no conflicts of interest, and no financial stake in any fitness clubs. The study is published in the journal PLOS ONE.
Lead author Elizabeth Schroeder, a former Iowa State graduate student, says that health club memberships can have more benefits than just weight loss, and she hopes these findings encourage more people to find a gym or fitness studio that works for them.
"Some people may enjoy being at a gym and doing their own workout routine, while others may desire group classes that potentially foster a social aspect, fun environment, consistent schedule, and a workout designed for you," she says. "Either way, they both involve accumulating physical activity, and that's the goal."