People were offered cash to go to the gym. Guess what happened?

Have you ever thought, “You couldn’t pay me enough to go to the gym”? You’re not alone.

When researchers offered new gym members $30, $60 or a gift worth about $30 for going to the gym nine times in six weeks, attendance increased only slightly, according to the “Can Financial Incentives Help People Trying to Establish New Habits?” study by the National Bureau of Economic Research.

Published in July, the eightmonth study separated 836 new members of a private gym in the Midwest into a control group and three incentive groups. On average, participants said they planned to exercise three times a week. What’s more, 43 percent said they had exercised on average one day or less per week in the prior year.

“The hope would have been that by targeting this, you could especially capture some of the people who early on fall off and get them to keep going for longer,” said Justin Sydnor, one of the report’s authors and a riskmanagement and insurance professor at the University of Wisconsin at Madison. “These incentive programs did increase slightly how often people went, but only by about one visit, and then it really has no lasting impact.”

A bigger sum wouldn’t have mattered, he said, because doubling the prize from $30 to $60 “didn’t really improve the trajectory at all, and so that makes us not have a lot of confidence that further increases would do a lot.”

Additionally, many participants didn’t go as often as they’d planned. Instead of three times, they went twice in the first week and were down to once a week by the end of the second month.

“I think a lot of that optimism is rooted in the fact that people join gyms at a moment of peak motivation,” such as on New Year’s Day or salient birthdays, Sydnor said.

More effective approaches may be based on social intervention, such as meeting a friend or trainer at the gym, or getting reminders to go.