Yifan Zhang of Boston and a fellow Harvard grad launched Gym-Pact, which uses "motivational fees" to prod club members to work out more often. By Susannah Snider, Staff Writer April 1, 2011 How does your business work? Gym-Pact helps people commit to working out. You pay a discounted membership fee to join a gym but agree to exercise a certain number of times per week. If you don't meet your goal, we charge you a $10 "motivational fee" for each day you miss.How do you make participants pay? We automatically charge their credit card weekly. What do the gyms get out of it? Our program entices people who otherwise can't make themselves work out to buy gym memberships. It also decreases membership turnover, which is a big problem for gyms. Where did you find the inspiration? I took a class in behavioral economics my senior year at Harvard. I learned that losing money gives you a bigger incentive than gaining the same amount of money. So I talked to my friend Geoff Oberhofer about what I was studying, and we came up with the idea for Gym-Pact. Where do you see Gym-Pact in the future? We don't see ourselves opening a chain of gyms. We just want to expand the program to existing gyms in more cities. Advertisement Did you always see yourself as an entrepreneur? Yes. I'm working full-time right now on another start-up that I launched at Harvard. It's a nonprofit called Styleta. We sell donated designer clothes online for charity. I'm very interested in people's incentives and how to turn those into some kind of social good. Are you a member of Gym-Pact? Geoff and I both do Gym-Pact, so we know how effective it is. We've both committed to working out four days a week -- and we've both slacked off and been charged the fees. We put them into the company. Can you re-create the incentive behind Gym-Pact without joining the program? We've seen that two friends agreeing to such a program can be very effective. If you have someone holding you accountable, whether or not there's a monetary incentive, it definitely can offer more motivation to fulfill your commitment.