"When you have a son," Nadal elaborated, "you are happy. But it's no comparison to the sadness you feel losing a son. When you earn $1 million, you are happy. But when you lose $1 million, it hurts more. If Rafa wins Wimbledon, he's happy, we're all happy. But what if he loses?"
Two recent Harvard graduates are wagering that this principle -- the pain of loss outstrips the pleasure of gain -- can motivate Americans (a people by and large less dedicated to fitness than, say, star tennis players) to keep their commitments to exercise.
Yifan Zhang and Geoff Oberhofer, class of 2010, have founded Gym-Pact.com, a service that charges users money for skipping planned visits to the gym.
"People don't like losing money and it's one of the strongest motivators, much more than winning money," Zhang told The New York Times.
The minimum deduction for playing hooky from the health club is $5, charged to a credit card kept on file, but people can choose higher monetary stakes if they need greater incentives.
But Gym-Pact is not all punishment and no reward: The money from truancy fees is pooled in a PayPal account and divvied out to members who meet their goals.
All you need to use Gym-Pact is a smartphone -- an iPhone at the moment, although Android and HTML5 devices will soon be supported. After joining, users "set their pacts," making what the site calls flexible personal commitments. The minimum pledge is thirty minutes of exercise once a week. ("Don't stress if your life is unpredictable," Gym-Pact explains, because "you can change your Pact any week.")
To validate gym visits, users check in to their facilities using an iPhone app, and a smartphone's ability to track its owner's location. (There are currently 40,000 gyms in the company database.) If you try to duck out of a session early, your phone will warn you that the truncated workout will not count.
Live up to the terms of your contract, as it were, and Gym-Pact offers positive reinforcement -- but not very much (in keeping with the theme of loss trumping gain). The amounts disbursed to virtuous users depend on how much the lazy have lost, but rewards have been averaging a meager 50 cents per workout. Health and fitness will have to remain their own rewards.
Gym-Pact bills itself as "a fun, social and real way to get yourself to the gym." How does it sound -- a clever solution to a lifestyle conundrum, or just a cheap gimmick destined to disappear faster than the New Year's resolution crowd at your local fitness center?