Motivating a gym class using game theory

One of my favorite parts about writing this blog is hearing stories of how people have used game theory in real life.

The other day I got an email from Jimmy who noticed game theory in action while at a group exercise class. Here is his story:

Hey Presh,

Thanks for taking the time to write and maintain Mind Your Decisions. I love the articles and read each one thoroughly.

As a fellow game theorist, I’m always amused when game theory rears it’s head in a practical manner. Figured I would pass along something that came up earlier this morning.

I work out at a group class in which an instructor calls out exercises for an hour. Today’s workout involved some creative use of game theory by the trainer to encourage everyone to work harder (for their own good of course).

He said at the beginning of the class that all of our exercises will start after the last person has finished with the previous exercise, but each exercise could not exceed 1.5 minutes (to make sure people actually finished).

This created an interesting situation as I planned how I would tackle each exercise.

On the one hand, I could work as hard as I could to ‘beat’ the rest of class and get a rest. On the other hand, I could slack off and hope that others would exercise lightly, meaning I would not need a breather. (We got right into the workout so that there was no collusion between the gym-goers.)

So how might this game play out?

We know that everyone goes to the gym to get proper exercise, but there is often a temptation to be lazy in the moment. This game adds a level of fun and social pressure that might inspire some people to work harder.

What are the incentives to each person? Let’s think about how someone’s effort may play out, considering also the role of how much effort the rest of the class is expending.

Here is how you might view the payouts of the various scenarios:

–If you take it easy and the group does too, you enjoy modest exercise (2)

–If you take it easy but the group does not, people may despise your laziness (-1)

–If you work hard but the group does not, you work hard and you get to rest in between exercises (3)

–If you work hard, and so does the group, the teacher keeps calling out exercises and you get too tired (1)

This gives us the following table of payouts (first number = your payout, second number = group payout):

Jimmy intuited these payouts and realized the game was meant to encourage everyone to work hard.

Regardless of what the group does, it was a dominant strategy to work hard. Ultimately this means everyone will work extra hard during the session.

The problem is like the prisoner’s dilemma: it is in the group’s best interest to go slowly and take up the whole 1.5 minutes. Individually, however, it is MUCH more beneficial to work hard and catch a breather (often times of up to 45 second to a minute).

And this is how the situation turned out: the group, as a whole, worked hard as each person tried to catch a breather. But as everyone was working hard, we just did more exercises in the one hour session.

Ultimately people wanted to exercise but it was hard to get them to push themselves in the moment. The game changed the incentives and a little bit of competition helped with motivation, showing that sometimes it is good to be caught in a Prisoners’ Dilemma.