Exercising judgment: The psychology of fitness

But why do some freshmen manage to stay fit while others quickly put on the “freshman 15”" Bray found that students’ sense of power in life — self-efficacy, in psychological jargon — is closely related to their level of physical activity. Their inability to cope with the environmental and social changes they face at college was a big reason why many stopped exercising. Many students, for example, are athletes in high school but are not talented enough to play on college sports teams.

Not only do they lose out on the vigorous exercise of playing sports, but they often lose their motivation to train, Bray says, which is why he argues that universities can help their students adapt by providing more intramural and club sport opportunities. For many, this change to a sedentary lifestyle then becomes something that persists through the rest of college and even into adulthood.

“Personally, I believe that if we can teach people to adapt, that’s going to be more successful and probably more efficient than having them adopt” new healthy habits later in life, he says.

And it’s not just college. This rule applies to many of life’s transitions — moving into the workforce, switching jobs or moving, getting married, having kids. In each of these moments, there is a chance for people to give up on exercise, possibly for good.

“What it comes down to at each of those points is if we have the skills to be flexible and keep believing that these things are good for us. … I can keep it a priority and make it something I schedule the rest of my life around,” Bray says. “Unfortunately, [exercise] is one of the first things that goes when we get busy with other things.”

Reasons for stopping exercise might not be the same across all age groups.

Rachel Newson, a psychologist at Flinders University in Australia, looked at this question of what motivates and prevents exercise in adults 63 and over. Barriers to exercise in Newson’s study included “adverse weather conditions” and “not knowing what you’re physically capable of.” But the most common reason her participants didn’t exercise was because of physical ailments and painful joints.

On the other hand, motivators for Newson’s participants ranged from “I want to get out of the house” to “I want to be physically fit” to “I like to be competitive,” and the most common responses were ones related to health and physical fitness, suggesting “that older adults are clearly aware of the potential health benefits of exercise,” Newson writes.

Even adults who are fully healthy, have adapted to their environment, and live in a climate ideal for exercising, find plenty of reasons to sit on the couch instead. Clearly, other factors are at play. For one thing, it helps to have the right kind of intentions.