Hold on! The ability to hold a grip predicts who has the willpower finish their schoolwork

There is not yet a clear cause-and-effect relationship between squeezing a handgrip and working up the willpower to tackle a school assignment, but it's clear there is a connection, says Matthew Stork, a PhD candidate in Kinesiology and lead author of a study published in The Journal of Health Psychology.

Stork and his co-authors looked at a group of 30 first-year university students, asking them their plans to engage in two tough challenges for students adjusting to university life: completing their school work and keeping up their exercise schedules. Both require high levels of self-control.

Next, they had them squeeze a grip-tester at half their own maximum power for as long as they could go, instructing them to "resist the temptation to quit."

Four weeks later, they compared the students' own projections to their actual results in getting their schoolwork and exercise done.

The researchers found that the students who had the greatest handgrip endurance were also those who worked hardest on their academic goals.

Conversely, those who let go earliest on the grip test were the least likely to resist the temptation to goof off, with implications for a wide range of other situations that demand self-discipline.

"If you have a high capacity for self-control you can have a high capacity in multiple domains," Stork says. "If you have a high level of self-control, it's not only for exercise or doing well in school, but it can also apply to other helpful behaviours as well, like regulating your eating or smoking habits."

The good news for those who gave up early in the grip test, Stork says, is that self-control can be trained and improved over time. The more times a person is successful at overcoming distractions or temptations on a regular basis, the more likely they are to learn how to successfully exert self-control in the future.