A study using smartphone technology found that people tend to drink more on days when they are more physically active.

The Northwestern Medicine study tracked 150 people ages 18-89 who recorded their physical activity and alcohol use in smartphones for 21 consecutive days at three different periods during the year.

“Monday through Wednesday, people batten down the hatches and they cut back on alcohol consumption,” lead author David Conroy said in a news release.

“But once that ‘social weekend’ kicks off on Thursdays, physical activity increases and so does alcohol consumption,” Conroy said.

Researchers say they hope further studies will help determine what drives people to drink more on days they exercise more.

“Insufficient physical activity and alcohol use are both linked to many health problems, and excessive alcohol use has many indirect costs as well,” Conroy said. “We need to figure out how to use physical activity effectively and safely without having the adverse effects of drinking more alcohol.”

The study relied on a daily diary method, whereas others have used a 30-day self-reporting method.

“We zoomed in the microscope and got a very up-close and personal look at these behaviors on a day-to-day basis, and see, it’s not people who exercise more drink more – it’s that on days when people are more active, they tend to drink more than on days they are less active,” Conroy said.

The study was published in Health Psychology.