People drink more alcohol on days when they are more physically active, according to a recent study.

Researchers from Northwestern University found that Thursdays to Sundays are when people both exercise and drink more. This is the only study to use smartphone technology and a daily diary approach for self-reporting physical activity and alcohol use.

"Monday through Wednesday people batten down the hatches and they cut back on alcohol consumption," said David E. Conroy, lead author of the study. "But once that 'social weekend' kicks off on Thursdays, physical activity increases and so does alcohol consumption."

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

For the study, Conroe and his colleagues collected data from 150 participants between the ages of 18 and 89. They recorded physical activity and alcohol use for 21 days at a time, at three different times throughout one year.

Through future studies at the Center for Behavior and Health at Feinberg, Conroy hopes to discover what drives people to drink more on days they exercise more.

"Perhaps people reward themselves for working out by having more to drink or maybe being physically active leads them to encountering more social situations where alcohol is consumed -- we don't know," Conroy said. "Once we understand the connection between the two variables we can design novel interventions that promote physical activity while curbing alcohol use."

The findings were published online in Health Psychology, an American Psychological Association journal.