Forget heart rate monitors and body fat measurements. The best gauge of fitness may be a tidy house.

NiCole Keith, an associate professor of physical education at Indiana University, set out to examine how physical activity is influenced by a range of factors for city-dwellers. Her study involved 998 people aged 49 to 65 living in St. Louis. She looked at the condition of sidewalks, the presence of outdoor lighting, and other environmental characteristics believed to affect an individual’s decision to be active. The result, she says “was not at all what we expected.” The interior condition of people’s houses turned out to be the only factor linked to their level of physical activity.

“If you spend your day dusting, cleaning, doing laundry, you’re active,” Keith said. Indeed, studies have shown that many household chores and gardening tasks burn enough calories to constitute moderate exercise–the equivalent of a brisk walk.

Keith thinks her findings could help health experts shape recommendations that people are actually willing to follow. While people may be reluctant to take 30 minutes to go for a walk, they may be willing to spend the same time cleaning.