Parents blame their children for a lot of things, like not being able to go to nice restaurants or drive more than an hour from home. They blame them for not being able to exercise, too. A recent study found, however, that rather than a real impediment to working out, kids were blamed for their parents’ faulty approach to exercise. Changing that approach could be more helpful than hiring a baby sitter.

Researchers at the University of Pittsburgh found that parents did exercise a lot less after their children were born. The problem wasn’t so much the kids, however, as the parents’ attitude that they had to set aside large blocks of time to work out.

The study tracked more than 800 participants, who averaged 24 years of age at the start of the study, for two years. The median amount of physical activity at the start of the study was 6 hours and 20 minutes, as self-reported by participants. The roughly half hour a day is nothing to brag about, but is above the minimum recommendation from the Centers for Disease Control of two and a half hours per week, which three-quarters of American fail to meet.

New parents fell well below this.

Those who had children during the study period reduced their exercise time by about three and a half hours per week during that time. New fathers lost the most, dropping four and a half hours from their previous eight hours a week.

Ethan Hull, an exercise physiologist at the University of Pittsburgh, said he decided to study the issue after hearing friends who had recently become parents talk about how tired and overwhelmed they felt. Mr. Hull presented the findings earlier this year at the American College of Sports Medicine annual meeting in New Orleans.

Lack of time and feeling guilty for being away from their children are frequent reasons mothers and fathers give for not exercising more.

To move beyond this, several experts suggest viewing exercise differently. Too many people think exercise means a specific program and a block of time. Figuring they can’t go to the gym for an hour or attend a yoga class three days a week, too many people opt to do nothing at all.

Walking with the baby in a sling, biking with a young child in a trailer and jogging for a half hour during a lunch break can add up to several hours of exercise in a week.

Physical fitness helps decrease the incidence of chronic diseases and improves mental health. In other words, it makes you a better parent.