The study, by researchers at the University of Queensland and the University of South Australia, was published in the journal Science and Medicine in Sport last month.
Although it is important to make time for physical activity, the actual timing can have positive or negative effects on health, says Dr. Sjaan Gomersall, a research fellow at UQ.
“When people undertake an exercise program, the time spent in other domains, such as sleep or screen time, must be reduced to accommodate the new activity,” she says.
“If a new exerciser chooses to reduce screen time to accommodate exercise, for example, then there will presumably be additional health benefits, given that sedentary time is a risk factor for mortality and cardiovascular disease,” Gomersall says. “Conversely, if they choose to sleep less, the benefits of physical activity may be reduced and ultimately lead to negative health outcomes.”
The sleep levels of participants decreased about 40 minutes a day during the study, which tracked 129 inactive adults, ages 18 to 60, in a six-week exercise program.