A four-day working week can help people exercise more and sleep better, leading to improvements in cognitive functioning and helping prevent serious illness, a new study has found.

The University of South Australia investigation showed holidays are generally good for people's health, even if only a three-day break.

"When people go on holiday, they're changing their everyday responsibilities because they're not locked down to their normal schedule," researcher Ty Ferguson said.

"In this study, we found that movement patterns changed for the better when on holiday, with increased physical activity and decreased sedentary behaviour observed across the board.

"We also found that people gained an extra 21 minutes of sleep each day they were on holiday, which can have a range of positive effects on our physical and mental health."

Extra sleep has been linked to improved cognitive function and productivity and could also help lower the risk of developing a range of health conditions such as obesity, diabetes, cardiovascular disease and depression.

Not surprisingly, the changes in sleep and activity increase in line with the length of the holiday.

But lead researcher Carol Maher said the study still offered support for a four-day working week, something already being trialled by companies across the world.

"Employees reported less stress, burnout, fatigue, as well as better mental health and improved work-life balance," Prof Maher said.

"This study provides empirical evidence that people have healthier lifestyle patterns when they have a short break, such as a three-day weekend.

"This increase in physical activity and sleep is expected to have positive effects on both mental and physical health."