Finding time to exercise can be hard, and the research shows that's especially true for mums.
"When you ask people 'why don't you do more physical activity', the most common reason is they don't have enough time," says Lyndall Strazdins from Australian National University.
"Half of the world are insufficiently active, and within that group there is the consistent gender gap which widens over time."
That gap is particularly profound in heterosexual couples with kids, Professor Strazdins' research published in 2022 found.
The researchers looked at data from the Household, Income and Labour Dynamics in Australia (HILDA) survey, focusing on the effects of both paid work and unpaid caring and domestic responsibilities on physical activity.
It shows as family demands increase, women's physical activity becomes more limited, but the same doesn't happen for men.
Why women are exercising less than men
It's well established women do more unpaid labour in the home and have less leisure time than their male partners.
And while the gender exercise gap exists even in childhood, Rebecca Ahern says six in 10 women say they were more active before having children.
She's the head of VicHealth's This Girl Can campaign, and mum of two young children.
"Juggling the priorities of caring responsibilities, the home, work — carving out that time [to exercise] is really tricky."
Professor Strazdins says women have less leisure time, and it's also the quality of that time that is an issue.
"It's often broken up into 10 minutes here, or five minutes there.
"Women try and kick two goals; do their exercise and look after the kids, or do exercise and get to the shops.
"They are constantly trying to fit their exercise around other things."
She says weaving together a "high-care environment" and exercise is "generally very difficult".
Other reasons women exercise less than men, cited by Ms Ahern, Professor Strazdins and VicHealth research, include:
- Women not feeling safe to exercise when they have the opportunity; for example, in the evenings
- "Mum guilt"
- The cost
- Unwelcoming environments
- Fear of judgement
- Feeling less confident about their body's appearance and abilities post-kids.
Men 'borrowing' women's time
One of the key findings of Professor Strazdins' research was men "borrowing" time from women to keep up their exercise routine.
For example, the study found even when women work fewer paid hours, men were more likely to access that "free" time for their exercise, rather than women being able to use it for themselves.
Men's time for jobs and health is "protected", whereas women's is "squeezed", Professor Strazdins says.
"When men work longer hours, they cut back on their family hours. When women work, they don't then do less family hours, they just add them on."
Dads 'locked out of care' by their jobs
Professor Strazdins says the way society values economy above all else is costing us our health.
"I've heard a huge regret and sadness from many men about the way they feel locked out of care by their jobs.
"So it's not just the cost to women, there is a cost to everybody."
She says there needs to be a national conversation about what is fair work hours, so we can talk about what is fair care hours.
"And you can't have that latter conversation without the first."
Closing the exercise gap in your home
Professor Strazdins says the global "crisis" of people not exercising enough is pushing huge disease burdens from the cardiovascular to the cognitive.
Joys Njambi from Naarm/Melbourne has always been active.
When she had her daughter 17 years ago, she says doing "mum and bub" classes allowed her to stay that way.
She says doing exercise in increments was helpful as life became busier with work and family, such as taking three 10-minute walk breaks during work days.
Ms Ahern says she has to be "really intentional" about carving out time to exercise.
"I walk the kids to school to get that incidental exercise, as well as planned.
"Going to the park with [my kids and] a ball is a great example of just trying to get out a little bit more movement into my day."
She says it's important for women to remember that "little bits" count and we shouldn't be too hard on ourselves.
"I can look at my step count and sometimes I hit 10,000 without even realising," she says, pointing to how much physical activity being a mum to young kids can involve.
Professor Strazdins says evening up care hours in the home, allowing both men and women to have enough time to stay healthy, is the first step in closing the exercise gap.
Ms Ahern says couples talking about prioritising exercise can help with that.
"My partner was a golfer and he let that go because that took all of Saturday morning, or the day even," she says.
"Now we both create time for ourselves on Saturday. He has also taken on cooking more meals."