As winter enshrouds the southern hemisphere and millions of us continue to be barred from accessing gyms, yoga studios, public pools and other fitness centres due to COVID-19 restrictions, there has been an alarming decrease in physical activity levels across the Australian population and an equally alarming increase in sedentary behaviour (sitting or lying down, while awake).

As the researchers who conducted a nation-wide cross-sectional survey of the physical activity levels of Australian adults during late April 2020 pointed out,

“Enforcing restrictions that encourage all Australians to stay at home unless they must leave for essential activities removes opportunities for activity and provides opportunities for sedentariness.”


The survey found that only 30% of Australian adults were meeting the very modest aerobic component of our national guidelines for physical activity, which recommends at least 30 minutes of moderate intensity exercise (such as brisk walking), on at least 5 days per week.

Of great concern, given the wide-ranging and long-term detrimental effects of inadequate physical activity (which we’ll get to in a minute), was the fact that young adults are the least active: only 20% of respondents aged 18-29 met the aerobic activity recommendations, compared to 41% of 60-69 ear olds.

And a startling 20% of respondents reported performing no aerobic activity at all in the week before the survey.

40% of respondents reported that they had engaged in muscle strengthening activities on at least 2 days in the previous week (52% of 18-29 years vs 34% of 70-79 year olds), but 51% reported performing no strengthening activities at all.

Finally, three quarters of respondents reported being sedentary for between 3 and 12 hours each day, with young adults being the biggest couch potatoes: 50% of 18-29 years spent over 9 hours per day on their behinds, compared to only 34% of 60-69 year olds.

Almost half of adult Australians report that they have decreased their physical activity levels since SARS-CoV-2 was declared a global pandemic, mirroring the trend been observed internationally.

But why should we care if lockdown is making us lazy? What’s so bad about being physically inactive anyway?

Plenty, as it turns out. Inadequate physical activity and excessive sedentary behaviour have both been well known for some time to increase the risk of cardiovascular disease, frailty in older adults, anxiety, and a host of other chronic ailments, and to increase all-cause mortality risk (the chance of dying, of any cause).

Recently-published research has highlighted additional risks conferred by inadequate physical activity:

1. Sitting too much increases your risk of dying of cancer

In a cohort study of over 8000 middle-aged and older US adults, those who spent the most time in sedentary behaviour (tracked by wearing a hip-mounted accelerometer for 7 consecutive days) had a 52% higher risk of dying of cancer than those who spent the least time on their butts – even if they engaged in moderate to vigorous physical activity at other times of day.

Remarkably, for every 30 minutes spent in light intensity physical activity instead of sitting, the risk of dying of cancer dropped by 8%, while replacing 30 minutes of sedentary time with 30 minutes of moderate to vigorous physical activity slashed the risk by 31%.

2. Physical activity slows brain aging

A preliminary study presented at the American Academy of Neurology’s 72nd Annual Meeting in April 2020 used magnetic resonance imaging (MRI) scans to measure the brains of almost 1600 older people (average age 75) with activity levels ranging from inactive to very active.

The cognitive decline that occurs with age is correlated with actual shrinking of the brain, but the researchers found a clear correlation between physical activity levels and brain size.

The least active people had significantly smaller brain volume than the most active people, equating to almost 4 years of additional brain aging. In other words, an 80 year old who gardens, plays tennis, goes to Zumba classes and walks their dog each day, has the brain volume of a 76 year old couch potato. And at that age, every year of brain aging counts for a lot!

The old trope of brain vs brawn urgently needs to be replaced with a new public health message: brawn supports brain.

3. Lack of exercise increases dementia as much as the major genetic risk factor

On a related note, researchers tracked 1646 older Canadian adults for 5 years in order to study the relationship between exercise, apolipoprotein E (APOE) genotype and risk of dementia.

Adults who carry one copy of the APOE e4 gene are three times more likely to develop Alzheimer’s disease than those with other variants of the gene, while those with two copies are 8-12 times more likely to develop this dreaded, incurable form of dementia.

Among non-APOE e4 carriers, those who did not exercise had almost double the risk of developing dementia in that time period as those who did, implying that lack of physical activity is almost as bad as carrying the high-risk gene for Alzheimer’s.

4. Decreased physical activity and increased sedentary behaviour worsen mental health

A cross-sectional study of over 3000 US adults conducted in early April 2020 found that participants who had previously been physically active had reduced their activity by one-third, while previously inactive participants had not significantly changed their activity level.

Large increases in sitting time and screen time were reported, with previously active participants posting the greatest rises in both.

Both no longer being physically active and increased screen time following COVID-19-related restrictions were consistently associated with worse current mental health, including increased depressive symptoms, loneliness and stress, and lower positive mental health.

Those who were self-isolating or in quarantine reported higher depressive and anxiety symptoms compared to those who were merely social distancing.

The bottom line:

The advice to stay home, avoid other people and watch Netflix in order to avoid catching a virus from which 99.75% of people will recover may be sowing the seeds for a bitter harvest of excess cancer deaths, cognitive decline, dementia and mental health problems in decades to come, that will far outweigh the harms done by the virus itself.

In order to protect our physical and mental health, all of us need to be prioritising regular physical activity (both aerobic activity, such as walking, cycling, running and dancing; and strength-building activity such as bodyweight exercises, resistance bands, Pilates reformer, and weight training).

Whenever you can, exercise outdoors in natural settings, in order to harness the remarkable health benefits of time spent in green spaces (see my previous article, Can getting in the green beat COVID-19?).

Bans on use of outdoor fitness equipment, outdoor fitness classes and access to walking trails and national parks are non-evidence based and should be vigorously challenged using any available legal avenues.

Now more than ever, we need to maintain and improve our fitness in order to protect both physical and mental health. Since public health authorities have been thoroughly mute when it comes to any recommendations aimed at improving the population’s health and reducing risk factors for serious outcomes of SARS-CoV-2 infection, it’s up to us to take responsibility for ourselves.