A sedentary lifestyle may double a coronavirus patient's risk of dying with the infection, research suggests.
Physical inactivity can trigger many conditions that are known to worsen coronavirus complications, like obesity, type 2 diabetes and heart disease.
With the impact of exercise itself being less clear, medics from the Kaiser Permanente Medical Center in California analysed more than 48,000 adults with the infection.
Results reveal those who were "consistently inactive" in the two years leading up to the pandemic were more than twice as likely to die than the patients who met exercise recommendations.
Physical inactivity was second only to old age and having had an organ transplant when it came to the risk of severe complications, exceeding smoking and "virtually all the chronic diseases studied".
Although unclear exactly why this may occur, regular physical activity has been linked to a stronger immune response and lower levels of inflammation; a key driver of the coronavirus-related disease COVID-19.
The NHS recommends adults be active every day, aiming for at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity exercise a week.
Exercising regularly has been linked to a reduced rate of viral respiratory infections in general, as well as less "intense" symptoms, the medics wrote in the British Journal of Sports Medicine.
Global lockdowns have forced gyms to close, with Britons also only being allowed to exercise outdoors once a day during the UK's first "stay at home" restriction.
To better understand the relationship between physical activity and coronavirus complications, the Kaiser medics analysed the electronic health records of tens of thousands of people – average age 47 – who caught the infection between 1 January and 21 October, 2020.
Just under two-thirds (62%) of the participants were women. Statistics have repeatedly flagged being male as a risk factor for coronavirus complications.
The participants' average body mass index was 31, classed as obese.
Nearly one in five (18%) had an underlying health issue, while almost a third (32%) had at least two pre-existing medical conditions.
The participants' physical activity levels were recorded at least three times between March 2018 and March 2020.
Being "consistently inactive" was defined as doing no exercise or just 10 minutes a week. "Some activity" was considered to be 11 to 149 minutes a week, while "consistently meeting guidelines" was defined as exercising for 150 minutes or more every seven days.
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The results reveal the patients who were consistently inactive were more than twice as likely to be hospitalised or die with the coronavirus than those who met the exercise guidelines.
They were also 73% more at risk of being admitted to intensive care.
Compared to the patients who did some physical activity, those who consistently did none were 20% more likely to be hospitalised, 10% more likely to be admitted to intensive care and 32% more likely to die with the coronavirus.
The results applied after adjusting for other factors linked to coronavirus complications, like old age and having a non-white ethnicity.
The medics have stressed their study was observational, and therefore does not prove cause and effect. The participants also self-reported their activity level, leaving room for inaccuracies.
Nevertheless, the medics added: "It is notable being consistently inactive was a stronger risk factor for severe COVID-19 outcomes than any of the underlying medical conditions and risk factors identified by [the US Centers for Disease Control and Prevention], except for age and a history of organ transplant.
"In fact, physical inactivity was the strongest risk factor across all outcomes, compared with the commonly cited modifiable risk factors, including smoking, obesity, diabetes, hypertension [high blood pressure], cardiovascular disease and cancer.
"We recommend public health authorities inform all populations that short of vaccination and following public health safety guidelines such as social distancing and mask use, engaging in regular [physical activity] may be the single most important action individuals can take to prevent severe COVID-19 and its complications, including death.
"This message is especially important given the increased barriers to achieving regular [physical activity] during lockdowns and other pandemic restrictions."
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