Regular exercise lowers your risk of developing Covid-19 or falling seriously ill with the disease, with about 20 minutes a day providing the greatest benefit, a global analysis of data suggests.

Regular physical activity is linked to a lower risk of Covid-19 infection, severity, hospitalisation and death, according to the new pooled data analysis of the available evidence published in the British Journal of Sports Medicine.

A weekly total of 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity physical activity appears to afford the best protection, the study suggests.

“Regular physical activity seems to be related to a lower likelihood of adverse Covid-19 outcomes,” the team of Spanish researchers wrote. “Our analysis reveals that individuals who engage in regular physical activity have a lower likelihood of Sars-CoV-2 infection, Covid-19 hospitalisation, severe Covid-19 illness and Covid-19-related death than physically inactive individuals, independent of design and instrument used.”

Experts know that regular exercise has a protective effect against the severity of respiratory infections.

Regular physical activity is associated with a range of health benefits, including the reduction of the incidence of risk factors for adverse Covid-19 outcomes such as being obese or having type 2 diabetes.

Due to the limitations of the analysis, however, the findings should be interpreted with caution, the researchers said.

Previous research suggests that physical activity can lessen both the risk and severity of respiratory infections due at least in part to its ability to boost the immune system.

The link between regular physical activity and Covid-19 severity is poorly understood, but probably involves both metabolic and environmental factors, say the researchers, who set out to try to quantify the threshold of physical activity that might be needed to lessen the risks of infection and associated hospital admission and death.

They searched major research databases for relevant studies published between November 2019 and March 2022. From an initial haul of 291, they pooled the results of 16.

The studies included a total of 1.8 million adults, just over half of whom (54%) were women. The average age of participants was 53. Most of the studies were observational and were carried out in South Korea, England, Iran, Canada, the UK, Spain, Brazil, Palestine, South Africa and Sweden.

The pooled data analysis showed that, overall, those who included regular physical activity in their weekly routine had an 11% lower risk of infection with Sars-CoV-2, the virus that causes Covid.

They also had a 36% lower risk of hospital admission, a 44% lower risk of severe Covid-19 illness and a 43% lower risk of death from Covid-19 than their physically inactive peers.

The maximum protective effect occurred at about 500 Metabolic Equivalent of Task (MET) minutes a week, after which there were no further improvements.

METS express the amount of energy (calories) expended in a minute of physical activity; 500 of them are the equivalent of 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity physical activity.

The researchers cautioned that the analysis included observational studies, differing study designs, subjective assessments of physical activity levels, and concerned only the Beta and Delta variants of Sars-CoV-2 rather than Omicron, all of which could weaken the findings.

There are plausible biological explanations for what they found, the researchers said. Regular moderate-intensity exercise may help to boost the body’s anti-inflammatory responses, as well as cardiorespiratory and muscular fitness, all of which may explain its beneficial effects on Covid-19 severity, they suggest.

“Our findings highlight the protective effects of engaging in sufficient physical activity as a public health strategy, with potential benefits to reduce the risk of severe Covid-19,” they wrote. “Given the heterogeneity and risk of publication bias, further studies with standardised methodology and outcome reporting are now needed.”