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ExerciseAug 22, 2022

Regular physical activity is linked to a lower risk of Covid-19 infection and less severe symptoms

Engaging in physical activity on a regular basis might help to reduce the severity of Covid-19 infection and even fend it off, a team of Spain-based researchers has suggested in article an online article published today (23 August) by the British Journal of Sports Medicine.

The best protection is offered by totting up 150 minutes of activity at a ‘moderate intensity’, or 75 minutes at a ‘vigorous intensity’, their analysis suggests. It had previously been suggested that physical activity can lessen both the risk of infection and the severity of respiratory infections due, at least in part, to its ability to bolster the immune system.

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Tipping point: weekly bouts of 'moderate' or 'vigorous' physical activity seem helpful


Metabolic and environmental factors likely to play a part

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

The team searched three major research databases for relevant studies published from November 2019 to March 2022, and from an initial haul of 291, pooled the results of 16. The studies included a total of 1,853,610 adults, just over half of whom (54 per cent) were women. The average age of the participants was 53.

UK-based studies included

Most studies were observational in nature and were carried out in South Korea, 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 per cent lower risk of infection with SARS-CoV-2, the virus responsible for Covid-19.

The participants also had a 36 per cent lower risk of hospital admission, a 44 per cent lower risk of severe Covid-19 illness, and a 43 per cent lower risk of death from Covid-19 than their physically inactive peers. The maximum protective effect occurred at around 500 metabolic equivalent of task (MET) minutes a week, after which there were no further improvements.

What is a metabolic equivalent of task (MET)?

METS express the amount of energy (calories) expended per minute of physical activity, and 500 of them are the equivalent of 150 minutes of moderate intensity, or 75 minutes of vigorous intensity, physical activity.

The researchers acknowledge that that their 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 may weaken the findings.

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 [Yasmin Ezzatvar et al.]

'Protective effects' of physical activity

The team acknowledges that there are plausible biological explanations for their findings. 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 conclude: ‘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. Given the heterogeneity and risk of publication bias, further studies with standardised methodology and outcome reporting are now needed.'

To see the full version of the article, titled Physical activity and risk of infection, severity and mortality of COVID-19: a systematic review and nonlinear dose–response meta-analysis of data from 1 853 610 adults, see: https://bjsm.bmj.com/content/early/2022/07/07/bjsports-2022-105733

Author: Ian A McMillan
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