Exercise and acute respiratory infections: might regular exercise help protect us?

Sarah Chapman looks at new Cochrane evidence, published this week, on whether exercise affects our susceptibility to acute respiratory infections.

Among the rapid changes that coronavirus (Covid-19) has brought with it is a new enthusiasm for exercise. My husband, who has spent much of his career working on strategies to get the nation exercising, has looked on in astonishment at each person striding past our window, kitted out for a walk, and at family units yomping the footpaths through the nearby fields. Many of us are even supplementing our daily allowance of outdoor exercise with indoor sessions stretching and jumping in front of YouTube, ‘doing Joe Wicks’ added to our lockdown schedules and vocabulary.

But might embracing regular exercise (at last!) offer us some protection from acute respiratory infections? This is an important question, and especially right now. Of all acute illnesses, these are the most common. They range from the common cold to illnesses such as pneumonia and now coronavirus.

Regular exercise offers health benefits that include better maximal oxygen uptake (VO₂ max), muscular strength, flexibility, and body composition. In theory, it could affect our susceptibility to acute respiratory infections by improving our immune function and stress resistance.

New evidence on exercise and acute respiratory infections

A Cochrane Review has been updated this week, bringing together the best available evidence on whether exercise has an effect on the number of acute respiratory infections people get over the course of a year, on how severe the symptoms are and on how long the illness lasts.

The review authors looked for studies up to 5 March 2020. They were able to include 14 studies involving 1377 healthy people aged 18 to 85, who were randomly put into groups to do regular exercise or no exercise. Exercise was mostly supervised and took place at least three times a week, typically sessions of 30 to 45 minutes of moderate-intensity exercise such as walking, cycling, treadmill, or a combination. We don’t know what kind of acute respiratory infections people in the studies got.

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People in the studies mostly did sessions of 30 to 45 minutes of moderate-intensity exercise such as walking, cycling, treadmill, or a combination.

Here’s what they found

When healthy people did regular exercise, compared with not exercising, this may have reduced the severity of symptoms when they got an acute respiratory infection and the number of days symptoms lasted whilst people were enrolled in the study.

However, exercise may have made little or no difference to the number of acute respiratory infections healthy people got in a year, or the proportion of people getting at least one, or the number of days symptoms lasted during each period of illness.

How certain can we be about these results?

Problems with the design of studies and the way they were done mean that the evidence was assessed as being ‘low certainty’, so we can’t be confident that these results are accurate. They may change when more and (hopefully) better studies are available to add to the review.

What about harms?

With any intervention (regular exercise in this case) it’s important to consider potential harms such as injuries. However, only one study here did this, so there is uncertainty about that too.

Where does this leave us?

Despite remaining uncertainties about possible effects of regular exercise on our susceptibility to acute respiratory infections, there are many established benefits to doing it. We need to be sure, of course, that we are observing the rules relating to this, wherever we are, in the extraordinary circumstances of the coronavirus pandemic. Things change quickly, but at the time of writing, here in the UK, we may leave our houses “for one form of exercise a day, for example a run, walk, or cycle – alone or with members of your household.” You can find the latest information here. Stay safe.

Take-home points

• Acute respiratory infections range from the common cold to more severe illnesses such as pneumonia. • A Cochrane Review (updated in April 2020) found that when healthy people did regular exercise, compared with not exercising, this may have reduced symptom severity when they got an acute respiratory infection and may have reduced the number of days symptoms lasted during the study period. • However, exercise may have made little or no difference to the number of people who had at least one acute respiratory infection during the study period, and may make little or no difference to the number of acute respiratory infections a person gets in a year or the number of days symptoms last during each period of illness.

How are you exercising during lockdown? Have you tried something new? Join in the conversation on Twitter with @CochraneUK @SarahChapman30 or leave a comment on the blog. Please note, we will not publish comments that link to commercial sites or appear to endorse commercial products.

Reference:

Grande  AJ, Keogh  J, Silva  V, Scott  AM. Exercise versus no exercise for the occurrence, severity, and duration of acute respiratory infections. Cochrane Database of Systematic Reviews 2020, Issue 4. Art. No.: CD010596. DOI: 10.1002/14651858.CD010596.pub3.

Sarah Chapman has nothing to disclose.


Sarah Chapman

About Sarah Chapman

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Sarah's work as a Knowledge Broker at Cochrane UK focuses on disseminating Cochrane evidence through social media, including Evidently Cochrane blogs, blogshots and the ‘Evidence for Everyday’ series for nurses, midwives, allied health professionals and patients. A former registered general nurse, Sarah has a particular interest making evidence accessible and useful to practitioners and to others making decisions about health. Before joining Cochrane, Sarah also worked on systematic reviews for the University of Oxford and the Royal College of Nursing Institute, and obtained degrees in History from the University of Oxford and in the history of women’s health and illness in early modern England (MPhil., University of Reading).

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