Exercise and Acute Respiratory Infections: Might Regular Exercise Help Protect Us?

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. (ShutterStock)

Among the rapid changes that swept in with the coronavirus (COVID-19) pandemic was a new enthusiasm for exercise. During the first lockdown, my husband, who spent much of his career working on strategies to get the nation exercising, looked on in astonishment at each person striding past our window, kitted out for a walk, and at family units marching thru the footpaths in the nearby fields. Many of us supplemented 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 in this era of COVID. 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.

Evidence on Exercise and Acute Respiratory Infections

A Cochrane Review Exercise versus no exercise for the occurrence, severity, and duration of acute respiratory infections (April 2020) brought 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.

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. In extraordinary times, many of us have discovered a range of benefits for ourselves. Let’s hope that more and better research will provide clearer answers to the question of whether it can reduce our susceptibility to respiratory infections.

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’s work as a Knowledge Broker at Cochrane UK focuses on disseminating Cochrane evidence through social media, including Evidently Cochrane blogs and blogshots, with a particular interest in making evidence quick and easy for patients and others making health choices, and healthcare professionals, to understand and use.

This story was originally published by the Evidently Cochrane Blog.