by Sophie E Harrison, Neil Walsh, Ross Roberts,The Conversation

Credit: RUN 4 FFWPU from Pexels

Marathons have quicklybecome a popular pursuit. Hundreds of thousands of people submit ballots each year to run in some of the most prestigious races. In 2024, arecord number of peoplecrossed the finish line at some of the world's biggest marathons. If you haven't run a marathon yourself, chances are you know someone who has.

While we know that running has a range of health benefits, including reducing your risk of illness, research also shows that runners are more likely tocatch a coldafter completing a marathon.

Scientists used to think this was caused by reduced immune function following prolonged exercise, alongside increased exposure to infection due to the large crowds that marathons attract. Butour latest researchshows that a person's anxiety, stress and mood may also play a role in whether they're more vulnerable to getting ill or not after a long run or marathon.

In our first study, we asked 406 runners to complete questionnaires about their anxiety and mood in the month and days before running a marathon. We also asked them to provide saliva samples before and after the race.

The mouth is one of the main routes of access for the majority of viruses and bacteria that cause respiratory infections. Thesaliva samplesallowed us to detect whether there were signs that the defense systems that normally stop these pathogens from entering the body (known as mucosal immunity) were suppressed.

We then tracked their common cold symptoms during the two weeks after their marathon.

Runners who were more anxious generally and those who experienced greater mood disturbance before the race (such as anger, frustration or tension) were more likely to experience a respiratory infection during the two weeks after the marathon. They also had a greater reduction in mucosal immunity.

In the second study, we asked 45 adults to run on a treadmill for an hour inside our laboratory. We asked them to complete questionnaires about their anxiety, stress and mood before they completed the run. We also measured their mucosal immunity in saliva before and after the run.

Men with higher anxiety levels, stress levels and greater mood disturbance were more likely to have a reduction in mucosal immunity after the run compared to men who had lower anxiety and stress levels before the run.

When examining the influence of stress, anxiety and mood on theimmune responseto one hour of running in women, findings were not as clear cut. There are many potential reasons for this—with factors such as hormone fluctuations, contraceptive use anddifferences in immune responsedepending on menstrual cycle phase all potentially having an influence. It will be important for future studies to examine this.

Together, the findings from our studies indicate that people who are more stressed or anxious before a run might be at greater risk of getting sick or catching a cold. This effect seems to apply not only to marathon-length runs, but to moderate-length runs of around an hour, too.

One possible reason for this link between stress and immunity is due to the way stress changes how the immune system functions.

Both psychological and physical stressors affect the body throughsimilar mechanisms—specifically through the hypothalamic-pituitary axis and sympathetic-medullary axis. These pathways link thenervous systemto the brain and play a role in the stress response. High psychological stress or prolonged exercise can suppress these axes and reduce immune function.

So when runners experience both psychological and physical stress, the impacts on the immune system might be more significant than if they were just experiencing psychological or physical stress alone.

For example, bothmucosal immunityand the immune system's ability torespond to new foreign pathogensare reduced following prolonged running in people with higher anxiety and stress levels. This shows just how significant the effects of both psychological stress and physical stress are when it comes toimmune function.

But before you cancel that 10k or withdraw your marathon ballot, it's important to remember that being physically active still reduces yourrisk of a respiratory infectioncompared to not exercising at all.

Physical activityalso reduces risk of many other severe health conditions including cardiovascular disease, cancer and diabetes. Running can also be beneficial forreducing psychological stress and anxiety.

Instead, it's important to prepare yourself well before your run by dealing with your stress and anxiety beforehand. Finding ways to reduce stress before a run should be treated the same way as you would ensure that you're hydrated and fueled well.

Some things you can do to reduce stress include relaxation exercises (such asbreathwork,mindfulnessor yoga) and getting agood night's sleep.

It can also help to monitor stress, anxiety and mood so that you can identify when your stress oranxietystarts to increase—or when your mood begins to worsen. This will help you identify triggers and take proactive steps to reduce the impacts before things progress and become worse.

If you're taking part in a race ormarathon, some easy ways to reduce stress include:

Of course, some of thebest waysto avoid getting sick involve sticking to the tried and tested techniques—such aswashing your handsproperly (and avoid touching your eyes, nose and mouth), aim to get at least seven hours of sleep each night, eat a well-balanced diet, plan a recovery week into your training every second or third week and never train if you have an injury.

This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.

Provided by The Conversation