Marathoners have fast become a popular pursuit. Hundreds of thousands of people submit ballots every year to enter some of the most famous races. In 2024, a record number of people has crossed the finish line in some of the world’s greatest marathons. If you haven’t run a marathon yourself, chances are you know someone who has.
While we know that running has a number of health benefits, including reducing the risk of disease, research also shows that runners are more likely to get cold after completing a marathon.
Scientists thought this was caused by reduced immune function after prolonged exercise, along with increased exposure to infection due to the large crowds that marathons attract. But our latest survey shows that a person’s anxiety, stress and mood can also play a role in whether or not they are more vulnerable to getting sick after a long run or marathon.
In our first study, we asked 406 runners to fill out questionnaires about their stress 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. The saliva samples allowed us to detect whether there were signs that the defense systems that normally prevent these pathogens from entering the body (known as mucosal immunity) had been suppressed.
We then monitored common cold symptoms during the two weeks following the marathon.
Runners who were generally more anxious and those who experienced more mood disturbance before the race (such as anger, frustration or tension) were more likely to develop a respiratory infection in 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 one hour in our laboratory. We asked them to fill out questionnaires about their anxiety, stress and mood before completing the run. We also measured salivary mucosal immunity before and after the run.
Men with higher levels of anxiety, stress levels, and greater mood disturbance were more likely to have decreased mucosal immunity after the run compared to men who had lower levels of anxiety and stress before the run.
When examining the effect of stress, anxiety and mood on the immune response to a one-hour run in women, the findings were less clear-cut. There are many possible reasons for this – with factors such as hormonal fluctuations, contraceptive use and differences in immune response depending on the phase of the menstrual cycle, all potentially affect. It will be important for future studies to examine this.
Together, the findings from our studies suggest that people who are more stressed or anxious before a run may be at greater risk of getting sick or catching a cold. This effect seems to hold true not only for marathon-length runs, but also for moderate runs of around an hour.
Immune function
One possible reason for this link between stress and immunity is because of how stress changes the way the immune system works.
Both psychological and physical stressors affect the body through similar mechanisms – specifically through the hypothalamic-pituitary axis and the sympathetic-medullary axis. These pathways connect the nervous system to the brain and play a role in the stress response. High psychological stress or prolonged exercise can suppress these axes and reduce immune function.
Thus, when runners experience both psychological and physical stress, the effects on the immune system may be more significant than if they experienced only psychological or physical stress.
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For example both mucosal immunity and the immune system’s ability to respond to new foreign pathogens are reduced after prolonged running in individuals with higher levels of anxiety and stress. This shows how important the effects of both psychological stress and physical stress are when it comes to immune function.
But before you cancel that 10,000 or withdraw your marathon ballot, it’s important to remember that physical activity still reduces risk of respiratory infection compared to not exercising at all.
Physical activity it also reduces the risk of many other serious health conditions, including cardiovascular disease, cancer and diabetes. Running can also be beneficial for reduction of psychological stress and anxiety.
Instead, it’s important to prepare well before the run by dealing with your stress and anxiety beforehand. Finding ways to reduce stress before a run should be treated the same way as making sure you’re hydrated and fueled well.
Some things you can do to reduce stress include relaxation exercises (such as breathing, awareness or yoga) and get a good sleep.
It can also help track stress, anxiety and mood so you can recognize when your stress or anxiety starts to rise – or when your mood starts to take a turn for the worse. This will help you identify triggers and take proactive steps to reduce the impact before things progress and get worse.
If you’re participating in a race or marathon, some easy ways to reduce stress include:
- Plan your travel route in advance and allow more time to avoid rush and stress
- If you can, try to arrive the night before the race to clear your route
- Plan some “what if” or “if/then” strategies so you’re ready to deal with anything unexpected on race day.
Of course, some of the better ways to avoid getting sick, you need to stick to tried and tested techniques – such as washing your hands properly (and avoid touching your eyes, nose and mouth), aim to get at least seven hours of sleep every night, eat a balanced diet, plan a recovery week into your training every second or third week, and never train if you have an injury.
