Survival of the Fittest

For forty years it has been widely accepted by the scientific community that regular, moderate-intensity exercise improves humans immunity to infection. But this fact has been tempered by the popular belief that more arduous exercise can suppress immune function in the short term, leading to an 'open-window' of heightened infection risk in the period immediately following exercise.

In what has been described as a groundbreaking study conducted by the University of Bath’s Department for Health in 2018, this 'open window' hypothesis was challenged by leading physiologists Dr John Campbell and Dr James Turner. They reported, in a peer-reviewed article, that the theory was not well supported by scientific evidence. They concluded that there is limited reliable evidence that exercise suppresses immunity, and all exercise is beneficial for immune function.

In fact, even in the short term, they found that exercise can actually help the immune system do its job of finding and dealing with pathogens. While in the long term, regular exercise works to slow down changes that happen to the immune system due to ageing, and also reduces the risk of infections.

In a more recent article, published in March 2020, leading experts - including Dr Turner and Dr Campbell - debated whether the immune system is affected in a negative or positive way immediately after exercise, and whether or not athletes get more infections than the general population.

The article concludes that infections are more likely to be linked to inadequate diet, psychological stress, insufficient sleep, travel and importantly, pathogen exposure at social gathering events, like mass participation sporting events, or gyms, rather than the act of exercising itself.

"Our work has concluded that there is very limited evidence for exercise directly increasing the risk of becoming infected with viruses. In the context of coronavirus and the conditions we find ourselves in today, the most important consideration is reducing your exposure to other people who may be carrying the virus. But people should not overlook the importance of staying fit, active and healthy. Provided it is carried out in isolation - away from others - then regular, daily exercise will help better maintain the way the immune system works - not suppress it."

"People should not fear that their immune system will be suppressed by exercise placing them at increased risk of Coronavirus. Provided exercise is carried out according to the latest government guidance on social distancing, regular exercise will have a tremendously positive effect on our health and wellbeing, both today and for the future."

To give yourself the best chance of warding off illness, aim to do regular moderate-intensity aerobic exercise, such as rowing, running, cycling or walking for around 150 minutes per week, or an average of just over 20 minutes per day.

Longer or more vigorous exercise is just as good and in no way discouraged, but the clear message from the scientists is that if the capacity to exercise is restricted due to lockdowns, a health condition or disability, “something is better than nothing” and the aim should always be to “move more” with even as little as 20 minutes exercise a day bringing numerous health benefits. Resistance exercise also has clear benefits for maintaining muscle function, which, they say can lead to more and better movement.

While we remain in a global pandemic, the researchers highlight the importance of maintaining good personal hygiene when exercising, including thoroughly washing hands following exercise.

Finally, to give the body its best chance at fighting off infections, they suggest in addition to doing regular exercise, people should pay attention to the amount of sleep they get and maintain a healthy diet, that is ‘energy balanced’ to account for the energy that is used during exercise.