Regular, daily exercise has a powerful, positive effect on people's immune systems – and the public should be encouraged to exercise and workout regularly even in lockdown.

That is the message from a study from the University of Bath, which suggests that being in isolation without access to gyms and sports clubs should not mean people stop exercising.

Over the last four decades, many studies have investigated how exercise affects the immune system. It is widely agreed that regular, moderate-intensity exercise is beneficial for immunity.

There has, however, been a view held by some that more arduous exercise might suppress immune function, leading to an ‘open-window’ of heightened infection risk in the hours and days following exercise.

The susceptibility to upper respiratory tract infections (URTIs) after physical exercise has been described with a J-shaped curve, suggesting protection from infections with moderate exercise – but an increased risk for URTI's due to "overtraining".

In a benchmark study in 2018, this ‘open window’ hypothesis was challenged by physiologists Dr James Turner and Dr John Campbell from the University of Bath’s Department for Health.

In a review article, the pair reported that the theory was not well supported by scientific evidence and that there was limited, reliable evidence that exercise suppresses immunity.

Now, Turner and Campbell have undertaken a new study, entitled Can Exercise Affect Immune Function to Increase Susceptibility to Infection? – published in the international journal Exercise Immunology Review – in which they debate whether the immune system can change in a negative or positive way 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 marathons, 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," Turner said.

"In the context of coronavirus and the conditions we find ourselves in today, the most important consideration is reducing your exposure from other people who may be carrying the virus.

"But people should not overlook the importance of staying fit, active and healthy during this period. 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.”

Co-author, Dr Campbell added: “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 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.”