• Charles Sturt University researchers say regular moderate exercise can potentially reduce the risk of COVID-19 symptoms and life-threatening complications
• The risk of COVID-19-related complications and mortality appears to be higher in individuals with co-morbidities and/or evidence of systemic inflammation
• Habitual exercise improves metabolic, cardiovascular and cardiorespiratory capacities, which provides resilience in the face of viral threats, such as COVID-19

Researchers at Charles Sturt University argue that habitual physical activity and exercise to minimise co-morbidities could be a strategy to mitigate the potential impact of COVID-19 on individuals and populations.

A recent study has shown that regular exercise can lessen the development of co-morbidities and improve the response of the immune system to COVID-19, potentially reducing the risk of symptoms and life-threatening complications if infected.

The research was led by Professor of Applied Physiology Frank Marino (pictured, inset) in the Charles Sturt School of Allied Health, Exercise and Sports Sciences with colleagues Dr Nicole Vargas, Dr Melissa Skein, and Dr Tegan Hartmann.

They reviewed the literature about COVID-19 (formally known as SARS-CoV-2) and its physiological complexities to assess the role and potential benefits of exercise to reduce infections and ameliorate the impact of COVID-19.

Professor Marino said the literature review appears to indicate that the rapid emergence and spread of COVID-19 in late 2019 infected millions of people worldwide, with significant morbidity and mortality and various responses from health authorities to limit the spread of the virus.

“Although population-wide vaccination is preferred, currently, there is large variation and disparity in the acquisition, development and deployment of vaccination programs in many countries,” he said.

“Even with availability of a vaccine, achieving herd immunity does not guarantee against reinfection from COVID-19, or a subsequent zoonotic disease which might erupt in a similar fashion.”

Professor Marino said while emerging evidence indicates that vaccines do not eliminate infection, but only protect against severe disease and potential hospitalisation, there will always be a portion of the population at risk ─ those that refuse to opt for vaccination even if there is herd immunity.

“In addition, there is some uncertainty as to the duration of protection once vaccinated,” he said.

“Therefore, while vaccines are essential, additional strategies which strengthen the immune system should be part of the discussion as this can help to reduce the overall health care burden and stem the rate of infection, independent of additional measures that health authorities might employ.

“One medium-to-long-term strategy is related to the response of the immune system to exercise.”

Professor Marino explained the emerging evidence indicates that the risk of COVID-19-related complications and mortality appears to be higher in individuals with comorbidities, and/or evidence of systemic inflammation.

When individuals that have these and other comorbidities become infected with COVID-19, they are likely to experience more severe symptoms and potentially poorer outcomes.

Acute and habitual physical activity is associated with reduced obesity and thus reduces the likelihood of systemic inflammation, and is known to improve metabolic, cardiovascular, and cardiorespiratory capacities which provides resilience in the face of viral threats such as COVID-19.

Professor Marino said a key outcome from engaging in habitual exercise is that it can improve and even reduce the prevalence of chronic disease conditions, such as cardiovascular disease and metabolic syndrome, because of the reduced chronic inflammation that is characteristic of these conditions.

“There is now good evidence, indicating that habitual, moderate exercise could in fact assist in risk reduction from upper respiratory tract infections compared with a sedentary lifestyle,” he said.

“Although the mechanism for improved immunity from habitual exercise is not fully understood, it appears that moderate training, especially in later life, is associated with maintenance of certain cellular immune function, such as T cells, and innate immunity.”

Professor Marino said at present, the relationship between COVID-19 and exercise is not at the forefront of mitigating the pandemic but could become important in the medium- to long-term management of the disease.

“Additional strategies which strengthen the immune system ─ such as regular exercise ─ should be strongly considered to assist in reducing the overall health care burden and stem the rate of infection because emerging evidence indicates that vaccines do not eliminate infection but protect against severe disease and potential hospitalisation,” he said.

The researchers published their findings in the journal Inflammation Research (published online 1 November 2021) as ‘Metabolic and inflammatory health in SARS-CoV-2 and the potential role for habitual exercise in reducing disease severity’.

This research was made possible by a Charles Sturt University COVID-19 Research Grant.