Physical exercise, immune response and susceptibility to infections --
current knowledge and growing research areas
Abstract
This review presents state-of-the-art knowledge and identifies knowledge
gaps for future research in the area of exercise-associated
modifications of infection susceptibility. Regular moderate-intensity
exercise is believed to have beneficial effects on immune health through
lowering inflammation intensity and reducing susceptibility to
respiratory infections. Infection-promoting consequences are attributed
to strenuous exercise as performed by professional athletes. In about
half of the athletes presenting respiratory symptoms, no causative
pathogen can be identified. Acute bouts of exercise enhance release of
proinflammatory mediators thus probably leading to appearance of
infection-like respiratory symptoms. Studies assessing influence of
regularly repeated exercise on immune response and systemic inflammation
are far less numerous than those regarding acute exercise effects. This
identifies another knowledge gap requiring further assessment both in
recreational and in professional athletes Additionally, ambient and
environmental conditions modify systemic inflammatory response and
infection susceptibility in particular in outdoor athletes. Both acute
and chronic regular exercise influence humoral and cellular immune
response mechanisms resulting in decreased specific and non-specific
response in competitive athletes. Most promising areas of further
research in exercise immunology include: detailed immunological
characterization of infection-prone and infection-resistant athletes;
efficacy of nutritional and pharmaceutical interventions as
countermeasures to infections’ symptoms; and influence of various
exercise loads on susceptibility to infections with respiratory viruses,
including SARS-CoV-2. Establishing uniform definition of “elite
athlete’ shall hopefully allow for comparable and straightforward
interpretation of data coming from different studies and settings.