6.1 Allergic athletes and susceptibility to infections
An increasing proportion of young athletes are atopic, i.e. show signs of IgE-mediated allergy which is, along with the sport event, a major risk factor for asthma and respiratory symptoms in athletes (104,105). The relative importance of allergy is growing, also because pollen exposure may become more prolonged and intense with global warming (106). A mixed type of eosinophilic and neutrophilic airway inflammation seems to affect especially swimmers, ice-hockey players, and cross-country skiers (107). The inflammation may represent a multifactorial aggression, in which both allergic and irritant mechanisms play a role. In allergic athletes, high level competition seems to exacerbate at least some components of the allergic immune response, such as airway hyperresponsiveness and airway inflammation. The question remains about how excessive exercise affects the Th1/Th2 balance. If exercise drives a Th2 response then a more difficult to control phenotype in the elite allergic athlete may be expected.
Growing points and areas for developing research Immunological changes associated with exercise form a potentially promising field of research with many gaps to be filled. Detailed assessment of microbiome involved in pathogenesis of respiratory symptoms in athletes is one of the most obvious and evident challenges that exercise immunologists and sports scientists are currently confronted with. Studies looking at the impact of exercise or physical activity on susceptibility to infection varied widely in respect to subjects, exercise load and methods (93). Further elucidation of processes lying behind respiratory symptoms without an ascertained pathogen is one of considerable research gaps. In this aspect, few studies have so far addressed the impact of regular chronic exercise training on humoral and cellular immunity in humans. Infection-like symptoms in subjects in whom no pathogen can be identified are not fully explained regarding underlying inflammatory mechanism, therefore, the role of pre-existing silent or latent infections should be taken into consideration in future studies. Over last 18 months, the COVID-19 pandemics created challenges for medical professionals irrespective of specialty (108). In the context of exercise training, key issues to be addressed are:
  1. Are the athletes who show more “immunodepression” more prone to URTIs during the weeks following exercise?
  2. Which are the clinically relevant outcomes to assess and predict meaningful exercise-induced immunodepression?
  3. Is downregulation of non-specific immunity after intense exercise a normal protective response, with mild immunodepression being an attempt to limit inflammation?
  4. When should the exercise-associated changes in non-specific immunity be considered pathological?
  5. What are the differences between healthy and illness prone athletes in the above-mentioned context?
  6. What is the efficacy, if any, of nutritional or pharmaceutical interventions as countermeasures to URTI symptoms? In conclusion, exercise - depending on its pattern, intensity and environmental conditions - modifies various aspects of immune response. The degree of clinical relevance of these modifications and the ways they may impact the sports performance remain promising field for future research.Figure 1A J-shaped model describing relationship between exercise load and the risk of URTI. Modified after NiemanFigure 2An S-shaped relationship between training load and infection rate, proposed by Malm (modified after ) REFERENCES
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