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Immunity – Risky Business

As an athlete, it’s good to know you may have a higher risk of infection so that you can address it. A risk of what, though? How? When, why and where? How can you reduce such chances? Fear not, for this article ticks all those boxes and more!

Youth Sport Nutrition, Immunity

Infection – The Invisible Villain

Upper respiratory tract infections (URTI) are most common in athletes. Those participating in intense training or endurance events are at higher risk of developing minor URTI symptoms (Gleeson and Williams, 2013; Svensden, 2015). Most know this as the common cold: a viral infection. Symptoms include coughing and sneezing, headaches, a sore throat, and a blocked or runny nose. These often last a week or two.

You can catch the virus from an infectious person by touching an object or surface contaminated by infected droplets (such as somebody’s skin) and then touching your mouth, nose or eyes; or inhaling particles with the virus when somebody coughs or sneezes.

Professor Asker Jeukendrup, Director of, illustrates the effect of exercise on the risk or URTIs.


When? Why? Where?

We are particularly vulnerable after vigorous exercise, when white blood cell functions are suppressed, giving viruses and bacteria a window of opportunity to take advantage of (Gleeson, 2016). Lack of sleep, psychological stress, exposure to extreme environments (e.g. very cold temperatures or high-altitude), malnutrition, and even competitions and being around others can increase our risk of developing systems.

During intense exercise, the higher breathing rates (lung ventilation) put your lungs at risk of airborne bacteria and your gut may become exposed to bacterial endotoxins; particularly with prolonged heat stress.

Air travel to another country has been associated with increased risk of infection, as well as getting cuts and abrasions on the skin.


Improving Immune Function – Fighting Back

General guidelines to lower the chance of developing immunodepression (Bishop, 2012; Gleeson, 2016  include:

  • Avoid very long training sessions (>2 h), overtraining and chronic fatigue
  • Keep life stresses to a minimum
  • Get enough sleep - quantity (at least 7 h) and quality
  • Avoid rapid weight loss
  • Vaccinate against influenza if competing in the winter

To reduce the potential for transmission of infectious agents:

  • Avoid sick people and large crowds in enclosed spaces if possible
  • Maintain good skin and oral hygiene: wash hands, use antimicrobial gels, brush teeth regularly and use antibacterial mouth rinse
  • Never share drink bottles, cutlery, towels etc
  • Don’t rub your eyes and nose with your hands

If you have developed symptoms already, the BASES expert statement and Ronsen (2005) suggest:

  • Day 1 of illness: Avoid vigorous exercise or competitions when experiencing URTI symptoms like sore throat, coughing, runny or congested nose. Avoid all exercise when experiencing symptoms like muscle/joint pain and headache, fever and generalised feeling of malaise, diarrhoea, or vomiting.


  • Day 2: Avoid exercise if you suffer fever, diarrhoea, vomiting, or increased coughing. If no fever or sickness is present and ‘above the collar’ symptoms are no worse; undertake light exercise (heart rate < 120 beats per minute) for 30-45 minutes (indoors during winter), by yourself.


  • Day 3: If fever and URTI (or gastrointestinal) symptoms are still present, consult your doctor. If no fever or malaise is present and there is no worsening of initial symptoms; undertake moderate exercise (heart rate < 150 beats per minute) for 45-60 minutes, preferably indoors and by yourself.


  • Day 4: If symptoms are not relieved, don’t exercise - ring your doctor. If it is first day of improved condition, wait another day without fever and with improvement of URTI or gastrointestinal symptoms before returning to exercise.


  • Cease training and consult your doctor if a new fever occurs or if initial symptoms become worse, coughing persists or breathing problems during exercise occur. Monitor your tolerance to increased exercise intensity. Take another day off if recovery is incomplete.

Don't let illness in sport get you down. Look after yourself and ensure your to always consult a qualified doctor or medical practitioner with regard to any illness.


NB: Any advice contained is offered as a general guide only. 




Gleeson, M. and Williams, C. (2013). Intense exercise training and immune function. van Loon LJC, Meeusen R (eds). Limits of Human Endurance, Nestle Nutrition Institute Workshop, 76, 39–50.

Svendsen IS. Factors influencing infection risk in endurance athletes. PhD thesis 2015. Loughborough University: UK

Gleeson, M., (2016). Immunological aspects of sport nutrition. Immunology and Cell Biology (2016) 94, 117–123. 2016 Australasian Society for Immunology Inc.

Bishop, Nicolette C. (2012). Overcoming microbial hurdles: Keeping the Olympics infection-free. Future Microbiology, 7(8), 913-5.

Walsh NP, Gleeson M, Shephard RJ, Gleeson M, Woods JA, Bishop NC et al. (2011). Position statement part one: immune function and exercise. Exerc Immunol Rev, 17, 6–63.

Ronsen, O. (2005). Prevention and management of respiratory tract infections in athletes. New Studies in Athletics, 20, 49-56.

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