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There was a long-held belief that vigorous exercise suppresses an athlete's immune system. More recent research suggests that exercise actually boosts our immune systems IF we find the 'sweet spot'.
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"}},"title":"Sports Scientist","headshot":{"file":{"url":"//images.ctfassets.net/428xzyjdw7rf/2LSPbzorht2w3T617jgC9B/1beb845600daec37a489940c839b58bb/Abs.png"}}},"scientificallyReviewed":null,"image":{"resize":{"src":"//images.ctfassets.net/428xzyjdw7rf/rpKawsSY78u6Jghky0sKb/82d5113235f6b8381b35f0e8379f3c49/female_gym_athlete_back.jpg?w=1200&h=630&q=70&fit=fill","width":1200,"height":630}},"socialMediaImage":null,"body":{"childMarkdownRemark":{"excerpt":"It’s been suggested that prolonged and vigorous exercise weakens (or suppresses) our immune system and increases susceptibility to 'opportunistic' infection…","html":"It’s been suggested that prolonged and vigorous exercise weakens (or suppresses) our immune system and increases susceptibility to 'opportunistic' infection. Certainly, this was the conclusion that researchers were drawing from studies in the 1980s and 1990s.
\nBut recent reviews of the research offer an alternative angle to this 'immunosuppressive' viewpoint as exercise has been found to boost our immune function and strengthen our resistance to illness and long-term disease, IF we find the 'sweet spot' when it comes to exercise duration and intensity...
\nEarly exercise-illness studies conducted at the end of the 20th century asked runners whether they were experiencing any symptoms of an upper respiratory infection (valid symptoms included a runny nose, cough, or sore throat) after competing in a mass participation, long distance event.
\nMany of the participants confirmed that they were indeed suffering one or more of these symptoms, which led to the link between exercise and a greater risk of infection.
\nAnd so the seed for the argument that exercise has an ‘immunosuppressive’ effect on people was sown...
\nThere was a fundamental limitation to these studies though. None of the self-reported ‘infections’ were confirmed by laboratory analyses. So, we can't be sure that they were genuine illness symptoms.
\nAdditionally, more recent evidence suggests that most of the symptoms reported after exercise are not real infections but are caused by other factors, such as an allergy.
\nWhat these early observations did encourage was further research into what really happens to the immune system after strenuous exercise.
\nDuring exercise, there's a dramatic increase in the number of immune cells found in the bloodstream. Just one example are the 'natural killer cells', which increase by 10-fold.
\nWhen exercise stops, the number of circulating immune cells decreases substantially, sometimes falling lower than pre-exercise levels and staying there for 3-72 hours, before eventually returning to ‘normal’.
\nAt the time, this was believed to be further evidence of a true 'immunosuppressive' effect and the concept was even given a name: the ‘open-window theory’.
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Since its proposal, this concept has been widely accepted. But, strong evidence now challenges the idea and suggests that the decrease in immune cells has been misinterpreted.
\nThe decline in immune cell numbers post-exercise doesn't mean they’ve been lost or destroyed (and therefore suppress the immune system), but we now know that the cells get redistributed - specifically to areas of the body which might have become infected. For example, redistribution to the lungs due to the increase in breathing rate and depth during exercise.
\nThis alternative explanation suggests that an acute bout of exercise actually enhances our antibacterial and antiviral immunity by increasing immunity surveillance.
\nAround the same time, another concept called the ‘J-curve’ of exercise immunity was established, which illustrates the relationship between training load and the associated level of infection risk.
\nThe theory suggests that if you push your performance too far into overtraining, or even near it, then your risk of infection goes up significantly. Interestingly, it appears it can even exceed the risk associated with doing no exercise at all.
\nMost importantly, the J-curve highlights the existence of a ‘sweet spot’ and the relationship between an appropriate training load and a lower risk of infection.
\nIn other words, athletes training moderately are better protected from coughs and colds than 'couch surfers'. But those training very, very hard run an increased risk of getting sick.
\nIt’s thought that this is because a demanding training load creates physical damage in the body, which in turn causes a range of stress responses.
\nToo much stress and the body is less adept at fighting off infection.
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The modern view is that it’s not the act of participating in a strenuous bout of exercise which increases a person’s risk of infection, but rather the factors around it.
\nThere’s a whole host of factors known to influence our immune function, including sleep disruption, temperature changes, fatigue, altered or inadequate diet, dehydration, psychological stress and/or environmental exposures.
\nIt’s a misconception to label exercise as 'immunosuppressive'. There’s limited reliable evidence to support this viewpoint, and it’s far more likely that frequent, moderate exercise improves the competency of our immune systems.
\nHaving said this, consistent overreaching in training will compromise your immune defences and should be considered highly counterproductive, particularly in times of high stress when your immune system may already be compromised.
\nA weakened immune system can lead to poor health and lacklustre performance. So, keeping the immune system as strong as possible gives it the best chance of fighting off any infections you do come into contact with and means you can continue with consistent training in the long-term.
\nHere’s a few simple tips to adhere to in order to keep your immune system tip-top:
\nBeing sensible in your approach to training around times of increased susceptibility could pay dividends by enabling consistency in the long run.
\nTo use a well-coined phrase - \"train smart\".
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