When we get sick, the most logical thing to do is turn to medication. But before we need this kind of treatment, we can think about the lifestyle we lead. A healthy diet, regular physical activity and enough rest are key factors in helping us stay healthy.
The benefits of an active lifestyle are numerous: less stress, improved metabolism, a lower risk of cardiovascular disease, better sleep, more energy and vitality, weight management, and much more. But whether and how does exercise affect our body’s ability to fight infectious diseases? This question is becoming increasingly popular today.
Recent research shows that even one workout every 2–3 days can help our bodies fight bacteria. Any kind of daily physical activity lasting 30–40 minutes is also guaranteed to improve our resistance to the flu. In this article, we’ll look at the facts. What does modern science say about the effects of exercise on health and immune defenses? Let’s find out.
Many people who work out and play sports have heard from friends and family that overtraining will weaken their immune systems and make them more susceptible to viral illnesses. This idea gained popularity in the second half of the 1980s, after studies showed that marathon running increased symptoms of illness among runners in the days and weeks after a race.
However, these studies relied heavily on marathon runners’ own assessments of their health. In experiments that examined runners in a laboratory after races, only a very small proportion were found to have respiratory infections. Common respiratory tract irritation and other non-infectious conditions were recorded much more often.
Subsequent studies of marathon runners and other athletes competing in endurance sports clearly show that these athletes take very few sick days each year. This supports the view that their immune systems are not weakened, but strengthened.
Since then, a large number of studies involving animals and humans have confirmed this conclusion. Several experiments conducted on mice in 2005 concluded that rodents running an average of 30 minutes a day for several weeks were much more likely to survive a severe case of the flu than rodents that did not exercise.
The theory that a single bout of very strenuous exercise negatively affects immunity and makes us vulnerable to viral illnesses for a certain period after exertion has also proven false. This claim is based on studies in humans and animals showing that immune cells flood the bloodstream after strenuous exercise and then rapidly disappear, theoretically because of the intense exertion. This apparent shortage leaves the body with lower levels of cells that recognize dangerous bacteria, allowing infection to develop.
Once again, however, more in-depth research has reached a different conclusion. In an experiment with rodents, scientists found that only a small number of immune cells actually die. Instead, they move to the lungs, stomach and other parts of the body that are particularly susceptible to bacterial attack during exercise. After a period of time, the cells return to the bloodstream and immune cell levels stabilize. This shows that our immune defenses do not actually weaken; they simply focus their attention elsewhere.
James Turner, Professor of Health Science at the University of Bath, says the following about physical activity and the risk of flu: “There is no credible evidence that physical exercise increases the likelihood of developing any viral illness. In fact, exercise will reduce the chance of infection.”
However, if you have no athletic experience then a flu outbreak may not be the best time to start particularly intense workouts. “A dramatic increase in physical exertion or workout duration, especially among people with no training experience, can negatively affect immunity,” says Jeffrey Woods, Professor of Kinesiology and Community Health at the University of Illinois Urbana-Champaign.