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Being physically active impacts your overall health and wellbeing in a variety of ways, but how does it affect your ability to withstand infection?
Firstly, what is your immune system? Your immune system is a network of cells and proteins that work together to sense potential pathogens (harmful viruses, bacteria, etc.) as quickly as possible and destroy them before they can have a significant negative impact on your body. Your immune system changes and adapts over the course of your life. Each time it is exposed to a new pathogen, it learns to recognize that intruder so the next time it can deal with it more quickly.
One of the reasons that an unfamiliar virus or bacteria can cause so much harm is that if your immune system has not seen it before, it won’t necessarily be recognized as a threat. This can allow a foreign germ to take hold and cause harm before your body has the chance to destroy it. The ability of your immune system to grow and learn is also why adults are often seemingly impervious to the minor illnesses that affect children: Adult immune systems have been exposed to the germs of those illnesses often enough that they are immediately recognized and neutralized before they can cause harm.
How does exercise come into the equation? As with many aspects of health and wellness, there is a relationship between how active you are and how healthy your immune system is, we call this a dose-response factor. Consistent, moderate level activity has been shown to boost the immune system, improving resistance to pathogens and reducing the risk of infections taking hold of your body. A recent study by Forte, Branquinho & Ferraz (2022) suggests that regular physical activity can actually change gene presentation, specifically those genes that respond to stress, inflammation, and tissue repair. This means that individuals who are able to increase and maintain regular physical activity may have improved stress tolerance, reduced inflammation, and be able to recover more quickly following an injury or illness.
The impact of exercise on the immune system is multifactorial: Staying or becoming active results in increased cardiovascular fitness, helps support metabolism and digestion, and can help improve sleep quality.
Like with every coin there is a flip side to this research. Exercise and immunity can have a negative relationship albeit temporary. Studies completed on competitive cyclists and long distance runners show evidence that immediately after long intense bouts of exercise, there is actually a brief suppression of the immune system. This suppression of the immune system only lasts for a few hours, and seems to be related to the increase in stress hormones that are released during higher intensity exercise. To mitigate these short term immune impacts of vigorous exercise, athletes can make sure they eat well, stay hydrated, get enough sleep, wash their hands, and manage other stressors to reduce their chance of getting sick.
Therefore there seems to be a sweet spot of consistent moderate physical activity that helps to support your immune system and not over tax it while having an overall improved physical health. Moderate exercise varies for each individual but a quick trick is to focus on your breath. If you can carry a conversation but not quite have enough breath to sing then you are pushing yourself at a moderate intensity. For some, getting out for a walk down a few blocks is enough to start while for others it requires a quicker pace or steeper terrain to feel they’ve pushed themselves. The key to remember is that whatever your starting point, choosing to be consistently active with a routine can help support your immune system and maintain a higher quality of life.
Reference:
The Relationships Between Physical Activity, Exercise, and Sport on the Immune System Forte, P, Branquinho, L, & Ferraz, R.(2022) Int. J. Environ. Res. Public Health 2022, 19(11), 6777; https://doi.org/10.3390/ijerph19116777
Video of detailed information on mechanism of immune function: