Our Immune System & How Exercise Can Influence It

Mollie Bracken – Exercise Physiologist

The link between exercise and a healthy immune system is something that has been quite prominent in the media over the past few months. In this blog you’ll get a broad overview of how your immune system fights for you daily, how exercise can help it function just that little bit more efficiently now and into later life and lastly what our current physical activity guidelines are.

Innate and adaptive immune systems

It is important to know that our immune system has a couple of lines of defence which work together and evolve as we are exposed to new nasties. These are identified as our ‘innate’ and ‘adaptive’ immune systems.

Our innate immune system is the first line of defence against many common microorganisms and begins at the outermost surfaces of our body, such as our skin and linings of our respiratory and gastrointestinal tract. If an infection makes it past those surfaces, our innate immune system utilises lots of different cells, including white blood cells such as ‘macrophages’ and ‘neutrophils’, to kill and remove the unwanted visitors from the body. This immune system is non-specific, meaning it defends against anything it deems to be foreign, and acts very quickly. It does a lot of the everyday clearing of foreign pathogens; however, it is not always able to detect and eliminate infectious organisms it has not encountered before.

This is where our adaptive immune system comes to our rescue. A key player in this immune system are our lymphocytes; another white blood cell which comes in two main types: B and T cells. These are made in our bone marrow and travel around in our blood and lymph tissue. Our adaptive immune system learns and evolves with each new infection our body encounters and is then more equipped to attack the same pathogens the next time around. This is how a vaccination works; our body is exposed to a small amount of a disease which is not enough to cause full blown illness, then for a period of time (sometimes months and sometimes years) our body can identify the same live pathogen if it enters our system and can quickly eradicate it before it takes hold. This makes the adaptive immune system ‘specific’, however it can take 4-7 days before it identifies foreign cells (1). The two systems work together to minimise the incidence of infection and illness we experience!

How exercise impacts our immune system

A lot of research has gone into analysing the impact exercise can have upon a person’s immune system. One finding is that a bout of exercise can help to clear bacteria from our lungs, helping to stop infections taking hold. This would require a bit of huff and puff, which ties nicely into another popular finding. There are strong links between the intensity of a person’s exercise regime and their susceptibility to upper respiratory infections. The J-shaped curve diagram below can be found in many studies discussing this fact, presenting the correlation between level of risk of upper respiratory infection and the intensity of a person’s regular exercise regime.

(http://www.sportsmed.epworth.com.au/exercise-and-upper-respiratory-tract-infection-urti-to-rest-or-play/ )

This diagram shows that there is a significant decrease in a person’s risk of suffering upper respiratory infections if they participate in regular moderate intensity exercise in comparison to living a sedentary lifestyle, some studies reporting a decreased risk of up to 50% (2)! If that isn’t enough to motivated you to roll out the yoga mat, slip into your grooviest patterned leggings and move that body of yours in isolation and throughout your life afterwards, I’d like to know what will!

It should be noted that on the higher end of the scale significant links have been made between extremely high frequencies and intensities of physical activity and an increased incidence of upper respiratory infections. This increased risk is commonly associated with elite athletes, not the average person who likes to partake in a few vigorous runs or HIIT sessions a week, which are incredibly good for you! New research has concluded that this increased risk is more closely related to athletes who have inadequate recovery regimes, considering sleep, regular overseas travel and diet (2).
Exercise in later life and the immune system

Interestingly, regular exercise into later life has been shown to support the regulation of the immune system for longer (2). Sedentary older individuals have an increased susceptibility to new infections as their body becomes less able to identify and dispose of them. This deterioration process is called ‘immunosenescence’ (2). Our adaptive immune systems are affected more by this than our innate, so infections we have not been exposed to before are likely to affect us more severely and take longer to recover from.

Australia’s Physical Activity Guidelines

Lastly, it is always helpful to refresh our memories on the current exercise recommendations for adults (18-64 years), which align quite nicely with everything else we have discussed. They are:

  • Doing any physical activity is better than doing none. If you currently do no physical activity, start by doing some, and gradually build up to the recommended amount.
  • Be active on most, preferably all, days every week.
  • Accumulate 150 to 300 minutes (2 ½ to 5 hours) of moderate intensity physical activity or 75 to 150 minutes (1 ¼ to 2 ½ hours) of vigorous intensity physical activity, or an equivalent combination of both moderate and vigorous activities, each week.
  • Do muscle strengthening activities on at least 2 days each week.
  • Minimise the amount of time spent in prolonged sitting.
  • Break up long periods of sitting as often as possible (3)

Now is as good a time as any to start or reboot your exercise journey! For exercise specific advice from novice to elite athlete, book in with one of our Exercise Physiologists and start reaping the endless benefits movement can give to you!


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