TRUE or FALSE?

Exercise helps to boost the immune system and can help fight off viral and bacterial infections?

Evidence has consistently shown that lifelong physical activity is a “potent means of reducing the risk of non-communicable diseases including cancer, cardiovascular disease, and […] diminishes the risk of contracting a range of communicable diseases including viral and bacterial infections (1).

During exercise, there is usually a dramatic increase in immune cells including a 10-fold increase of natural killer cells and 2.5-fold increase of CD8+ T-cells. (2) However, there was a so-called “open window” hypothesis proposed in the 1980s which claims that after exercise, there is a dramatic decrease in the frequency of immune cells in the bloodstream, thus putting you at risk. This occurs approximately 1-2 hours post-exercise and lasting till 24hr.

This “open window hypothesis” however, is likely not entirely true. Instead, contemporary evidence shows that this sudden ‘drop’ of immune cells post-exercise actually reflects a redistribution of the immune cells to sites where pathogens are likely to be encountered during/after exercise (i.e. lungs, gut) (3).

This redistribution actually represents a “heightened state of immune surveillance and immune regulation” (4).

So in the end, exercise not only helps to boost your immune cells during exercise, but the entire immune system becomes even more alert and widespread post-exercise, particularly going to the vulnerable zones.

The beneficial effects of exercise on the immune system are likely to be greatest for elderly people exhibiting the age-associated decline of immune function! (4).

Our recommendations:

• Exercise is beneficial to strengthen your immune system during and after exercise
• This effect can help reduce the decline of the immune system due to aging
• Be conscious of where you are doing exercise. Training in public gyms or crowded areas can increase your exposure to pathogens
• Wash your hands and the equipment after use
• Make sure to properly hydrate before and after exercise

1)Health benefits of physical activity: a systematic review of current systematic reviews. Warburton DER, Bredin SSD Curr Opin Cardiol. 2017 Sep; 32(5):541-556. 2) Campbell JP, Riddell NE, Burns VE, Turner M, van Zanten JJ, Drayson MT, et al. Acute exercise mobilises CD8+ T lymphocytes exhibiting an effector-memory phenotype. Brain Behav Immun (2009) 23(6):767–75.10.1016/j.bbi.2009.02.011 3)Shephard RJ. Adhesion molecules, catecholamines and leucocyte redistribution during and following exercise. Sports Med (2003) 33(4):261–84.10.2165/00007256-200333040-00002 4)Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan, John P. Campbell* and James E. Turner*