The role of exercise in immunity

During this time of quarantine,  the topic of IMMUNITY is front and center on our minds.  We may be looking for ways to give our body's defenses a little boost to ward off a certain viral infection going around right now!   My goal here is to dig and sift through peer-reviewed research, and summarize the key findings on the role that exercise plays in our immunity.   The topic is very well researched, and I'm sure I only scratched the surface. However, I believe I've seen enough to decipher certain consistencies. Some things may surprise you!  

Physical activity has long been linked to countless positive health benefits, to where it is easy to attribute  any and all health benefits to it.  But does it actually impact our IMMUNITY in a positive and meaningful way?   I think most would argue that yes, of course it does!  How could it not??  The broad medical and health/wellness community holds that as a fundamental truth.  But lets look at some more!

​In regards to basic relationship:

• Research suggests that there is indeed a very strong relationship between physical activity and immunity.  The immune system is very responsive to exercise, with the extent and duration reflecting the degree of physiological stress imposed by the workload (more on this below!).
• Randomized clinical trials consistently support the inverse relationship between exercise training and incidence of upper respiratory tract infections.   The direct linkage between exercise and long term defense against more serious medical conditions, like cancer, metabolic disease, etc,  is a bit tougher see, but still widely considered a MUST as part of an overall strategy to boost the immune system.

Main takeaway:  Overwhelming evidence that there IS indeed linkage between exercise and our immunity.  Check!  Now let's explore some more.

In regards to aging:

• Word of the day:  immunosenescence  - refers to the age-related decline of immune system function, including increased susceptibility to infections, autoimmune diseases, neoplasias, metabolic syndrome, osteoporosis, and neurologic disorders. 
• Recent evidence supports that immunity can be remodeled during the aging process as a result of interactions with the environment and lifestyle and is instrumental in shaping immune status in later life (sourced here).  Thus,  as we age, exercise becomes more and more important in order to slow the decline of our immune system.  
• Habitual exercise is capable of regulating the immune system and delaying the onset of immunosenescence, and has been associated with the following
  •Enhanced vaccination responses,
  •Proliferation of T-cell activity (T-Cells are responsible for recognizing, attacking, and eliminating foreign and dangerous cells)
  •Lower circulatory levels of inflammatory cytokines (cells that signal the body to create inflammation)

Regarding training mode, and Chronic (long term) VS Acute (short term) effects

• Exercise has a very distinct acute effect on immunity,  and to a lesser extent chronic effect (sourced here).
• The acute immune response to exercise depends on the intensity and duration of effort 
• Acute exercise bouts of less than 60 minutes of light-moderate activity enhance immediate immunoserveillance by boosting the action of blood-circulating agents of immunity (T-Cells, white blood cells, inflammatory cytokines, and more), and in turn prevent stress hormones from driving their suppressant nature (sourced here).
• SURPRISE FINDING ALERT!   Overwhelming research findings indicate that high metabolic activity like heavy exercise bouts (above 60% HRMax), or that done in a high intensity group fitness class or a typical regimen done by an athlete, actually show an acute DECREASE in immunity!  (Sourced here) In fact, the measurement of immune responses to prolonged and intensive exercise by athletes continues to receive high attention. The best evidence supports that high exercise training workloads, competition events, and the associated physiological, metabolic, and psychological stress are linked to immune dysfunction, inflammation, oxidative stress, and muscle damage!   So much so, that load management is a key strategy, according to the International Olympic Committee,  to decrease illness incidences and subsequent drop in performance, interruptions in training, missed competitive events, and risk of serious medical complications for athletes!   2%–18% of elite athletes experience illness episodes, with higher proportions for females  (sourced here)  See the graph below
• This finding underscores the importance of proper recovery from exercise,  in order to quell the effect of stress hormones that circulate after heavy metabolic activity!  
• In terms of upper respiratory tract infection (IE, the common cold), exercise during the incubation phase or during peak sickness can actually slow down the body's response time, and exacerbate symptoms!
• The chronic effect of exercise on immunity seems to be secondary, as part of an overall healthy lifestyle, rather than a singular factor.  ​​

Regarding carbohydrate consumption, exercise and immunity
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• High carbohydrate diets produce a lower stress hormone response. This is associated with less post-exercise immune suppression. Research shows that feeding carbohydrate during exercise can further reduce stress hormone production. This, in turn, seems to keep the immune system strong during and after your exercise session.   (Sourced here)
• Ensure your everyday diet provides an ample supply of carbohydrate at all times. Up to 60% of your daily calories might come from carbohydrates, depending on your training volume. 
• ​Further studies confirm that preventing carbohydrate depletion helps to prevent post-exercise immune suppression.

Key Takeaways: 

• Think of exercise as stirring up a cocktail of all blood-circulating immune cells,  proliferating cell-to-cell, and cell-to-tissue communication and function!

• Acute immune response to exercise depends on training intensity and duration. 
• The strongest immunity boosting form of exercise is light to moderate,  below 60 minutes!  This should serve as a great news to those who stand to benefit the most:  the elderly, obese, and sedentary individuals.   Even better, the effect is strongest immediately!   
• ​Exercise slows down immunosenescence!  Thus, as we age, exercise plays a larger role in our immunity.  The 60+ crowd are suggested to be the highest responders to exercise, in terms of immunity
• If you are already sick with the cold or flu,  it is best to just let it be, rest, and recover faster.  There is no such thing as "sweating it out" when it comes to recovery.   In contrast, more serious medical conditions like cancer and metabolic syndrome benefit greatly from exercise, and is an essential part of recovery.
• Coaches, athletes, and those who enjoy chronic heavy exercise loads,  should recognize the short-term risk of illness associated with heavy metabolic activities.   
• Enjoy a diet full of healthy carbohydrates, especially before and after exercise.  Consume unprocessed, wholegrain bread, pasta and cereals, rice, corn. Include all types of fruit and vegetables, beans, peas and lentils in your diet. This is important, even on days when you don’t train. It’s during these rest days where you can really top up depleted muscles and glycogen reserves. Remember, your immune system is still doing its best to ward off infection on the days where you don't exercise.
• 20 minutes of light-to-moderate activity is all that is needed to give your immune system a boost!   We are all able to do at least that during our time of quarantine. 

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So get outside, go for your walk, jog, or ride, and be confident that you are giving your immunity a boost today and every day!

​Until next time!