Recent News and Events

by Cuyler Hudson, PT, DPT, FAFS

Posted in Blog.

April 14th, 2020

Your Immune System and Exercise

There is no doubt that we are living in an unprecedented time. With a virus running rampant around the world, now more than ever, people are concerned about their health. However, with stay at home orders issued for the vast majority of Americans, another interesting phenomenon is occurring. People are exercising much more. While there is an interesting dichotomy occurring between a record number of people getting sick and a record number of people getting fit, it is important to consider the link between the two. There is a well-established literature base that shows while moderate exercise does improve your immune system over time, heavy exercise WEAKENS your immune system acutely, making you MORE likely to become infected by a virus for a few hours immediately post-exercise. And there is a linear relationship, the more intense/ longer duration of exercise performed, the worse your immune system functions. So the question is, what can I do to mitigate this effect in order to keep up my exercise while maintaining a strong immune system?


Let’s start by breaking down exactly how your immune system responds to a virus. There are 2 types of immune defenses we employ. The first is called innate immunity. This refers to the physical defenses we have (skin, mucus barriers, stomach acid, cough reflex etc), that is designed to keep a virus out of our system. If these fail, and a virus manages to penetrate one of our cells, we start to employ our acquired immunity. This is designed to find and kill the virus, and occurs at the molecular level. Once a virus enters a cell, its one and only job is to replicate itself using the host’s highly-tuned genetic machinery. A virus cannot survive without a host. Once this occurs, the race is on to find and eliminate the virus before it has replicated too many times. The first thing that happens is the cell has to push a signal to the outer layer of its membrane that it is under attack, an SOS of sorts. From there, 2 types of lymphocytes (white blood cells) called T cells and NK cells (short for natural killer cells, badass name, I know), are tasked with recognizing the infected cell, binding to it, and then releasing toxic chemicals which will kill the cell and the virus within it. Once the cell is killed, another type of lymphocyte will start the process of creating antibodies, which will be able to recognize a similar virus entering your system immediately, and attack it. 


Consistently, studies have shown that intense exercise impairs a number of important immune functions. Firstly, T and NK cell activity slows down, meaning there are less cells looking for other cells infected with a virus. Secondly, all lymphocyte proliferation decreases, meaning less T and NK cells will be around to look for infected cells, and lastly there is decreased antibody production, so fewer cells are being created to protect against viruses. This all occurs as a function of stress hormones that get released during exercise, namely cortisol and adrenaline. There are, however, things you can do to decrease the effect of these stress hormones and keep your immune system humming. 

  1. Ensure you are eating enough protein. Protein gives your body amino acids, which it uses to maintain almost every immune function. Those who are deficient in protein have been consistently shown to have worse function in almost all aspects of immunity and have a higher incidence of infection. Hopefully for those who are already regularly training, you already know this, but it is recommended that you eat 0.4g of protein per pound of body weight, and even more if you are in a heavy training cycle.
  2. You need to make sure you are consuming an appropriate amount of micronutrients. Deficiencies in vitamins A,E,C, B6, B12, and folic acid have all been consistently shown to impair immune function and increase infection incidence. The BEST way to get these is by ensuring you have a well rounded diet with lots of vegetables and fruit. However, if you feel like you fall short in your diet, a multivitamin will help. It’s also important to not take the “megadoses” of individual vitamins, which has actually been found to have a detrimental effect on the immune system. So stop chugging those 5 glasses of emergen-C daily!
  3. Exercising in a carbohydrate-depleted state skyrockets the hormonal response of cortisol and adrenaline in your body. As we discussed, these hormones are the ones that directly impair your immune system. Studies have shown that by drinking a carbohydrate sports drink like gatorade before and during exercise can greatly reduce this effect, and keep those T and NK cells humming! So if you’re performing a long/intense workout, it’s a good idea to bring a Gatorade along with you at this time. 


While exercising during this crisis is absolutely recommended, and a great thing to do for a number of reasons, it’s important now more than ever to understand what you are putting your immune system through while doing so. Taking the appropriate steps to mitigate the negative effect of exercise on your immune system is another useful tool in fighting this terrible virus and keeping us all healthy. 


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