Should You Exercise While Sick?

The benefits and the dangers of exercising when you are under the weather, ailing, rundown, or just straight up sick.

Brock Armstrong
Episode #371

a woman exercising while sick

I am currently getting over a cold. In fact, as I write this I have a warm drink and a box of tissues right beside my laptop. It isn’t a bad cold (or even a man cold), it’s just enough to annoy me, interrupt my sleep, and cause me to miss a few workouts. It's the off-season for me so it isn't a big deal, but when it happens in the spring or mid-summer, I am not so cavalier about missing training sessions. In fact, I can get downright ornery.

It doesn’t seem to matter how many times I get sick during the training season or how many times the athletes I coach fall prey to a seasonal flu, I still do a lot of hand-wringing over whether or not I should be jumping on my bike or prescribing a heavy lifting session for my clients.

But don’t worry. This wouldn’t be the Quick and Dirty Tips if I didn’t have a few guidelines that you can follow. But before I get to those, let’s talk about the immune system.

What is the Immune System?

Your immune system is comprised of six components that do their best to protect you from foreign invaders.

  1. Lymph nodes and lymphatic system, which recognize and fight invading pathogens;

  2. Respiratory system, which creates mucus, coughs and sneezes to trap and remove contaminants;

  3. Skin, a relatively thin but effective barrier against invading pathogens;

  4. White blood cells, which attack pathogens in your blood and other tissues of your body;

  5. Your spleen, a major organ that helps protect you from bacterial infections;

  6. Your stomach and intestines. Your stomach acid kills harmful bacteria and the good bacteria that live there help to fight pathogens and absorb nutrients. Antibodies secreted by your intestinal cells also help to fight off foreign invaders.

What Does Immune Health Mean?

We actually swallow a surprisingly high number of bacteria and pathogens every single day, 

Every day we come in contact with thousands of different viruses and bacteria. We touch things like a seat on a bus or a cart at the grocery store and then we touch our face. The bugs can then get access into our bodies through our mucosal surfaces (eyes, nose, mouth, or a break in our skin).

The majority of the time the invading foe will be thwarted by our mighty white blood cells, which capture and kill the bugs before they can replicate and enter our bloodstream.

We actually swallow a surprisingly high number of bacteria and pathogens every single day, but most of them die in our saliva or in the acid and healthy bacterial environment of the stomach. Unfortunately, some bugs are stronger than others or have mutated in ways to evade our immune response, and then we are susceptible until our immune system adapts and finds a way to kill the new version of the invader.

What Does Immunocompromised Mean?

The dictionary definition is: A state in which a person's immune system is weakened or absent. But for us exercise enthusiasts, it gets more complicated than that.

When we engage in an acute bout of heavy exercise, that workout actually induces immune system responses, which are similar to those induced by infection. Normally, if you are well rested, you will recover from this quite quickly but in times when you are loading on the extra training sessions or loaded down with other life stresses (or both), these immune responses persist and your chances of getting sick are much higher.

In particular, endurance exercise and long bouts of training, if not properly managed by a dedicated coach, can weaken our immune system. The recruitment of white blood cells to fight off pathogens may be reduced and elevated levels of stress hormones (especially cortisol) can weaken the inflammatory component of the immune response and that can allow the pathogen to paint the town red.

Even if this doesn’t result in some gross and snotty illness, once in our system, pathogens and their accompanying toxins can cause inflammation and require energy to expunge from our bodies—the precious energy which we normally would be using to optimize our muscular recovery and manage our adaptation from all our hard training.

The main factors which can suppress the immune system are: Increased intensity of exercise, increased duration of exercise, sleep deprivation, psychological stress, nutrient-poor diet, calorie restriction, low body fat, frequent travel, and heavy drinking.

Let’s get into the good news.


About the Author

Brock Armstrong

Brock Armstrong is a certified AFLCA Group Fitness Leader with a designation in Portable Equipment, NCCP and CAC Triathlon Coach, and a TnT certified run coach. He is also on the board of advisors for the Primal Health Coach Institute and a guest faculty member of the Human Potential Institute. Do you have a fitness question? Leave a message on the Get-Fit Guy listener line. Your question could be featured on the show. 

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