Y.E.S. News

Exercise When You’re Sick?

Everybody gets sick. But it’s tough to know what to do about it. Should you “sweat it out’ in the gym? Or get some rest instead? In this article we will clear up the confusion. So the next time you come down with the flu or a cold, you will know what to do.

Every single day, bacteria, viruses, fungi, and parasites come at us. The most common invaders are upper respiratory tract invaders, or URTI’s such as colds, influenza, sinusitis, tonsillitis and middle ear infections.

Luckily our immune system has a plan. When faced with foreign attack, it works hard to defend us. Without the immune system, we’d never have a healthy day in our lives.

Our immune cells originate in our bone marrow and thymus. They interact with invaders through the lymph nodes, the spleen, and mucus membranes. This means they first make contact in your mouth, gut, lungs, and urinary tract.

Our innate (natural) immune system is our non-specific first line of defense. It includes: physical/structural barriers like the mucous lining in nasal passages, chemical barriers like our stomach acids, and protective cells like our natural killer cells, white blood cells that can destroy harmful invaders. This immune system develops when we’re young.

Interestingly, women tend to have a stronger overall innate immune response.

Then there is the adaptive (acquired) immune system. This is a more sophisticated system composed of highly specialized cells and processes. It kicks in when the innate immune system is overcome.

The adaptive immune system helps us fight infections by preventing pathogens from colonizing and by destroying microorganisms like viruses and bacteria.

Cue the T and B cells. These specialized white blood cells mature in the thymus and bone marrow, respectively. Believe it or not, they actually have a kind of memory. It is this memory that makes them so effective. Once they “recognize” a specific pathogen, they mobilize more effectively to fight it. This is what we mean when we talk about “building immunity”. This is why kids get sick so often, because they have not had as much exposure so their adaptive immune systems are less mature.

What is more, the acquired immune response is the basis for vaccination. Subject your body to a tiny dose of a pathogen, and it will know what to do when confronted with a bigger dose.

So should we exercise while sick? Let’s understand that there is a difference between “working hard” and “physically moving the body”. A structured workout routine, one where you are breathing heavily, sweating, working hard, and feeling some discomfort, awakens a stress response in the body. When we’re healthy, our bodies can easily adapt to that stress. Over time, this progressive adaptation is precisely what makes us fitter and stronger.

However, when we are sick, the stress of a tough workout can be more than our immune system can handle. Still, there is no reason to dive for the couch the minute you feel a cold coming on. Unless you are severely out of shape, non-strenuous movement should not hurt you, and it might even help.

What is non-strenuous movement? It might include: low intensity, non-panting “cardio”, walking outdoors, low intensity bike riding, gardening or T’ai Chi. In fact, all of these activities have been shown to boost immunity. They are not intense enough to create serious immune compromising stress on the body because they are done with minimal heart rate elevation. Instead they often help you feel better and recover faster while feeling under the weather.

There are low intensity workouts and high intensity workouts. What is low to one person might be high for another. So  how can you decide what level of intensity counts as strenuous? Let your own perceived level of exertion be your guide. In general, a low to moderate intensity workout will leave you feeling energized. A high-intensity workout, on the other hand, delivers an ass-kicking. If you are sick, it is recommended to avoid the ass-kicking workout.

Exercise may play a role in both our innate and our adaptive immune response. Here is how:

  • After one prolonged vigorous exercise session we are more susceptible to infection. For example, running a marathon may temporarily depress the adaptive immune system for up to 72 hours. This is why so many endurance athletes get sick right after races.
  • One brief vigorous exercise session doesn’t cause the same immune-suppressing effect. Further, just one moderate intensity exercise session can actually boost immunity in healthy folks.
  • Interestingly, chronic resistance training seems to stimulate innate (but not adaptive) immunity. While chronic moderate exercise seems to strengthen the adaptive immune system.

In the end, here is the pattern:

  • Consistent, moderate exercise and resistance training, can strengthen the immune system over time. So, train hard while you are healthy.
  • A single high intensity or long duration exercise session can interfere with immune function. So take it easy when you are feeling sick.

A group of scientists gathering data on exercise habits and influenza found: people who never exercised got sick pretty often. People who exercised between once a month and three times a week did the best. People who exercised more than four times a week got sick most often.

Exercise is not the only factor that affects the immune system. Stress plays a big role too. Here are some of the different stressors a person might face on any given day.

  • Physical stress: exercise, sports, physical labor, infection, etc.
  • Psychological stress: relationships, career, financial, etc.
  • Environmental stress: hot, cold, dark, light, pollution, altitude, etc.
  • Lifestyle stress: drugs, diet, hygiene, etc.

Stress triggers an entire cascade of hormonal shifts that can result in chronic immune changes.

  • Acute stress (minutes or hours) can be beneficial to health.
  • Chronic stress (days to years) can be a big problem.

So if you are angry, worried, or scared each day for weeks, months, or even years at a time, your immunity is being compromised and you are more likely to get sick. If you are fighting an infection, your immune system is already stressed. If you add the stress of prolonged vigorous exercise you might, overload yourself. That will make you sicker. A healthy body might adapt to all that, but a body that is fighting an infection is not a healthy body.

What is more, sudden increases in exercise volume and/or intensity may also create new stress, potentially allowing a new virus or bacteria to take hold, again kicking off a sickness.

Exercise therapy is often recommended for patients with cancer because of how it modulates the immune system. Exercise seems to increase cell activity and lymphocyte proliferation. Exercise for people with HIV seems to prevent muscle wasting, enhance cardiovascular health, and improve moods.

Some guidelines to follow for exercise while sick are:

  • Day 1 of illness: only low intensity exercise with symptoms like sore throat, coughing, runny or congested nose. No exercise when experiencing muscle/joint pain, headache, fever, malaise, diarrhea, vomiting.
  • Day 2 of illness: if body temperature is greater than 99.5-100 F, do not exercise. If no worsening of “above the neck” symptoms: light exercise (pulse <120 bpm) for 30-45 minutes.
  • Day 3 of illness: if no symptom relief, no exercise: consult a doctor.

Let your symptoms be your guide and use common sense. Remember the distinction between exercise and working out.

 Resource: Precision


Michelle’s ability to wear many hats has made her a valuable asset to the Y.E.S. Fitness team.