Should You Exercise When You’re Sick

With winter upon us, unless you’re lying underneath a rock you will be exposed to a large number of people that are sick, and yes everybody gets sick! But it’s tough to know what to do about it, as coaches we get asked these question all the time “Should I exercise when sick or not? Should you sweat it out? Or should I get some rest instead?”

In this blog let’s try to clear up the confusion so that the next time you come down with a cold or flu, you’ll know exactly what to do!

You’re at the gym, you’re all warmed up and ready for a great workout… Then, all the sudden, Mr. Sneezy walks by coughing, sniffling, and heavy mouth-breathing. He’s spraying all over the benches and equipment. Awesome.

You think to yourself “Dude, shouldn’t you just stay home and rest? And, while you’re at it champion stop sharing those nasty germs!”.

But maybe Mr. Sneezy’s onto something. Maybe he’ll be able to sweat the sickness out of his system, boosting his immune system along the way?

What’s the right approach? Let’s explore it

The immune system: (A quick and dirty intro)

Every single day, bacteria, viruses, fungi, and parasites come at us from everywhere. As you know it’s a germ jungle out there and you can’t or shouldn’t avoid it.

The most common invaders are upper respiratory tract invaders, or URTI’s. Yep, I’m talking about:

• colds,
• coughs,
• influenza,
• sinusitis,
• tonsillitis,
• throat infections, and
• middle ear infections

Luckily, our immune system has got a plan for it all. 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.

The innate (natural) immune response

Our innate (natural) immune system is our non-specific first line of defence and 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 ‘NK’ 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. (Maybe this is why they often do better than men when it comes to colds but they suffer more often from autoimmune diseases.)

The adaptive (acquired) immune system.

This is a more sophisticated system composed of highly specialised 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 colonising and by destroying microorganisms like viruses and bacteria.

Cue the T and B cells. These specialised white blood cells mature in the thymus and bone marrow, respectively. And believe it or not, they actually have a kind of memory.

It’s this memory that makes them so effective. Once they “recognise” a specific pathogen, they mobilise more effectively to fight it. This is what we mean when we talk about “building immunity.”

Ever wondered why kids get sick with viruses more often than adults? It’s because they haven’t had as much exposure so their adaptive immune systems are less mature.

What’s 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. It’s genius!

So, should you exercise while sick?

Let’s get one thing clear from the start by saying that there’s a difference between “working out” and “physically moving the body”.

A structured workout routine which is one where you’re 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 without any problems. Over time, this progressive adaptation is precisely what makes us fitter and stronger.

But when we’re sick, the stress of a tough workout can be more than our immune systems can handle at that moment in time.

Still, there’s no reason to dive for the couch the minute you feel the sniffles coming on and roll up and die. Unless you’re severely out of shape, non-strenuous movement shouldn’t hurt you and it might even help you.

What do I mean by “non-strenuous movement”?

Well, it might include:

• walking (preferably outdoors),
• low intensity bike riding (again, outdoors),
• gardening
• practicing T’ai Chi etc

In fact, all of these activities have been shown to boost immunity by reducing stress levels and deceasing cortisol levels.

They aren’t intense enough to create serious immune-compromising stress on the body. Instead, they often help you feel better and recover faster while feeling under the weather.

That’s why we often recommend low intensity non-panting “cardio” when suffering from colds. Done with minimal heart rate elevation, preferably outside, these activities seem to offer benefits.

What about “working out”?

Non-strenuous movement and purposefully working out are different as we now know. Plus, as you probably know, not all workouts are created equal. There are low intensity workouts and high intensity workouts and all sorts of workouts in between!

But what’s low to one person might be high to 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 energised and feeling good. A high intensity workout, on the other hand, delivers an ass-kicking and a beat down! If you’re sick, it makes sense to avoid the ass-kicking… Let’s take a look at why.

How exercise affects the immune system

Exercise may play a role in both our innate and our adaptive immune response.

Here’s how:

• After one prolonged vigorous exercise session we’re 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.
• However, 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 people.
• 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’s the pattern:

• Consistent, moderate exercise and resistance training can strengthen the immune system over time. So, by all means, train hard while you’re healthy.
• But single high intensity or long duration exercise sessions can interfere with immune function. So take it easy when you’re feeling sick.

Exercise, stress, and immune function

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.

Enter the J-shaped curve theory.

In simple terms, being sedentary or exercising too much can lower immunity, while something in the middle can improve immunity. (Here’s that conversation about moderation again!)

The role of stress

Exercise isn’t the only factor that affects the immune system. Stress plays a big role too.

Let’s take a look at 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 to hours) can be beneficial to immune health.
• Chronic stress (days to years) can be a big problem.

So, if you’re angry, worried, or scared each day for weeks, months, or even years at a time, your immunity is being compromised. And you’re more likely to get sick.

Sickness and stress

It’s pretty obvious that if you’re actually sick and fighting an infection, your immune system will already be stressed and if you add the stress of prolonged vigorous exercise, you might, quite simply, overload yourself. That will make you sicker.

Plus, your history of infections can influence how the immune system responds during exercise. This can include everything from the common herpes simplex virus, varicella zoster, and cytomegalovirus, to hepatitis and HIV.

A healthy body might adapt to all that. But a body that’s fighting an infection is not a healthy body.

Overtraining and infection

What’s 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.

Consider the 1987 Los Angeles Marathon, where one out of seven marathon runners who ran became sick within a week following the race. And those training more than 60 miles per week before the race doubled their odds for sickness compared to those training less than 20 miles per week.

This seems to work the opposite way as well. Chronic infections may actually be a sign of overtraining.

Other factors affecting immunity

Besides stress, there are a host of other factors that can affect our immunity, and these can interact with exercise, either offering greater protection or making us more likely to get sick.

We’ve already touched on some of these. Here are a few more.

Age

 Our innate immune response can break down as we get older. But here’s the good news: staying physically active and eating a nutritious diet can offset many of these changes.

Gender

Menstrual phase and oral contraceptive use may influence how the immune system responds to exercise. Estrogens generally enhance immunity while androgens can suppress it. (Again, this may explain why women tend to do better with colds than men.)

Sleep

Poor quality sleep and/or prolonged sleep deprivation jeopardises immune function.

Climate

Exercising in a hot or cold environment doesn’t appear to be that much more stressful than exercising in a climate controlled environment.

For example, exercising in a slightly cool environment might boost the immune system. But full-fledged hypothermia may suppress immune function. While using a sauna or hot bath may stimulate better immunity in those with compromised immune function.

Altitude

Exposure to higher altitudes has a limited influence on immunity.

Obesity

It’s unclear exactly how obese folks respond to exercise in terms of immunity. Changes in insulin sensitivity and inflammation at rest may blunt or exaggerate their immune response to exercise.

Mood

There’s evidence that immune alterations affect mood and inflammation. Clinical depression is two to threefold higher among patients with diseases that have elevated inflammatory activity.

(Note: moderate exercise appears to act as an anti-inflammatory in those with inflammatory conditions).

IL-6

There is a theory that IL-6 (a compound released after prolonged intensive exercise) may be produced in abnormal ways in some people, leading to fatigue, flu-like symptoms, and depressed mood.

Training age

The more “trained” you are, the better your body tends to handle exercise. In other words, it’s not as much of a stressor.

Just in case you glossed over the previous sentence I’ll reiterate it: a higher level of fitness is protective as it may limit the stress response to exercise.

Textbook guidelines for exercising while sick:

Day 1 of illness:

• Only low intensity exercise with symptoms like sore throat, coughing, runny nose, congested nose.
• No exercise at all when experiencing muscle/joint pain, headache, fever, malaise, diarrhea, vomiting.

Day 2 of illness:

• If body temp >37.5-38 C, or increased coughing, diarrhoea, vomiting, do not exercise.
• If no fever or no worsening of “above the neck” symptoms: light exercise (pulse <120 bpm) for 30-45 minutes, by yourself, indoors if winter.

Day 3 of illness:

• If fever and symptoms still present: consult doctor.
• If no fever, and no worsening of initial symptoms: moderate exercise (pulse <150 bpm) for 45-60 min, by yourself, indoors.

Day 4 of illness:

• If no symptom relief, no exercise. Go to doctor.
• If fever and other symptoms improved, wait 24 hours, then return to exercise.
• If new symptoms appear, go to doctor.

Note: Some illnesses can indicate serious infections. So if you aren’t feeling better and recovering, see your doctor.

Also note: Ease back into exercise in proportion to the length of your sickness. If you were sick for 3 days. Take 3 days to ease back in.

To exercise or not? What the pros recommend

Now you know something about the immune system and how exercise interacts with it. But you still might be wondering whether you should exercise when you’re sick. I asked some of the best in the business for their insights.

The consensus is let your symptoms be your guide and use common sense and remember the distinction between exercise and working out.

Exercise activity cheat sheet and activities to consider when you’re sick:

• Walking
• Jogging
• Swimming
• Biking
• Qi gong
• T’ai Chi
• Yoga

All of these would be done at a low intensity, keeping your heart rate low. They’d also preferably be done outdoors in mild temperatures. Inside is fine, though, if you can’t get outside.

Activities to avoid when you’re sick:

• Heavy strength training
• Endurance training
• High intensity interval training
• Sprinting or power activities
• Team sports
• Exercise in extreme temperatures

And, for the sake of the rest of us, stay out of the gym. At the gym, you’re much more likely to spread your germs to others. Viruses spread by contact and breathing the air near sick people.

So, if you feel up to physical activity, again: do it outside or at your home gym.

We all thank you.

What you should do if you feel healthy and simply want to prevent getting sick:

• Stay moderately active most days of the week.
• If you participate in high-intensity workouts, make sure you’re getting enough rest and recovery time.
• Manage extreme variations in stress levels, get plenty of sleep, and wash your hands.

If you are already feeling sick, let symptoms be your guide:

• Consider all the stress you’re managing in your life (e.g., psychological, environmental, and so forth).
• With a cold/sore throat (no fever or body aches/pains), easy exercise is likely fine as tolerated. You probably don’t want to do anything vigorous, no matter how long in duration.
• If you have a systemic illness with fever, elevated heart rate, fatigue, vomiting, diarrhea, muscle and joint pain/weakness, and enlarged lymph nodes, get some rest! If you have a serious virus and you exercise, it can cause problems.

f you would like to know how Miyagi Fitness could help you, visit www.miyagi.fitness today or watch the below video to find out more