too sick to run

Unsure if you should run or rest when you feel sick? I’ll explain how to know if you are too sick to run and how to get back to training safely.

Click here to listen to the podcast version of this article.

As I type this, I’m a little under the weather.  Thankfully, it’s not COVID, but it’s just your regular, run of the mill cold or mild flu.  I know that I’m not the only runner this time of year that’s suffering, so I thought it would be the perfect time to dive deep into the topic of running while you’re not feeling your best.

I’ll explore:

  • when it’s okay to exercise when you are sick,
  • what precautions and modifications you should make to your routine, 
  • when it’s not a good idea to run, and
  • how long it takes to return to fitness after some time off
run or rest when sick

Your Mom Was Right

For a little perspective, the idea of running while sick if you are not a habitual runner sounds a little crazy.  No one’s mother said to any child, “oh you are not feeling well?  Go for a run!”  Most moms (and dads) will tell you to rest, drink your fluids, and try to eat something.

And that advice still holds true for runners.  When you first start feeling the symptoms of a cold, the flu, or COVID, take a rest day and skip your run.  Running is a deliberate stressor on the body, which is a good thing when you are healthy, but can needlessly divert healing resources away from your illness.  If you want to get better faster, then allowing your body to attack your invader without distraction is the best route.

Mild Symptoms

But what if your sickness is mild, but lingers on for days or even a couple weeks?  Surely, you don’t have to give up running for that long, right?  Well, maybe, maybe not.

Clearly, while we are still fighting a pandemic, it’s not a good idea to hop on the treadmill at the gym while you are coughing and sneezing.  I mean, that was never a socially acceptable thing to do anyway, but we are all hyper aware of that now.  But going for a run alone in your neighborhood or in the woods might just be the thing that makes you feel a little better.

Before you try, however, I encourage baby steps.  I’ll get to those in just a minute, but first, let’s try to outline some guidelines about whether you should even be thinking about a run right now.

The Above the Neck Rule

A general rule of thumb is that if your symptoms are above the neck, a run could be okay and might even help move things around a bit.  That would include a little nasal congestion or a runny nose.  But if you have a fever, body aches or fatigue, sore throat, coughing, nausea, or chest congestion, it’s far better to stay home and rest.  

Anything that is affecting your lungs is a clear sign you’re too sick to run.  If you try to run anyway, you’ll likely feel a burning sensation in your lungs or the top of your throat as your body struggles to stop you from doing such a foolish thing.

Your heart is forced to work harder as it tries to both power your run and deal with the stress of the illness.  If you happen to have an underlying heart issue, either known or unknown, running while sick can expose you to extra risk.

Another time to toss out the rule of thumb is when you go ahead and run with a head cold and you come back feeling worse.  That’s your body telling you to chill out and relax with a cup of hot tea.

Your Fitness Won’t Be Affected Much By Rest

Taking a couple days off or even a couple weeks off will not impact your fitness very much at all.  Another good rule of thumb here is that you can gain back any fitness lost in about the same time as you took off.  So if you were too sick to run for two weeks, you can get back to your pre-sickness level in about two weeks.  This is all very individual, of course, with some runners bouncing back quicker than others, but taking the time to heal will not completely derail all your progress.  But fighting this process certainly can.

Okay, so running is on the shelf for a while.  What can you do to help get better faster?  And is there any kind of exercise that is acceptable when you’re under the weather?

Play It Safe

When you’re too sick to do much of anything, it’s pretty clear you should stay in bed and rest.  But when you are more borderline, it can be hard to know what makes sense.  After all, runners hate to get out of their routines or risk their hard-earned fitness, right?

But you will get through this as long as you play it safe and don’t try to push through it.

Hydration

Besides rest, the first thing you’ll want to focus on is hydration.  When your body is fighting an active infection, it needs more fluids than usual to do its job.  Dehydration will make everything worse.  This is one of the times where drinking to thirst may not be enough, so aim for a little more than usual.  If your urine is pale yellow, that’s a good sign that you are doing it right.

Nutrition

Next up is nutrition.  You might not feel like eating much of anything, especially if your illness has affected your sense of taste or if you have nausea.  Again, this is where your mom was right, try to eat a little something anyway.  If it’s really bad, just try to eat whatever you can tolerate.  

If you can tolerate a variety of foods, this is definitely the time to focus on the most nutrient dense options, like a rainbow of fruits and vegetables.

As far as supplements go, a standard multivitamin is probably sufficient for most people.  There have been some interesting studies showing that for marathon runners or other heavy exercisers, taking a little  extra vitamin C can help prevent and shorten the common cold.  But too much of a good thing can cause nausea, diarrhea, and even cause kidney stones, so stay away from mega-doses.

A few studies have shown zinc to be helpful, but again, it’s probably better to get it from real foods like chickpeas or pumpkin seeds rather than a supplement. 

Alternatives to Running

When you know that a run is out, what can you do instead?  If your issues are mainly in your lungs, but the rest of your body is feeling okay, you can try some gentle non-aerobic activity.  That could be light yoga, some mobility or stretching, or even some lighter strength moves that don’t get you breathing hard.

If you are feeling up to moving a bit more, try heading out for a walk instead of a run.  This should also be your first choice before you attempt a run.  You’ll know fairly quickly if it was the right choice if it feels pretty good during and after.  If you are wiped out after your walk, it’s time to go back to another rest day.  Then the following day, you can try a walk again.

How To Transition Back to Running

Once you have a day or so of walking behind you and you are feeling better, you can try a run.  I always advise a shorter and slower than normal run, just as a test to make sure that you are really on the mend.  If that goes well, you should be able to return to your normal routine in a couple of days.

Warning Signs to Watch Out For

Of course, if you have any cardiac-related symptoms while running, that is also a sign that you should stop immediately and talk to your doctor.  This would be shortness of breath, heart palpitations, irregular heart beats, chest pain, wheezing.  These are serious signs that shouldn’t be ignored, whether you are recovering from an illness or not.

The typical common cold lasts about 7-12 days, so try to be patient and allow your body’s defenses to do their job.  You’ll be back to running before you know it without losing much fitness at all.

For me, I’m at the stage where walking and a little light strength training feels good right now.  I’m laying low and drinking lots of hot tea with lemon, just like what my mom used to make me when I was little.  Hopefully, by the time this airs, I’ll be back to my running routine, but I plan to take my own advice and be patient.


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About Claire


Coach Claire has helped hundreds of runners chase their dreams and conquer big goals. Her coaching philosophy combines science-based training, plant-based nutrition, and mindset techniques to unlock every runner's true potential. She's an ASFA certified running coach, sports nutrition specialist, a 2:58 marathoner, mom, and borderline obsessive plant lover.

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