How to Exercise When Sick

With the change of seasons it seems like almost everyone I work with is battling some kind of cold or virus at the moment.  One of the most common questions I get is “Can I work out when I’m sick?” 

The answer, of course, is it depends.  When your immune system is battling a pathogen it’s marshaling a ton of your physical resources to do so, hence the common drop in perceived energy level.  Believe it or not, it's the same systems that fight off viral and bacterial infections that also help you recover from exercise.  

If you put too much into your workout you can steal resources from the fight to get healthy and prolong or even worsen your condition.  Let's take a look at what types of exercise you can get away with when you’re sick and which ones aren’t worth the risk. 

Light Cardio

Light aerobic activity such as walking or Zone 1 work is something you can and should do no matter how you’re feeling.  Zone one refers to a heart rate zone of 50-60% of your max heart rate and can be achieved by steady efforts of low intensity similar to walking at a brisk pace or pedaling easy on a stationary bike. Light stretching, lwo intensity calisthenics, and yoga also belong in this category. 

This type and intensity of exercise helps your cardiovascular and lymphatic systems work more efficiently but doesn’t create enough of a stress to drive athletic adaptation.  Because it’s low stress and improves lymphatic flow, your body’s trash removal system, it can improve how well your immune system responds to infection.  

I recommend to all my clients that they take a walk or get on the bike at an easy pace for 20-30 min a day even when they’re sick due to the immune boosting effects. Keep the intensity low and be respectful of your energy levels. If all you want to do is crawl into bed and sleep, you’re probably better off resting than moving. 

Walking can boost your immune system response to a cold.

Lifting 

The next least stressful form of exercise is weight lifting.  I’m talking about resistance training done in 3-6 sets of 3-8 reps with several minutes of rest in between each set.  Believe it or not lifting isn’t nearly as stressful on your body as say long endurance cardiorespiratory training or HIIT making it an option if you’re feeling a little sick, but not down for the count. 

If you have a head cold that’s primarily congestion, nasal drainage, etc. you can usually get away with lifting without prolonging your sickness.  An exception to this rule is if you have a fever. If you’re running a temperature or have body aches you’re better off sticking to Zone 1 or just resting.  

It’s also important to note that while you’re sick it’s important to reduce your lifting intensity by at least 10% or more from your common loading. You are still sick and your body will not be ready to perform at peak weights.  Despite the reduction in loading, you can still expect to preserve strength through a cold or upper respiratory infection. Many of my athletes report feeling better after a reduced intensity lifting session while they’re sick. 

Endurance Training

For those of you involved in endurance sports like cycling, running, rowing, and swimming, it’s best to leave this kind of training until you’re feeling better.  Most endurance training done at Zone 2 or higher (60% of max heart rate plus) puts too much of a strain on your immune system.  

While you can get away with Zone 1 training while you’re sick, anything more intense poses a substantial risk and could make you sicker or prolong your infection by compromising your body’s ability to fight pathogens.  If you’re not feeling well it’s best not to go for a run or a ride until your energy level has returned to normal and symptoms have subsided. 

It’s probably best to avoid endurance training while sick. 

HIIT

The most stressful kind of training on your body is high intensity interval training and other forms that look similar like CrossFit metcons, bootcamps, OTF, etc.  Not only should you avoid this type of training while you’re not feeling well, it’s advisable to not train this way unless your body is fully recovered. 
Having trained athletes in CrossFit for 15 years it’s one of my favorite types of workouts. It’s unique in its potency and can provide a bigger dose in a smaller package than any other type of training.  For optimal results, it’s important to respect this level of intensity and only apply it where appropriate, which is to say a fully recovered body.

Wait to hit your HIIT or CrossFit class until you’ve slept well, are well fed, hydrated, and ready to train hard.  It’s also worth saying that if you train in a group fitness environment you should stay home or opt for another venue if you’re not feeling well. 

It’s disrespectful and irresponsible to subject other classmates, coaches, and gym members to the germs you’re fighting.  Athletes that would show up to my gym while they were sick would quickly expect to be sent home not just for the health of others, but also so they could mend as quickly as possible. 

In Review

Light Cardio + Zone 1 > Lifting > Endurance > CrossFit + HIIT

If you’re not feeling well and fighting off a bug, give yourself permission to stay home and get extra rest.  Stay well hydrated, avoid alcohol, eat lots of clean food, and sleep as much as possible.  This is not an excuse to eat junk food, stay up late watching netflix, or knock back a few hot toddies. When you’re sick, your top priority is to get healthy first so you can get back to working on your health and fitness goals at full speed.