A Science-Backed Guide To Working Out When You’re Sick

What do you do with your workout routine when you’re under the weather? Are you someone who ignores the symptoms to crank out your daily training sessions at all costs? Maybe you’re the type who ghosts your workout partner at the slightest hint of a stuffy nose? 

What if neither approach is optimal? 

Here’s the scoop on how to approach exercise when you’re sick.

Exercise can and should be an extremely beneficial part of a healthy lifestyle. We know that a little exercise is better than none, moderate amounts are quite good, and a lot of exercise could turn out to be negative.

When we engage in any physical activity, our body shifts out of homeostasis or baseline function, and we stimulate several physiological systems including our musculoskeletal, cardiovascular, lymphatic, neuroendocrine, and immune systems. 

Humans are designed for movement and when we’re active enough these systems work together to coordinate adaptations to our environment. We become adapted and resilient to a given “dose” of movement and when we move the “right” amount at the right times (not too little, not too much), we can strengthen our immune system. It’s a balancing act.

When you’re not feeling well or are fighting off an illness, it’s important to approach your exercise a bit differently.

Being active and “exercising” are not the same though, so for the purposes of this article, the term “exercise” refers to structured training modalities that are used to intentionally break a sweat, burn some calories, or break down muscles. “Activity” or “being active” refers to other nonsedentary parts of your lifestyle, such as walking, standing, doing laundry, or walking the dog — the times you’re moving, but not in ways that’ll prepare you for that half marathon or adventure race. 

General health guidelines suggest we should exercise for a at least 150 minutes per week, in addition to being active frequently throughout the non-exercising hours each day. For optimal health and fitness, we should include three to four bouts of resistance training as well as two to three bouts of cardiovascular training each week. 

These are generalities, of course — and they refer to the minimum effective dose for health, so do not encompass the total training recommendations for competitive athletes. 

Listen to your body. 

Our bodies tend to respond best when they’re challenged physically, then allowed to properly rest, recover, and repair. We often respond negatively if we exercise to exhaustion each and every session, so it’s helpful to pay attention to how you balance the frequency, intensity, time, and type of exercise relative to your individual state of fitness and health.

If you listen, your body will give you plenty of clues on how to manage your training choices. Or, you can work with an experienced coach to bring better logic, objectivity, and art to your program. 

Exercise introduces two main forms of stress on our bodily systems: mechanical stress and/or metabolic stress. Mechanical stress refers to the physical damage to muscle tissue induced by resistance training or high intensity, long duration cardio. Metabolic stress refers to the short-term demand for higher-than-normal energy output that cardiovascular training places on our bodies. 

Both types of stress are necessary when we’re trying to change our fitness or physique, but depending on the total volume and intensity of the stress, it may take up to 72 hours for your body to return to its baseline homeostasis. If you’re sick, the entire training plan may need to shift temporarily.

As a general rule, if you feel too rundown to get out of bed or leave the house, you’re probably better off postponing any strenuous training sessions. If you’ve got a fever, you’re coughing up gunk, or aren’t brave enough to stray more than a few feet from the toilet, I’d suggest rescheduling any taxing workouts on your plan, too. 

These symptoms are your body’s way of showing it may be preoccupied fighting for something other than that last rep or interval. It’s telling you it’s not ready to adapt to any new physical feats, though you may be able to tolerate (or even benefit from) some lighter workouts or scaled back versions of familiar training sessions.

Many experts make training recommendations based on whether or not the symptoms are manifesting above or below the neck, and there may be some truth to it. Research suggests that moderate duration, moderate intensity exercise has neutral or even helpful effects on the common head cold.

I suggest you also use objective measures, such as resting heart rate or heart-rate variability (HRV) to monitor your body’s health, fitness, and readiness for advancing your training. If you measure these factors before and while you’re fighting off illness, you’ll discover some very strong correlations between illness and poor training readiness, performance, and your ability to adapt positively.

Be active, but be humble.

When we exercise we stimulate the activation and circulation of important immune cells throughout our body. Depending how you’re balancing your frequency, intensity, time and type variables, this may be a good thing.

However, if you’re increasing volume or intensity faster than your body is ready for it (like when you’re ill), you’re risking injury, prolonged illness, or, at the very least, plateaus in performance.

Tissue damage from intense resistance training or oxidative stress from higher intensity, longer duration cardio training can temporarily suppress the immune system and make us more susceptible to illness. Some accounts suggest the immune system is “weakened” for several days to a few weeks following a competition or taxing sports event, opening up a window of opportunity to become ill or exacerbating current illness.

When your immune system is fighting infection, it requires key nutrients (vitamins, minerals, amino acids, glucose, essential fatty acids), extra rest, and a bit of relief from your normal stressors. These are the same nutrients your body needs to repair from strenuous or challenging exercise sessions, so if you’re fighting illness and physically taxing your body with exercise, you’re likely to run low on nutrients and building blocks to maintain your resilience.

When working out during an illness, you’re not going to set any personal bests, and you might even notice you can’t even do your “normal” routine. Be humble and accept scaled-back versions of your workouts. 

If you have a fever or below-the-neck symptoms, you’re probably due for a few days to one week of complete rest from all strenuous exercise.

On the other hand, if you’re battling a head cold, sinus congestion, or sore throat but you feel like sticking with your planned exercise sessions, you’re probably fine to proceed with a few modifications. 

Here are a few ways to adjust the FITT variables of your program to work with your body, rather than against it:

• Frequency: If your training plan calls for four hard sessions this week, consider scaling back to just three.
• Intensity: Dial back the weight or heart rates by 20 to 30 percent from your normal, or keep the intensity level at less than 60 percent of your VO2 max.  This will allow for a milder stimulation without overtaxing your body’s resources.
• Time: Decrease the total time under tension (number of sets and/or reps) in your resistance sessions, or cut back from 60 minutes to 40 to 45 minutes for cardiovascular sessions.
• Type: Opt for a walk or jog instead of a run, or settle for body-weight resistance training or yoga versus a more strenuous weight room session.

Doing some exercise or activity when you’re ill is helpful for another reason: Physical movement is necessary for our lymphatic system to function. The lymphatic system is a network of vessels similar to the arteries and veins of your circulatory system, but instead of transporting blood, the lymphatic system transports immune cells, antibodies, and fatty acids throughout the body. It plays a critical role for our immune system, but unlike the circulatory system, we need to move our bodies in order to keep lymph moving — there’s no pump. We are the pump.

Use extra time to optimize other lifestyle patterns.

I always challenge my clients to consider why they became sick in the first place. Oftentimes we discover there may have been lifestyle patterns that may have made them more susceptible.

It’s well known that unresolved mental stress, undernourishment, inadequate sleep, quick weight loss, and improper hygiene (e.g. hand washing) are all factors that are associated with impaired immunity. Occasionally, their “go-hard-or-go-home” attitude toward exercise plays a role too, so we learn valuable lessons about the significance of “de-load” phases of training.

So, as we’re dialing back the volume and intensity of workouts to facilitate faster healing, we can turn our focus and “extra” time to addressing overall lifestyle patterns. Here’s the checklist I typically use:

• Elevate sleep hygiene. Recalibrate nighttime routines to facilitate at least eight hours for sleep, quicker sleep onset, and deeper, more restful sleep by setting parameters for screen time after sundown, temperature (less than 68 degrees F), and darkness in the bedroom (blackout shades might just change your life). Proper, restful sleep is the ultimate healing mechanism and reset button — there’s no shortcut around it.
• (Re)connect with the value of “downtime” to build resilience. In our go-go-go culture, we seldom make time to just be present, but deep breathing and meditation actually play critical roles in balancing our neuroendocrine and immune systems in ways that can improve our immune health and facilitate recovery. Laughter is always good, too — anything to help the lymphatic system pump and your spirit rejuvenated.
• Invest in meal-prep routines. Eating a wholesome, nutrient-dense, and minimally processed diet based on ample produce and adequate protein is a simple idea, but it’s not always easy to master. It takes time, practice, and sometimes a bout of feeling really crummy to inspire us to devote the energy to optimize our nutritional lifestyle. The rewards are worth it, especially if it helps you get back to your training program faster. A skilled Nutrition Coach can help you make your nutritional lifestyle easier and healthier in a hurry, so if you struggle with this skill set, hire a coach.
• Master a daily supplement routine. As one micronutrient researcher says, “Most nutrients act in all tissues, all tissues need all nutrients; therefore, inadequate intakes may adversely affect every body system . . . ” This statement emphasizes the importance of consistently getting an adequate daily intake of vitamins, minerals, and essential fatty acids to keep your body operating as designed. In my experience, even if clients are trying their best to eat a pile of produce the size of their heads, ample protein, and unprocessed carbs each day, they still need to support their plan with a solid supplement routine starting with our Foundational Five: A high-quality multivitamin, omega-3 fatty acids, vitamin D, magnesium, and digestive enzymes — plus, oftentimes, a greens supplement.

Sadly, none of these lifestyle patterns will fix themselves, so if you’re downgrading your workout commitments during a bout of illness, you cannot go wrong with spending time optimizing the lifestyle patterns that will support even better training responses once you’re back up to speed. 

Ramp back up reasonably. 

That brings up the final tip: When you’ve dealt with whatever plagued you (which could take a few days to a few weeks, depending on the type and severity of illness), it’s unrealistic to expect your fitness, energy, or performance to snap back to your previous baseline. As tempting as it may be to jump straight to your pre-illness frequency, intensity/loads, time/volume, or type of training, allow yourself a gradual return to your normal routine to reduce the risk of relapse or catching a different illness. 

Prioritize resistance training, yoga, or Pilates over steady-state cardio — they naturally follow an interval/intermittent effort structure rather than a steady-state effort model that may more easily wear you down. Muscle contractions and deep breathing are also better at stimulating lymphatic drainage, so if there are any residual antibodies or immune response you need to “flush out,” lifting weights is a more beneficial activity than steady-state cardio. 

Increase volume and/or intensity week over week, but be cautious not to increase both at the same time. A general rule of thumb is to increase by just 10 to 20 percent in total volume week over week, as well as follow an undulating progression model that allows for a moderate “de-load” or “regression/maintenance” week every month or so. If this sounds too technical to follow, I’d recommend meeting with a fitness professional to review your goals, experience, and overall lifestyle program and plan a reliable path to success.

Now that you have a better understanding of how to handle your exercise when you’re feeling under the weather, remember to listen to your body and modify your approach so any illness you experience passes quickly and you can get back to living your healthy lifestyle. And as always, visit your doctor to address any of your medical concerns, or to evaluate the need for possible treatment.

If you’ve noticed specific setbacks or repetitive delays when it comes to getting back into your normal workout routine after common, everyday illnesses, it may be time to work with a fitness professional. By working with a fitness pro they’ll be able to help develop a comeback plan that is personal to you and keeps you on track toward achieving your goals.