A science-backed guide for working out while sick
Tuesday, April 23, 2019
LifeTime WeightLoss in Paul Kriegler, functional training, immune health, workouts

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 workout at all costs? Maybe you’re they type who ghosts your workout partner at the slightest hint of a stuffy nose? 

What if neither approach is optimal? 

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, but a lot of exercise could turn out to be negative.

When we engage in any physical activity that causes our body to shift out of homeostasis or baseline functioning, we’re stimulating several physiological systems including our neuroendocrine, musculoskeletal, cardiovascular, lymphatic, and immune systems. 

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

That’s why it’s important to approach your exercise a bit differently when you’re also fighting off an illness or not feeling well. Read on to get the scoop on how to approach exercise when you’re sick.

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 intentionally used to break a sweat, burn some calories, or break down muscles.  

“Activity” or “being active” refers to other non-sedentary parts of your lifestyle like walking, standing, doing laundry, or walking the dog – the parts that won’t really prepare you for that half marathon or adventure race. 

General health guidelines suggest we should exercise for a total of about 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 two to three 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. 

The net effects of your chosen exercise depends on the overall Frequency, Intensity, Time and Type of training you choose as well as your ability to withstand and adapt to the various stressors of the training program (on top of the demands of life itself, too). 

Listen to your body. 

Our bodies tend to respond best when they’re challenged physically, then allowed to properly repair, rest, and recover. We tend to respond negatively if we exercise to exhaustion each and every session, so it’s helpful to pay attention to how the FITT principle relates 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 stressors 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. 

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].

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 workout 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, but you may be able to tolerate (or even benefit from) some lighter workouts or scaled back versions of familiar training sessions.

I suggest you also use objective measures like 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 adaptations.

Be active, but be humble

When we exercise we stimulate the activation and circulation of important immune cells throughout our body, and depending how you’re balancing your FITT 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 very least plateaus in performance.

Tissue damage from intense resistance training or oxidative stress from higher-intensity/longer duration cardio training can suppress the immune system and make us more susceptible to illness [ii] [iii]. 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 [iv] [v].

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 an illness and physically taxing your body with exercise you’re likely to run low on nutrients and building blocks to maintain your resilience [vi].

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 find 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 [vii]:

Doing some exercise or activity when we’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 our circulatory system, but instead of transporting blood, the lymph 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 [viii]. 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, and often times we discover there may have been lifestyle patterns that may have made them more susceptible. It’s well known that unresolved mental stress, undernourishment, quick weight loss and improper hygiene (i.e. handwashing) are all factors that are associated with impaired immunity [ix]. Occasionally their ‘go-hard-or-go-home’ attitude towards exercise plays a role too, so we learn valuable lessons about the value of “de-load” phases of training.

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

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 or Yoga/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’s 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 10-20% 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.

After reading this post, if you think you’ve got a better understanding of how to handle your exercise when you’re feeling under the weather, just remember to continue listening to your body and modify your approach so any illness you experience passes quickly and you get back to living your healthy lifestyle.

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 pro. 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.


In health, Paul Kriegler, Registered Dietitian and Life Time - Nutrition Program Development Manager. 

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.  

[i] https://www.ncbi.nlm.nih.gov/pubmed/9813869

[ii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1320353/

[iii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2803113/

[iv] http://eir-isei.de/2011/eir-2011-006-article.pdf

[v] http://eir-isei.de/2011/eir-2011-064-article.pdf

[vi] http://www.scielo.br/pdf/rbme/v18n3/en_15.pdf

[vii] https://www.ncbi.nlm.nih.gov/pubmed/9129268

[viii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5551392/pdf/nihms890943.pdf

[ix] https://www.ncbi.nlm.nih.gov/pubmed/9129268

[x] http://www.annfammed.org/content/10/4/337.full.pdf

[xi] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4109789/pdf/1475-2891-13-72.pdf

[xii] http://www.lifetime-weightloss.com/blog/2016/10/23/why-greens-should-be-a-part-of-your-supplement-routine.html

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