Training During Illness - The Muscle PhD

Training During Illness

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At the time of this writing, cold and flu season is in full swing and wouldn’t you have guessed it, I’ve come down with a cold. This got me thinking about doing some more research on how to train while you’re sick, because in the past I’ve always just blasted my way through any illness. After doing some reading and taking a few notes, I decided to change my training plan when I come down with a bug, and here’s why you should too.

Training and Immune Impairment

The first thing to understand is that intense training in general can increase the incidence of illness – i.e. you might get sick more often if you train really hard (3,4,16,20). This is probably due to the fact that an intense workout can actually impair immune system function for up to 72-hours after the training session (16). This effect is more than likely due to the increase in stress hormone production that occurs following an intense workout, because we don’t see the same effect with moderate or low intensity exercise (16). In fact, studies show that individuals who workout at, “moderate,” intensities are 23% less likely to develop an upper respiratory infection (URI) than individuals training at higher intensities (13).

Another important component to this subject, and gains in general, is sleep. Studies have shown that sleep can have a huge impact on both recovery and, interestingly enough, immune function. One particular study found that subjects who slept less than 7-hours per night were almost 3x more likely to experience a cold than participants who slept more than 8-hours per night (1). This same study found that sleep efficiency was also a strong predictor for developing an illness. Sleep efficiency is simply the time you actually sleep divided by the total amount of time you spend in bed, so however long it takes you to fall asleep, periods of restlessness, etc. do not count as sleep time. It was discovered that participants who had a sleep efficiency of 92% or less were 5.5x more likely to experience cold symptoms than subjects who had sleep efficiencies of 98% or greater (1).

Combating Immune Impairment

So both intense training and poor sleep can lead to increased susceptibility to colds and illness. What is the busy bodybuilder supposed to do? The first step would be to add some form of moderate exercise to your training, such as biking, hiking, walking an energetic dog, etc. Several studies have found that moderate exercise can actually be beneficial for immune function (5,16,17) so adding some type of moderate activity to your program on off days or between workouts can help improve immunity. Many of these activities are also great active recovery protocols so you can garner more than just immunity benefits from them. Vitamin C supplementation can also help immune function but has some caveats: 1) consuming vitamin C after developing a cold will have no benefit to reducing symptoms or the longevity of a cold (16); and 2) vitamin C may negatively impact protein signaling and gains, so you’ll want to take it at least 4-hours away from your workout (19). So the takeaway with vitamin C is that it may help prevent colds, but it’s best to start taking it at the onset of cold/flu season and not just when you start to feel sick.

Another great way to improve immunity is to adopt a routine of a post-workout meal/snack. We know the whole myth of the tiny, “anabolic window,” has been well-debunked, but a post-workout meal can have immune benefits that are still incredibly important for a bodybuilder, especially during cold/flu season. Studies show that consuming carbohydrates following exercise may reduce immune system impairment following a training session (10,15). Another study found that consuming protein after a workout reduced the stress response to the exercise which could also reduce immune impairment following intense training (14). So the takeaway here is pretty easy – eat your carbs and protein after your workout!

So finally, on to the good stuff. We know that hard training can impair immune function. We know of a few ways that a bodybuilder can reduce this immune impairment, including sleep, moderate exercise, and post-workout nutrition, but what happens if you still get sick?

Training While You’re Sick

The first step to training through illness is assessing your condition. If your symptoms are just neck-up, like runny nose, sore throat, etc. you can continue to train at moderate intensities (16). Once you start feeling better, you can resume intense workouts (7,11). However, if your symptoms are more systemic/full body, such as muscle aches, fever, nausea, etc. you should definitely take a few days off (16). Continuing to train through a more severe illness can easily lead to overtraining as the body is already under immense stress from the infection (12,18). Training while sick can also increase the severity of your symptoms and the longevity of the illness (2,8) which all just sounds absolutely terrible.

Now, we get it, we’re meatheads too and we still want to keep training even when we have a fever of 104 F (40 C) and we’re vomiting like an active volcano. You, “can,” still perform somewhat intense training. I say, “can,” tentatively because you have to be very careful. Cut your volume big time – fewer sets and fewer reps are absolutely necessary. You can somewhat maintain intensity (weight on the bar) but you can’t push yourself as much as you can when you’re healthy (16). Let’s say I’d do a typical workout of 4×8 at 75% on squats, Romanian deadlifts, leg press, and lunges. You can still work at a 70-75% intensity, but I’d shoot for 3-sets tops of 4-6 reps instead. You’ll be able to maintain strength/size at this rate without aggravating symptoms further and risking overtraining. You can even add in tools like slower tempos, holds at the bottom of movements, etc. to make lighter weights more taxing on the muscle without, “technically,” training harder.

The big key to training when you’re sick is taking in enough food and water. People often lose weight when they’re sick because their appetite slows down and they lose excess water through fever sweats, mucus production etc. When you lose weight during a period of illness, your chances for symptoms getting worse or lasting longer greatly increase (14,16). Force feed and keep a bottle of water on hand at all times when you’re sick – it will suck but it’s a great way to keep symptoms from getting worse.

So, what’s knowledge without application? I tried some of these methods this week when I was sick. I backed off my training volume big time and even took a day off in the middle of the week. I force fed quite a bit and drank as much water as my bladder would allow. Typically when I get sick I have a day or two of, “Damn, I might be getting sick,” then I feel like absolute garbage for about 2-days, and then I slowly get better over the next 7-10 days. This time around I had one really rough day but I’ve bounced back much, much better than I have in the past when I would train through the sickness and not modify my diet at all. This whole science thing really does work…


In conclusion, training hard and not sleeping/eating well can reduce immune system function. Moderate intensity workouts, improving sleep duration and quality, and post-workout meals can all play a role in improving immune function during periods of hard training. Supplements like zinc and glutamine can also improve immune function and won’t have any of the negative side effects of vitamin C. If you do get sick but want to keep training, back off on the intensity and volume and ramp up your calorie and water intake. And also try to get some extra sleep to assist in overall recovery.

Severe illnesses require you to take a few days off as it’s very easy to develop overtraining symptoms if you try to keep training through it. And let’s be honest, if you workout at a public gym, coughing and sneezing all over the equipment may not be the most polite thing to do to your fellow gym members. Getting sick is a part of life, but knowing how to deal with it and how to continue making gains is important for the bodybuilder or athlete looking to maximize their potential.


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