Program: Is it OK to exercise when you're sick?

Norman Swan: You sound a bit sick, Tegan, what's going on?

Tegan Taylor: I'm sick as a dog, Norman, but never too sick to talk to you. 

Norman Swan: Oh, that's very nice of you. Would you like to lie down and tell me all about it, and get your Medicare card out?

Tegan Taylor: Lie down on the couch, the doctor's couch? No, I'm literally sitting on a bed while we record this because I'm at home, and maybe I'll just have a lie down halfway through the podcast recording if I get too tired.

Norman Swan: So you're going to lie down on the bed…do you think that's the best thing for you?

Tegan Taylor: Well, I don't want to say that I put my body on the line for science and journalism, but today I really have, because aptly we're talking about sickness today on What's That Rash?.

Norman Swan: The podcast where we answer the health questions that just everybody's asking.

Tegan Taylor: So this week's question comes from Margaret, who says, 'Hi, What's That Rash?. Today is day one of cold or flu symptoms. I'm starting to feel lousy.' And she asks, 'As a rule of thumb, how much should we exercise when we have a cold or flu?' And then she goes on to flex that she says, 'I usually exercise in the mild to moderate category four to five times a week, either a brisk 30-minute walk until I'm a bit breathless and sweaty, or a stretch and exercise class at the gym. I'm 70 and otherwise healthy.' And she adds in brackets, '(But other listeners aren't.)' So yeah, Norman, let's talk about…

Norman Swan: What, aren't 70 or aren't healthy?

Tegan Taylor: I think our listeners are of both all and neither of those things. We are a broad palette. So exercise and sickness is the topic for today.

Norman Swan: It is. And the question is, should you exercise? Should you lie down to it? So let's start with talking about what exercise might do to the immune system.

Tegan Taylor: Yeah, because I think that my gut tells me, although my gut is not to be trusted these last couple of days…

Norman Swan: Too much information thanks, Tegan.

Tegan Taylor: That exercise is good for helping you not get sick, but does it actually help you if you're already sick? 

Norman Swan: Good question. So let's start with the basics, as we often do on What's That Rash?, and look at the evidence for exercising affecting the immune system, because there's a bit of mythology here around it. So just in general, moderate to vigorous exercise, and so the sort of exercise that you're recommended to do, 150 minutes a week, there are effects on the immune system. Nobody's quite sure how it happens, but they're pretty sure about what happens. 

So there are two or three elements to the immune system, broadly. There's what's called the innate immune system, which is the first barrage that the immune system puts up when it's threatened by something coming in, like a pathogen, in other words a virus or a bacterium, or they're not quite sure what's happening and they put up this barrier, which is also called inflammation. 

And there's the adaptive immune system, which you can say is in two parts, which is our antibodies, and actually the cells of the immune system which hold memory. But by and large we just call it the adaptive immune system, which is the immune system learns what the actual attack is from and develops a response to it. So let's start with inflammation, because inflammation has been blamed, quite rightly, for ageing, one part of the ageing process, and speeding up ageing.

Tegan Taylor: Yeah, we think of inflammation as being a bad thing, but I'm hearing you saying that in some instances it can be a good thing.

Norman Swan: You need it. And where it's bad is where it's an overreaction or it's prolonged. So in other words, you want an inflammatory reaction when you're under threat, but when you're no longer under threat you want that inflammation to disappear so that your body can get on with business and your immune system returns to normal. 

Tegan Taylor: What is it doing for you when it is spiking or flaring up? 

Norman Swan: It's alerting cells such as macrophages, the cells that chomp up invaders. It's also alerting hormones like interferons which act over short distances to stimulate the immune system and activity, and it's also activating cells, which get alerted to detect what might be coming in. So there's a variety of things that are going on. 

Now, what exercise appears to do is paradoxical. So when you exercise, these macrophages seem to come out a bit more than they otherwise would. So it looks, at a superficial level, that in fact what exercise does is activate inflammation. But in fact what's happening is, even though those cells might come out a little bit with exercise and it looks as though you're getting inflammatory responses, in fact what exercise does is teaches the immune system to regulate itself better. So the macrophages and the mitochondria, the energy producing factories inside cells, they all operate more efficiently and also operate with less oxidation, in other words biological rust, so there's less oxidative stress.

Tegan Taylor: So it feels like in a similar way to the way exercise stresses your body to get your body to be more efficient with using oxygen for aerobic exercise or getting your muscles to be stronger for strength-based exercise, it's also having a similar effect on our immune system. 

Norman Swan: Yeah, that's the simplest way of looking at it, and that's obviously more complicated than that, but that's right, and the result is that you don't get an overreaction from this innate immune system. It comes up, it goes down, and goes back to bed quite quickly, and producing less damage along the way. So overall what exercise does, particularly if you're doing it on a regular basis, is that this training of the immune system, if you like, this first part of the immune system, accumulates. So it's a cumulative benefit. So somebody who is exercising a lot, such as Margaret, is accumulating good regulation of this first part of the immune system, not suppressing it, it just works better. 

And then there's the adaptive immune system, and there's a fair bit of evidence that the adaptive system also works better, identifies pathogens coming in faster, and mobilises itself in a more effective way to particularly infections. It may well also be one way that exercise has an effect on cancer, more effective treatment or even cancer prevention. In other words, if you've got a more effective immune system, it may be better at mopping up cancer cells or helping cancer treatment to mop up cancer cells.

Tegan Taylor: That's a pretty big jump from a respiratory infection, something pretty mild that we know is going to go in a couple of days, to having such a big effect on something that's like the big scary thing that we fear often, which is cancer.

Norman Swan: And heart disease. So exercise, this modulation of inflammation, making it more efficient and effective, also has an effect on coronary heart disease, because atherosclerosis, the process of blocking your arteries, relies on an inflammatory response, in other words this innate immune system coming in, responding to the saturated fat cholesterol in your blood vessels and creating an inflammatory reaction which swells it up, scars the tissue and makes it more fragile as well and more likely to clot and cause a heart attack or stroke. So the same sort of mechanism not only has an effect on your resistance to infection, but your resistance to other diseases as well. So all that is good news in terms of the sort of exercise the average person would do if they're committed to physical activity.

Tegan Taylor: Okay, so my question; if a little bit of something is good, then is a lot of it even better? Or is there an inflection point here?

Norman Swan: Well, this is where you get a mixed picture in the literature. The literature suggests that elite athletes are more liable to develop infections, particularly viral infections, and the assumption is that this efficiency that you get with moderate exercise becomes a bit immunosuppressive when the exercise is extreme, and it also affects, by the way, how they approach athletes who do get sick. 

Now, there is controversy here. In animal experiments, laboratory experiments, there is a sense that you might get a bit of immune suppression with athletes, but there's also a more pragmatic answer. For example, marathon runners have been shown in a few days after a marathon to be much more liable to catch a viral infection, to have a viral upper respiratory tract infection, people involved in team sports. Now, some people say, well, that's nothing actually to do with immune suppression, it's actually got to do with the fact that if you're in a marathon or you're in a fun run, you're coming into contact with thousands of people…

Tegan Taylor: Who are breathing heavily.

Norman Swan: Exactly, so you're more likely to catch an infection. If you're playing a team sport and you're coming back and you're breathing heavily and you go into the changing rooms, there's more likelihood of an exchange of viruses and upper respiratory tract infections. Or it may be a combination of them both. If there is a bad effect, an untoward effect on the immune system of elite exercise, of highly vigorous exercise, it looks as though it's transient and is not a permanent thing. So in other words, while you get accumulative effect of benefit from moderate exercise, that acute effect of really vigorous exercise, if it does cause immune suppression in a minor sense, it seems to disappear after a couple of days.

Tegan Taylor: Okay, so that is good news, that you can over-exercise absolutely, it can do you harm, but it's not doing you the same kind of harm as the level of benefit that you're getting from your baseline physical lifestyle. The question from Margaret though is whether you get any benefit from exercising while you're sick, which, in my current state, I just want to kind of be like; why? Why don't you just go to bed, Margaret, it's fine. It's fine to go to bed for a day or two, isn't it? 

Norman Swan: Well, again, there's almost no evidence that bed rest helps to speed up the healing from infection. There's a little bit…

Tegan Taylor: Counterpoint; what if you really, really want to be in bed? 

Norman Swan: Well, again, you've got to be pragmatic about this. So if you're feeling really tired and fatigued and unwell, then sleep is really important, and go to bed and have a sleep. That's a different story from the country GP arriving in the 19th century and making sure that you go to bed for three days and you're not allowed to get out of your bed. What you're doing is responding to your body, having a sleep, getting up, making a hot drink and having a cold drink, making sure you're hydrated, that's a different story.

So what Margaret wants to know is, well, could I speed up my recovery by going out and exercising? So let me just talk about the big caveat here. The big caveat is the worry that some people have with excessive exercise when you've got a fever and you're unwell with a virus, is that it could spread to the heart and cause a myocarditis. And people are particularly worried about that in elite athletes.

Tegan Taylor: Myocarditis, it's an inflammation of the heart muscle, and we've heard a lot about it in recent years, because it can be a rare side effect of COVID-19 vaccination.

Norman Swan: Yeah, and that's probably an immune phenomenon from the vaccine, and tends to affect young men, not children, but young men, sort of late adolescence, early young adulthood, as opposed to the myocarditis that you get with COVID-19 and other viruses as well, which is partly immune but also can be an actual infection of the heart itself and can be very serious.

Tegan Taylor: In an elite athlete whose job is performance, it could really set them back in their career.

Norman Swan: Now, let's come to Margaret's situation and the average person's situation, there is no evidence that we can find in the literature of any risk at all from moderate, sensible exercise when you've got a viral infection. In other words, if you want to go out for a walk, go out for a walk, but what you probably do not want to do is stress your body with a major jog. So, gentle, modest exercise is likely to stimulate the immune system. There is no proof that it speeds up recovery, but there's no proof that it does any harm either. And there is evidence that prolonged bed rest is damaging to the immune system. So we're talking about many days, and they've studied astronauts, for example, where in the old days they didn't get up and move around the capsule, they were just lying down for their total space experience, there was a detrimental effect on the immune system. So prolonged bed rest is not a good thing. But there does not seem to be any harm at all from just getting up and doing some gentle exercise and keeping yourself active. And the likelihood is that in fact it will stimulate the immune system to do its job a bit better. 

Tegan Taylor: So Margaret's got a cold, and if she feels like getting up and going for a walk, that's good. Let's talk about other mild, transient illnesses, but the sorts of things…like, tell me, Norman, if this is something that's true, I feel like I read in a men's health magazine one time, like 20 years ago, that if your symptoms are above the neck then you're good to exercise, but if they're below the neck (i.e. muscle aches, chills, diarrhoea) then don't exercise. 

Norman Swan: I don't think there's strong evidence on that one way or the other. I think what that's trying to say is if you've got a cold and all you've got is just a sore throat, a runny nose, a cough, but you're otherwise okay, then that's a sign of a mild infection. But if you've got a high fever, you've got rigors and you're shivering at night and you're just generally feeling rotten and you've got symptoms elsewhere in the body, that's a sign that the virus is affecting your body in a more profound way. I can't imagine that you'd want to do exercise in that situation, you'd want to go to your bed and have a couple of paracetamols and phone me in the morning sort of thing. So in other words, you follow the messages from your body. But in the literature we can't find any evidence that, you know, if you felt okay to do a little bit of exercise and go out for a walk, even if it was a virus that seems to be affecting other parts of your body and you're just feeling a bit rotten with muscle aches and so on, that that actually has any detrimental effect. We can't find any evidence that it has a beneficial effect either. But of course a lot of this is really difficult to study. 

Tegan Taylor: Well, one study that we looked at was trying to see basically what happened in humans, because a lot of these studies were in animals. This one (a step up from animals) they used uni students…

Norman Swan: Yeah, some researchers say that uni students are only a small step up from rodents, but anyway…

Tegan Taylor: A small step up from hamsters. They got them to save all of the tissues that they used during the course of their illness, and they weighed them to compute the weight of the nasal discharge.

Norman Swan: So what was the bottom line here in terms of the snot-weight and exercise?

Tegan Taylor: Snot-weight reveals basically what you already said before; it doesn't appear to affect illness, symptom severity or duration. 

Norman Swan: So keep your paper hankies handy when you're up for your walk, Margaret.

Tegan Taylor: But keep your germs to yourself, please, Margaret, no fun runs until you're clear, I think.

Norman Swan: Very sensible. 

Tegan Taylor: Well. Margaret, thank you so much for the question. We love having a go at the questions that you send us, and you can send them to us at thatrash@abc.net.au.

Norman Swan: So is this making you feel better, this sort of verbal exercise, Tegan?

Tegan Taylor: It's taken all of the strength of my body to sit up for this long and chat, Norman, but it has been very informative.

Norman Swan: You don't feel your macrophages being recruited by the effort?

Tegan Taylor: My macrophages are eager to chop up all of the viral particles that remain in my body.

Norman Swan: Unfortunately macrophages aren't the key cells, they're the other cells, the lymphocytes. But anyway, I'm just covering myself…

Tegan Taylor: I wasn't listening closely enough, obviously.

Norman Swan: …for all the immunologists that are listening to this, that we do have a passing knowledge of the immune system. So, two postage stamps rather than just one postage stamp. Let's get the feedback.

Tegan Taylor: Yes, yes. So we spoke a week or so ago about emu oil and the various health claims associated therewith. Richard said, 'When you read out the list of remedies that emu oil claims, including sore muscles and hair loss, I was reminded of a similarly exhaustive set of claims for a medicinal extract from one of Australia's other iconic animals, Goanna Salve.' And he says, 'It's now out of production. It had a lovely smell, redolent of liniment in the footy change rooms, as does Tiger Balm which is common in Singapore and Malaysia.' Richard says, 'It seems if you are an iconic animal, it's best to keep a low profile,' which did of course lead me to Google the phrase 'is Tiger Balm made with bits of real tiger', and I'm happy to report that it is not. 

Norman Swan: And these things don't have a lovely smell. I hate the smell.

Tegan Taylor: So the emu episode also prompted Raphael to email us, saying, 'Your episode on emu oil reminded me of a time I was driving to Melbourne from Adelaide. We stopped in Keith for a break and some coffee, and the coffee shop we chose also happened to sell various locally made emu oil products, but mostly things like moisturisers, liniments and sunscreens.' Raphael said, 'As a boy, I was intrigued by one which was labelled as a treatment for erectile dysfunction. Then I read the instructions, which simply said; apply liberally and rub in well.'

Norman Swan: Oh really? Do you think that would work? I'm not sure.

Tegan Taylor: There's no way for us to know for sure. Well, Raphael and Richard, thank you so much for your feedback. Feedback comes to the same email address as the questions, thatrash@abc.net.au.

Norman Swan: And all we'll say about What's That Rash? is that you should apply liberally. I'm not sure you should rub it in well though. 

Tegan Taylor: We'll see you next week. 

Norman Swan: See you then.