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The 'Strange Science' Behind The Big Business Of Exercise Recovery

From sports drinks to cold and heat therapy, journalist Christie Aschwanden looks at the science of exercise recovery.




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Other segments from the episode on February 11, 2019

Fresh Air with Terry Gross, February 11, 2019: Interview with Christie Aschwanden; Interview with Adam Savage.



This is FRESH AIR. I'm Terry Gross. So many people are going to gyms, working out, running marathons, climbing mountains, playing basketball, tennis, football and other sports that a new set of recovery products and services has grown up around them, a recovery industry, recovery as in what to do to avoid dehydration, the loss of important nutrients and minimize muscle aches and cramps. The recovery industry includes products like sports drinks with electrolytes, protein bars and powders, various products for icing, as well as new and old therapies including massage therapies, cryotherapies, compression therapy, laser therapy and cupping. Let's not forget over-the-counter non-steroidal anti-inflammatories is like ibuprofen, which many marathon runners refer to as vitamin I.

My guest, Christie Aschwanden, has written a new book called "Good To Go" examining the physiology that helps us adapt to and recover from exercise and what the new science of recovery has to say about which approaches are effective. Aschwanden is the lead science writer for Nate Silver's site FiveThirtyEight and is a former health columnist for The Washington Post. She's also an athlete who was a high school state champion in the 1600-meter run and a national collegiate cycling champion.

Christie Aschwanden, welcome to FRESH AIR. So I want to start with something really basic, and it's not like - you don't need technology for it or anything. I want to start out with, like, sports drinks because they're so popular now. They're just sold like all over in your convenience store, your supermarket. A lot of them are even in like, you know, health food stores. So the big thing about them is that they have a lot of electrolytes. So what's the sales pitch for electrolytes after running a marathon or working out?

CHRISTIE ASCHWANDEN: Yeah. It's actually really clever. So electrolytes is just a fancy - or I should say scientific name for salts. So these are things that we get in all of the food that we eat. And in fact, you know, some doctors may be telling you you need to cut down on your salt. But these sports drinks are coming with these salts in the fluid. And so the idea is that when you're exercising, you're sort of creating these extraordinary needs. And it's this, you know, really intense physiological state that you're in, and so you need to replace these salts that you're sweating out. And so when you sweat, you do lose some salts. You lose fluids. And so the idea behind sports drinks is that they're replacing those.

GROSS: I'm not a sweater, so, like, even if I'm doing like, you know, exercise or something, I'm unlikely to be sweating. And that might be true of a lot of other people, too. So how much do you need to sweat before you really need to replenish with a sports drink? And by sports drinks, we mean, like, the biggest brand name here is Gatorade. And it was also like the first in the market there. So that's what we're talking about.

ASCHWANDEN: Yeah. And I think Gatorade has really become synonymous for a lot of people with sports drinks. So the answer to that is really, you know, there are all sorts of formulas you could find online. There are products now that will promise to find your individual sweat rate and individual salt loss rate. But it turns out we really don't need - you don't need a scientist looking over your shoulder to figure out how much you need to drink or how much salt you need after exercise. Our bodies have this really sophisticated mechanism for helping us determine this, and it's called thirst.

GROSS: (Laughter).

ASCHWANDEN: You've probably experienced this before if you've been exercising in the heat, at some point, you get thirsty. And another really interesting fact that I learned while researching the book is that, you know, I've always noticed that in the heat and when I'm really feeling dehydrated that a glass of water just tastes so good, so good. And I always just thought that's, you know, because I'm really thirsty, which it is. But it turns out that we have these receptors in the back of our throats that actually do like - there's something physiological going on there where water really does taste better when you're thirsty. And if you don't need it, if your body isn't, you know, really craving that water, it won't taste as good.

GROSS: So a lot of people are always walking around with water nowadays because there's a sense that you have to constantly be hydrated, and you have to drink a lot of water all the time. And we've really become obsessed with hydration, but there is the problem of over-hydrating. So what's that problem?

ASCHWANDEN: Yeah, it's fascinating. And I was really surprised to learn this. So basically, we've been given this message for so long and so much of it is marketing, this idea that, you know, by the time you're thirsty, it's too late. You have to always be drinking and hydrate, hydrate, hydrate. But it turns out that this just isn't true. And this idea and this concept that we have to be drinking even when you're not thirsty has led to this problem that can actually be deadly. It's called hyponatremia. It's also called water intoxication. But this is something where people drink too much water and they end up diluting their blood to the point where they have all sorts of issues, including - your brain can swell, and it can actually be fatal.

GROSS: You describe some marathons because of this fear of dehydrating had, like, sports drinks or water at the finish line and along places, you know, in places along the way, and people were actually over-hydrating.

ASCHWANDEN: Yeah. Oh, it's quite tragic. In fact, there have been multiple people now who have died in marathons from drinking too much. And one of the things that makes this really scary is that some of the symptoms of over-hydration look very similar to the things that we think of as being symptoms of dehydration. So for instance, dizziness, confusion, fatigue, things like this. And so in some cases what's happened is you have someone who collapses at a race and they're given an IV and given more fluids, which is exactly the wrong thing at that point for them.

GROSS: So one of things a lot of people do after workouts or whatever it is that is stressing your muscles is icing. Even in physical therapy, you're often given heat before the therapy and ice after. But according to your book, the thinking about icing is starting to change. So what's the premise behind icing, and how is the thinking about icing starting to change?

ASCHWANDEN: Yeah. So the idea behind icing is that it's a way to address inflammation, and it's a way to reduce inflammation. So when you ice something, you are reducing the blood flow to that area. So basically, if your extremity gets cold, your body sort of shunts the blood into the core to try and keep you warm. And so during this time, the blood flow is less to that area, you're getting less circulation of these inflammatory things that are part of the inflammatory process. And so the idea here is that you're going to reduce inflammation. And that was for a long time really considered a good thing.

GROSS: And now?

ASCHWANDEN: And now - so now the thinking is really changing. And it's interesting because, again, this is one of those things where we used to think one thing, and now as we're learning more and science is uncovering some of the mysteries of our bodies, we've learned that inflammation is actually a really important part of the training response. And so if you are doing an exercise in hopes of getting fitter, faster, stronger, you really need inflammation. You need that inflammatory process. You need your immune system bringing in these inflammatory things that are coming in to make those repairs. So the inflammation process is actually the repair process, and so without it, you're not going to get the same adaptations to exercise that you would otherwise.

GROSS: So what you're saying is applying to vigorous workouts or events. You're not talking about injuries. Like, you haven't really studied what the science is about icing injuries. I just don't want to confuse the two for people.

ASCHWANDEN: Correct. Some of these ideas apply to injuries as well, but it's a little bit different scenario. So the advice that I'm giving here is really about icing that's done and cooling that's done in hopes of reducing soreness and in hopes of helping athletes recover better. And in this scenario, it turns out that it doesn't seem to be helpful, and, in fact, it may actually be hurtful.

There is one interesting study that I looked at where they had people do an exercise program either with their legs or their arms and then they iced just one limb. And this was over the course of like a four or six-week training program. And they actually found that the limb that was iced had more fatigue, it recovered less fast, but also they had fewer gains and muscle strength and reduced activation of some of the key proteins and muscles in that limb that had been iced. So that seems like some pretty good evidence that icing may actually, you know, reduce your training effect and may prevent you from making the gains you'd otherwise make when you're doing these exercises.

GROSS: And what about heat as a therapy for muscles? If the purpose of cold therapy is to prevent the blood from surrounding the muscle with inflammatory agents, then you'd think that heat therapy after a workout would be bad because it would increase the blood flow and therefore potentially increase the flow of inflammatory agents to the soon-to-be-sore muscles. So what's the latest thinking about heat in addition to the fact, like, it feels good?

ASCHWANDEN: Yeah. Well, it feels good. It definitely feels good. And I want to come back to the feel-good part because that's a really important point. But basically, increasing the blood flow is probably a good thing because you get these inflammatory agents into these sites, so that's a good thing. I mean, if you think of them as sort of repair crews, you want them to get to the site of the injury as soon as possible and to do their work. So in that sense, I think it does seem like a good thing.

GROSS: Yeah. The thing with inflammation, though, is that sometimes the inflammation seems to last a whole lot longer than it needs to. And, you know, you're healing, you don't really need all that swelling, but it's going to take forever for the swelling to go down. And the swelling itself can cause pain because that can start pressing on nerves.

ASCHWANDEN: Right. Right. That's right. And, you know, there are still legitimate and probably good reasons to ice, one of them being it does help a lot with pain. You know, I've rolled my ankle many times, and putting ice on it can feel good. It tamps the pain for a little while. And so that's not necessarily a horrible thing. And, you know, you don't want to go around walking around with a football-sized ankle. So reducing swelling could be a good thing under some scenarios. And I think an injury scenario like that is a little bit different than most of the recovery scenarios that we're talking about. But ice can feel good, and so I think that is one reason you might still want to do it even if you know you may be reducing, you know, the benefits that you'll get just a little bit.

GROSS: You've tried several different kinds of massages as an athlete and then as the author of this book when you were trying out a lot of different recovery therapies. So what are some of the massages that you've tested?

ASCHWANDEN: Yeah. So one kind that's really popular these days - there are various brands that make these sort of pneumatic compression boots. They also make these things that you can put your arms and shoulders in, but they're basically, like, little sleeping bags that you put your limb in. And then you turn on the button, and the sleeping bag part blows up sort of like a balloon and pushes against the muscle. And they can do it in a way where it's almost sort of kneading your muscle. And it feels really good (laughter). I can tell you that I really enjoyed the feeling of it. And this was probably one of the newfangled recovery toys that is most popular among athletes and something that people really want to have. It just feels really nice. It's like a mechanized massage. So that's one type of massage. And then there's just sort of, like, the regular massage that, you know, people traditionally get from a massage therapist. And oftentimes, you know, that might be a specialized sport massage with the idea here being that you're flushing things out of your muscle and increasing blood flow and things like that.

GROSS: So what have you learned about the effectiveness of massage in limiting or preventing muscle soreness?

ASCHWANDEN: Yeah, there's not much good evidence that it works for that. Yeah, there are a few small studies that maybe are slightly suggestive. But if it has an effect, it's not a powerful one in terms of flushing things. And there really isn't any evidence that it's like, say, flushing lactic acid or flushing things out of your muscles. But what it does do is make you feel really good. And I think one of the takeaways in the book is that recovery is really about rest and relaxation. And anything that makes you feel relaxed, that's working (laughter). And so that's a legitimate tool. That means that it's working, and I think one thing that makes massage so good is it's just making you take an hour out of your day to relax, to sort of unwind, to let everything else go. You're not looking at all of those distractions. You're relaxing your body, maybe closing your eyes. And that's something, I think, we just don't do enough these days.

GROSS: Let me reintroduce you. If you're just joining us, my guest is Christie Aschwanden. Her new book is called "Good To Go: What The Athlete In All Of Us Can Learn From The Strange Science Of Recovery." We'll be right back after we take a short break. This is FRESH AIR.


GROSS: This is FRESH AIR. Let's get back to my interview with Christie Aschwanden. She's the lead science writer for Nate Silver's site FiveThirtyEight and a former health columnist for The Washington Post. Her new book is about the science of recovery - that is, recovery from exercise or sports. It's called "Good To Go."

Let's talk about ibuprofen, the nonsteroidal, anti-inflammatory - Advil is maybe the best known version of ibuprofen. A lot of people take it before or after or before and after a big athletic event or a marathon in the hopes of staving off inflammation and, therefore, pain. So what have you learned about ibuprofen and when to take it and how effective it is in - you know, for athletes or people working out?

ASCHWANDEN: Yeah, it's really common that athletes will take it prophylactically. So they'll take it before a workout or before a race even. One scenario where it's really popular is among ultramarathoners. So these are people that are running, say, 50 or a hundred or even more miles. And they will take these drugs during the event or before. But even - I remember back in my high school track days, one of my teammates was popping two ibuprofen before practice every day. And I know now after researching this book that that's a pretty bad idea. And there's a couple of reasons for that. The first is that, again, inflammation is your friend if you're working out. That is how your body repairs itself. And so there's actually some pretty intriguing evidence that taking ibuprofen can impair the repair process from an injury. And that refers both to the type of micro injury that you get from a hard workout - you know, the little damage to your muscle that your body comes in and repairs, and that's what makes you stronger - but also to injuries like, say, a sprained ankle and things like this. So taking a nonsteroidal, anti-inflammatory drug or taking ibuprofen can actually impede the healing process. And I don't think anyone wants to do that. At the same time, I will say, though, if you're in a lot of pain, these are really good painkillers. And that's probably a good reason to take it, but you want to limit it. And so you only want to take it when you really, really need that pain relief and not sort of in expectation that you're going to feel pain.

GROSS: Well, let's talk a little bit about the healing process. As you've said, you know, in your book, recovery used to just mean rest.


GROSS: And now it's, like, an activity. It's, like, things you're supposed to get done to you, like massage...


GROSS: ...Or compression therapy or, you know, things that you, you know, drink or eat. What about rest? How long are you supposed to rest after a vigorous workout or running a race?

ASCHWANDEN: That's a really good question, and there isn't a hard and fast answer. And I think that's part of the reason these devices and techniques and everything have sprung up because we don't know for sure. And everyone wants to sort of recover faster and be ready for that next workout right away. But lots of times, it is just a matter of waiting and really paying attention to how you're feeling. And so one of the things that I learned while writing this book is the most important skill that any athlete can develop is a sense of how their body is responding to exercise, how they're responding to their workouts, how they're feeling, what it feels like for them to be recovered or under-recovered. I know for me - if I wake up in the morning with even the slightest hint of a sore throat, that's my body telling me that it's tired. And it needs more rest, but those signs are very individual. And so it's really sort of a process of learning and listening to your body and, you know, trial and error a little bit. There aren't any hard and fast rules or any formulas that can tell you exactly, for you, how much recovery or how much time or how much rest you need in between workouts. And, in fact, this was something I observed when I was a collegiate track runner. The team could go and do a workout. And one person group would recover right away and the next day be fine. And another person might be really, really tired. And it wasn't that one person was better or worse than the other. It's just that our bodies respond differently to training. And I think all of us have had an experience where you go and you do some workout and one person gets a lot better right away, and the other person takes longer. And that's - I think it's related to that.

GROSS: Is pain a good indicator of how to proceed? If you're still in pain - if your muscle still feel sore from an event or a workout, does that mean you're not ready yet to start it up again?

ASCHWANDEN: Yeah, I think that's a good rule of thumb is to go by feel. And you know, just because you're sore doesn't mean you can't do anything. I mean, it depends on what level that you're doing things. But it certainly means that if you're experiencing a lot of muscle fatigue or a lot of overall fatigue, that it's probably not a good idea to do another hard work out again. Maybe it's better to go for an easy walk, spin on the exercise bike. But do something that is not too taxing.

GROSS: So what's something else that you've tried that's relatively new on the market that you were intrigued about?

ASCHWANDEN: So one thing that's become really popular - and I think it's become more popular than it was back when I was a serious athlete - are our foam rollers. And these are sort of hard - there's many different iterations of these. But you're basically sort of using a cylinder to mash your muscles. And the idea here is that you're getting at this tissue called fascia, which is almost like - I had it described to me as sort of like saran wrap that wraps around your muscles in the body. And so the idea is that you might have adhesions here or that this might be a source of soreness in some cases. And so the idea is that you're sort of mashing it and smoothing it out and unwrinkling, you know, any kinks that you would get in this fascia.

It's a really interesting hypothesis. It's also really early days in the study of this. And so when I looked into the science, I found that there are some really intriguing ideas. But we don't really have hard and fast answers yet on how this works.

So one thing that's really interesting about the foam rollers, though, is that - so people love them. And I found out while researching this book, this was one of the things people probably asked me about the most was foam rollers. And I'll just say here, too, that they tend to be really painful. You know, doing this is not something that's pleasant in the way that the pneumatic compression boots are. This is something that's like, yeah, you're really getting into it in the sense that it's really hurting, so it must work.

But one really interesting thing the science has showed is that there've been some studies where they did things like they would do the foam roller on one leg but not the other. And what they found is that they were able to reduce soreness and find benefits in both legs. So there seems to be some sort of neurological component in it. And this must be working somehow on the brain as well as, you know, the fascia right there. So it's a really interesting line of research that people are looking into, and it's still early. So I don't think that we have absolute answers yet. But it's some intriguing stuff.

GROSS: Christie Aschwanden, thank you so much for talking with us.

ASCHWANDEN: You're very welcome, Terry. It's my pleasure.

GROSS: Christie Aschwanden is the author of "Good To Go" and is the lead science writer on Nate Silver's site FiveThirtyEight. After we take a short break, we'll hear from Adam Savage, the former co-host of "Mythbusters" and now the host of the Science Channel's "Mythbusters Jr." in which he and some super smart teenagers use science and engineering to test out the validity of myths, urban legends and movie scenes. I'm Terry Gross, and this is FRESH AIR.


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