TERRY GROSS, HOST:
This is FRESH AIR. I'm Terry Gross.
A lot of what you know about exercising, running and stretching may be wrong. My guest Gretchen Reynolds writes about conventional wisdom about exercise and fitness that is being overturned by new scientific studies. Her new book is called "The First 20 Minutes: Surprising Science Reveals How We Can: Exercise Better, Train Smarter, Live, Longer." Reynolds writes the "Phys Ed" column for The New York Times Well blog.
Gretchen Reynolds, welcome to FRESH AIR. So...
GRETCHEN REYNOLDS: Oh, thank you very much for having me.
GROSS: My pleasure. Let me tell you my dilemma. I was reading your book, which was convincing me that I have to exercise more, but, of course, I couldn't exercise because I had to finish your book before I went to sleep.
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GROSS: Which is kind of what happens to me every night. Most people have their equivalent reason of why they can't exercise. So just to make us feel a little bit worse, and to scare us a little bit more about the consequences, what happens to your muscles or your tendons if you sit still for too long?
REYNOLDS: Well, sitting is, unfortunately, very unhealthy. And I do it constantly, so it worries me. What science is finding is that sitting for long periods of time - when you don't stand up, don't move at all - tends to cause changes physiologically within your muscles that cause a whole hosts of changes, the most dire being that you stop breaking up fat in your bloodstream. You start getting accumulations of fat. And what that causes is you get accumulations of fat, then, in your liver, your heart, your brain. And you just get sleepy. You gain weight. You basically are much less healthy than if you're moving.
GROSS: And what happens to your muscles and your spine?
REYNOLDS: Terrible things. Your muscles become much more slack. They're much less able, then, to respond when you do stand up. And your spine, you get back pain. You have all sorts of unhealthy changes that make it that much harder, then, to move later. So the big, big problem with sitting a lot is it makes it harder, then, to move later, which is what you need to be doing.
GROSS: Right. So you get into this vicious cycle. So give us some of your suggestions for people who, because of their, work are pretty chair-bound a good deal of the day and, you know, it's hard for them to get up and exercise. And maybe the workplace doesn't even have a good option for you to get up and move around.
REYNOLDS: Well, the very, very best thing is to simply stand up. And that sounds so simple, but it actually has profound consequences. If you can stand up every 20 minutes - even if you do nothing else, even if you don't move to the window - you change how your body responds physiologically. You start using the big muscles in your legs, because you have to to hold you upright. They start contracting. That actually releases enzymes that break up the fat in your bloodstream. It improves your blood flow. It lessens the amount of fat that you'll wind up having in your heart. It decreases your chances of getting diabetes. It decreases your chance of getting heart disease, and all it requires is standing up.
GROSS: For how long?
REYNOLDS: Two minutes. There actually was a very interesting study that came out that showed two minutes of standing up every 20 minutes reduced people's chances of getting diabetes by a pretty large amount. If you can also walk around your office, walk to the window, walk to the next cubicle, you get even more benefits. You'll lose weight. You will improve your heart, lessen your risk of heart disease. And you will improve your brain. But if you can do nothing else, stand up.
GROSS: So in your book, you describe yourself as, like, taking phone calls while standing up, conducting interviews while standing up.
REYNOLDS: I do all of that. I actually have started, because I - as I also say in the book, one of the very worst things for your fitness is to write about fitness. I sit all day long. So I started, in self-defense, standing up when I did phone calls, when I did interviews. I bought a music stand, which costs next to nothing. You can put papers on it and read standing up. I make notes to myself standing up. I try and walk down the hall at least once an hour. That's enough to break up the physiological changes that sitting otherwise causes.
GROSS: Well, it's reassuring to hear that you could just do, like, a couple of minutes of walking or standing, and it actually amounts to something if you do it every 20 minutes or so.
REYNOLDS: Well, the best part of all - at least for me, because I am, honestly, very shallow - is that standing up appears to increase the number of calories that you burn. So if you do nothing else during the day, if you stand up regularly, you will almost certainly burn more calories and be at least a little less likely to gain weight.
GROSS: So the science is really changing and contradicting a lot of previous wisdom about what we should do if we want to be physically fit. So let's start with how science is changing about stretching. A lot of people stretch, for instance, before they run or before they exercise, and some researchers are saying, maybe not such a good idea.
REYNOLDS: Almost all the research is, in fact, suggesting that that stretching before a workout - which all of us were taught to do in our own phys-ed classes - is probably counterproductive. It actually seems to cause the brain to think that you are about to tear those muscles. When you stretch and hold that pose, you lean over and touch your toes and hold that position for 30 seconds, the brain thinks you're about to damage yourself, and it sends out nerve impulses that actually tend to tighten the muscles, that the brain is trying to keep you from overstretching that muscle. But the result is you're less ready for activity, not more ready for activity. So it seems quite clear that stretching before you exercise is not actually a good idea.
GROSS: Is there a good time to stretch, or are scientists starting to think that stretching maybe isn't so healthy after all?
REYNOLDS: Well, stretching, unfortunately, doesn't really do what most of us think that it does. For most people, it won't really make you much more flexible. Most of us are born with most of the flexibility that we'll have. It's quite genetic. And so you can stretch for 15, 20 minutes a day, and unless you do that for months and months, the science suggests you will not increase your flexibility very much. If you like stretching, by all means, do it. It doesn't appear to hurt, although it's not wise beforehand. If you stretch afterwards and you enjoy it, that's great. It probably is not essential.
GROSS: So how have you changed your stretching regiment?
REYNOLDS: I never stretched.
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GROSS: You never, ever stretched?
REYNOLDS: It's actually very nice when science validates what you were doing, anyway. I never liked stretching, and I'm one of those people who was born quite flexible, which is interesting, because there are some studies that clearly indicate that being very flexible is not good for athletics, and that's especially true if you're a runner. If you have really flexible hamstring muscles, you tend to be less efficient as a runner. You actually use more oxygen. So when I became a little less flexible, as I grew older, I actually became a faster runner, which was interesting. And that's because a really tight muscle is like a very well-stretched piece of elastic, and it returns energy extremely efficiently. So if you have tight hamstring muscles, you can be a very fast runner. You're also somewhat prone to more injury.
GROSS: Do you warm up before you run, and if so, what do you do?
REYNOLDS: I jog for a short period of time before I start to run. And the science suggests that a very easy warm-up - maybe all that most of us need - what you want to do when you warm up is to literally warm up the tissues. You want to get the muscles, the tendons, all of the parts of your body warm, raise the internal temperature. And the best way to do that is to use those tissues. That means if you're going to go for a run, start out by jogging. If you're going to be playing tennis, start out with a little bit of jogging, and then make sure you do something that moves your shoulders.
There is a new theory about warming up that says people should do dynamic stretching, which is quite different than the old-fashioned stretching that most of us did.
GROSS: What is it?
REYNOLDS: Dynamic stretching is, essentially, movement. It's not even really stretching at all. It means if you are going to be using a joint, warm up by using it. If you're going to be playing golf, do some practice swings. Move the joint. Do not stretch it and hold it. If you're going to be hitting a tennis ball, do jumping jacks so that your arms are up over your head. Get the tissues warmed up and get them in motion. Then you'll be ready to safely do much harder actions, like actually hitting a tennis ball or hitting a golf ball or running.
GROSS: My guest is Gretchen Reynolds. Her new book about the latest scientific research into exercise and fitness is called "The First 20 Minutes." Before we continue the interview that I recorded yesterday, I should mention something that she told me. Even though new studies are disproving some conventional wisdom about static stretching before working out, she says certain stretches - like a calf stretch - are helpful in preventing plantar fasciitis, a painful inflammation of the plantar fascia, the connective tissue on the bottom of the foot. If you have heel or foot pain, she suggests you might want to see a physical therapist.
We'll hear more from her after a break. This is FRESH AIR.
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GROSS: If you're just joining us, my guest is Gretchen Reynolds and she writes the "Phys Ed" column for the Well blog on The New York Times online. She's the author of the new book "The First 20 Minutes." That's about the science of exercise.
So you're a runner, and you've been a runner for decades.
REYNOLDS: I am. Mm-hmm.
GROSS: What does science say now about the benefits and the risks of running?
REYNOLDS: Well, the benefits are unequivocal. Running is a wonderful way to reduce your risk of heart disease, reduce your risk of diabetes. If you run regularly, it does maintain your weight. It also has a very strong impact on the brain, which may be the single most important reason that I run. There's very good science that running for even half an hour or so doubles the number of brain cells in portions of your brain related to memory. Running is wonderful for the health of your body. It also leads almost inexorably to injury. The injury rate among runners is extremely high. By some estimates, it's 75 percent of runners will get injured almost every year. So running can be very hard on the body at the same time that it's very good for the body.
GROSS: What about walking? I mean, there doesn't seem to be much of a downside to walking. What are the benefits of it?
REYNOLDS: Oh, walking is, I would say, without a doubt, the single best exercise that exists. It is very low-impact. Certainly, you could hurt yourself if you want to. You can trip over something. You can overdo it.
GROSS: There's always something to trip on.
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REYNOLDS: You can run into things, which I've done before.
REYNOLDS: I actually used to read and walk. When I was in college, I would try and read my textbooks while walking, and I did, a few times, run into stop signs. So that's one way to injure yourself. Otherwise, walking appears to be what the human body is built for.
There have been some very good studies showing that the most efficient stride for the human body is a walk, not a run. That means we use less oxygen, we use less energy when we walk than when we run. We are built for that movement. It does definitely stimulate all of the health benefits that you want from exercise. Walking for 30 minutes or even 20 minutes, even 15 minutes will reduce your risk for heart disease and for diabetes. It will change your brain, and it will prolong your life.
There was a really interesting study out of England showing that walking for 30 minutes at least four or five times a week increased people's life spans by 20 percent. If you tripled that amount of exercise, if you ran for 90 minutes four or five times a week, you prolonged your life span little bit more, but only by four percent. So you get most of the benefits from just going for a walk.
GROSS: So you know the kind of power walker who has, like, a weight in each arm and they're moving their arms back and forth and, like, their jaw is kind of clenched and like...
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GROSS: ...and they're, like, striding through the street, and it's like looks like they're really exerting themselves a whole lot more than I certainly do when I walk. Is that helpful?
REYNOLDS: It depends completely on what you're trying to get from your exercise. If you're trying to get enjoyment, I would say no. If you are trying to become more fit, which is a different thing than trying to become healthier, then yes, you have to go at a higher intensity. You do have to raise your heart rate more. You do have to get more tired.
It does have to feel uncomfortable. That will increase your aerobic endurance. It will not necessarily make you a whole lot healthier. You can become healthy with a much lower amount and much lower intensity of exercise.
GROSS: Let's talk about hydrating in general. You know, a lot of people think, and we've been told, I mean, we should drink like eight glasses of liquids a day. You know, water's fine. The impression I get from your book is that that's being disproven.
REYNOLDS: Yes. Yet again. When you actually put it to the test, that very entrenched myth turns out to not be true. We don't need eight glasses of water a day. Thirst mechanism is extremely, exquisitely attuned to telling us how much fluid we need. Most of us have been taught - and I've run several marathons now. The last time I ran a marathon, which was 15 years ago now, I was told drink as much as you possibly can before the race, during the race, after the race, constantly. Stop at every water stop. Do not let yourself get thirsty. Well, the result of that is that some runners developed what is called water intoxication. They actually had so much water in their bodies that it became an unhealthy and even critically dangerous condition.
What we now know, and what seems clear from the science, is that if you drink to thirst, if you listen to the little voice in your head that says you need water, you will drink as much as you need. You don't need to stay ahead of your thirst. Drink what you want and you will almost certainly be fine.
GROSS: So you said if you're exercising for more than an hour you do need to replenish on the sugars and the good news is that chocolate milk is apparently a nice balanced drink for that - assuming you're not lactose intolerant.
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REYNOLDS: Oh, chocolate milk. The science of chocolate milk is one of my favorite discoveries. Chocolate milk is actually an almost ideal recovery beverage and that means for in the period after you exercise, not during exercise. That much protein and milk would probably cause gastrointestinal distress during exercise but if you've worked out, again, for at least an hour, so you have burned a certain number of calories, then you do need to replenish the fuel that you've lost.
You also need to give your body some protein to help to rebuild the muscles. Chocolate milk seems to have an ideal ratio of carbohydrates, the sugar, to protein. And it tastes wonderful. So in the hour after you exercise, have some chocolate milk. You will probably recover better. If you've gone for a 30 minute walk, I'm sorry, chocolate milk is probably not your exercise drink of choice.
If you want to lose weight, just remember calories in, calories out. Whether you've worked out or not you have to be realistic about how many calories you just burned. If you walked for 30 minutes you didn't burn enough calories to have chocolate milk.
GROSS: My guest is Gretchen Reynolds. Her new book about the latest science of exercise and fitness is called "The First 20 Minutes." We'll talk more after a break. This is FRESH AIR.
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GROSS: If you're just joining us, my guess is Gretchen Reynolds. She writes the phys ed column for the Well Blog on The New York Times website and now she's the author of the new book "The First 20 Minutes" which is about the new science of exercise. Are there any exercises that you've stopped doing because you've learned through your research that they're more harmful than helpful?
REYNOLDS: Well, I actually don't run fast anymore, which is partially the result of the fact that I'm older, but there also is some science showing that faster and harder you run, the more likely you are to get injured. If you want to compete you're going to have to run hard, you're going to have to run fast.
If you want to be healthy and fit - which is really my goal now; I want to be around for another 40 years. I want to be able to exercise for another 40 years. So I have reduced the speed at which I run. I've also actually reduced the amount that I run because I can get a lot of benefits with less exercise. And anyone can do the same. If you want to be healthy, you can become healthy by doing anything.
Getting up from your chair, gardening, anything at all where you do where you move your body will definitely make you healthier.
GROSS: But are there actual exercises besides running that you've stopped doing because of the research that you've read?
REYNOLDS: Not really. What I have started doing are exercises that I actually thought were unhealthy and turned out not to be. I do squats, which look very ungainly but I've had several scientists tell me that if they can only do one exercise on any given day, they will do squats because squats, they burn calories, they build the muscles in your legs and your bottom.
They make you stronger. It's also the squat is essentially an exercise that can guarantee that you will be independent all through your lifespan, because one of the things that happens as people get older is you lose muscle mass, you lose strength, and you become unable to get up out of your chair. If you're doing squats, you will always be able to stand up.
So I now do 20 squats at least a few times a week. I don't use weights. You don't have to hold a dumbbell. Just squat down, stand up, and do it again. I also do...
GROSS: So when you say squats you mean like deep knee bends? Same?
REYNOLDS: Yes, exactly.
GROSS: Yeah. Mm-hmm.
REYNOLDS: And if that's hard...
GROSS: I had heard those are really bad for your knees, right? Didn't they say that?
REYNOLDS: And they're not.
GROSS: They're not. OK.
REYNOLDS: In fact, it appears pretty clearly that if you do it correctly it's good for your knees because it builds the muscles and the tendons all around your knee. It makes it more stable. So in fact, doing squats appears to be a very good thing for your knees. Do it carefully. If it hurts, don't go all the way down until your thighs are parallel to the ground.
Maybe keep your thighs at a 60 degree angle to the ground, but it should, for someone who has healthy knees, it should make your knees stronger. You can also, if you find a regular squat really difficult, do what are called wall squats, meaning you lean against the wall and go up and down. Then when that's easy, move away from the wall, do 20. It really has made a big difference, I think, in my leg strength.
GROSS: So how did you end up writing about exercise and having a kind of sedentary life as a result of it instead of your running?
REYNOLDS: Well, I have always been interested in exercise. I actually have been writing about health and fitness in various forms for, oh, more than 20 years and became especially interested as, frankly, I started aging. And I began to find it harder to exercise. I found that I was slower. And I did become really interested in what was happening inside my body now.
And then coincidentally, I was given the opportunity to write about physiology and many of my columns and certainly some of the most popular, as well as some of the information in the book, is about what happens to our body as we age and how much of that is inevitable, how much of it is a consequence of inactivity.
And the good news is, a lot of it is inactivity and not biological aging and that we can change. And that's the best news I think that I've gotten from researching physical activity is we can control a lot of what happens to our body.
GROSS: So what's the most popular column you've written?
REYNOLDS: I would say it's between stretching - I wrote one about that we don't need to stretch before exercise - and then secondly the most popular topic by far is exercise and the brain. Because none of us want to lose our memories, none of us want to develop dementia, and the evidence is very strong that exercise improves your ability to think at whatever age you are.
GROSS: OK. Another reason to exercise.
REYNOLDS: Well, the really great thing is that exercise actually changes the structure of your brain. It increases your ability to make new brain cells and it increases the volume in the brain where you process memories. So there's really strong evidence that if you exercise, and again, it doesn't have to be a lot - walking for 30 minutes improves your ability to think well into your 80s.
GROSS: Well, Gretchen Reynolds, I'm going to end this interview so I can take a walk.
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REYNOLDS: Please do.
GROSS: OK. Thank you so much for talking with us.
REYNOLDS: It was my pleasure. Thank you.
GROSS: Gretchen Reynolds' new book about the new science of fitness and exercise is called "The First 20 Minutes." You can read a chapter on our website freshair.npr.org, where you can also download podcasts of our show. And you can follow us on Twitter @nprfreshair and on Tumblr at nprfreshair.tumblr.com.
I'm Terry Gross.
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