Exercise Actually Remodels Your Heart

17:38 minutes

a colombian woman holds flyweights over her head at a competition
Colombian weightlifter Lina Marcela Rivas Ordoñez competes at the 2016 Olympic Games in Rio de Janeiro. Credit: Shutterstock

You’ve heard the news that smoking is bad for your health. But it turns out not exercising could be even worse for your chances of survival, according to a recent study in the journal JAMA Network Open. But is it possible to overdo it? While you’re trying to boost your overall health, could you instead be doing damage to your heart? In this segment, Wael Jaber of the Cleveland Clinic and Maia P. Smith of St. George’s University talk about how sports like weightlifting stack up to running and cycling in terms of health effects, and how the sport you choose could actually reshape your heart.

Further Reading

  • Check out the October 19, 2018 study in JAMA Network Open on the longterm health on patients undergoing exercise treadmill testing.
  • Learn more about the effects of weightlifting on cardiovascular disease in a study published in Medicine & Science in Sports & Exercise.
  • Read about various viewpoints and studies on running and its changes on the heart.

Segment Guests

Wael Jaber

Wael Jaber is a professor of medicine at the Cleveland Clinic in Cleveland, Ohio.

Maia P. Smith

Maia P. Smith is a sports medicine epidemiologist and assistant professor at St. George’s University School of Medicine in Grenada. 

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. We all know that smoking is bad for your health. But you know what could be even worse for your chance of survival? Not exercising. That’s one of the findings of a recent study in the Journal of the American Medical Association Network Open. And we get it, we’ve heard this before– exercise is good for you. Right. But the thing we’ve got to be wondering was, what exactly does this miracle drug, exercise, do for your health? And is it possible to overdo it, maybe doing damage to your heart while you think you were doing the right thing? 

If you’re a runner or a weightlifter or a cyclist or a roller derby skater, we want to hear your questions about exercise, your heart, and your health, so give us a call. 844-724-8255. You can also tweet us at @scifri. My next guest is an author on that JAMA study and a professor of medicine at the Cleveland Clinic in Ohio. Wael Jaber, welcome to Science Friday. 

WAEL JABER: Thank you so much. This is a great pleasure to be on the show. It’s one of my favorite public radio shows. Thank you so much, it’s been my companion on many of my runs and cycling expeditions. 

IRA FLATOW: Well, thank you very much. That’s very kind of you. Let’s talk about your runs and cycling expeditions because I know that your study found that neglecting exercise is actually right on par with, or maybe even worse than, smoking and diabetes in terms of your health. 

WAEL JABER: So what we did– it actually was out of personal interest. We looked at about 122,000 individuals who showed up at the Cleveland Clinic for various reasons to have a stress test, which is a routine stress test that many individuals are familiar with. You get on a treadmill, they hook you up to an EKG machine, and they assess how far you can go on the treadmill. And we were fortunate that we have that database to follow up or the tools to follow up these individuals over the past 25 years almost. Mean follow-up for these patients was about eight years. 

And we looked at one important outcome– I think the most important outcome– which is death. And we found out– after we sorted out these individuals into their age groups, their gender or sex differences, and their level of exercise– that the lowest quintile group, which is the bottom 20% or so of the individuals, had the highest mortality in each age group and in both males and females. And the benefit from getting fit actually does not plateau out. So if you’re fitter, you improve your chances of not dying, and the next level gets better, the next level gets better. 

And then we focused on an elite group of athletes. Those are individuals who are in the top 2% or so of the group. And we found that these individuals benefited the most, in both males and females, as well as in all age groups all the way up to individuals in their 80s. 

IRA FLATOW: But the bottom percentage– how much exercise is minimum to get benefit from it? 

WAEL JABER: In our study, this wasn’t an objective observation of what people can do. So most of the prior studies looked at self-reported level of exercise, so they show up to the office, we tell them, how much do you do? And there is a lot of bias in that and optimism, I would say, about how people how much they think they exercise. 

At the bottom part, if you compare the lowest fifth group, let’s put it, the people who are least fit, and compare them to individuals who are the most fit– you almost have a hazard a ratio of 5, which is almost about 500% difference in mortality. This is huge. So if you take smoking, for example, it gives you about 40% or so, in our study at least, higher risk of mortality. 

If you take things that people are very familiar with, including, diabetes, high blood pressure, all these other things– so usually, they give you a risk about 20% to 40% risk of higher mortality. Whereas in the lowest to the highest fit individuals, the risk difference is about 500%. 

IRA FLATOW: That’s amazing. Let’s talk about the heart because part of this study says that the type of exercise you do actually shapes your heart. It can actually shape it? 

WAEL JABER: So this is derived not from our study, but from other parts of the literature. So exercise, as far as its impact on muscles and heart, is not the same. So this is not my area of expertise, but let’s say if you’re a swimmer, your heart remodels in a different way than if you’re a runner than if you’re a cyclist than if you’re a weightlifter or a rower. 

So each type of exercise exerts a different type of demand on the heart, as well as different type of pressure loading, and requires different conditioning for the heart. So the shape of the heart would look much different in a swimmer than, let’s say, a biker. 

IRA FLATOW: Right, that’s interesting. And I think what’s also interesting from your study is what you said before, that you can keep improving your heart doing more and more exercise. 

WAEL JABER: So you can keep improving your risk or your odds for dying by being more fit, so that’s probably the most important message. 

IRA FLATOW: All right, I want to bring on another guest now who has compared the health effects of strength training to aerobics activities, like walking and biking. Maya P Smith is a sports medicine epidemiologist, assistant professor at St. George’s University School of Medicine in Grenada. Welcome to Science Friday. 

MAYA SMITH: I’m glad to be here. Thank you. 

IRA FLATOW: You looked at the effects of weight training versus walking and biking on heart health, and you found that weight training is more important than we think it is in maintaining heart health. 

MAYA SMITH: Yes. I looked, again, at the self-reported data that you were talking about a minute ago. Number of people reported, do you do weight training and/or do you walk or bicycle? And then we look to see how many and how badly did they have these four major markers of heart problems, namely hypertension, overweight, diabetes, and cholesterol problems. 

And for everything that both weight training and walking and cycling were associated with, weight training was better. And for many things, weight training was the only thing that mattered, and walking and bicycling didn’t seem to be associated at all. 

IRA FLATOW: Now, what level of weight training were you talking about– me going to the gym and lifting a few weights or working out on the machines? Or are we talking about Olympic-level deadlifts and squats and stuff like that? 

MAYA SMITH: I may have misspoken when I said weight training. This was only resistance training. This could be like doing a couple of push-ups a couple of times a week. This is push-ups, chin-ups, free weights, anything at all designed to strengthen your muscles. And this is what I was actually interested in looking at. Are the levels of activity that the average American is willing to do on their own without a major sustained intervention– are those enough to have a significant effect? And the answer is yes. 

IRA FLATOW: Wow, that’s terrific. Let me go to the phones. Jerome, from Grand Torrance, California. Hi, Jerome. 

JEROME: Hey there. 

IRA FLATOW: Go ahead. 

JEROME: My question is almost specific to that, with regard to Olympic weightlifting, because I used to do only muscle-specific lifting, like a bodybuilding style, and I switched to Olympic lifting. And I feel like I’ve seen more results as far as having more strenuous workouts. So I was curious if that’s better or has anything been proven that is better? 

IRA FLATOW: Dr. Smith? 

MAYA SMITH: My study was a population-based study. I really wouldn’t be able to inform on that. And I know, as a matter of fact, that there’s a great deal of individual variation in how quickly strength develops, how easy it is to injure yourself, what kind of workout is best. So the study I did is really not equipped to answer that, except that the biggest effect was people who did any and people who did versus people who did not. So if you found a workout that works for you, that you’re willing to keep on doing, then that is the best one for you. 

IRA FLATOW: Now why would building muscle– because that’s what you’re doing when you’re doing this strength training– why does that reduce the effects of, say, diabetes? 

MAYA SMITH: Because muscle is an organ. And when muscle contracts, it secretes various substances. They’re called myokines, chemokines, et cetera, and they have effects throughout the body. And one of the known effects they have is improving blood sugar control. 

IRA FLATOW: That’s interesting because I don’t think any of us believed in that or thought well, you can’t just do weight training, you have to do aerobics and things like that. That’s quite interesting. Well, you saw the biggest benefit of exercise in your study was in people over 70. Why might that be? 

WAEL JABER: So this was one of the biggest surprises we had because we expected to see the benefits in middle-aged individuals like myself. But what we noticed here, and at least this is the hypothesis, is that these are individuals who are probably– I compared myself to almost like a 403b or 401k account, which is basically you’re depositing. These probably are individuals who have deposited in that fitness bank all along their life. Probably these are individuals who are genetically different than other individuals, who were able to stay active all their life. 

Or probably these are individuals who live in neighborhoods that are favorable for walking, staying fit. They have lived near a park, they have a zip code that allows them to do that. So it’s probably a combination of all of the above. But at least my belief is this is something that you don’t arrive to be fit when you’re 80 or 75 by accident. You arrive to it by depositing in that fitness bank all throughout your life. 

IRA FLATOW: And in fact, Dr. Smith, you looked at older adults in your study as well, people up to 85 years old. Did they benefit from weight training? 

MAYA SMITH: Yes. The effect was somewhat smaller in older adults, but that’s because they started out at a much higher risk. The absolute risk reduction was probably greater in those groups. You know, 10% of 80% is a much larger number than 50% of 2%. 

IRA FLATOW: We hear that older people begin losing muscle mass as they get older. Is it possible to regain it or stop it or even add to it? 

MAYA SMITH: Yes. As you get older, you tend to lose muscle mass if you don’t do anything about it. However, this interesting study came out, it was in the American– I forget where it was. I think was in the journal, Circulation. They found out that randomizing people to high-intensity workout for two years actually reversed the signs of aging in their heart, specifically. Their left ventricle became less stiff and more flexible. 

IRA FLATOW: Wow, that’s interesting. Let’s go to the phones. Let’s go to Eric in Waterbury, Connecticut. Hi, welcome to Science Friday. 

ERIC: Hi, thank you for taking my call. 

IRA FLATOW: Go ahead. 

ERIC: I have a question. I’m a 50-year-old male cancer survivor and I’m recently going to the gym about twice a week. And I get on the elliptical and I work my brains out for about 45 minutes, and my heart rate gets up to about 190. I’m wondering, is that an exercise that I should continue? 

WAEL JABER: I can take that. 

MAYA SMITH: To me, that’s amazing, a heart rate of 190. I almost wonder if you’ve got some kind of artifact in that measurement there because I would not have believed that was possible. I can’t get mine up to 190 and I’m in my 30s. 


WAEL JABER: So we should never answer a question specific to an individual because, myself and Dr. Smith here, these are population studies. Again, your target heart rate should be– so you’re 50, you said. Your target heart rate should be 220 minus 50, so you should be about 170, and that’s the maximum heart rate. That’s why we’re both surprised to see that you can get to 190. 

IRA FLATOW: Well, I have a tweet here from Robert. He says, “an avid cyclist for 40 years, able to easily ride with avid cyclists in their late 20s. For someone of my age, isn’t it all anecdotal because there are 50 plus years of history of what I’ve been doing from my heart?” And Abby says, “I have anxiety and sometimes I’m anxious. I worry I’m going to have a heart attack. I run regularly and very much enjoy it. I avoid going on my run while anxious because of these concerns. Is it possible that I have a heart attack in this way?” 

MAYA SMITH: It’s possible to have a heart attack at any time, but physical activity is actually shown to be a good treatment for, I know, depression. Anxiety, specifically, I haven’t looked into, but at least one study has shown that moderate exercise, 30 minutes of aerobic activity three times a week– totally doable for the average person– is about as good for depression as Prozac. 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios. That’s an amazing statistic that you just quoted– as good for depression as Prozac. 

MAYA SMITH: Yep. There was a fairly small study. I would love to see more follow-ups on it. But in any case, if you have depression, then exercising out of depression is one therapy that a lot of people have reported success. 

IRA FLATOW: Let me ask this question about stretching out your exercise during the day. If you’re saying to do 30 minutes, can you do that in five or 10-minute chunks during the day? Wael, then Maya, you can follow-up. 

WAEL JABER: I don’t think this has been studied very well but, as far as we’re concerned, the maximum effect you’re going to get is from cumulative exercise. So it’s not like you have to go and hit the gym for an hour and a half to get the benefit. I think if you can divide it for most individuals who have jobs, like myself and you and Dr. Smith, if you can divide into chunks and do it 15 minutes for let’s say, being on the bike 15 minutes for weight lifting, 50 minutes for swimming– I think you will get probably same, if probably more, benefit than doing it all in one time and then injuring yourself. 

IRA FLATOW: Dr. Smith, let me ask you this question about weight lifting. How do I know I’ve lifted enough weight? Do my muscles get tired? Do I get fatigued? How much should I know? 

MAYA SMITH: Working to failure is a generally good rule. Go until you can’t do any more. And to minimize the risk of injury, especially once you’re just starting out, you want to do a large number of repetitions and with a relatively low weight. Aiming for being able to do 10 to 30 reps until you get to failure is about right for many/most people. But again, my study was population-based. My general rule for working out is go to the gym, pick out someone who looks the way you want to look, and ask them. 


IRA FLATOW: Most people are afraid of the gym now because they don’t look like the fit people working out. They feel self-conscious, but they’re not. 

MAYA SMITH: That’s like making fun of a homeless person going to a job fair. 


IRA FLATOW: Well, they do feel that way. Finally, let me ask you, Wael, what is your routine? How would you say the best routine to go about staying fit is? 

WAEL JABER: So I came to about this like most people come about, which is family history, having a strong family history of heart disease. Having moved from actually a city where you can walk around, from New York City to Cleveland, where it’s not as easy to walk around, I noticed I started gaining some weight after I moved from New York City to here. So I started slow– that’s what I always say, start slow, find a routine that you’re comfortable with. 

Myself, I vary. I run some days, I bike some days, I walk some days, I snowshoe other days in Cleveland. So I think variability is important, too, so you don’t enjoy yourself and you can work different muscles. And for the average individual, that’s probably the best advice is to have a variable exercise program. 

IRA FLATOW: And your study says, basically, bottom line– just do something. 

WAEL JABER: Moving from a lowest fit category to the next fit– you don’t have to be in the elite group– gives you enough benefit to equal many of the medications we give. Actually, probably more than many of the medications we give for blood pressure or cholesterol or diabetes. Just moving around and getting from the least fit category to the next one, I think, is sufficient. 

IRA FLATOW: All right, we’ve run out of time. I have to move on. I want to thank Maya Smith, sports medicine epidemiologist and assistant professor at St. George’s University School of Medicine in Grenada. And Wael Jaber is professor of medicine at the Cleveland Clinic in Ohio. Thank you both for taking time to be with us today. 

WAEL JABER: Thank you, and have a good day. 

MAYA SMITH: Thank you. 

IRA FLATOW: You’re welcome. After the break, how do you plumb the depths of a black hole’s immense gravitational force? Well, you do it with light, also somewhat indirectly. We’re going to look at some new research that’s talking about black holes, including the discovery of one that’s spinning at half the speed of light. Details after the break.

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