Friday, March 13, 2015

Is Running a Marathon Healthy?

Many people turn to physical exercise, such as running, to increase their cardiovascular and overall health. It seems to be common sense that running must be healthy—in fact, it is beneficial to nearly every biological structure and function in the human body. Running burns calories and builds muscle, helping exercisers maintain healthy body weights. Running releases chemicals in the brain that improve mood. Running even prevents diseases, such as diabetes and heart attacks, and extends life expectancy.  


Many professional and amateur athletes focus their training on the marathon, the 26.2-mile (or 42-km) idol of running culture. In recent years, however, the health benefits of running a marathon have become quite controversial. Namely, concerns have been raised that the marathon distance is too extreme and poses significant cardiovascular risks to partaking runners.

Endurance exercise such as training for and running a marathon requires the body to feed hardworking skeletal muscles by pulling in extra oxygen, which must be transported through the bloodstream by a pumping heart. Endurance training results in changes in heart functioning to accommodate these additional physiological requirements, including increases in heart rate, stroke volume (how much blood is pumped from one ventricle per heartbeat), systolic blood pressure (the pressure in the heart when it contracts), peripheral vasoconstriction (narrowing of blood vessels), and vasodilation (widening of blood vessels). In simpler terms, the heart is working harder and faster to produce more pressure to move more blood. Athletes who undergo intensive endurance training develop what is known as “athlete’s heart,” which is not only larger and thicker, but has a cardiac output (how much blood is pumped through a ventricle per minute) five to six times greater and a slower resting heart rate than an average heart.  

https://en.wikipedia.org/wiki/Heart#/media/File:Diagram_of_the_human_heart_(cropped).svg

In young athletes, the physiological changes associated with athlete’s heart do not appear to have negative long-term health effects. However, it is unknown if athletes who begin running when middle-aged (rather than in their youth) are able to develop athlete’s heart. In fact, many studies that measured heart health indicators in middle-aged athletes have demonstrated signs of injury or reductions in function due to endurance exercise.

Methods including echocardiographic imaging and magnetic resonance tomography imaging are used to look at the heart directly before and after running a marathon. These types of studies have discovered negative changes in left ventricle systolic and diastolic function, right ventricle structure and function, myocardial scarring, and myocardial fibrosis. Serological biomarkers, such as troponin, have also been monitored and indicate heart damage after endurance exercise. More severe conditions associated with marathon running include atrial fibrillation and ventricular ectopy, both of which involve irregular changes in heart rate.

In most of these studies, however, the measured parameters returned to normal levels within 24 hours after the race, indicating a period of “cardiac fatigue” after endurance exercise. Additionally, the more severe conditions are relatively uncommon and usually result from a combination of endurance exercise and underlying heart disease.

However, there are long-term effects of endurance running, including benefits to the vascular system. Endurance exercise has been shown to reduce peripheral blood pressure, peripheral arterial resistance, arterial stiffness, and blood pressure, as well as increase blood vessel function and myocardial capillary density. In sum, running seems to make blood flow more smoothly and slow down vascular aging. Endurance exercise has also been shown to enhance the blood clotting system.

Endurance exercise allows the heart to better withstand some stressors. One example is the heart’s ability to withstand myocardial ischaemia, or a partial or complete blockage of an artery, which can lead to heart attacks. Running also increases the coronary flow reserve, or the maximum increase in blood flow that can occur through the coronary arteries. This is important because during bouts of intense activity, the heart needs to pull in more blood for increased oxygen distribution.

An important note is that most of these studies are done on middle-aged men, many of whom began running later in life. This means that these findings are not directly transferrable to women or young people who develop high cardiovascular fitness early in life. Middle-aged men is the largest cohort of marathoners, attracting most of the current research; more research needs to be done to evaluate the cardiovascular impacts of running a marathon on women and other age groups.  

The bottom line is that intensive endurance exercise such as running a marathon presents a special challenge to the human body and until more research is conducted, it is difficult to understand its full range of effects. For many people, the benefits will outweigh the risks—they will reap the rewards of a higher level of health and fitness throughout their lifespans. However, for those who push themselves too far or have underlying cardiovascular issues, running a marathon will increase the risk of cardiovascular complications. If you are an endurance athlete, consider evaluating your own risk by getting an ECG or other screening procedure.

Source: Predel, H. G. (2014). Marathon run: cardiovascular adaptation and cardiovascular risk. European heart journal, eht502.

16 comments:

  1. While it seems strange to suggest that running marathon is potentially dangerous, it makes perfect sense that middle-aged people should not push themselves too hard in exercising. However, I'm wondering if it is possible for them to build up their endurance slowly without hurting themselves? The blog mentions that endurance training changes heart functioning to accommodate the additional physical requirements and suggests that it is unclear whether middle aged people can benefit from this change. Why is that the case? What distinctive feature in middle aged bodies prohibit them to adapt to the extra physical exercise? The answers to these questions might shed some new light on what types of exercise benefit middle-aged people best

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  2. Interesting post...While I guess I am now considered middle aged (yikes!), I have been running for almost 25 years - hopefully my heart is 'young' as your post suggests. True, I do have a low heart rate and low pressure.
    Another thought - it is disappointing that these studies always start with men - this goes back to the now increasing knowledge (or should I say acceptance) that women's cardiovascular health is different from men. There are many, many women my age running, AND many do just start once they find themselves in this age group, their metabolism slowing, and the weight coming on!

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  3. I wonder if these benefits, seen in middle aged men who I can assume are of good health, translate to people with impaired cardiovascular function. Could running be a good therapy for those with heart problems? Obviously it would be important to slowly build up endurance, but is it possible to avoid unnecessary strain on the heart while still incurring these great benefits?

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  4. While I found this post interesting because I have always wanted to complete a marathon, I can relate. In my father's early 40s, he participated in four consecutive Ironman Triathlons (2.4 mile swim, 112 mile bike, and a marathon). After completing one, he would give himself at least a month to allow his body to recover before her went back to training. If studies are discovering the negative effects that training and performing a marathon has on an individual, I wonder how it affects the body of an Ironman athlete. The time to complete an Ironman can range from 8 to 17 hours. Imagine your heart performing at it's maximum effort for almost half a day?

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  5. The line that really caught my eye was this one: "many studies that measured heart health indicators in middle-aged athletes have demonstrated signs of injury or reductions in function due to endurance exercise." Now I consider myself a fit individual and I played sports all throughout high school, but my activity level since coming to college has drastically dropped. I see this in my higher resting heart rate and the ease with which I get exhausted after exercise. But do the above studies suggest that I should start exercising now as opposed to later in life in order to avoid the negative effects of middle-aged "athlete's heart"? Because I have always told myself that I would get back into shape once I have more time and once I'm done with the stresses of school, but maybe I should run now and reap the benefits of running in my youth.

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  6. You mention in your post that most of the research on this topic has focused on middle-aged men. If men are the ones running most marathons, this makes sense to me in terms of allocating research resources. That said, I am curious how clinicians use the findings available to them when treating patients outside of study demographics. I know many of us in the physiology class will be attending medical school, and I wonder how prepared we will be to deliver care to the broader population when so much of the data presented to us has come from studies of men. Even in our textbook, most values are donated as for "healthy men."

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  7. As Rehman mentioned, heart health in many studies is actually found to have reduction in function due to endurance exercise. The development of the athlete's heart, or the thickening of the heart muscle and increase in output might actually have something to do with that. High blood pressure is something that can result in the thickening of heart muscle as well, leading to less of a relaxation of the heart in between beats. In older individuals, this "sudden" change in how the heart is pumping blood after having pumped it in a certain way for so long could result in this adverse effect of the thickening of the heart muscle, even though there is technically increased endurance. The inability to relax actually does not allow the heart to fill up as much in between strokes, and ends up leading to a lower volume of blood being pumped. So this may explain, at least some part, of why endurance running in middle-aged men may actually lead to deleterious health effects.

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  8. I hate running without a purpose, and the idea of running a marathon has never enticed me. This post has given me all the more reason to stay away from endurance running. Running 26.2 miles seems like an impossible, superhuman feat that shouldn't be possible, but in reality, humans are the best animal at running and moving long distances. Our ability to sweat through pores located all over the body and the ability to breathe more than once per step (something that is actually quite rare among mammals) make us the perfect form for running. African tribes such as the Massai people have shown the true power of humans conditioned to endure long distance running. Members of this nomadic tribe would often run 40-60 miles per day, chasing prey until it tired out, or simply to find a better place to live for the short term. Living this lifestyle surely brought plenty of long term damage to joints and muscular structure, but it is fascinating that it is possible at all.

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  9. This is extremely interesting! I love running and running a marathon someday is actually one of my goals, so this is definitely an interesting thing to consider. I am curious whether similar conditions can develop with other cardiovascular-intensive sports? I'm sure professional athletes reach the point of overexertion regularly, so I would be curious to know whether there have been similar studies done looking into other sports.

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  10. As a fairly avid runner, I would be very interested to see what effects of beginning running in middle-aged men has. In my experience, running has always had its physical risks, whether that be the wearing down of joints, arthritis or something else entirely. However, previous to this, I had never heard of running affecting the heart in a negative fashion, but rather helping prevent heart disease, heart attacks, and various other complications that typically occur later in life. While I think that there is an importance in finding the truth about the possible negative affects of running for middle-aged individuals, for now, the benefits outweigh the risks. This is especially the case if running is done in the proper fashion. Slowly increasing mileage and pace is essential to building up a proper aerobic capacity. It could be hypothesized that those who train inappropriately may be more subjective to the risks brought up in this blog.

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  11. I would like to know the specifics of the tests done on the middle aged men. It makes a lot of sense to me that older individuals should not be pushing themselves too hard when it comes to running. However, this post didn't really delve deeply into how hard they were training and over what period. I think this can serve as a cautionary tale to middle aged men looking to push themselves to the extreme, but I certainly wouldn't want to deter anyone from exercising and staying healthy.

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  12. I have always thought of long distance runners, especially marathon runners as extremely healthy. I think this post is very important and interesting because it shows how our culture's extreme forms of exercise and focus on sports can be harmful. I think it is also interesting to think about things like the link between Alzheimer's and Concussions in NFL athletes. We focus so much on athletes being our health idols, but more and more research is showing that sports at the extreme levels we take them too may not be good for your physical or mental health. Recently in the hockey world there has been a large outcry from prominent players and even the Canadian olympic team player Haley Wickenheiser about the high rate mental heath problems that professional athletes. I think all these things are very important to think about talk about as we encourage young children to play increasingly competitive sports in order to stay "healthy".

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  13. This is very interesting because both my brother and my dad are avid runners. It's nice to know that the health benefits of running usually outweigh the risks. I feel like in my family's case this is especially true because they don't run long, marathon-length distances. However, I do feel compelled to suggest that my dad get and ECG to test the health of his heart in the case that his heart has become damaged at all by years of aging and running. I'm upset that there isn't more information concerning women. Hopefully in the coming years there will be more information available.

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  14. Interesting for sure! I would think that if you build up your endurance starting at shorter distances and different training methods you would be able to allow your heart muscle to grow and adapt healthily. I also wonder if some people are born with certain physical advantages which make them fit the runner mold making running less of a struggle for them.

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  15. I feel as though a lot of people tend to follow the saying 'what doesn't kill you makes you stronger' and consistently push themselves to their physical limits. From this post it seems that this may not be a problem, that is if you know your limits. For those who do not know their limits, or choose to ignore them, pushing themselves to hard physically, could actually kill them. I think it is very important for people to understand both the benefits and risks of exercising and to realize that the most difficult and strenuous activities are not always the best.

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  16. I feel as though a lot of people tend to follow the saying 'what doesn't kill you makes you stronger' and consistently push themselves to their physical limits. From this post it seems that this may not be a problem, that is if you know your limits. For those who do not know their limits, or choose to ignore them, pushing themselves to hard physically, could actually kill them. I think it is very important for people to understand both the benefits and risks of exercising and to realize that the most difficult and strenuous activities are not always the best.

    ReplyDelete