Scientists are beginning to investigate the effects of long distance running on our bodies. Scientific tests are being performed to investigate particular aspects of this issue, and other aspects of this issue are ignored in those tests. This means that an individual scientific test doesn't give the full story about the issue. It is, therefore, necessary that all scientific tests be studied to give one a better understanding of what is actually happening.
This page was created to give my thoughts about and our health. Keep in mind that I'm not a scientist or a doctor, and my thoughts may be naive. Also, I'm sure that tests have been conducted that aren't described in this page, and I will appreciate having links to such tests emailed to me.
Amount of Training Prior to a MarathonThe Boston Globe, in an article dated April 17, 2006, reported on the effect of training prior to a marathon on the cardiactic health of the runners. The conclusion of the tests was expressed by Dr. Malissa Wood, a cardiologist and codirector of the Massachusetts General Hospital Women's Cardiovascular Health Center. Dr. Wood is a runner and has completed four marathons.
Among marathon runners, the biggest cardiac risk seems to arise in people who train the least. People who worked up to a marathon by running at least 45 miles a week for at least three to four months ''were golden. They didn't get into any trouble at all," said Wood. ''If they trained less than 35 miles a week, they were in big trouble."The article summarized the effect of marathon running on our bodies.
As for marathoners, Wood and her Mass. General colleagues have found that running 26.2 miles can lead to clear signs of cardiac stress. They have found that cardiac troponin, a chemical that shows up in blood tests only when heart muscle is damaged, rises in 60 percent of runners, and in some, it rises so high that ''if you had just looked at these scores, these people would have been admitted to the hospital for heart attacks," Wood said.
They've found that another chemical, BNP, or brain natriuretic peptide, another red flag for cardiac dysfunction, goes up after a marathon in 60 percent of runners. Platelets also become activated and more likely to form the clots that can trigger heart attacks, according to a just-published paper by Siegel and Alexander Kratz, director of the hematology lab at Mass. General. And, as shown on echocardiograms, the heart's ability to relax after each beat remains impaired for at least several weeks in most marathoners.
Age of the MarathonersIn an article dated August 31, 2010, ScienceDaily reported on tests conducted on older marathoners (average age of 50) who were not elite runners. The results of the tests were described in the article.
Immediately after finishing the marathon, there were some significant changes of the parameters of diastolic and right heart function. However, even though these changes were statistically significant, they were all within the normal levels and therefore do not seem to be clinically relevant. All parameters had returned to normal two weeks later, and the most likely cause of the changes were tachycardia and dehydration during the race. Also, for some runners, there was an increase in certain myocardial biomarkers but no correlation could be drawn between this increase and any myocardial dysfunction. It is believed that the temporary increase was probably caused by functional changes of the cardiomyocytes while running and not by myocardial damage.The article concluded by stating
As a result of this study, it would appear that elderly amateur runners can continue to compete in marathon races without increasing their risk of sustained heart damage.
Heart Damage May Be TemporaryThe study referred to above about the age of runners was a study of runners completing the 2006 and 2007 Berlin marathons. As indicated in the quote given above, the symptoms of heart damage were gone two weeks later.
The October 25, 2010 issue of ScienceDaily reported on MRI tests of runners completing marathons. The MRI tests allowed doctors to look at individual segments of the hearts. The tests showed that damage does occur to hearts. Runners who wern't properly trained for their marathons had more damage to their hearts, but the damage was temporary.
His research found that the magnitude of abnormal heart segments was more widespread and significant in a group of less fit runners. During the marathon, they had signs the heart might be at greater risk of damage than that of runners who had better training or at least had better exercise capacity.
His research found that the magnitude of abnormal heart segments was more widespread and significant in a group of less fit runners. During the marathon, they had signs the heart might be at greater risk of damage than that of runners who had better training or at least had better exercise capacity.Canadian researchers found that marathons may cause damage to our hearts, but that damage is likely temporary and reversable. However, we need to do long-distance LSD enough that we become "fit" runners.
"Without proper training, marathon running can damage your heart. Fortunately the exercise-induced injury is reversible over time," said Dr. Larose. "But it could take up to three months to completely recover."
Investigators who studied a group of recreational marathon runners have established that strenuous exercise such as running a marathon can damage the heart muscle. Although they found the effect is temporary and reversible, they warn that these effects are more widespread in less fit distance runners and that recreational distance runners should prepare properly before marathons. Their findings are published in the October  issue of the Canadian Journal of Cardiology.
Another Look at Marathons and UltramarathonsThe New York Times reported that British researchers have learned that half of the older elite athletes who were tested and who trained hard have scarring within their heart tissue. The tests were performed with a new type of MRI.
The results, published online a few weeks ago in The Journal of Applied Physiology, were rather disquieting. None of the younger athletes or the older nonathletes had fibrosis in their hearts. But half of the older lifelong athletes showed some heart muscle scarring. The affected men were, in each case, those who’d trained the longest and hardest. Spending more years exercising strenuously or completing more marathon or ultramarathon races was, in this study, associated with a greater likelihood of heart damage.The Times article also reported on tests made on laboratory rats that showed that prolonged running by the rats did cause scarring of their hearts.
The rats had begun their regimens with perfectly normal hearts. At the end of the training period, heart scans showed that most of the rodents had developed diffuse scarring and some structural changes, similar to the changes seen in the human endurance athletes. A control group of unexercised rats had developed no such remodeling of their hearts. The researchers also could manually induce arrhythmias, or disruptions of the heart’s natural electrical rhythm, much more readily in the running rats than in the unexercised animals. Interestingly, when the animals stopped running, their hearts returned to normal within eight weeks. Most of the fibrosis and other apparent damage disappeared.Not only runners are affected by long distances. Long-distance skiers have similar effects.
Dr Andersen said the study was important because, although there have been other studies looking at the effects of endurance exercise on various cardiovascular problems such as ischemic heart disease and stroke, there have been only a few, smaller studies of its effect on heart rhythm disturbances, and they have tended to look at people who are less physically active, or compared very sedentary people with those who were very active.Most runners aren't in the elite group that was the subject of the research, and the concluding paragraphs of the Times article may serve as a guide for us.
So for now, the best response to the emerging science of excessive exercise is to just keep exercising, but with a low-level buzz of caution. If your heart occasionally races, which could indicate arrhythmia, or otherwise draws attention to itself, Dr. Nattel said, consult a doctor.
But if you exercise regularly and currently have no symptoms, “I think it’s safe to say that you should keep it up,” Dr. Thompson said.
A Word of Caution
I found the following paper on the web that discusses the effect of endurance exercise on the heart. The paper is titled, The endurance athletes heart: acute stress and chronic adaptation. The paper, itself, is too complex for me to understand, but the Conclusion was written in terms that I could understand.
It is, however, entirely likely that for the vast majority of endurance athletes, the stress of acute exercise will lead to healthy, physiological adaptation in the heart. For a very small minority, though, there is emerging evidence that endurance exercise may be part of a patho-physiological cascade that clinicians must be aware of and respond appropriately too.
Since none of us know if we're in the "vast majority" or the "very small minority" of endurance athletes, it would be wise for persons considering running a marathon to have a good health examination before they begin marathon training. If they're already in marathon training, it might be wise for them to push their marathon plans out a few months and do significantly more long distance runs before the race, and to provide time for a good health examination prior to the race.
Ultra-Endurance RunningScienceDaily, in an article dated August 31, 2010 reported on the cardiac effects of running 50 and 100 miles in difficult conditions, including hills, thunderstorms, and strong rain. The athletes had trained for that distance, and all athletes had been running marathons and ultras for over two years. The athletes had no known heart problems. The article described the results of the testing.
The ECGs at the start of the race displayed the typical features of an athletic heart, with the slow heart rate and electrical changes commonly seen in athletes. At the finish, there were significant electrical changes in over 50 percent of the ECGs, and in some there were bizarre electrical changes not commonly seen in normal ECGs, either at rest or during exercise. However, the changes in cardiac Troponin I did not correlate with specific electrical changes on the ECGs. Further data, to be presented at EUROECHO later this year, will show that baseline heart function was normal, but there was a 6 percent drop in heart function at the finish, which may also be relevant. Whether these changes reflect undiagnosed cardiac conditions was undetermined.
The following statement by Professor John Somauroo of the Countess of Chester Hospital concludes the article.
"This study suggests that running continuously over 50 or 100 miles may not be good for the heart. 96 percent of the finishers developed a significant increase in cardiac Troponin I, which can be an indicator of heart muscle damage -- and 12 percent showed signs suggestive of significant cardiac damage. They also developed significant electrical changes on their ECGs and, in some cases, quite bizarre changes. However, there was no proven correlation between the changes in cardiac Troponin I and the ECG changes."Read the full article in the link given below for more details about adverse effects of extreme workouts.
"Physical exercise, though not a drug, possesses many traits of a powerful pharmacologic agent. A routine of daily physical activity can be highly effective for prevention and treatment of many diseases, including coronary heart disease, hypertension, heart failure, and obesity," says lead author James H. O'Keefe, MD, of Saint Luke's Hospital of Kansas City, MO. "However, as with any pharmacologic agent, a safe upper dose limit potentially exists, beyond which the adverse effects of physical exercise, such as musculoskeletal trauma and cardiovascular stress, may outweigh its benefits."
The Duration of a RaceFifteen runners completing an ultra event that lasted from 5 to 7 days were tested for cardiac fatigue, and none was found.
If cardiac muscle were to respond in the same way as skeletal muscle, the expectation would be for lower contraction velocities after exercise. However, the results of the study show that this was not the case. It is worth noting that these results are not consistent with other studies of endurance events such as marathons or triathlons. The researchers believe that this may be because average intensity was relatively low despite competitors exercising for extended durations that averaged 150 hours. Therefore, a possible conclusion may be that it is exercise intensity rather than exercise duration that is the primary source for cardiac fatigue.
Some Marathoners DieEven though most marathoners recover from the heart-damage of their marathons, a few runners have died during the race or shortly thereafter. There is speculation that those runners may not have been able to handle the stress of the damage.
A new study finds that marathon runners experience temporary heart damage during their 26.2 mile (42.2 kilometer) races. The damage is reversible, but it may be one reason that seemingly healthy people sometimes die during long races.However, researchers at Harvard University discovered that deaths in runners usually occurred in persons who had previous, underlying damage to their hearts.
Other Effects Besides the HeartIn addition to studying effects of distance running on the heart, scientists are looking at possible effects on other organs. A report was recently issued about possible buildup of liquid in the lungs of marathon runners. Keep in mind that only 26 runners at one marathon were tested.
Lead author, Dr Gerald Zavorsky from the Marywood University, USA, said: "Marathon running is linked to an increased risk of pulmonary edema, and it seems that women are at higher risk than men regardless of marathon finishing time. While pulmonary edema can be a negative consequence of marathon running, regular exercise can also keep you fit and healthy. We do not yet know the impact of this finding on long-term health of runners."One effect on our health of distance running that has received little attention is the effect on our bladders.
"The added stress on the body that comes with running a marathon can cause urinary stress incontinence problems during the race or down the road," said Melinda Abernethy, MD, fellow, Division of Female Pelvic Medicine and Reconstructive Surgery, Loyola University Chicago Stritch School of Medicine. "People who already suffer from incontinence also are at risk for bladder-control issues while running."Dr. Abernethy admits that more research needs to be conducted on bladder-control, but she says "that runners should monitor their fluid intake and go to the bathroom at least every few hours during a marathon".
The Big PictureAs I read these articles, I'm beginning to see what seems to me to be the "big picture" of the effect of long distance running on our bodies, particularly on our hearts. Here is a summary of my understanding of this.
- Run at least 45 miles per week for several weeks prior to a marathon.
- Be aware that irregularities in your heart may occur right after a marathon, but those irregularities will likely return to normal within two or three weeks after the race. However, some runners may not recover from the damage.
- Older runners can run marathons without permanent damage (assuming, of course, they have properly trained for the marathon distance, and have been cleared by their doctor to run marathons).
- Use caution in deciding to run ultras. The effect of ultras on your heart is more severe than the effect of marathons.
- Use caution in the intensity of your training. Heart damage may occur in older runners who have run marathons and ultras for many years and have trained hard for those races.