Are there risks to excessive endurance training? A retired pro examines the evidence and shares his story.


This article was originally published in the Nov./Dec. 2013 issue of Inside Triathlon magazine.

In June 2009, I called it quits. I announced my retirement with a news release headlined, “Danish Xpress Stopped by Heart Malfunction.” The irony was that what had made me successful as an athlete, my strong heart, was the very thing that ended my 18-year career as a professional triathlete, which included a podium finish at the 2007 Ironman World Championship and two ITU Long Distance World Championship titles in 2004 and 2006. Prior to the announcement, my family and I had lived through two of the most difficult months in our lives dealing with far more important issues than whether or not I could swim, bike or run.

During the Wildflower Long Course Triathlon in early May of 2009, I felt an uncharacteristic gradual fatigue during the bike. In the final miles I could barely hold a heart rate of 110 beats per minute despite pushing the pedals as hard as I could. My arms and lips were tingling, my vision was blurred and I had to really focus just to get down that last steep hill into T2. As I got off the bike, my breath was out of control, and I sat down near the fence that surrounded the transition area. I was hyperventilating, my tongue was in spasms and I was scared. Really scared. It went on for several minutes while volunteers and paramedics rushed to help. I slowly got my breath under control and was put on a stretcher in the medical tent. After being checked by the doctors and resting for a good half hour, I could finally stand up. I talked to my wife, Mette, and my coaches back in Denmark and drove to my race accommodation. Something inside me changed. I did not know what, how or why, but something was not right.

Four years prior, in 2005, I experienced chest pain during a hard swim workout. I jumped out of the pool scared and managed to get an appointment with a cardiologist the following day. During the examination he found nothing that could cause the pain, but he did find a congenital anomaly called a bicuspid aortic valve. We later found out that the chest pain stemmed from a thoracic vertebra that was slightly out of place, which was easily adjusted by a chiropractor.

A bicuspid aortic valve is the most common heart condition, found in 1 to 2 percent of all people. It means that you have two leaflets instead of three in the valve that opens the blood flow from the heart out into the body. In addition, I had a minor leak at the valve and a slightly enlarged aorta, which is common for people with this condition. The leak meant that 5 to 10 percent of the blood pumped with each heartbeat would return back into the heart. So my heart basically had to work 5 to 10 percent harder than a normal heart. It was used to this, though, and overall very strong. A bicuspid aortic valve can also be associated with enlargement of the aorta, the blood vessel that carries blood away from the heart, but the size of my aorta was normal in 2005.

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Despite the discovery of the condition, my doctors felt it was OK for me to train and race as a professional as long as my heart, the leak or the aortic diameter did not start to grow. I had checkups every year and before my last Wildflower, in February 2009, my heart showed no signs of what was about to happen. Before that race I felt amazing. I had just clocked some of my best splits ever in training. But the race did not go as planned, and after an extensive medical evaluation, I was forced to retire.

My story is not unusual, at least among top endurance athletes. Other professional triathletes have gone through similar or worse scenarios. The most prominent were Greg Welch and Emma Carney, both of whom ended their careers in the early 2000s due to a dangerous arrhythmia called ventricular tachycardia. Welch went through an incredible nine heart surgeries to stabilize his condition, but lives and blesses the sport with his ever-positive spirit to this day. Chris Legh discovered a hole in his heart in 2003, but still competes at age 41 and this year came a mind-blowing fifth at the stacked Ironman Melbourne. And finally you may recall that two years ago two-time Ironman world champion Normann Stadler was rushed through valve repair and aortic replacement surgery because of an aortic diameter of 70 millimeters (nearly twice the norm) and a big leak at his valve. He has a similar condition to what I have, but did not discover it in time. In addition, hundreds if not thousands of age groupers have lived through similar conditions.

Obviously, many of them have asked themselves whether their heart problems are caused by the extreme demands we put on this vital organ as endurance athletes. Is it dangerous for us to train hard for 10, 20 or 30 hours a week, year in and year out? Is it dangerous to put our hearts through the demands of a grueling eight- or 17-hour Ironman? Is there a risk of dying suddenly when you push your limits?

To answer those questions requires a bit of knowledge about various heart conditions and their causes, as well as the anatomy of the heart.

Anatomy Of The Heart

The heart consists of two sides, a right side that pumps deoxygenated blood from the body to the lungs and a left side that pumps oxygenated blood from the lungs to the body. Each side of the heart has two chambers, a small one called the atrium and a large one called the ventricle. When the heart contracts it happens in a coordinated fashion where the atria contract first and then the ventricles follow so the blood is pushed through the heart out into either the vascular system in the lungs or the body. One of the cardiologists I saw told me that the heart not only contracts but kind of wrings itself like a dishcloth to get the most out of every beat every second of your life. It is amazing to experience how the body develops efficiency in every aspect.

Sudden cardiac death is in general very rare, but it happens and is the cause of most deaths during sport activities. In some cases it can be due to heart attack — or myocardial infarction — caused by lifestyle diseases such as atherosclerosis, but in other cases where the person is young and otherwise healthy it is most often related to an undiscovered congenital heart condition. Typically your physician can rule out most of these by screening your family history, lifestyle and the various acute symptoms related to cardiac events such as sudden breathlessness, chest pains and incidents of fainting. In addition, it is possible to do more advanced screening using EKGs and echocardiograms if the doctor suspects something is not right or you want it for your own safety.

Congenital heart malfunctions such as the hole in Chris Legh’s heart or the bicuspid valves in Normann Stadler’s and my own heart are present from birth and, as such, not caused by endurance sports. Doing sports at a high level can in some cases make an existing condition worse or it may be dangerous to compete with certain heart conditions. This needs to be assessed by a cardiologist who has experience with athletes. In most cases guidelines developed by expert panels are available with respect to how much and what kinds of athletic activities are safe to do when you have a heart condition.

Conditions that are not present from birth and develop over time, such as various forms of arrhythmia (abnormal heart rhythms), are trickier. They may have a genetic component, but can also be influenced by stress and intense training. Arrhythmias are a general label for a condition where the heart rhythm is disturbed from its common pattern in various parts of the heart. They can be more or less dangerous depending on their speed, how long they last and which part of the heart they affect.

Ventricular tachycardia, or V-Tach, is a rare form of arrhythmia that causes one of the ventricles to contract upward of 170 beats per minute. Another arrhythmia is ventricular fibrillation in which the electrical activity of the heart becomes so disorganized that the blood simply stands still within the heart. Needless to say, V-Tach can be dangerous and may in some cases result in sudden death, if not discovered and treated as in the cases of Greg Welch and Emma Carney.

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Other forms of arrhythmia, where the rhythm is disorganized in the smaller atria, are rarely as dangerous, but nevertheless clearly felt through chest discomfort, breathlessness and a reduced work capacity. These kinds of arrhythmia can last hours or even days and can most often be treated. Arrhythmias are more common in the elderly. By age 70, according to cardiologists, 15 percent of us can expect to develop some sort of arrhythmia.

When we train intensively for an endurance event such as the Ironman, several adaptations occur to our hearts. The most common is that our resting heart rate goes down due to our improved heart function. Many endurance athletes will experience the sensation of skipping a beat. Actually, this is most often due to premature beats: a premature ventricular contraction (PVC) if it originates in the ventricle or a premature atrial contraction (PAC) if it originates in the atrium. Both PACs and PVCs are quite common in well-trained athletes and often are not dangerous.

‘Athlete’s Heart’

Intense training for many years causes the heart to grow in many endurance athletes and is termed “athletic bradycardia,” or “athlete’s heart.” Usually the heart only grows when something is wrong, so for years this was considered somewhat dangerous by cardiologists. Today we know that most athletes’ hearts reverse themselves to more normal proportions when cutting back on training, and this condition is not considered dangerous. The only complication is that it can be difficult to establish whether or not a big heart is caused by training or by a possible heart condition, so diagnostics may be more complex when working with athletes.

With the growth of extreme endurance sports such as the marathon, long-course triathlon and ultra-running, more interest has been given to the potential adverse acute effects of long and intense training and racing on the heart. Studies of the heart function in athletes after finishing an Ironman show that some blood markers, such as troponin, a protein involved in muscle contraction, are at increased levels, indicating damage to the heart muscle, similar to what is measured from skeletal muscle after prolonged intense exercise. Also heart function may be slightly reduced and there may be slight leaks at the valves directly following extreme exercise. However all of these factors usually reverse within a 48-hour period. So it seems that the heart recovers after races just as other muscles do.

If one goes through such intense exercise bouts day in and day out, week after week, year after year, however, long-term changes may occur in the heart muscle. In studies done on athletes who have run more than 100 marathons and veteran Ironman athletes, scientists have identified, in 12 to 15 percent of these individuals, scarring in various parts of the heart. Again this is similar to what is seen in the skeletal muscle of long-time marathon runners. However, the consequences may be more severe when it comes to the heart muscle. While there are still many things we do not know when it comes to the effect of extreme exercise on the heart muscle, one pattern is evident: In the scientific literature, at least 12 studies found a four-fold increased risk of developing arrhythmia in athletes who have trained vigorously for 10 or 15 years, compared to people who exercise in more moderate amounts. Most of these arrhythmias are not acutely dangerous as many people live with them and still exercise. But as is the case with my own condition, heart troubles are always complex to deal with, and arrhythmia may bring other adverse effects such as a higher risk of stroke as you age. In addition, some of these cases may be more serious and in very, very rare cases certain arrhythmias may be fatal. Other studies indicate that high-level training may increase calcification and stiffening of the aortic wall in addition to arrhythmia.

Obviously it would be nice if physicians could establish training guidelines for how much is too much, but since each person is unique and we all have a different tolerance for training, that’s not possible — at least not now. One typical patient for sports-related arrhythmias, according to physicians I spoke to who deal with this issue, is a person with a 10- to 15-year career on an elite level plus another 10 years of continued intense training after that. The other pattern doctors have noticed in their studies is that it is the hours done rather than the intensity that affects the development of arrhythmias. Almost any athlete can be affected, though. Life stress and genetic factors, in addition to the training, may count as a trigger as well, even when training is less intense over fewer years.

Dean Harper, one of triathlon’s early greats, put in decades of intense training and this year turned 60. In the early ’80s, while our sport was still in its infancy, before wetsuits and triathlon-specific bikes, Dean raced and trained with the big four: Mark Allen, Dave Scott, Scott Tinley and Scott Molina. He won the U.S. Long-Course Championships and the first edition of the Wildflower triathlon in 1983, and he was on the cover of the first issue of Triathlete in May of 1983. If there were ever a “big five” in triathlon, Dean would likely have been part of this elite group.

While the lifestyle back then was more relaxed than it is today, his training philosophy was rather simple: Train more than Dave Scott. Dean and Dave had competed against each other while swimming and playing water polo in college and sometimes trained together. Since Dave is one of the hardest workers in the sport, doing more meant pushing the limits daily. In those years Dean usually completed 25,000 yards of swimming, 400 miles of biking and 80 to 90 miles of running each week. After winning several other pro races in the shorter distances, Dean retired from pro racing in 1986 to raise a family and practice law. During the following 16 years he still trained about an hour a day. Often it was intensive threshold work, but he did not race.

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In 2002 he took up the sport again as an age grouper. While training for Ironmans he would push the training upward of 25 hours a week, which is incredible considering he is a partner in a law firm and has an active family life with three children. In 2008, he won a USA Triathlon National Championship and, later that year, came in third in his age group in Kona. The year after, in 2009, he won an ITU Age Group World Championship in the 55–59 age group. However, in those years, Dean also developed various arrhythmias in his right atrium, most likely due to all the years of intense training.

Dean had his first premature ventricular contraction back in 1986 after a hard swim practice. If you have not had one, it feels like your heart skips a beat and then contracts very forcefully. It scared him, so he went to his physician to get checked out. He was told not to worry, but it began again when he resumed his competitive training some 16 years later. The PVCs became more regular and in 2003 at the age of 50 he experienced his first case of what he now knows is atrial fibrillation, where the atrium beats in a chaotic rhythm. It lasted 24 hours, but he was already used to having PVCs quite often. For the following years while training and racing as an age grouper he would experience an A-fib about twice a year, usually after really hard or long training sessions. He had it once during an interval workout on the track and went from running 6:30 miles to barely being able to hold 10-minute pace as the fibrillation causes the heart to become far less efficient while it is beating. After some years Dean also started to experience atrial flutter, which is a sustained heart rate of 120 to 150 beats where the heart does not pump as much blood as it should.

In 2009, after winning short course worlds, Dean was set on the world champs in Kona. It was on his bucket list to win his age group at the Ironman World Championship. Before the race, though, he developed a viral and fungal infection in his throat and was on medications leading into the race. He still started the race, but immediately felt he was off. He could not bear the thought of not finishing and held on despite the illness in his body. Looking back, Dean says he was probably pushing the envelope too much, as he started to experience more regular bouts of atrial fibrillation and atrial flutter after the race. His doctor recommended that he see a specialist, who suggested ablation surgery, in which some of the cells causing the abnormal heart rhythm are cauterized. The first surgery caused his heart to go into fibrillation without coming back before it was shocked. He got another surgery from one of the leading experts in the field, which was successful in terms of the arrhythmias, but at the same time greatly reduced Dean’s physical capacity. Today, Dean’s resting heart rate is 60, instead of 40, and despite intense training he is unable to perform at the level he once was. He still enjoys doing four-hour rides with his youngest daughter, Shelley, an elite collegiate swimmer now competing as a triathlete, and he still races, but he is no longer able to pursue his original goals. Had he known this before the surgery he says he would have waited and exploited alternative strategies such as meditation to reduce the arrhythmic incidences. This underlines the importance of always finding a doctor who knows about sports and an athlete’s mentality.

While Dean’s story may be extreme, it may be the story of a growing number of triathletes. Both professionals and elite amateurs embrace our sport as an identity in which they train and race under the motto “never quit.” Those two words, along with huge training volumes, are weaved into the “iron culture.” We may think that we as athletes are strong and healthy, but as my story, as well as Greg’s, Emma’s, Normann’s, Dean’s and many others show, some of us and especially those who push the limits to extremes, may only be a heartbeat away from an ambulance and a hospital bed.

Does this mean you will die in your next race? No! Deaths are very, very rare in triathlon and compared to other risks in life, endurance sports are quite safe. A recent study from USA Triathlon investigating swim deaths concluded that from 2006 to 2011 the mortality rate in triathlons was only one in 76,000. In other words, for every 76,000 participants there was a death from cardiac or other reasons. As a point of reference the risk of dying each time you get in your car is around one in 20,000.

Is triathlon dangerous for your heart health? No, triathlon is for the vast majority of us a very, very healthy activity that prevents a multitude of diseases and brings us joy every day. But when the training and the racing are taken to extremes, when the mantra “never quit” forces you to train and race through illness and injury and when your “iron will” makes you disregard the messages you receive from your body on the brink of collapse, you are in the gray zone and face risks above the norm in terms of developing arrhythmia and potentially other heart malfunctions.

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Health is an individual thing. In medical terms, health is often reduced to how long you live, not how you live. For all of us, it is important to consider the longevity, quality and meaningfulness of our lives. Endurance sports such as triathlon are to most of us a very meaningful part of life, providing fuel for our identity and experience.

As Dean puts it, “I love to train and stay in great shape. Although my condition limits my ability to compete at the highest level, I will never stop training unless it became life-threatening. It has brought, and continues to bring, great happiness. And I am hoping that medical science will continue to progress so that my type of issue is better understood and dealt with in athletes.”

I can understand why some choose, as I did for many years, to chase the dream. However, life is long and what you see as acceptable risks now may not be acceptable later on. We need to chase our dreams, as our ability to do that makes our lives meaningful, but we also need to balance and control the risks we take in the process. After all, that is what leads to peak performances in sport and in life.

‘Something Was Not Right’

When I came home from California after my heart problems at the Wildflower race in May of 2009, I saw a sports doctor to get some blood work done. He felt I should see a cardiologist due to the drop in my heart rate. All the other symptoms including hyperventilation were not necessarily caused by the heart, but the drop in my heart rate indicated something was not right with my most vital organ. I met with one of the best cardiologists in Denmark who works with elite athletes. After a routine ultrasound examination — an echocardiogram — he wanted to run several other tests. The leak looked to be moderate in size, and my left ventricle was a massive 74 millimeters in diameter, which is very big, even for a world-class endurance athlete, but we needed more data to figure out how bad it was.

The following months were filled with uncertainty and worries. It was unclear whether I needed valve replacement through open-heart surgery, which is a complex and massive procedure, and it was unclear whether I could continue as an athlete, which was our family’s primary income at the time. At the same time, my wife’s father was in the final stages of terminal prostate cancer, with only months left to live, which obviously affected all of us deeply. On the sunny side, but on an equally life-changing level, my wife, Mette, was nine months pregnant with our second child. The emotional burden was beyond words. We talked, hugged and gave space to process all that was going on.

On May 29, I was scheduled for a transesophageal echocardiogram, where the doctors inserted an ultrasound probe through my throat into my esophagus, just behind the heart, to get a better look at the condition of my heart valve. Needless to say this was a very uncomfortable examination. While I was being sedated and gagged with a tube the size of a garden hose, Mette stayed with me even though she went into labor and drove me home despite her contractions. After 28 hours in labor, she gave birth to our wonderful daughter Marie.

More tests followed: various echocardiograms, heart stress tests, a two-day monitoring for arrhythmias and an MRI of the heart, which is extremely complicated as the bugger won’t stand still. By the end of June, the doctors had a good overview of my condition. My leak had grown to a moderate size, which meant that 20 percent of the blood returned to the heart with each beat. My aortic diameter had also grown to 45 millimeters, which was in the gray zone in terms of doing sports, but not indicative of the need for immediate surgery. The bigger leak put more pressure on my heart during exercise and at rest, which had caused the left ventricle diameter to increase by 10 millimeters since February. Needless to say, the doctors advised that I stop elite sports immediately and start lowering my training by doing one to two hours of moderate-intensity training a day. Over time we would see whether that relieved enough pressure for the ventricle and aorta to shrink, or whether I needed valve replacement surgery. The insecurity continued, but the first follow-up showed clear signs of improvement, which continued to the point where my numbers a year later stabilized at less than what they were during my career.

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No one knows why the leak or my heart suddenly grew. The only study I found done on elite athletes with a bicuspid aortic valve suggests that my high levels of training had no influence on its development, so this may have happened regardless of my triathlon career. But once the leak grew to a moderate stage, serious training was no longer possible and I considered myself lucky that reducing my training was all it took to stabilize my condition. Going forward I don’t know whether the leak or the diameter of the aorta will develop again anytime soon, or whether it will remain like this for the rest of my life. I still exercise and enjoy being out in nature, but I’m not allowed to train hard or race anymore, which is fine by me. After all, I have experienced more than I ever dreamed of in my professional career, and I can still be active at a level I enjoy.

As my case shows, having something go wrong with your heart is not like having to deal with a jumper’s knee or a sprained ankle. It touches some of your deepest fears when you consider that the organ you depend upon every second of your life may fail. It took months before I understood how afraid I had been during the incident in Wildflower and the months that followed. It took even longer before I was able to trust my body again and convince myself that my heart is just a muscle like any other. If my condition worsens I know I have a great family and great doctors who can help. No matter what life I am handed, I know that my attitude, not the circumstances I live under, determines my happiness and quality of life.

Tips For A Long And Healthy Life

Whether you are 40, 50, 60 or older, you still have many years to compete. Here are my four basic tips:

1. React Immediately To Serious Symptoms
If you ever experience shortness of breath, severe chest pains or loss of consciousness either during exercise or at rest, you should seek medical assistance immediately and get a thorough examination from a cardiologist.

2. Get Checked
Get a checkup from your doctor involving at least a basic questionnaire screening for risk factors and a standard electrocardiogram. This will rule out most congenital factors and should be done at least once in your career. Preferably, you should get a checkup once a year while you train and race. If you train seriously to compete in your age group you can consider an echocardiogram, which is more expensive but enables a more comprehensive screening — although it will not rule out everything.

3. Chase Your Dreams, But Respect Your Body
It is safe to train regularly and with high intensity, but adequate recovery and respect for illness and injury are paramount to athletic health. Do not train or race while ill, and do not overtrain. How much is too much? That depends on many individual factors. If you prepare your body gradually for the once-in-a-lifetime Ironman, you may be OK, but if you race and train several iron-distance races a year and you do that for several years in a row you may be in the gray zone in terms of developing arrhythmia and other potential malfunctions later in life.

4. Change Triathlon’s Overachieving Culture
I know many athletes who train too much. I know many athletes who have triathlon as their single identity. I know many athletes who would rather risk their health than DNF in a race. Choosing to do so is an individual choice and, if that choice is informed, I am fine with that. Too often, though, these choices are affected by the overtraining culture in triathlon. People sometimes sacrifice their health for something that seems meaningful now but is not in hindsight. In my view, this is not OK and we need to change this as a sport through information, more research and the way we salute our heroes.

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