Is there such a thing as TOO MUCH ENDURANCE TRAINING?

Introduction

After close to 30 years away from Queensland’s Gold Coast, I’ve returned to the beach to live and take up work as Professor and Head of Exercise and Sport Science at Bond University. I’ve also reconnected with a number of training buddies from the surf lifesaving and (very early) triathlon scenes. I’ve been amazed at how many of them have had heart-related issues. Indeed, three of them, including a former world champion age group triathlete, now have pacemakers inserted to keep their heart rates down and regular.

I’m just over 60 years of age now and am starting to think ‘will I be next?’. So I did some reading on what the research says about this relatively newly-discovered phenomenon that suggests too much high intensity endurance training over too many years may be pushing your luck when it comes to the ticker. I found that chronic exposure to high levels of endurance training over many years and at high intensities may lead to adverse cardiovascular outcomes in some people. These negative outcomes include loss of the benefit of living longer, atrial fibrillation, pathologic heart remodelling and even atherosclerosis or hardening of the arteries, something we always thought endurance exercise prevented. Let’s look at each in turn.

1. Too much strenuous exercise and competition over too long a period of time may lead to increased mortality. A study of 1098 joggers published in 2015 showed that, as expected, joggers who trained lightly or moderately had significantly improvements in mortality. However, those that trained strenuously had death rates similar to those of inactive non-joggers. This supports a classic study published in 2014 where 55, 137 people (13,016 runners and 42,121 controls) across all ages showed that moderate running reduced all-cause deaths by 30% and heart-related deaths by 45% but that in runners running six or more times a week or approximately more than three hours a week, these benefits were reduced.

2. Atrial fibrillation has consistently been shown to be associated with high levels of endurance exercise. Atrial fibrillation is a disturbance of the electrical activity of the heart. Sometimes it’s called arrhythmia or dysrhythmia but it’s always associated with an abnormal heart rhythm. It’s very common in older people and those with cardiovascular risk factors and disease. Now it seems to be appearing more commonly in some endurance athletes who do too much endurance training and competition over too many years. A meta-analysis (a review using statistical analysis of the outcomes of previous studies) is a very powerful piece of evidence in summarising research.  A meta-analysis of prior controlled studies published in 2009 showed the risk of atrial fibrillation on endurance athletes was five times higher of that of non-athletes with men being at greater risk than women. Confirming this finding, a 2013 study of 52,775 competitors in a mass cross-country skiing event followed 919 participants who suffered atrial fibrillation over many years and found those that competed more often and finished with the faster times were more at risk of arrhythmias.

3. Overdoing endurance exercise may lead to heart remodelling. In particular the right ventricle that pumps blood to the lungs appears to be the part of the heart most affected. It’s been suggested that repeated training of high intensity and extended endurance exercise may induce hardening of the right ventricle walls and reduced blood pumping ability of the blood from this heart chamber to the lungs.

4. Atherosclerosis or hardening of the arteries may be higher in endurance athletes undertaking consistently long training and competition. We’ve long known that physical activity reduces atherosclerosis which is the leading cause of heart-related morbidity and mortality in the developed world. Two studies, one in 2008 and the other in 2014, showed that older marathoners had similar levels of atherosclerosis to non-athletic controls, although family history, smoking history and other baseline measures relevant to heart disease were not collected. Some researchers suggest that the repeated stress on the coronary arteries may cause damage to the arteries. When combined with the increased amount of calcium in the blood following hard training or competition, the damage to the arteries may lead to the atherosclerosis.

The Bottom Line

I’m not trying to alarm masters athletes with this ever-increasing body of knowledge. I’m simply raising awareness. We are all different as a result of our genetics, our training and competition histories, our training patterns, and our lifestyles, all of which appear to affect our risk of cardiovascular issues. Based on current research it appears that long-term, high-intensity and long distance endurance training and competition may predispose some people to the above cardiovascular issues. If in doubt, do as I do. Speak with your family doctor about it, read about it, and maybe, as I now do as a result of lessons learnt from training mates, visit a cardiologist and get a yearly exercise stress test with echocardiography. These tests look at both the electrical and pumping and structural capacities of your heart. Indeed, I had one two days ago. I do have one risk factor – atrial (the collecting chambers of the heart) enlargement but it’s no different in size to last year. One of the other risk factors is elevated pulmonary artery pressure which appears normal in my case. I also know my other risk factors (blood lipids, blood pressure etc) are all good. Apart from these yearly tests I also treat my heart muscle as I would a swimming, cycling or running muscle. I don’t hammer it each day. I let it recover and rest. So far so good.

I also need to say that the key paper I used to inform this article concluded by stating: At present, there remain no definitive data that support practitioners to advise against ‘excess’exercise in healthy athletes and recreational exercisers engaged in high level and extreme doses of physical and athletic activity. Stay active for life!

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