Is Endurance Sport Damaging our hearts.

Some of you may have read a report published through the BBC News website.The headline is Marathon training may pose heart risk’. A few folk have asked my opinion on this report. So here I will write a few words that i feel are pertinent to this topic.

heart endurance exercise damage

The article quotes directly from Dr Sanjay Sharma who is the medical director of the London Marathon and an eminent London cardiologist.

I was lucky enough to spend time as a medical student and cardiologist under his tutelage and remember thinking at his lectures that the heart was far more complicated that I could ever imagine.

The study reported by the BBC looked at the heart’s of 40 people before and after completing ‘challenging sporting events’. These people were considered ‘highly trained’ after devoting 10 or more hours a week to their chosen sport.

Findings were that most of the ‘athletes’ hearts showed signs that part of the heart muscle had been stretched as a result of the strenuous activity.
I do not have the link to the original paper to hand, however, I am assured that the majority of competitors did have a degree of stretching of the heart muscle as evidenced by MRI scanning and the presence of a hormone called BNP. (more on that shortly).

Prior history of heart problems had been ruled out in the research participants.

So that’s all very well.

We know when we’re out there on the road whether partaking or competing that we are straining our bodies. We expect our muscles to ache at the end of the event knowing that we will have caused muscle damage. But we know whether it be a few hours, or a few weeks, the ache will go.
Why is the heart any different? It is a muscle after all – albeit a very clever one.

Where this study (and others have had similar results – see link below)… is interesting to me is in that 5 out of the 40 participants studied had residual (lasting) heart damage one week after the race. Even more interesting and perhaps counter-intuitive, is that these 5 were more highly trained and had been competing for longer than the rest. One would think that being better prepared would mean the heart would cope better with the demands of the event. So with age, sex and weight being controlled for – does this intimate that competing in ‘challenging sporting events’ can cause heart damage. 

Well no.

Its not that cut and dry. Science never is. What is tells us exactly is that a week after a challenging event the hearts of some highly trained and event-adapted athletes had residual heart changes.
What do we know about these athletes? Are they overtrained? Do they have other stressors in their lives.
As per usual in such studies – the sample size is too small to make valid and widespread assumptions from the data gathered. Having said that the findings most definitely warrant further studies. Prospective and perhaps interestingly retrospective. (Any ultra-marthoners or retired Ironmen get in touch 

Are these changes – even if persistent – damaging?

If the heart is still stretched will this not trigger cellular changes so that it some beneficial ventricular enlargement occurs? In other words, will this damage stimulate the heart to grow and adapt to the new challenges it will be expected to play a big part in?

The answer is we don’t know. Which is why further longitudinal research – where research participants are followed over time – is needed.
Most of you will know that the heart gets bigger with persistent exercise. One of the reasons that your heart-rate slows down with increasing fitness. Simply put – bigger hearts can pump more blood. However this is only the case when the heart muscle is healthy and refers mostly to the wall thickness of the left ventricle. This is called athletic hypertrophy and is a normal response to repetitive and strenuous exercise.

See: http://en.wikipedia.org/wiki/Athletic_heart_syndrome

The study reported by the BBC suggested that the heart muscles of the 5 most highly trained participants had scarring as well as being dilated.
Scarred muscle does not contract properly and hence the pumping action of the muscle will be less fluid. The more muscle affected – the more this action will be impaired. In a similar vein (excuse the vague pun) a dilated floppy heart cannot contract properly either.

As with any muscle – efficient contraction aids performance of that muscle. Without an efficient heart, we ain’t going very far.

What we don’t know is if this scarring and dilatation persisted or whether is returned to normal or indeed if the hearts adapted and were stronger as a result. Scar tissue forms after cells have been damaged and as a norm doesn’t become normal tissue again in the heart. Other normal parts of the heart muscle take over the function of the scarred tissue, but this compensation may not be effective in the long term (this is what happens after a heart attack where large areas of heart muscle are damaged and then scar).

The other finding was that levels of a hormone called BNP were raised. BNP is synthesised in and secreted from atria (top chambers of the heart) and plays an important role in body fluid and cardiovascular homeostasis as a cardiac hormone with a wide range of potent biological effects, including:

  • natriuresis, (loss of sodium through the urine)
  • diuresis (loss of water through the urine, and
  • vasodilation (dilation of blood vessels)

This study published in 2001 looked at 10 healthy men completing an 100km ultra-marathon. 9 out of the 10 men looked at showed significant heart damage after the event.

http://www.medscape.com/viewarticle/409229

I remember speaking to Sanjay Sharma (medical director at London Marathon) when I was a junior doc & starting out in triathlon. He asked me if I’d ever noticed that I don’t/can’t pee for a while after an event, but then a few hours later I’m pee’ing all the time? (or at least fairly frequently)

Rehydration accounts for some of this but the presence of raised BNP in the blood (released by stretched heart muscle) causes the kidneys to lose more water and hence dilute pee.

I definitely have this. But only when I’ve worked damn hard. Never in training, but often after tough races I notice this pattern. Maybe I should get my heart scanned for scarring?

;)
Thesse ultrasound images show the difference in chamber size of the hearts of a trained athlete and non-athlete. Notice Left ventricle wall thickness is increased in athlete v. non-athlete also to drive a stronger contraction and volume of blood pumped.

Thesse ultrasound images show the difference in chamber size of the hearts of a trained athlete and non-athlete. Notice Left ventricle wall thickness is increased in athlete v. non-athlete also to drive a stronger contraction and volume of blood pumped.

The two questions are:

  1. Should you be worried?
  2. Am I worried by this research?

The short answer is probably not.

I have never believed that doing Ironman triathlon is a healthy thing to do – for anyone.
Every part of your body is going to suffer and be damaged as a result. The essence is, however, that the more you train, the better prepared you will be come race day to mitigate the ensuing emotional and physical damage. Research now suggests that this may not be the case. I will be interested to see if further research can identify risk factors for cardiac damage and in turn reveal potential damage limitators.

What I would take away from this research is that allowing recovery time is pertinent to everyone. Being in tune with your body and to coin a phrase ‘listen to your heart’. Look after yourself outside your training. The stresses of family life, work life and sleep deprivation all affect your heart. For most people no doubt the beneficial effects of regular exercise will out-way any risks of heart damage. However, if you are finding yourself on your 4th Ironman or ultra of the year (non-pro’s) its time to ask yourself some serious questions.

If you have a family history of heart disease, high cholesterol (no matter how strict your diet) or any sudden death in the extended family – then get a cardiac screening. Any reasonable GP can refer you for a trace of your heart (ECG) and even just getting his stethoscope to your chest may reveal any cause for concern.

This is not the time to be writing about exactly what your body goes through during an Ironman or an ultra-marathon, but suffice to say it is not healthy and will invariably be worse for some than others – due to factors as diverse as nutrition and genetics.
What is healthy, however, is the community of the sport and the drive it awakens in people to exercise regularly, to eat better, to drink less etc.

Most of us are on that start line – aware of the risks. But if we were to spend our lives pondering what could be – we’d never experience those magical moments that ultimate drive and define us.

In the end, it’s not going to matter how many breaths you took, but how many moments took your breath away

– shing xiong

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