Exercise is good for the heart… but is there a limit? | Q&A Follow-up

A big thanks to all the commenters that showed interest in yesterday’s article Exercise is good for the heart, but is there a limit? My motivation for posting it was that I can talk at conferences and to colleagues all I like but the research is meant to be about athletes.  It is not always easy to translate science into the ‘common press’ and I apologise for the simplicity of some of the discussion.  I am really pleased to see the interest that it has generated.  Don’t take my word as gospel.I have a favourite saying: “the only person who is wrong is the person who is sure that s/he is right”.  I have enjoyed reading the discussion.  To me that is motivation to write some more.

I will not always have time to respond to all comments and I would rather try to summarise some of the comments into discussion points.  I hope that you find this of interest.

On the issue of drugs…

“The other unknown in some of these unexpected deaths of apparently fit, healthy young or young-ish athletes might be the drugs that they had taken at some stage in their careers, surely?”

And, from Tommy_P explaining his hospital treatment after the doctors found out he was a cyclist:

“…It was suspected that I had structural heart issues caused by doping. Apparently a very common issue for us bike riders and one that the hospital specialised in. I was asked which drugs I was taking”

This is a big issue, obviously.  Cycling Tips recently did a great job covering the doping conference in Geelong and it is clear that performance enhancing drug use is all too common in cycling (and probably other sports to a similar degree if they looked as hard).  Some drugs are clearly implicated as a health risk whilst some doctors have actually suggested that drugs are necessary to minimise the risk to athletes in arduous cycling tours (a view that I do not share at all).  Lastly, whilst drugs may not have been eliminated from sport, WADA and the UCI can take some credit from reducing drug use from ‘horse doses’ to micro-dosing – this surely must be safer from a health view point.

In terms of the effects of drugs and to what extent we can blame drugs for heart events, the simple answer is that we do not know!  My one plea to everyone interested in this is please do not attribute everything that happens to drugs.  This is beautifully illustrated by Tommy_P above and I have heard Emma Carney describe her first time in Hospital after a cardiac arrest where she says that she was asked what she was taking by every doctor she saw.  I recently spoke to a colleague about a young cyclist who tragically died and was told “let’s just wait for the toxicology” – the toxicology and autopsy did not reveal a cause.  Finally, following the death of Ryan Shay (US marathoner), Frederiek Nolf (Belgian cyclist), Steve Larsen (US cyclist/ triathlete) and the recent cardiac arrest of  a the chat sites were full of accusations of drug use.  Sometimes it seems that the default position is that death in an elite athlete is due to drugs until proven otherwise.  I believe that this is completely unacceptable.  Firstly, it is SO unfair on the athlete and family and, secondly, it stops us thinking about and investigating the real cause.  Please do not conclude that I am condoning drug use or that I am ignoring an important issue.  However, please do not be like Tommy’s doctors and clutch at the easiest answer rather than considering all possibilities.

On the issue of illness…

“I’m of the view that heart scarring probably occurs when the athlete trains when sick (ie. with a respiratory complaint such as bronchitis). Unknowingly athletes could be doing some real long term damage, when it’s a lot safer to sit out a session.”

“I thought that Ryan Shay’s death was Sudden Cardiac Death due to heart arrhythmia caused by scar tissue that was as a result of a virus.”

Thank you to these astute readers, it was an omission not to discuss this in my article.  Before suggesting that exercise can cause scarring of the heart, we need to think about conditions that are PROVEN to cause scarring of the heart.  The most common of these (especially in people aged >35 years) is a heart attack, sometimes these even go unrecognised.  Probably the second most common is a condition called ‘myocarditis’.  This is when the heart becomes infected and inflamed as part of an illness – usually a virus like the flu or a gastro virus.  It is possible that this may be severe enough to cause permanent heart damage but yet the person does not feel too unwell at the time.  It is also possible that athletes are at greater risk of this because there is some evidence that exercise can compound the effects of ‘myocarditis’ and athletes will often train through anything.

To complicate things, however, if you exercise rats intensely you can cause myocarditis even without illness.  Chen and colleagues (Chen, Serfass et al. 2000) made rats swim for their lives for 3-5 hours with weights on their tales (yes it did get ethics approval) and demonstrated the same changes that we would see with viral myocarditis.  This study does not provide all the answers by any means (rats are very different to humans) but it does provide food for thought.

People will have assumed that Ryan Shay’s heart scars were due to a past viral infection and this may be true.  However, there is absolutely no way of knowing.  It is probably most likely and please don’t interpret my article to suggest that exercise causes heart scar but rather that it is POSSIBLE that exercise MAY cause heart scar.  As I suggested, it may even be better that researchers like myself forget the whole issue because it can damage the reputation of sport.  This is something that I would hate to do as those of you who know me will be aware.  However, from a scientific viewpoint and for the Emma Carney, Greg Welch’s etc who are left asking why, I think that we need to try and find out.

On the issue of causes of sudden cardiac death….

“What about cases like Antonio Puerta?”

Sudden cardiac death (SCD) in athletes is very rare, somewhere between 1:100,000 and 1:250,000 The cause can be ascertained in the majority (unfortunately often in  retrospect).  This was the case for Antonio Puerta.  I will write a post on the causes of SCD at a later stage and will avoid making it too medical.  Screening tests have been proposed to minimise athletes’ risks although they are controversial.  A complicated topic but I will have a crack.

On the issue of symptoms…

“This is a timely post. I have ridden seriously for around four years, and one day after a Sunday bunch ride while I was riding solo, without any warning, I suddenly blacked out and crashed. I have been through a battery of heart-related tests (MRIs, CT scans, EPS, stress tests) and so far nothing has come up. I am getting a loop recorder inserted under my skin (think HRM) that can record for up to three years to detect arthymias.”

It is not appropriate for my blog to turn into a medical on-line consultation service because good medicine cannot be performed remotely.  This was not the intent of this person’s post and I really appreciate the opportunity to make an important point.  I spend 95% of my sports cardiology consultations reassuring athletes.  Most often athletes have been referred following a test which is ‘abnormal’ but completely normal for an athlete – an enlarged heart for example.  I enjoy telling people that they can get back on their bike without a single concern.

However, there are some symptoms that SHOULD NOT BE IGNORED.  Passing out whilst exercising is one of them and something that we take very seriously.  It may be that you are fine but a potentially serious cause really must be excluded.  It sounds like you are being managed very well and I would agree entirely with the tests and advice that you have been given.

The reason that I bring this up (and I really hope that I am not causing unnecessary concern) is that occasionally we see athletes who had a serious symptom but ignored it thinking that exercise made them bullet proof.  Exercise definitely makes you healthier but there are no 100% certainties so please don’t ignore symptoms that worry you.

In this case, well done for seeking and getting the right advice and chances are that you will be inconvenienced a lot and nothing will come of it.  I promise that this is better than the alternative.

Final word…

“Interesting but I’m not sure I agree. I was born with a heart defect that has resulted in 3 heart surgeries so far in my life. I see my cardiologist every year for an annual check up and they told me I could ride as hard as I want and there is nothing I could do on a bike that would hurt my heart or expedite another surgery.

So does that mean that we just don’t know enough about exercise induced scarring or does my cardiologist think I’ll never push myself hard enough to hurt myself?”

A great point and shows me that I misplaced the emphasis in my article.  I agree with your specialist entirely.  There is absolutely no evidence that proves that high level exercise is not safe.  I do not recommend that any healthy person avoids exercise and there should be no restrictions.  I intended to point out in the article that there are some small unanswered questions.  The relevance of these in the ‘here and now’ is that I would recommend giving thought to your heart whilst training.  By all means train and train hard.  But, remember that just as running 50km a day can cause stress fractures, doing a 100km time trial on the bike every day may not be helpful.  It does not help you improve and (maybe) it is too much for the heart.  Sensible training (even at the highest levels) is good for the heart, I agree.

Oh, and…..

Whilst we’ve got the heart expert here, a quick question. Why is my max HR for cycling so much lower than running? I max out at 205 whilst running but have only ever hit 195 whilst cycling? And don’t just say “ride harder”!”

This is normal, although varies a bit between people.  It is all to do with posture and the fact that blood returns to the heart in greater volumes (greater venous return) when you are lying flat vs upright.  Max HR is lower when swimming than running and cycling sits in between.  You won’t be able to “just go harder” that’s all you’ve got my friend.

REFERENCES

Chen, Y., R. C. Serfass, et al. (2000). “Cardiac troponin T alterations in myocardium and serum of rats after stressful, prolonged intense exercise.” J Appl Physiol 88(5): 1749-1755.