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The Herald Sun newspaper in Melbourne published an article entitled “Exercise may cause heart attack” in reference to this study.
There have been numerous studies into whether extreme exercise is bad for the heart and at present there are no clear answers. What is clear is that the heart is the most important organ in the body - if it stops, you stop! Therefore, working out how much exercise is good for the heart is an extremely important issue. In this article I shall attempt to clarify the issues involving exercise and the heart and what we still need to find out.

What we do know -exercise is good for you!

1. Regular exercise reduces your risk of dying from a heart attack.
Exercise has been well established as a powerful way of reducing the chance of death from heart disease2,3. It has been clearly shown in very large studies that longer duration and greater intensity of regular exercise has a graded protective effect on the heart. Similarly, overall fitness shows the same graded effect. That is, the fitter you are, the less likely you are to have a heart attack.

One study of 45,000 men4 compared different  types of exercise. Running caused the greatest risk reduction with rowing, weight training and brisk walking also having positive effects.

2. Athletes have bigger hearts than non athletes

Analysis of multiple trials5 has clearly shown that and thicker muscle. This enables athletes to pump more blood with each beat. Therefore, at rest, the heart does not have to beat as quickly (Miguel Indurain's resting heart rate was 28!!) and during exercise the heart can pump more blood than in a non-athlete. So yes, you do have the heart the size of Phar Lap's!

3. Exercise reduces your blood pressure

This occurs even in people with normal blood pressure, but has an even greater effect in people with high
blood pressure (called hypertension)6. Hypertension is a strong risk factor which predisposes to heart attacks and strokes. So exercise is recommended as a lifestyle prescription in people with high blood pressure.

What we don’t know – Is extreme exercise bad for you?

As already explained, regular exercise is clearly a a good thing. Speculation is rife, but true answers are not yet available. To explain what all the fuss is about, I will first explain some of the tests.

– Cardiac troponin – this is one of the proteins found in heart muscle and is found nowhere else as that which occurs as a result of a heart attack, troponin is released and can be measured on a simple blood test. Normally there is no detectable troponin in the blood.

– Echocardiogram – this is our best test for determining how well the heart muscle is working. It is an ultrasound performed with a probe on the skin of the chest – it is completely safe and pain free. The heart is simply a muscle
pump which has an electric circuit which tells it when to pump. It requires oxygen and glucose both of which are supplied by the blood from  the coronary arteries. If there is a blockage of one of these arteries or inflammation of the
heart then the affected muscle stops pumping.
This shows up on the ultrasound as a section of muscle that is not moving. Using special techniques we can also determine whether the heart is relaxing properly and whether there is increased strain on the heart muscle.
In the study following the Hawaii Ironman Triathlon written by Rifai and co-workers, 23 athletes had troponins performed immediately before and  after the 1994 Hawaii Ironman Triathlon. 12 of these and athletes also had echocardiograms performed. Of these, two athletes had small rises in troponin and another four had extremely slight increases. The echocardiograms were abnormal in nine of the 12 athletes. They showed varying amounts of heart muscle that wasn't moving normally. Overall it was shown that the athlete's hearts were pumping 25% less effectively than before the race.
These are potentially concerning results. In simple terms, it is like two of the athletes had small heart attacks and a heart attack occurs, the area of affected muscle know whether there has been heart muscle death or whether the heart muscle is simply ‘stunned’ or fatigued from the intensity of the exercise and will recover completely.
We know that many of the muscles are severely damaged during an Ironman, but they soon recover completely or even ‘super-compensate’ to be stronger than before the race.

Does the heart do this?

Unfortunately there was no further testing done on the athletes in Rifai's study and we do not know whether the changes they saw recovered or persisted.
Clearly this is an extremely important question which needs to be resolved before claiming that ultra-endurance triathlons cause heart damage.
In an attempt to clarify this issue, our research group from St Vincents's Hospital in Melbourne performed a study on 16 participants in the 2000 Ironman Australia Triathlon which was recently published (7). We also used troponins and echocardiograms for testing. However rather than get results immediately after the race, we obtained results five days after the event. Our results showed a very slight trponin rise in one athlete and heart muscle weakness in another on the echocadiogram.
In both athletes the changes resolved within a further three weeks. That is, all athletes returned to normal after the race and we found NO evidence that Ironman distance triathlons cause damage to the heart.

The most obvious problem with our study is that we failed to find as many heart abnormalities in our testing after
the race than those seen after the Hawaiian event. We could therefore not say whether our athletes’ hearts were affected as much as those in Rifai’s study and recovered by the time we tested at five days or whether they never had any effects from the race.

It could be argued that it doesn’t really matter – either way, we showed that our 16 athletes had no detectable lasting adverse effects from the race. We do, however, think it is important to try and further clarify whether extreme exercise such as an Ironman triathlon does have adverse effects on the heart and whether the effects are reversible, as the popularity of these events is increasing and the cumulative effects of multiple events may not become apparent until years to come. To best clarify these issues, it would be ideal to test athletes immediately after the race and
then repeat the testing regularly to see what happens.
If we can demonstrate changes immediately after the race and then follow them until resolution, we will be able to better understand the effects of an Ironman event on the heart and provide a better insight into whether these changes are likely to be harmful. We are planning to do this study at the 2004 Ironman Australia in Forster.
Until these things are clarified the take home
message of all of this mumbo jumbo is that exercise is definitely good for your heart. Extreme exercise can cause detectable abnormalities in testing of the heart, but at present there is no evidence that this results in any long-term damage.

Dr Andre La Gerche MBBS, FRACP
Cardiologist, PhD student
St Vincent's Hospital Melbourne
www.svhm.org.au

References

1. Rifai N, Douglas PS, O’Toole M, Rimm E, Ginsburg GS.
Cardiac Troponin T and I, electrocardiographic wall
motion analyses, and ejection fractions in athletes
participating in the Hawaii Ironman Triathlon. Am J
Cardiol 1999; 83: 1085-89

2. Paffenbarger, RS Jr, Hyde, RT, Wing, AL, et al. The
association of changes in physical-activity level and
other lifestyle characteristics with mortality among
men. N Engl J Med 1993; 328:538.

3. Lee, IM, Sesso, HD, Paffenbarger, RS Jr. Physical activity
and coronary heart disease risk in men: does the
duration of exercise episodes predict risk?. Circulation
2000; 102:981.

4. Tanasescu, M, Leitzmann, MF, Rimm, EB, et al. Exercise
type and intensity in relation to coronary heart disease
in men. JAMA 2002; 288:1994.

5. Pluim BM, Zwinderman AH, van der Laarse A, van der Wall
EE. The athlete’s heart: a meta-analysis of cardiac
structure and function. Circulation 1999;100: 336-44

6. Shepherd, JT. Circulatory response to exercise in health.
Circulation 1987; 76(V1):V13. 38. Fagard, RH, Tipton, CM.
Physical activity, fitness, and hypertension. In: Physical
activity, fitness and health: international proceedings and
consensus statement, Bouchard, C, Shephard, RJ, Stephens,
T (Eds), Human Kinetics, Champaign 1994. p.633.

7. La Gerche A, Boyle A, Wilson AM, Prior DL. No evidence of
sustained myocardial injury following an Ironman
distance triathlon. Int J Sports Med. 2004 Jan;25(1):45-9

Acknowledgements
St Vincent’s Hospital Cardiac Investigation Unit would
like to thank the 16 athletes who volunteered their
time to participate in the study. We would also like
to thank the organisers of the Ironman Australia
triathlon for their assistance. Thanks to Dr Prior and
my colleagues at St Vincent’s CIU.