Athlete’s heart debate: ‘Too much’ exercise increases risk of heart problems, claims Manchester uni study

Those that fit into the bracket of being ‘super-fit’ face a greater risk of suffering from heart problems, according to new research from The University of Manchester.

The research claims athletes who are at the pinnacle of fitness are more likely to be diagnosed with abnormal heart rhythms once they reach an older age.

The University of Manchester study has also shed light on why heart arrhythmias are more common in elite sports stars.

Vigorous exercise can lead to a molecular change in the heart’s pacemaker, resulting in an increased risk of heart problems, the research claims.

Neil Thornton, 32, an Elite Performance Trainer from Sale, told MM: “Most people think that all exercise is good for the heart and in the most part they would be correct.

“However, athletes that push their bodies to the brink often suffer from serious health issues when they get older.

“One of the main problems that endurance athletes suffer from is often heart arrhythmia which is caused by vigorous training.

“It is great to see that research has uncovered one of the reasons why this happens so it can be prevented in the future.”

The research, which was funded by the British Heart Foundation, was carried out on rodents.

Experiments show that molecular changes in the heart’s pacemaker occur during exercise.

This means elderly athletes with a lifelong history of training and competing in endurance events like marathons, triathlons and iron man challenges can have heart rhythm disturbances.

Long-term training for these events can slow the heartbeat down, which increases the risk of arrhythmias.

The University of Manchester’s Dr Alicia D’Souza, the first author on the paper, said: “The heart rate is set by the heart’s pacemaker, but this is controlled by the nervous system.

“The ‘vagal’ nerves lower the heart rate and therefore it was assumed the low heart rate of athletes is the result of over activity of the vagal nerves, but our research shows this is not the case.

“Actually the heart’s pacemaker changes in response to training and in particular there is a decrease in an important pacemaker protein, known as HCN4, and this is responsible for the low heart rate.”

The average adult has a resting heart rate between 60-100 beats per minute, whereas endurance athlete’s heart rates can beat 30 times per minute or even lower when they are sleeping.

Cyclist and Olympic legend Sir Chris Hoy reportedly had a resting heart rate as low as 28 beats per minute when he was in peak physical condition.

Professor Mark Boyett, lead researcher on the study, added: “This is important because although normally a low resting heart rate of an athlete does not cause problems, elderly athletes with a lifelong training history are more likely to need an artificial electronic pacemaker fitted.

“Although endurance exercise training can have harmful effects on the heart, it is more than outweighed by the beneficial effects.”

Professor Jeremy Pearson, Associate Medical Director at the British Heart Foundation, said: “This study shows the heart’s electrical wiring changes in mice that exercise for long periods, and these changes in heart rhythm are sustained afterwards. 

“If the findings are reproduced in humans they could have implications for heart health in older athletes. But much more research is needed before we could draw that conclusion.”

The finding, reported in Nature Communications, overturns the commonly held belief that an increased activity of the autonomic nervous system causes this specific reaction to endurance training. 

Image courtesy of Martti_, with thanks.

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