Health & Wellness

Endurance exercise 'interferes with heart rhythm'

BBC News
Tue, 13 May 2014 08:34 UTC

Athletes beware - endurance training may make it more likely that you will need a pacemaker, scientists believe.

A British Heart Foundation team found exercise in mice triggers molecular changes in the part of the heart that generates its natural beating rhythm.

This may explain why elite athletes have low resting heart rates and a higher risk heart rhythm disturbances, they told Nature Communications.

However, the benefits of exercising still outweigh any risks, experts say.

Super-fit

Endurance athletes are generally very fit.

Yet, paradoxically, they are more likely to have heart rhythm disturbances, known as arrhythmias, especially as they get older - although the risk is still small.

Experts have suspected that this is because long-term training for extreme endurance events such as marathons and triathlons slows the heartbeat down.

While normal adults have resting heart rates between 60-100 beats per minute, hearts of endurance athletes can beat only 30 times per minute or even less at night time when there can be long pauses between heart beats.

Cyclists Sir Chris Hoy and Miguel Indurain reportedly had resting heart rates of 30 and 28 beats per minute.

The heart rate is set by the heart's pacemaker, which is controlled by the nervous system.

And so it was assumed that the low heart rate of athletes was a result of the autonomic nervous system going into overdrive.

But Prof Mark Boyett and colleagues, from the University of Manchester, say their new research suggests this is not the case.

Instead, the heart's in-built pacemaker changes in response to training.

By studying mice, they found that endurance exercise led to a decrease in an important pacemaker protein, known as HCN4, and that this was responsible for the low heart rate.

Prof Boyett said: "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."

But he added: "Although endurance exercise training can have harmful effects on the heart, it is more than outweighed by the beneficial effects."

Prof 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."

Comment: Do the benefits of extensive aerobic training truly outweigh any risks? As Nora Gedgaudas, author of Primal Body Primal Mind, writes:

I hardly see marathon running and prolonged strenuous exercise as healthy pastimes. In fact, I see them as far more "health challenging" than health promoting. There is, in fact, what is treated in the press as a paradoxical phenomenon where cases of actual heart failure among distance runners (and other distance athletes) is becoming increasingly common. Remember, too, that Jim Fixx - the father of the modern running movement - also dropped dead from heart failure. Not all distance runners do damage to their hearts - but that doesn't mean that marathon running should be considered the path to optimal heart health. The following is borrowed from a publication called Peak Performance Newsletter (one of many, many sources commenting on this phenomenon):
... Taken together, these results suggested that younger, fitter athletes, who put more stress on their hearts (via greater training volume and higher racing intensities), were the ones most likely to incur myocardial damage.

On the other hand, anaerobic (short, intense bursts of exertion) training or resistance training seems to be beneficial. For more information, see: Resistance Training: Why You Should Lift and Lower Heavy Things

Reader Comments

Beauzy · 2014-05-14T16:52:13Z

No kidding

All the running,endurance freaks I've ever known always look bloody sick,pale,skinny,and joint issues later in life.
Whatever floats your boat I suppose.
They can have it.

lilies · 2014-05-15T02:42:53Z

Safety Buffer

If you pursue athletic activities your joints will gradually be destroyed over the years until you find hard & painful to move. This is your Safety Buffer: stretch of years during your joints remain usable.

Injuries exacerbate this effect, athletes becoming cripples, neck, elbow, knee, hips, shoulders, disks destroyed.

If you didn't do any sport in your life and begin exercise in your later years, you are maneuvering in your Safety Buffer (my term).

Gurdjieff warned about (professional modern) sport, possibly because of chronic energy depletion causing organ failure and further inhibits development of essence: the moving center even more frequently is robbing energy from intellectual and emotional centers.

Time is a major factor:
Not many scientists are known as professional athletes, who are exhausting themselves daily spending lot of time training and are able to achieve in their field creating famous papers, eh?
[Link]
Think about the exhaustion of the brain depleted of calories and minerals needing days of extended sleep & re-mineralizing caused by strenuous sport activities, that is too much for your body. A day after you just want to sleep, not really fit for work.