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Endurance cycling tied to lasting heart damage

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9:36pm, November 21, 2005
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From Dallas, Texas, at a meeting of the American Heart Association

People who compete in grueling long-distance bicycle races are in great physical shape. But a study now suggests that the endurance training they undergo could do long-term harm to their hearts.

Researchers in Switzerland located 62 Swiss bicyclers, all men, an average of 38 years after they had competed in the Tour de Suisse race. As a control group, the researchers examined 52 men whose chief exercise for much of their lives had been golf. The researchers took a blood sample from each man and checked for signs of heart trouble. Men in both groups had an average age in the mid-60s and had comparable body weights and blood pressures. Although the former cyclists were exercising slightly more, both groups had similar heart-pumping capacity.

The blood samples revealed that the former cyclists averaged more than twice as much b-type natriuretic peptide, a natural compound that can identify people at risk of heart failure. Eight of the cyclists, but only one of the golfers, had worrisome concentrations of peptide, says cardiologist Christine H. Attenhofer Jost of HerzGefässZentrum, a Zurich clinic.

Further tests revealed that the former cyclists' hearts had significantly larger left and right atria than did the golfers'. Increased size of these heart chambers could be a sign of permanent damage, Jost says. Enlarged atria are associated with heart-rhythm problems, but in this study, anyone with rhythm abnormalities had been excluded from the start.

The large atria didn't come as a complete surprise, Jost says. "We're seeing so many of these patients who were formerly professional athletes in endurance sports 20 and 40 years out." Some need pacemakers for heart-rhythm irregularities, she says.

People pursuing most sports, even strenuous ones, need not be concerned, she says. "This was the extreme end of the spectrum," she says. However, she cautions, "marathon runners will fall into the same category" as the elite bicyclists.

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