Endurance Athletes and Heart Arrhythmias: Exercise Overdose?

A new book, The Haywire Heart, examines the symptoms, prevention, and treatment of a condition dubbed “athlete’s heart.”

Haywire Heart

It’s a paradox going against everything we’ve been told: When pushed to extremes over long periods, too much exercise can actually be dangerous to your health.

Numerous masters endurance athletes around the globe are suffering surprising heart arrhythmias, or abnormal heart rhythms, that can curtail or end their sports participation — and even result in sudden death.

We’re learning the hard way that more isn’t always better.

Several prominent athletes have been sidelined with arrhythmias in recent years, including Basque Tour de France contender Haimar Zubeldia and Norwegian Olympic cross-country skier Marit Bjørgen. Legendary ultramarathoner Micah True, who died at 58 in 2012, and former NFL star defensive end Reggie White, who died at 43 in 2004, both suffered fatal arrhythmias. And prominent bicycle racer Lennard Zinn — who quit racing in 2013 due to an arrhythmia — says, “Everyone I knew could name six guys with arrhythmias. I started to see it as this defining problem among people like me.”

Arrhythmias are not the same as overtraining, it’s important to note. Instead, they are electrical misfirings in the heart’s lower ventricles that cause extra heartbeats — sometimes up to 220 heartbeats a minute or more. “Athlete’s heart” can manifest as atrial fibrillations (AF or AFib), premature ventricular contractions (PVCs), and other heart irregularities.

The Haywire Heart: How Too Much Exercise Can Kill You, and What You Can Do to Protect Your Heart is the first book to examine the issue of abnormal heart arrhythmias in athletes — and what can be done to prevent or treat them.

The book is written by Zinn, VeloNews managing editor Chris Case, and John Mandrola, MD, a cardiac electrophysiologist as well as endurance runner and cyclist. It grew out of a groundbreaking article authored by Case with participation from both Zinn and Mandrola, “Cycling to Extremes,” which brought national attention to the issue.

Nine case studies of athletes with arrhythmias are presented, along with explanations of the medical science behind the condition. The science is well explained — and backed up by color diagrams and a handy glossary — so any reader can understand the issues.

Ultimately, though, this is a hopeful book on a deadly subject. The authors look at prevention, protection, early detection, and the variety of treatments being pioneered, including magnesium and other supplements, training and rest modifications, effective medications, and cardiac-ablation procedures.

For more on arrhythmias, see “Out of Rhythm.”

is an Experience Life deputy editor.

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