Can endurance sports training damage the heart? Scientists can’t agree
New German study of elite master athletes finds no evidence of damage, contradicting 2012 results from Belgian research
Is endurance training bad for you?
The short answer: maybe not. The facts: increasing health consciousness among Hongkongers is one of the main reasons for the rising popularity of endurance sports such as marathons, ultratrails and ironman triathlons in this city. However, the potential hazards that such endurance endeavours pose to the heart is a long-debated subject in the medical and sports communities.
The latest word on this topic is from sports medicine physicians in Germany who say they’ve found no evidence of heart damage from long-term endurance training in a study of elite master athletes. The scientists from Saarland University in Saarbrucken tested the conclusions of a 2012 study by Belgium’s University Hospital Leuven that found repeated bouts of intensive endurance exercise at the elite level may result in the pathological enlargement of the heart’s right ventricle, which is associated with potential health hazards, including sudden cardiac death.
The Belgian study established a link between extreme endurance exercise training and the acute enlargement and functional impairment of the right ventricle immediately after exercise. More precisely, they observed enlargement and reduced functionality of the right ventricle in athletes who had taken part in several hours of competitive endurance sport. This condition is known as exercise-induced arrhythmogenic right ventricular cardiomyopathy (ARVC).
The new German study published in the journal Circulation refutes this – which is good news for endurance junkies. Led by cardiologist and sports medicine physician Dr Jürgen Scharhag and Dr Philipp Bohm, the Saarbrücken scientists examined 33 elite master athletes of an average age of 47 years and compared them to a control group of 33 men who were similar in terms of age, size and weight but who had not done any kind of endurance exercise.
The group of athletes, which included former Olympians as well as previous ironman participants and champions, have been training at an elite level for around 30 years and still train for an average of about 17 hours a week. The athletes’ hearts, as expected, were significantly larger and stronger than those of members of the control group.
“But we found no evidence of lasting damage, pathological enlargement or functional impairment of either the right or left ventricle in athletes who had been doing long-term intensive elite-level endurance exercise,” explains Bohm, who is now working at the Cardiology Centre at the University Hospital Zürich.
It’s unlikely, however, the debate over the link between endurance training and heart damage will end with this German study – especially with regular media reports of sudden cardiac death in endurance athletes.
Just a few weeks ago, it was reported that Dutch professional cyclist Gijs Verdick had died in hospital a week after a double heart attack during a race.
In March 2012, Micah True, a legendary ultra-marathoner also known as Caballo Blanco who was made famous by the bestseller Born to Run, died suddenly while on a routine 19 kilometre training run. An autopsy showed his heart was enlarged and scarred; he died of a lethal arrhythmia (irregularity of the heart rhythm). Although speculative, the pathologic changes in the heart of this 58-year-old may have been manifestations of “Phidippides cardiomyopathy”, a condition caused by chronic excessive endurance exercise.
“Physical exercise, though not a drug, possesses many traits of a powerful pharmacologic agent. A routine of daily physical activity can be highly effective for prevention and treatment of many diseases, including coronary heart disease, hypertension, heart failure and obesity,” says Dr James H. O’Keefe, lead author of a report published in the June 2012 issue of Mayo Clinic Proceedings.
“However, as with any pharmacologic agent, a safe upper dose limit potentially exists, beyond which the adverse effects of physical exercise, such as musculoskeletal trauma and cardiovascular stress, may outweigh its benefits.”
O’Keefe and colleagues at Saint Luke’s Hospital in Missouri reviewed the literature and presented emerging data suggesting that extreme endurance training can cause transient structural cardiovascular changes and elevations of cardiac biomarkers, all of which return to normal within one week. For some individuals, over months and years of repetitive injury, this process can lead to the development of patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, and an increased susceptibility to atrial and ventricular arrhythmias.
O’Keefe points out that many people don’t understand that “the lion’s share of health benefits accrue at a relatively modest level”. He says: “Extreme exercise is not really conducive to great cardiovascular health. Beyond 30-60 minutes per day, you reach a point of diminishing returns.”