Athlete’s heart in kids: A word of caution

It has long been known that the heart responds to significant amounts of physical exercise by enlarging its silhouette on the chest X-ray.¹ The advent of echocardiographic techniques has allowed this finding to be further refined into the assessment of enlarged chamber dimensions, wall thickness and functional parameters. By and large it has been established that chronic endurance training of more than 5 hours per week causes widening of dimensions and induces secondary hypertrophy by Laplace’s law, while myocardial function remains normal both in systole and diastole, the latter being an important discriminatory tool from pathological structural cardiac changes.

What we still do not know for sure is whether the changes of the so-called athlete’s heart are fully reversible or if they are an important cofactor for developing cardiac disease when hypertension or other forms of strain on cardiac structures occur later in life.

If this were indeed the case it would seem wise not to let athlete’s heart develop at an excessive amount or at too early an age. It is this last point that has been investigated by a Norwegian group.² They report on 76 very young cross-country skiers (<13 years of age) who had been pursuing an intense training (7 hours per week) for a mean of 5 years. Changes in cardiac morphology and function were assessed using echocardiography and were compared with a group of matched controls with a usual physical activity pattern. Indeed the findings of developing athlete’s heart were very marked, with left ventricular diastolic enlargement of over 17%, which obviously was necessary to produce the observed increase in maximal oxygen consumption (VO_2max) of nearly 50%. Ventricular function as assessed by three-dimensional ejection fraction and also by such advanced echo tools as longitudinal and circumferential strain remained normal. In these kids the mean relative increase in left ventricular dimension, while still within normal limits, was substantially exceeding that observed in adults, whereas there was a much smaller increase in left ventricular mass,¹ in other words: kids’ hearts dilate more than they hypertrophy. Unfortunately, any comments on accompanying ECG changes are missing in the report.

It is also not possible to put the results into a broader perspective by comparing them to disease-related changes in this age group. It would seem that a differentiation from disease cannot be made by the amount of changes alone, as was attempted in adults.³

A longitudinal follow-up is very much needed to study the capacity of cardiac changes to regress after detraining. We simply do not know whether the changes of athlete’s heart in preadolescents alter their reaction to challenges on the heart occurring later in life.

Thus despite the relatively comforting finding of cardiac function remaining intact, I myself would be hesitating to recommend such an excessive training schedule to youngsters of my own family, even though an Olympic medal may therefore be out of reach.

Declaration of conflicting interests

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author received no financial support for the research, authorship, and/or publication of this article.

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