The heart adapts to exercise by getting bigger and stronger and, therefore, better at delivering blood to working muscles. An endurance athlete’s heart can be up to 50 percent bigger than a nonathlete’s heart.
In an endurance athlete the atria, the upper two “filling chambers” where blood arrives in the heart, are enlarged, as are the ventricles, the two lower chambers that pump blood to the rest of the body. The vessels that supply blood to muscles of the heart are able to expand more to allow more bloodflow during exercise even when there are some cholesterol deposits. This ability to dilate makes it easier for blood to get around any partial blockages.
How the heart of the endurance athlete differs…
The heart of an endurance athlete is more than likely to demonstrate changes in morphology, function and electrical activity. This may place some endurance athletes in the diagnostic ‘grey-zone’ and it is crucial that an accurate determination of physiology or pathology is made.
The endurance athlete’s heart is viewed as healthy, highly responsive to acute exercise and resistant to fatigue and damage. This pervasive view has been challenged by recent reports of an acute reduction in cardiac function and the release of cardiac biomarkers, which are highly specific for stress or damage, in response to acute bouts of (ultra)endurance exercise.
During (ultra)endurance exercise, the total cardiac work is considerable and the heart must also cope with an elevation in core temperature, increased levels of catecholamines, increased mechanical work & altered pH.
Prolonged exercise could impair intrinsic cardiac contractile function of the heart – ‘exercise-induced cardiac fatigue’.
The heart of the endurance athlete is placed under great stress during training and competition. Cardiac adaptation to exercise training encompasses morphological, functional and electrical changes that are referred to as the ‘athletic or athletes’ heart’.
Acute (ultra)endurance exercise bouts represent a significant stress to the heart and there is now substantive evidence of ‘cardiac fatigue’ associated with prolonged activity. It is likely that for the vast majority of endurance athletes, the stress of acute exercise will lead to healthy, physiological adaptation in the heart. For a very small minority, though, there is emerging evidence that endurance exercise may be part of a physiological cascade that clinicians must be aware of and respond appropriately too.
When it comes to the heart and exercise we know:
The endurance athlete will develop morphological, functional and electrical characteristics of the athletic heart and for a small minority this will place them in a diagnostic ‘grey-zone’.
Developing techniques, such as 3D and speckle-tracking echocardiography as well as cardiac magnetic resonance, that accurately assess cardiac structure and function at a global and regional level will likely impact upon any diagnostic dilemmas.
The cardiac work performed during endurance exercise can be profound to the point that ‘cardiac fatigue’ and biomarkers of cardiac damage have been reported in endurance athletes after acute exercise.
In the vast majority of endurance athletes, the chronic accumulation of acute exercise stress will produce a healthy, physiological adaptation. In a small number, endurance exercise may be implicated in various pathological cascades that are of relevance to the athlete and their medical support team.