|MadSci Network: General Biology|
Hello Jeremy, Thank you for your interesting question about heart sounds. I have found a web site that may interest you in listening to heart sounds, it can be found at http://www.wilkes.med.ucla.edu/inex.htm. This site includes normal heart sounds and examples of many different types of heart murmers. However it does not give any differences between the heart sounds of the trained athlete and the sedentary. I have been unable to find anywhere that mentions differences between the heart sounds of these different groups of people and there may be no difference between the two. The heart sounds are made as the valves in the heart close during the different phases of the cardiac contraction cycle. The first heart sound occurs as the ventricles of the heart contract, which closes the mitral and tricuspid valves, shutting off the blood flow to the atria. The second heart sound occurs as the ventricles start to relax and the aortic and pulmonary valves close stopping regurgitation of ejected blood back into the heart. If the valves are working correctly then these sounds should sound the same in both the athlete and the untrained individual. There are two further heart sounds, which are much more difficult to detect, the third heart sound occurs shortly after the second and is associated with the start of the filling of the ventricles and the fourth heart sound is from the contraction of the atria just before the first heart sound. When sounds are heard in addition to the normal heart sounds these are called heart murmers and are an indication of a disease state. Therefore differences in heart sounds are used to diagnose disease states rather than to distinguish between athletes and untrained individuals. To distinguish between bradycardia and the slow heart rate of a trained athlete you could measure the heart rate during exercise such as on a treadmill. The trained athlete should have a very high exercise tolerance level and be able to achieve normal elevated heart rates. (Estimated maximum heart rate = 220 - age. A trained athlete should be able to maintain exercise level at 70-80% of this maximum heart rate). However if the individual has bradycardia then they will be less able to perform in the exercise and may not be able to achieve 70% of the estimated maximum heart rate. I hope that this answers your question and thank you for your interest. Regards Dr. David Burton
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