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Athletic heart syndrome, (AHS) also known as athlete's heart,〔Graf Ch., e.a.: ''Fachlexikon Sportmedizin: Bewegung, Fitness und Ernährung von A-Z'', Deutscher Ärzteverlag, 2008, p. 209, ISBN 3-7691-1223-7, (here online )〕〔Reuter P.: ''Der grosse Reuter: Springer Universalwörterbuch Medizin, Pharmakologie und Zahnmedizin'', Birkhäuser Verlang, 2005, p. 1300, ISBN 3-540-25104-9, (here online )〕 athletic bradycardia or exercise-induced cardiomegaly is a non-pathological condition commonly seen in sports medicine, in which the human heart is enlarged, and the resting heart rate is lower than normal. Athlete's heart is common in athletes who routinely exercise more than an hour a day, and occurs primarily in endurance athletes, though it can occasionally arise in heavy weight trainers. The condition is generally considered benign, but may occasionally hide a serious medical condition, or may even be mistaken for one.〔Woolston, Chris. "Ills & Conditions – Athletic Heart Syndrome". CVS Caremark Health Information. 17 January 2007. http://healthresources.caremark.com/topic/ahs〕 Athlete's heart most often does not have any physical symptoms, although an indicator would be a consistently low resting heart rate. Athletes with AHS often do not realize they have the condition unless they undergo specific medical tests. This is because athlete's heart is a normal, physiological adaptation of the body to the stresses of physical conditioning and aerobic exercise. People diagnosed with athlete’s heart commonly display three signs that would usually indicate a heart condition when seen in a regular person: bradycardia, cardiomegaly, and cardiac hypertrophy. Bradycardia is a slower than normal heartbeat, at around 40–60 beats per minute. Cardiomegaly is the state of an enlarged heart, and cardiac hypertrophy the thickening of the muscular wall of the heart, specifically the left ventricle, which pumps oxygenated blood to the aorta. Especially during an intensive workout, more blood and oxygen is required to the peripheral tissues of the arms and legs in highly trained athletes' bodies. A larger heart results in higher cardiac output, which also allows it to beat more slowly, as more blood is pumped out with each beat.〔 Another sign of athlete's heart syndrome is an S3 gallop, which can be heard through a stethoscope. This sound can be heard as the diastolic pressure of the irregularly shaped heart creates a disordered blood flow. However, if an S4 gallop is heard, the patient should be given immediate attention. An S4 gallop is a stronger and louder sound created by the heart, if diseased in any way, and is typically a sign of a serious medical condition.〔Moses, S., (2008) Athletic Heart Syndrome. Family Practice Notebook.(here online ).〕 ==Cause== Athlete's heart is a result of dynamic physical activity such as (more than 5 hours a week) aerobic training, rather than static training such as weight lifting. During intensive prolonged endurance or strength training, the body signals the heart to pump more blood through the body to counteract the oxygen deficit building in the skeletal muscles. Enlargement of the heart is a natural physical adaptation of the body to deal with the high pressures and large amounts of blood that can affect the heart during these periods of time. Over time, the body will increase both the chamber size of the left ventricle, and the muscle mass and wall thickness of the heart.〔Lohr, John Thoman. (1999). ''Athletic Heart Syndrome''. Gale Encyclopedia of Medicine.〕 Cardiac output, the amount of blood that leaves the heart in a given time period (i.e. liters per minute), is proportional to both the chamber sizes of the heart and the rate at which the heart beats. With a larger left ventricle, the heart rate can decrease and still maintain a level of cardiac output necessary for the body. Therefore, it is very common for athletes with AHS to have lower resting heart rates than nonathletes.〔Heart Diseases". Cardiovalens.com Matters of the Heart. 22 April 2005. http://my.cardiovalens.com/articles/articledisplay.asp?articledetail_id=dhm_athlete&ar 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Athletic heart syndrome」の詳細全文を読む スポンサード リンク
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