Cardiovascular Adaptations to Prolonged Physical Effort

Abstract

Studies of the cardiovascular system were made among 26-mile marathon runners after at least five yearms of physical training. Studies made with the subjects at rest showed an electrocardiogram characterized by a vertical or semivertical electrocardiographic position of the heart in the chest, bradycardia, high voltage of the QRS complexes and high T and U waves. T waves which were low with respect to the height of the R waves were not encountered. Etiologically the heart was enlarged. Immediately after running 26 miles the transverse diameter of the heart was decreased considerably.

Electrocardiographic T wave changes with heavy exercise

“…The increase in the amplitude of the T wave resulting from ten weeks of strenuous cross-country training agreed with previous findings (Tuttle and Korns 1941, Wolf 1953, Beckner and Winsor 1954, Cureton 1958, Rose and Dunn 1964, and Pioletman and Miller 1968. The slight reduction in the T wave amplitude from T-2 to T-3 in supine rest and the very slight position gains in the remaining conditions are supported by the findings of Cureton (1958).…”

“…There was noted elevation of the T wave amplitude in this condition but no evidence of a bifid tendency. This data coincided with most studies in which effort tests Had been employed (Beckner and Winsor 1954, Strandell 1963, Rose, et al 1966). …”

“…Positive changes in the electrocardiographic T wave accompanying exercise are well established (Tuttle andKorns 1941 andBeckner andWinsor 1954). Reduction in T wave amplitude or its inversion are considered pathological signs of coronary insufficiency (Seneback 1946).…”

Radioelectrocardiographic Changes during Strenuous Exercise in Normal Subjects

“…The following were considered as "probably abnormal": (1) isehemic ST-segment depression or T-wave inversion, appearing in a few cycles; (2) biphasie T waves; (3) appearance of U waves of high amplitude; and (4) appearance of a few premature beats as an isolated finding. Results…”

“…The P wave regained its normal amplitude within the first minute of rest in more than half of the cases in which it had been increased during the period of exercise. The ST-segment depression sh-en ons i't 'Citsc (riding a bic cloe att 2 ) n]} joi/)! 3 inl/ites) in, (a normal subject.…”