Exercise for Cardiovascular Disease Prevention and Treatment From Molecular to Clinical, Part 1

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oxygen demand of tissues [ 2 ]. Strength training (or isometric exercise, such as

weightlifting, wrestling or throwing heavy objects) is an anaerobic exercise in

which the muscle fibers retain the initial length during the exercise but contract to

develop tension against the afterload increase. Moreover, it implies the improve-

ment of strength, anaerobic work and dimension of skeletal muscles. The improve-

ment of oxygen provision and of the cardiac output are not necessary during

isometric exercise, that determine a prevalent increase of the blood pressure, heart

rate and peripheral vascular resistance [ 2 ].

Long-term cardiovascular adaptation to endurance exercise produces increased

maximal oxygen uptake due to increased cardiac output and arteriovenous oxygen

difference, while strength exercise results in little or no increase in oxygen uptake

[ 3 ]. Thus, endurance exercise determines a predominant volume overload and

strength exercise a predominant pressure overload.

In this chapter, we describe separately the acute and chronic cardiac effects of

physical exercise on the left ventricle (LV), the right ventricle (RV), the left atrium

(LA), the right atrium (RA) and the aortic root (AoR). In the 1899 Henschen, by

using only the physical examination, discovered that cross-country skiers had larger

heart and concluded that the enlargement involved both the right than the left ven-

tricle [ 3 ]. Today various techniques are available, but most of data about the adapta-

tion of cardiac structures to the exercise derive from the color-Doppler

Echocardiography and from the new diagnostic technologies such as Doppler myo-

cardial imaging, two-dimensional speckle tracking echocardiography (STE) and

cardiac magnetic resonance which are able to anticipate some modifications before

they become evident to the standard echocardiography. The aim of the application

of all these techniques to the study oh athlete’s heart is not only to describe the

adaptation of the heart to the exercise, but also to differentiate this benign adaptation

from pathologic conditions such hypertrophic (HCM), dilated cardiomyopathy

(DCM) and arrhytmogenic right ventricular cardiomyopathy (ARVC).

Electrocardiography (ECG) is the first tool to examine the athletes, both the ath-

letes with symptoms suggestive of cardiac disease than for the asyntomatic athletes

in pre-partecipation screening. Adaptive ECG characterizes on healthy athletes tipi-

cally include sinus bradycardia, sinus arrhythmia, hearly repolarization pattern [ 4 ]

and increased QRS voltage [ 5 ]. Other signs as left bundle brunch block, repolariza-

tion abnormalities such as ST-segment depression or T wave inversion and patho-

logical Q waves are abnormal signs and are closely associated with underlining and

occult cardiomyopathy- in these cases further diagnostic evaluation are necessary in

order to make an accurate diagnosis. Between the normal and the pathological signs

there are some one that are collocated in the “grey zone”. One of these is the right

bundle branch block (RBBB), complete or incomplete. RBBB could be an early

manifestation of cardiomyopathies that involves the right heart, such as the

ARVC. But often it can be detectable in healthy athletes with a normal heart. It has

been demonstrated that the presence of RBBB and its duration correlates with the

biventricular enlargement and is associated with a reduced rest systolic function.

These two aspects are frequent in healthy endurance training athletes [ 6 ]. Complete

2 Acute and Chronic Response to Exercise in Athletes: The “Supernormal Heart”