restricted access 25. Trained Athletes
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PART IV Iatrogenic Aspects of Sport Cardiology and Lifestyle Modifications Giovanni Campanile John B. Kostis Ihor B. Gussak INTRODUCTION Regular physical exercise is a therapeutic lifestyle intervention for achieving optimal cardiovascular (CV) and overall health, as several international guidelines have emphasized (1–4). Physical activity triggers beneficial physiological effects on the entire body (5) and can be a valuable tool for preventing and treating chronic diseases such as hypertension, coronary heart disease, heart failure, obesity, diabetes, and metabolic syndrome. Furthermore, regularly monitored physical activity represents the cornerstone of cardiological rehabilitative intervention following myo­ car­ dial infarction or cardiac surgery (6) ­ because of its beneficial effects on coronary flow reserve, myo­ car­ dial capillary density, endothelial function, arterial blood pressure, heart rate, and lipid profile (see ­ Table 25-1). A safe upper-­ limit dose, beyond which the adverse effects of physical exercise may outweigh its benefits, potentially exists. An observational study has shown that runners covering distances of 1 to 20 miles per week, at a speed of six to seven miles per hour and a frequency of two to five days per week, may display a 19% lower risk of all-­ cause mortality compared with a nonrunner control group. However, physical activity beyond ­ these limits is associated with a worse survival rate (7). Highly trained athletes performing daily strenuous exercise accumulate workloads fivefold to tenfold greater than the ones associated with standard exercise training and in the pro­ cess expose themselves to high risk (8). This chapter examines the physiological changes associated with regular physical exercise as well as with endurance training in professional athletes. It looks at (a) CV adaptations to exercise, (b) prob­ lems of sports-­ induced cardiac arrhythmias and sudden death, and (c) electrolyte and fluid alterations associated with abnormally intense physical activity. Also discussed are the effects on the CV system of dietary interventions and doping procedures for potentiating physical endurance. The last part of the chapter focuses on the ­ legal aspects related to the medical assessment of patients with CV disease in relation to their eligibility for a physical activity program . It also shows the criteria issued by the International Olympic Committee to determine eligibility or disqualification of competitive athletes with CV diseases. CARDIOVASCULAR ADAPTATIONS Space restrictions do not allow for a discussion of the CV impact of ­ every sports activity. However, ­ because the CV system of a trained athlete differs structurally and functionally CHAPTER 25 Trained Athletes Gino Seravalle, Guido Grassi, and Giuseppe Mancia 310 / Trained Athletes training and strength training. Most athletic activities combine the two, and training-­ related physiological alterations represent a complex set of central and peripheral mechanisms operating at structural, metabolic, and regulatory (functional ) levels. Cardiac Remodeling In about 50% of athletes, physical training triggers the development of cardiac remodeling (9–14). This consists of alterations in ventricular chamber dimensions, including increased left and right ventricular and left atrial cavity size (and volume), associated with normal systolic and diastolic function. Left ventricular remodeling with changes in mass is a dynamic pro­ cess in nature and may develop and pro­ gress relatively rapidly or more gradually ­ after the initiation of physical conditioning (9, 15). Changes to the heart have been shown repeatedly to be reversed by the cessation of training (16). A multivariate analy­ sis of the large database assembled at the Institute of Sports Medicine and Science in Rome, Italy, has revealed that 75% of variability in left ventricular cavity size is attributable to non-­ genetic ­ factors, such as gender, age, body size, and type of sport (17). The remaining 25% of variability is dependent on unexplained ­ factors, possibly gene related. Indeed, an association between left ventricular remodeling and the angiotensin-­ converting enzyme gene I/D and/or angiotensinogen polymorphism (AGT M/T) has been found (17, 18). Exercise-­ induced cardiac remodeling also affects the right ventricle; and enlargement of this cardiac chamber has been shown to parallel the one affecting the left ventricle, a finding that supports the concept of balanced biventricular enlargement (12). Studies performed in both animal and­ human species have demonstrated that, ­ until cardiac structural dimensions are not altered, physical activity is associated with an inhibition of sympathetic drive (19), suggesting its usefulness as a nonpharmacological therapeutic intervention in several pathophysiological conditions. It has also been shown that volume-­ sensitive receptors located in the cardiac walls and in the pulmonary vascular bed (the cardiopulmonary receptors), with their power­ ful influence on sympathetic vasoconstrictor tone and renin release from the kidneys, are functionally impaired in the from...