EVALUATION OF MAXIMAL LEFT-VENTRICULAR PERFORMANCE IN ELITE BICYCLISTS

Aim of this work was to study in a group of elite cyclists, undergoing laboratory testing, the trend of the left ventricular systolic and di astolic function, echocardiographically and Doppler derived, simultane ously with the evaluation of ergospirometric parameters during maximal exercise. We studied a group of male subjects, consisting of 10 profe ssional elite bicyclists (mean age: 25.1 +/- 3.2 years) during competi tive activity (VO2/kg max: 78.5 +/- 7.7 ml . kg . min(-1)). The maxima l exercise test, conducted with Wind Loaded Simulator for optimisation of ergometric capacity, showed, at the end of exercise, at a speed of 49.2 +/- 2.4 km/h, a VO(2)max of 5365 +/- 543.4 ml/min, with a calcul ated Cardiac Output (CO) of 19.3 +/- 3.7 l/min. A linear regression re lationship was found between VO(2)max and CO (r = 0.84; p < 0.0001) as well as between VO(2)max and maximal reached speed (r = 0.97; p < 0.0 001), During the aerobic period a slight but significant increase in E nd Diastolic Volume (EDV) was observed due to the greater venous retur n from exercising muscles. At stop, in anaerobic period, the EDV remai ned substantially constant. Ejection Fraction (EF) also increased duri ng exercise through the Frank-Starling mechanism activation. The sligh t, but not significant, increase in EF at stop level may be explained by an activation of homeometric control of contractility with a sympat hetic modulation on myocardial fibres, The early diastolic mitral flow velocity (Peak E) increased significantly during exercise, in compari son with basal upright values. The left ventricular diastolic complian ce observed in athletes permits a good left ventricular filling, parti cularly in early diastolic phase; this allows an excellent left ventri cular systolic performance. Based on echocardiography and pulsed Doppl er measurements, calculated cardiac output is underestimated by approx imately 20%.