[Left ventricular function in physically active and sedentary subjects during physical exercise]

An exercise program based on growing intensity loads (50 watts) was applied to 21 healthy, middle-aged subjects, who were divided into two groups: the physically actives and the sedentaries, according to their physical activity habits. During exercise, which was made on a treadmill, the following variables were measured: oxygen intake (VO2), cardiac frequency (FC), left ventricule ejection time (TEVI), maximal value of the first derivative of ear ensitogram (VMPDDO) and indirect arterial pressure. The active group reached higher values of power and VO2 (absolute and by pulse) and lower values of FC at under maximal works; these data therefore show their best cardiopulmonary capacity. The TEVI in the active group was higher at 150 watts because of the lower FC presented by its assigned subjects. For a maximal exercise condition, both groups had similar ejection times, but the reduction rate of actives' TEVI decreased, which in turn indicates the handling of higher stroke volumes. The VMPDDO relation with the successive increments of work loads was non linear. This index had higher values in the active group, for an exercise strength over 100 watts; this fact allowed the statistical differentiation of both groups. Accordingly, the VMPDDO did indicate the higher left ventricular function of the active subjects during exercise; this findings supports the notion which establishes that resistance training enhances myocardial contraction. In the recovery stage, the sedentaries' VMPDDO increases in a significant way, due to a possible mechanism as to hold stroke volume. In conclusion, the active subjects heart is a more efficient pump than the sedentaries', because of its capacity to handle under maximal exercise higher stroke volumes in the same ejection time, and thus in a higher ejection rate, with equal cardiac frequencies arterial pressures and myocardial oxygen intake.