Sixteen highly trained masters endurance athletes, 59 +/- 6 yr, were compared with 16 young athletes, with whom they were matched on the basis of their training regimens, and with 18 untrained middle-aged men. On echocardiographic evaluation, both groups of athletes had a significantly greater left ventricular volume and mass than the untrained men; their were no significant differences in percent fiber shortening or velocity of fiber shortening among the three groups. Maximum O2 uptake (VO2max) averaged 15% less in the masters than in the young athletes (58.7 vs. 69 ml.kg-1.min-1). When expressed in terms of lean body mass to correct for differences in body fat content, VO2max of the masters athletes was about 60% higher than that of the middle-aged untrained men. Maximum heart rate was 14% lower in the masters athletes than in the young athletes (169 vs. 197 beats/min). The O2 pulse during maximum exercise (i.e., VO2max/heart rate at VO2max) was identical in the masters and young athletes. This finding suggests that the major factor responsible for the lower VO2max of the masters athletes, compared with the young athletes, is their slower heart rate.
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