Cardiovascular responses during prolonged exercise at ventilatory threshold in boys and men

Purpose: The purpose of this: study was to examine the cardiovascular respo nses during prolonged exercise in boys and men at an intensity set relative to ventilatory threshold (VT). Methods: Eight boys (10-13 yr) and 10 men ( 18-25 yr) completed an orientation trial, a maximal exercise test, and a 40 -min submaximal exercise bout at an intensity equal to the (V)over dotO(2) at VT (similar to 64.5% (V)over dotO(2max)). Results: Hrart rate (HR) was h igher and stroke volume (SV) was lower in the boys compared with the men (P less than or equal to 0.05). From 10 to 40 min, HR significantly increased 9.5% and 13.6% and SV significantly decreased 8.8% and 11.6% in the boys a nd men, respectively. Despite the tendency for the changes in HR and SV to be greater in the men, the group-by-time interaction was not significant. C ardiac output was greater in the men (P less than or equal to 0.05) but rem ained constant over time (P > 0.05). In men, mean arterial blood pressure w as higher (P less than or equal to 0.05) and decreased 4.2% over rime. In b oys, mean arterial blood pressure remained constant, which resulted in a si gnificant group-by-time interaction. Total peripheral resistance (TPR) was significantly higher in the boys and remained constant over time (P > 0.05) . From 0 to 40 min, the decrease in plasma volume was significantly greater in the men (- 10.2%) than the boys (-5.7%) but was unrelated to the change s in SV in either group (P > 0.05). Conclusion: In conclusion, the cardiova scular responses during prolonged exercise are similar in boys and men, alt hough there is a tendency for the magnitude of cardiovascular drift to be g reater in the men.