A transient increase in left ventricular emptying has been reported in adults during the early recovery from submaximal upright exercise.
Purpose: To investigate whether this "overshoot" occurs also after maximal exercise, and whether it is an age-related phenomenon.
Methods: Ten healthy young men (mean age: 22.5 +/- 1.5 yr) and 17 healthy prepubertal boys (11.5 +/- 0.8 yr) performed an upright cycle test until exhaustion. Respiratory gas exchange, heart rate, left ventricular dimensions (two-dimensional echocardiography method) as well as blood pressures (manual sphygmomanometry) were assessed and systemic vascular resistances were calculated at rest, during the final minute of the test, and during a 10-min recovery period.
Results: An improvement of cardiac emptying, characterized by a decrease in left ventricular end-systolic diameter, was observed in adults only. Moreover, during the first minute of recovery, a larger decrease in heart rate -21.8 +/- 7.6% and -13.7 +/- 6.3 beat.min, respectively, in children and adults, P < 0.01) and a larger increase in systemic vascular resistance (+24.1 +/- 18.2% and +6.4 +/- 12.6%, P < 0.05) were observed in the boys rather than in the adults.
Conclusion: Our results suggest that a higher increase in cardiac afterload and a more prominent decrease in heart rate may be responsible in part for the absence of cardiac overshoot in children.