Cardiovascular responses to exercise in children.

The cardiovascular system of children responds to exercise differently than does that of an adult, although the mechanisms behind the differences are unclear. During dynamic exercise, it has been reported that heart rate (HR) response to the initiation of exercise is both faster and slower in children than adults. Furthermore, HR recovery has been reported to be faster in children. During submaximal steady state exercise, HR and total peripheral resistance are higher, while stroke volume [SV (ml)] and cardiac output [Q (L/min)] are lower in children at a given rate of work. At maximal exercise intensities HR is higher while SV and Q are lower in children than adults. Differences in cardiovascular responses to dynamic exercise between young boys and girls have also been reported. The majority of studies report that HR is lower and SV is higher in boys than girls at a given rate of work, although data to the contrary have been reported. These differences seem to be related to larger hearts in the boys. Further, the majority of the studies report that Q is similar in young boys and girls at a given rate of work. Few studies have reported differences between boys and girls at maximal intensities of exercise, and the results of those studies are inconsistent. Less is known about cardiovascular responses of children to static exercise compared with adults. A number of studies have reported that HR response to handgrip exercise is greater in children than adults, while others have reported no difference in this response. Even fewer studies have compared boys and girls in their cardiovascular response to static exercise and the results of these studies are also inconsistent. During prolonged exercise both children and adults exhibit cardiovascular drift (gradual increase in HR and decrease in SV). The direction and degree to which these changes differ between children and adults is unclear, with both greater and lesser responses being reported in children. Few studies have investigated differences in cardiovascular response to prolonged exercise between boys and girls. Those that have, report no difference between young boys and girls.