Cardiac Output of 10- to 11-year-old Children during Exercise under Different Ambient Temperatures

Abstract

Cardiac output (Q) was measured by the CO2 rebreathing method in 10 boys and 9 girls. They performed cycle ergometer exercises at 300 and 450kgm/min in ambient temperatures kept at 20, 30, and 40*. For a given oxygen uptake (Vo2), stroke volume (SV) tended to be reduced and heart rate (HR) increased in a 40 * environment in both sexes. Accordingly, Q at 40* was maintained at a level similar to that in cooler conditions. A lower HR and a higher SV at a given Vo2 were shown in boys than in girls. The regression equation of Q on Vo2 in boys was found to be similar to that in girls. The values of Q in relation to Vo2 in the children studied were compared with those in children and adults who had been previously studied. The children in the present study were found to have a Q response that represented roughly an average of those of children described in the literature cited, and to have a lower Q as compared with most adults.

Cardiovascular responses to submaximal treadmill running in 11 to 13 year olds

“…The available data indicate that the child's cardiovascular response to exercise is not fundamentally different from that of an adult but the relative contributions of Q, SV, HR and a-vO 2 diff : to V Ç O 2 appear to vary with age (2)(3)(4). Q Ç at a given submaximal exercise intensity has been reported to be higher (7), lower (5) or the same (8) in girls compared to boys. This is attributed to a lower SV, which is only partly compensated for by a higher HR.…”

Cardiovascular responses to submaximal treadmill running in 11 to 13 year olds

“…Even when comparing younger and older children, SV is lower in the younger children (3). Q Ç at a given submaximal exercise intensity has been reported to be higher (7), lower (5) or the same (8) in girls compared to boys. Although boys' higher SV and lower HR at a given submaximal V Ç O 2 or exercise intensity than those of girls are consistent ndings (5,9), sex differences have not always been demonstrated to be statistically signi cant (4).…”