CARDIOVASCULAR ADAPTATIONS IN 8-YEAR-OLD TO 12-YEAR-OLD BOYS FOLLOWING A 14-WEEK RUNNING PROGRAM

This study examined the effects of a 14-week running program on VO(2)m ax, as well as cardiac output (Q) and arterial-venous O-2 difference ( a-vO(2) dif) at submaximal intensities corresponding to 50 and 75% of vO(2)max. Thirteen boys (mean age 10.6 +/- 1.2 yrs) served as experime ntal subjects while 13 other boys of similar age (mean age 10.2 +/- 1. 2 yrs) served as controls. Mean VO(2)max in the runners increased 13%, from 44.2 +/- 7.0 to 49.9 +/- 6.3 ml . kg(-1) . min(-1). Posttraining VO2 during submaximal and maximal exercise was significantly (p < 0.0 5) greater in the runners than in the controls. Q and SV exhibited an increase of 10% at each intensity, but posttraining differences betwee n groups were not significant (p > 0.05). A-vO(2) dif increased by 8% at 50% of VO(2)max and by 6% at 75% of VO(2)max, and was significantly greater in the runners following training. These results indicate tha t increases in submaximal relative VO2 in children are mediated by inc reases in a-vO(2) dif and Q.