EFFECT OF PROLONGED INACTIVITY ON AEROBIC FITNESS OF CHILDREN

Prolonged bed rest diminishes maximal aerobic power in adults, but no information is available regarding the physiologic responses to extend ed periods of inactivity in children. This study evaluated the impact of 9 weeks of bed rest on recovery peak VO2 in 5 children ages 7-11 ye ars (3 boys, 2 girls) treated for femoral fractures. Beginning 2 weeks after initial ambulation during convalescence, maximal treadmill test ing with measurement of gas exchange parameters was performed monthly for 4 months and again at 6 and 9 months. The difference between peak VO2 on the initial test and subsequent plateauing of peak VO2 on subse quent serial tests was considered indicative of alterations resulting from prolonged bed rest. Peak VO2 increased 13.3% to a plateau at 3 mo nths while maximal aerobic power did not change significantly in five healthy control subjects. Between tests 1 and 3 treadmill endurance ti me improved 98% in the subjects and 1% in controls. These findings sug gest (1) habitual activity in children accounts for approximately 13% of aerobic fitness levels, (2) following prolonged inactivity, aerobic fitness is regained by 3 months, and (3) improvements in performance far exceed those accounted for by changes in peak VO2 following extend ed bed rest in children.