Physiological responses to treadmill exercise in females: adult-child differences.

Physiologic differences between children and adults during treadmill exercise have been defined principally utilizing male subjects. To determine whether these variations are valid in females, responses to treadmill testing to exhaustion in 18 premenarchal girls were compared with an equal number of young adult females (mean age 28.7 yr). Except at the lowest workload, the girls demonstrated significantly higher oxygen consumption and ventilation per body weight at maximal and submaximal speeds. Differences in submaximal running economy disappeared when VO2 was related to body surface area. The children exhibited a greater respiratory rate and lower tidal volume (per kilogram) at a given ventilation as well as inferior breathing efficiency (higher ventilatory equivalent for oxygen). The absolute ventilatory breakpoint was higher in the girls, but there was no significant difference in this parameter between the groups when expressed as percent VO2max. The heart rate at the ventilatory breakpoint was greater in the girls, however. These findings indicate that pre- and post-menarchal females exhibit similar differences in physiologic responses to treadmill running as previously observed in adult and child male subjects.