Hemodynamic, Hematological, and Hormonal Responses to Submaximal Exercise in Normobaric Hypoxia in Pubescent Girls

The aim of this study was to investigate hemodynamic, hematological, and immunological responses to prolonged submaximal cycle ergometer exercise at a simulated altitude of 3000 m in pubescent girls.

Ten girls, 12.8 ± 1.0 years old, exercised on a cycle ergometer for 60 min at a work rate corresponding to 50% maximal oxygen consumption measured at sea level, under two environmental conditions; sea level (normoxia) and a simulated 3000 m altitude (normobaric hypoxia).

There were no significant differences in tidal volume, ventilation, oxygen consumption, cardiac output, stroke volume, and heart rate between the two exercise conditions. However, reticulocyte, adrenocorticotropic hormone, and cortisol concentrations increased significantly from pre- to postexercise in the hypoxic environment. Leukocyte and T-cell count increased and B-cell count decreased after exercise under both conditions. There were no significant changes in natural killer cell count.

Our simulated hypoxic environment provided a mild environmental stressor that did not impose a heavy burden on the cardiovascular, hematological, or immunological functions during submaximal exercise in pubescent girls.