Journal of Applied Physiology, Vol 49, Issue 3 367-373, Copyright © 1980 by American Physiological Society
Physiological adjustments of women to prolonged work during acute hypoxia
J. A. Wagner, D. S. Miles and S. M. Horvath
Five women (23-32 yr) performed bicycle work in a hypobaric chamber for 2 h
at 41% of their respective altitude maximal oxygen uptakes (VO2) at 758,
586, 523, and 446 Torr barometric pressures (PB). Steady-state VO2 was
achieved within 5 min work at all altitudes. Pulmonary ventilation (29.2
+/- 1.9 (mean +/- SE) 1/min, BTPS), respiratory rate (22 +/- 2
breaths/min), cardiac output (8.5 +/- 1.4 1/min), heart rate (115 +/- 6
beats/min), and stroke volume (75 +/- 13 ml) were similar at all altitudes,
but time-related changes differed with altitude. Blood lactates did not
change with work duration and were similar at 758 and 586 Torr PB but
progressively elevated at 523 and 446 Torr. Blood norepinephrine, measured
only at 758 and 446 Torr PB, increased with work but not altitude;
epinephrine increased only at altitude. Norepinephrine levels and
respiratory, cardiovascular, and thermoregulatory functions were
essentially dependent on relative work load; blood lactates and epinephrine
levels were not. Many physiological functions in these women performing
sustained light work during acute altitude exposure were remarkably stable
in contrast to previously reported studies on men.
