Journal of Applied Physiology, Vol 68, Issue 2 720-725, Copyright © 1990 by American Physiological Society
Metabolic effects of exposure to hypoxia plus cold at rest and during exercise in humans
K. A. Robinson and E. M. Haymes
Department of Movement Science, Florida State University, Tallahassee 32306.
To determine effects on metabolic responses, subjects were exposed to four
environmental conditions for 90 min at rest followed by 30 min of exercise:
breathing room air with an ambient temperature of 25 degrees C (NN);
breathing room air with an ambient temperature of 8 degrees C (NC); hypoxia
(induced by breathing 12% O2 in N2) with a neutral temperature (HN); and
hypoxia in the cold (HC). Hypoxia increased heart rate (HR), systolic blood
pressure (SBP), pulmonary ventilation (VE), respiratory exchange ratio (R),
blood lactate, and perceived exertion during exercise while depressing
rectal temperature (Tre) and O2 uptake (VO2). Cold exposure elevated SBP,
diastolic blood pressure (DBP), VE, VO2, blood glucose, and blood glycerol
but decreased HR, Tre, and R. Shivering and DBP were higher and Tre was
lower in HC compared with NC. HR, SBP, VE, R, and lactate tended to be
higher in HC compared with NC, whereas VO2 and blood glycerol tended to be
depressed. These results suggest that cold exposure during hypoxia results
in an increased reliance on shivering for thermogenesis at rest whereas,
during exercise, heat loss is accelerated.
