Diurnal Oxygen Consumption and Rectal Temperature of Man During Continuous Cold Exposure

¹ From the Physiology Branch, Environmental Protection Research Division, QM Research and Development Center, Natick, Massachusetts

Effects of continuous cold stress on daily patterns of oxygen consumption (Vo₂) and rectal temperature were studied in five men. Cold stress consisted in living continuously in a chamber at 60°F for 14 days, wearing only shorts and with minimal physical activity. Resting Vo₂ and rectal temperatures were measured at 8 a.m., 12 m, 4 p.m. and 8 p.m. The cold period was preceded and followed by 2 weeks at 80°F. Activity and dietary composition were the same for all periods. Resting Vo₂ during warm periods exhibited gradual and characteristic increases during the day. This pattern was also found during cold exposure, but at a higher level; Vo₂ in the cold was 20% higher at 8 a.m., 16% at 12 m, 16% at 4 p.m. and 11% higher at 8 p.m. than at corresponding hours during control periods. Basal metabolic rate did not change throughout the experiment. Rectal temperatures at noon, 4 p.m. and 8 p.m. throughout the cold period did not differ from those at 80°F. Rectal temperatures at 8 a.m. were significantly higher in the cold than at 80°F. The results indicate that rectal temperature was well maintained during cold exposure and oxygen consumption appeared to respond in such a fashion as to subserve this maintenance.