Edward S. Potkanowicz

The Effect of Cold Exposure on the Hormonal and Metabolic Responses to Sleep Deprivation

Abstract Objective.—The purpose of this study was to determine the effect of 12°C cold exposure for 180-minutes on the hormonal responses of sleep-deprived individuals. Methods.—Participants underwent 2 cold-air trials: 1 after a normal night of sleep (ie, 6–8 hours) and 1 after 33 hours of sleep deprivation (SDEP). A venous blood sample was taken at baseline and then at 90-and 180-minute cold-exposure time points. Repeated-measures analysis of variance was used to determine significance between a normal night of sleep and SDEP for norepinephrine, epinephrine, cortisol, insulin, thyroid hormones triiodothyronine and thyroxine, glucose, and non-esterified fatty acids. Results.—There was no significant main effect for time, trial, or interaction for insulin, thyroid hormones, epinephrine, cortisol, and glucose (P ≤ .05). A significant main effect for time for norepinephrine and non-esterified fatty acids was demonstrated (P < .001). Discussion.—The lack of significant differences in the hormonal and metabolic responses to cold exposure combined with SDEP may have been because of an ability of the individual to continue to respond despite the environmental stressor or the physiological effect elicited from cold exposure, thereby possibly masking physiological responses of SDEP. Conclusions.—On the basis of these data, SDEP combined with protracted cold exposure apparently was not a great enough stressor to cause a differential response in the hormonal and metabolic parameters.

Thermal sensation of old vs young males at 12, 18, and 27°C for 120 min

Research in the field of aging has provided data that suggests that there are physiological changes that occur as ones biological age increases. The present investigation examined the age-related alteration and differential response between old (OLD) and young (YNG) individuals with respect to subjective thermal sensation (TS). Participants were all regularly active and of average percent body fat relative to their age. Subjects were exposed to three different temperature trials (12, 18, and 27°C) on three separate occasions (separated by 48 h) for 120 min, wearing only a bathing suit or shorts. Subjects were instructed to insert a rectal probe to monitor rectal temperature and were instrumented with four thermocouples to monitor skin temperature. Each subject rested for 30 min in a thermoneutral environment outside the environmental chamber, during which time baseline measures were taken. Following the completion of the baseline period, the subjects were wheeled into the environmental chamber. Each trial lasted 120 min or until rectal temperature was less than or equal to 35°C, at which point the subject was immediately removed from the environmental chamber. TS was assessed using both the Gagge and Modified Gagge TS scale. At the completion of each trial the subject was removed from the chamber and allowed to exercise on a cycle ergometer. Both the Gagge and Modified Gagge scale demonstrated main effects for time and trial. Neither scale exhibited significant differences between the groups or interactions relative to the experimental groups. These data suggest that when exposed to a thermal stressor OLD and YNG subjects do not demonstrate a differential response in TS during acute cold exposure.

The Effects of Nicotine on the Metabolic and Hormonal Responses During Acute Cold Exposure

Abstract Objective.—To examine the effects of nicotine on the metabolic and hormonal responses during acute cold exposure. Methods.—Participants in this study included 6 men and 5 women between the ages of 19 and 25 years. Each subject performed 2 cold-air trials (CATs) consisting of a 30-minute baseline (BASE) period and a 120-minute exposure to 10°C air. One CAT was performed after a nicotine (NIC) dosing using a 21-mg transdermal patch, whereas the other CAT was performed after a placebo (PL) treatment. Blood samples for metabolic and hormonal measurements were obtained at the end of BASE and immediately after the cold exposure. Results.—When examining the sexes separately, there was no difference in norepinephrine between PL and NIC (P = .066). There was also no difference in epinephrine between PL and NIC in either sex (P = .634). From BASE to 120 minutes of the CAT, there was a significant decrease in cortisol (P = .036), but this response was similar between the 2 treatments (P = .077). Glucose and glycerol concentrations were not different between the PL and NIC treatments. At BASE, nonesterified fatty acid (NEFA) concentration was lower during PL compared with NIC (P = .021); however, at 120 minutes of the CAT, NEFA was greater during PL compared with NIC (P = .035). Conclusions.—During 120 minutes of cold exposure, NIC resulted in alterations in the responses in NEFA, whereas the other blood measurements were not significantly different between the 2 groups.

The influence of ethnicity on thermosensitivity during cold water immersion

PURPOSE This investigation evaluated the influence of ethnicity, Caucasian (CAU) vs. African American (AA), on thermosensitivity and metabolic heat production (HP) during cold water immersion (20 degrees C) in 15 CAU (22.7 +/- 2.7 yr) vs. 7 AA (21.7 +/- 2.7 yr) males. METHODS Following a 20-min baseline period (BASE), subjects were immersed in 20 degrees C water until esophageal temperature (Tes) reached 36.5 degrees C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. Arm and thigh cuffs were then inflated to 180 and 220 mm Hg, respectively, for 10 min (OCC). Following release of the inflated cuffs (Post-OCC), the slope of the relationship between the decrease in Tes and the increase in HP was used to define thermosensitivity (beta). RESULTS ANOVA revealed no significant difference in thermosensitivity between CAU and AA (CAU = 3.56 +/- 1.54 vs. AA = 2.43 +/- 1.58 W.kg(-1). degrees C(-1)). No significant differences (p > 0.05) were found for Tsk (CAU = 24.2 +/- 1.1 vs. AA = 25.1 +/- 1.1 degrees C) or HP (p > 0.05; CAU = 2.5 +/- 0.8 vs. AA = 36.5 +/- 1.8 W.kg(-1)). However, a significant (p < 0.05) main effect for ethnicity for Tes was observed (CAU = 36.7 +/- 1.8 vs. AA = 36.5 +/- 1.8 degrees C). CONCLUSION These data suggest, despite a differential response in Tes between AA and CAU groups, the beta of HP during cold water immersion is similar between CAU and AA. Therefore, these data demonstrate that when faced with a cold challenge, there is a similar response in HP between CAU and AA that is accompanied by a differential response in Tes.