Table 1.

Physiologic changes during cold exposure and hormonal profile during cold exposure and exercise tests in 10 subjects.

Physiologic variables
Body temperature (°C)	27°C	18°C	16°C	14°C	12°C	Trend p-value
Core	36.9±0.2	36.9±0.2	36.9±0.2	36.9±0.2	36.9±0.2	0.65
Skin	32.1±0.5	31.7±0.7	31.1±0.8	30.7±0.9	30.0±1.0	<0.0001
Gradient, core-skin	4.5±0.8	4.8±0.9	5.4±1.1	5.9±1.2	6.5±1.2	<0.0001
Gradient, arm-hand	−6.7±1.7	−7.1±1.8	−7.4±1.8	−7.2±1.8	−7.3±1.5	0.01
Gradient, supraclavicular-chest	1.04±0.03	1.05±0.03	1.06±0.04	1.07±0.05	1.09±0.06	<0.0001
Resting EE (kcal/day)	1488±196	1731±337	1926±673	2100±785	2235±738	0.007
Respiratory quotient	0.78±0.03	0.85±0.07	0.79±0.07	0.77±0.07	0.79±0.08	0.001
Surface electromyography (×10−6 RMS)	2.5±5.7	3.1±2.1	4.0±4.0	4.7±3.6	4.9±3.3	0.044
Hormonal variables
	Cold exposure		Maximal exercise		Sub-maximal exercise
	Baseline	End	Baseline	End	Baseline	End
Epinephrine (pg/ml)	38±25	110±73*	237±418	300±316	180±406	311±558*
Norepinephrine (pg/ml)	658±306	1101±449*	727±264	1568±541*	714±173	974±209*
Glucose (mg/dL)	84±3	86±2	91±6	117±22*	87±4	90±10
Insulin (U/L)	4.2±1.1	5.3±1.1	6.8±3.6	21.4±22.6*	6.6±3.5	7.9±5.2
HOMA IR	1.0±0.8	1.3±0.8	1.5±0.9	6.5±6.7*	1.4±0.8	1.8±1.2
NEFA (μEq/L)	0.55±0.07	0.57±0.07	0.49±0.19	0.45±0.19	0.47±0.23	0.65±0.22*
TSH (mlU/L)	1.9±0.3	2.1±0.3	2.1±0.7	2.5±0.9*	1.9±0.6	1.9±0.7
Free T4 (ng/dL)	1.0±0.0	1.0±0.0	1.0±0.1	1.0±0.1	1.0±0.1	1.0±0.1
Free T3 (pg/dL)	320±17	346±13	299±43	296±47	312±45	311±41
Total T3 (ng/dL)	134±22	139±17	115±29	114±16	121±23	117±17
ACTH (pg/ml)	17±9	19±6	27±16	156±133*	19±10	37±31*
Cortisol (μg/dL)	12±3	15±5	16±5	18±6	14±4	16±5
FGF21 (pg/ml)	129±76	98±90	135±80	102±97	119±79	97±85

^*P<0.05 compared to baseline. Data are presented as mean ± SD.