Objective: 

During cold exposure many hormones play essential roles in thermoregulatory functions (vasoconstriction, heat production, etc.). Occupational, athletic, and military activities often demand high physical performance during cold exposure. The purpose of this study was to examine the nervous and endocrine responses to the combined interaction of exercise and cold stress.

Methods: 

Ten healthy, normal weight male subjects, dressed in shorts and t-shirts, exercised on 6 separate days. They walked or ran (50% and 70% of maximal oxygen consumption respectively), for 60- min on a treadmill in a climatic chamber set at 22°C (Neutral, NT), 0°C (Cold, CD), or at 0°C following a low-intensity shivering cooling period (Cold-Shivering, CS). Core temperature (Tco), and weighted mean skin temperature (Tsk) were averaged every 15- min. Blood samples were collected before exercise (baseline), and at 30- and 60-min, to determine changes in thyroid hormones (TSH, T3, FT3, FT4,), epinephrine, norepinephrine, adenocorticotropic hormone (ACTH), cortisol, total and bioavailable testosterone (TEStot, TESbio), and sex hormone- binding globulin (SHBG).

Results: 

Tco and Tsk were lower from NT to CD to CS, and in walking (P<0.01). FT4 was higher in NT compared to CD (P<0.05). ACTH was higher in NT at 60-min running compared to CD and CS (P<0.01). Cortisol, TEStot, and TESbio were higher in NT at 60- min compared to CD and CS (P<0.05). Finally, norepinephrine was higher in NT and CS compared to CD at 60-min and 30-min, respectively. Other parameters were not influenced by environmental conditions.

Conclusions: 

Cold environmental conditions significantly influenced neuro- endocrine responses during short-term exercise but did not seem to acutely modulate thyroid endocrine functions.