Physiological responses to acute cold exposure in young lean men

Area of Science:

• Human Physiology
• Thermogenesis Research
• Metabolic Studies

Background:

• Understanding non-shivering thermogenesis is crucial for metabolic regulation.
• Acute cold exposure elicits complex physiological responses.
• Mechanisms of thermoregulation require further elucidation in healthy populations.

Purpose of the Study:

• To comprehensively describe physiological responses to mild cold in young lean men.
• To investigate the regulation of non-shivering thermogenesis.
• To analyze changes in energy expenditure, substrate metabolism, and thermal perception during cold exposure.

Main Methods:

• Recruited 11 young lean men (age 23 ± 2 years).
• Measured resting energy expenditure, substrate metabolism, skin temperature, thermal comfort, muscle activity, hemodynamics, and heart rate variability.
• Utilized a controlled cooling protocol involving air-conditioning and a water cooling vest until shivering onset.

Main Results:

• Energy expenditure increased significantly (31.7%) by the shivering threshold.
• Fat oxidation increased by 72.6% early in cold exposure, with no change in carbohydrate oxidation.
• Skin temperature and thermal comfort decreased, while superficial muscle activation increased at the shivering threshold.

Conclusions:

• Mild cold exposure stimulates non-shivering thermogenesis, primarily through increased fat oxidation.
• Significant physiological adaptations occur within the initial 30 minutes of cold exposure.
• These findings enhance our understanding of thermoregulation and metabolic responses to cold.