Autonomic nervous function during whole-body cold exposure before and after cold acclimation

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Environmental Physiology

Background:

• Cold habituation influences sympatho-vagal balance, impacting cold stress responses.
• Understanding cardiovascular autonomic function during cold exposure is crucial for managing physiological stress.

Purpose of the Study:

• To investigate changes in cardiovascular autonomic function at the sinus node level.
• To examine responses during controlled breathing and isometric exercise.
• To assess effects before and after cold acclimation.

Main Methods:

• 10 male subjects underwent controlled (25°C) and cold (10°C) exposures for 10 days.
• Heart rate variability (HRV) was analyzed using time and frequency domains.
• Cardiovascular and catecholamine responses were measured during isometric handgrip tests.

Main Results:

• Acute cold exposure increased HRV parameters, including total, low, and high frequency power.
• Cold acclimation led to higher mean skin temperature and reduced norepinephrine response.
• Post-acclimation, cold exposure showed a blunted heart rate and blood pressure increase during exercise.

Conclusions:

• Cold exposure initially increases sympathetic activity, which is attenuated by cold acclimation.
• Parasympathetic activity, initially slightly increased by cold, is further enhanced after acclimation.
• Cold habituation shifts autonomic balance towards increased parasympathetic activity and reduced sympathetic activation.