Autonomic Nervous System Response to Far-Infrared Sauna Exposure in Firefighters

Area of Science:

• Physiology
• Occupational Health
• Environmental Medicine

Background:

• Firefighters face carcinogen exposure and autonomic nervous system (ANS) dysfunction post-emergency calls, potentially increasing sudden cardiac death risk.
• Heightened sympathetic activity and delayed parasympathetic reactivation indicate incomplete ANS recovery, a concern addressed by post-fire call protocols like far-infrared sauna (FIRS) use.
• Elevated body temperature from saunas might impede full ANS recovery.

Purpose of the Study:

• To investigate autonomic nervous system (ANS) responses to far-infrared sauna (FIRS) exposure in firefighters.
• To compare ANS responses in firefighters with (EX) and without (NONEX) prior maximal exercise.

Main Methods:

• Sixteen career firefighters underwent measurements of body temperature, heart rate, heart rate variability, blood pressure, and blood lactate.
• Measurements were taken at baseline, post-maximal exercise (EX only), and post-15-minute FIRS exposure for both NONEX and EX conditions.

Main Results:

• In the NONEX group, body temperature increased significantly (P < 0.001) with no changes in heart rate, heart rate variability, blood pressure, or lactate.
• In the EX group, body temperature, heart rate, and lactate increased significantly (P < 0.001) post-FIRS, while heart rate variability significantly decreased (P = 0.018).
• Blood pressure remained unchanged in the EX group post-FIRS.

Conclusions:

• Far-infrared sauna (FIRS) exposure following maximal exercise partially supports autonomic nervous system (ANS) recovery in firefighters.
• FIRS may interfere with optimal restoration of body temperature and parasympathetic nervous system reactivation.
• These effects could potentially influence post-call cardiovascular risk in firefighters.