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Heart rate variability during high ambient heat exposure
Stewart S Bruce-Low1, David Cotterrell, Gareth E Jones
1University of Chester, Chester, Cheshire, UK. s.brucelow@chester.ac.uk
Aviation, Space, and Environmental Medicine
|September 13, 2006
Summary
High ambient temperatures significantly increase heart rate (HR) by boosting sympathetic activity and reducing parasympathetic drive. This study measured heart rate variability (HRV) to assess autonomic nervous system responses in extreme heat.
Area of Science:
- Physiology
- Environmental Health
Background:
- Heart rate variability (HRV) quantifies autonomic nervous system balance.
- HRV is used in medicine and exercise but not extensively in extreme environments.
- Understanding sympathovagal activity in heat is crucial for health and safety.
Purpose of the Study:
- To investigate changes in sympathovagal activity during high ambient temperature exposure.
- To assess the impact of extreme heat (74°C) on heart rate and HRV.
Main Methods:
- Ten healthy males participated in the study.
- Subjects were exposed to 74°C for 15 minutes while wearing Polar HR monitors.
- Heart rate variability (HRV) was measured to analyze autonomic function.
Main Results:
- Heart rate (HR) significantly increased from 66.5 bpm to 106.0 bpm during heat exposure.
- Parasympathetic drive significantly decreased, indicated by reductions in pNN50, RMSSD, and HF norm values.
- Sympathetic drive significantly increased, shown by elevated LF norm values and an increased LF:HF ratio.
Conclusions:
- High ambient temperature exposure significantly elevates HR.
- The increase in HR is mediated by enhanced sympathetic and reduced parasympathetic activity.
- HRV analysis effectively detects autonomic nervous system changes in extreme heat environments.
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