Summary
Brief cold exposure (cold showers, ice baths) triggers acute parasympathetic activation and HRV increase. The effect is immediate but duration of benefit for regular practice is less well established.
Methods
Review of cold exposure studies measuring autonomic response
Key Findings
- Cold triggers dive reflex and vagal activation
- HRV increases acutely during and after cold exposure
- 2-3 minutes of cold exposure sufficient for effect
- Regular practice may enhance stress resilience over time
Limitations
Long-term studies on habitual cold exposure and HRV are limited
What This Means for You
Cold showers or brief ice baths do activate your parasympathetic system. Start with 30-second cold finishes to showers and work up. Don't expect miracles—the effect is real but modest compared to sleep and exercise.
Source
Read the original paper in Sensors ↗
Added to HRV Zone: 2025-01-07