lecture

The Mammalian Dive Reflex – We Measured a 20% Heart Rate Drop in 30 Seconds

In this video, we demonstrate the mammalian dive reflex and measure its effect on the autonomic nervous system in real time. Using ice water facial immersion, pulse oximetry, blood pressure monitoring, and heart rate variability (HRV) tracking, we recorded: • 20% reduction in heart rate • 40% increase in HRV (RMSSD) The mammalian dive reflex is a built-in survival mechanism present in all mammals. When cold water stimulates the face — especially the area innervated by the trigeminal nerve — signals are sent to the brainstem, activating the vagus nerve. This leads to: • Bradycardia (slowing of the heart) • Peripheral vasoconstriction • Increased parasympathetic tone • Redistribution of blood toward vital organs This demonstration shows how rapidly the autonomic nervous system can shift — and how that shift can be objectively measured. At TerraMD, we focus on measurable resilience: Measure → Intervene → Re-measure.