Free-diving - Physiology of Freediving

Physiology of Freediving

The human body has several adaptations under diving conditions, which stem from the mammalian diving reflex. These adaptations enable the human body to endure depth and lack of oxygen far beyond what would be possible without the reflex.

The adaptations made by the human body while underwater and at high pressure include:

• Reflex bradycardia: Drop in heart rate.
• Vasoconstriction: Blood vessels shrink. Blood stream directed away from limbs for the benefit of heart, lungs and brain.
• Splenic contraction: Releasing red blood cells carrying oxygen.
• Blood shift: Blood plasma fills up blood vessels in the lung and reduces residual volume. Without this adaptation, the human lung would shrink and wrap into its walls, causing permanent damage, at depths greater than 30 meters.