The Mammalian Diving Response (MDR)
Here is an overview of the four main diving responses of the human body, collectively known as 'Mammalian Diving Response' (MDR):
Trigger: Breath-holding, facial immersion in water, increased pressure
Response: Blood vessels in the extremities of the body (arms, legs) constrict to keep blood prioritised for the vital organs of the body
FACT: A disadvantage of reduced blood flow is increased carbon dioxide and lactic acid build up, but tolerance to these can be increased through training
Trigger: Facial Immersion in (cold) water, breath-holding
Response: Heart rate slows down by 10-25% in untrained, or up to 50% in trained freedivers, thus conserving blood Oxygen
FACT: In diving seals, heart rate has been measured going from 125bpm to below 10bpm during a dive!
Trigger: Breath holding and increased pressure on repetitive deep dives
Response: The spleen contracts and releases more red blood cells which aid oxygen transportation in the blood
FACT: The spleen is not an essential organ, but holds a reserve of blood and is important as part of the bodies immune system
Trigger: Increased pressure on deeper dives
Response: Blood plasma swells the alveoli of the lungs filling the chest cavity area to prevent barotrauma injury from increased pressure at depth
FACT: Only as recently as the 1970's did scientists begin to understand this phenomenon once divers such as Enzo Maiorca returned from 50m+ dives, injury free!
Sign up for AIDA3 (Intermediate) Course at One Breath Freediving to learn more about the Mammalian Diving Response and to reach new depths underwater.