In this video model Iara Mandyn holds her breath for about 3 minutes 20 seconds for this underwater mermaid shot. Some of the scientific and physiological changes while holding your breath could be:
- Heart rate rises initially, then drops gradually throughout (bradycardia)
- Blood vessels in the arms and legs constrict (vasoconstriction), to pool blood for brain/heart, where it is needed
- CO2 levels increase, which trigger defense mechanisms
- CO2 eventually causes involuntary abdominal contractions (usually just termed contractions), which increase blood flow to the brain
- Elevated CO2 levels cause oxygen to be more easily released from the blood (Bohr effect
- When arterial blood oxygen saturation (SaO2) drops below around 30% (in elite divers), a blackout occurs (BO for short, or ‘samba’ which means hypoxic seizure)
- If exercising while holding breath (i.e. swimming), then the vasoconstriction in the arms and legs forces anaerobic metabolism to occur there = build up of lactic acid, and causes myoglobin in the muscles to release oxygen.
For motionless breath holding, the time you can hold your breath for is determined by:
- Psychological resistance to the urge to breathe
- Total oxygen storage capacity (= lung volume + blood volume + hemoglobin concentration in blood)
- Oxygen consumption rate ( = metabolic rate), determined by body temperature, fitness level, vasoconstriction level, and relaxation level; also requires an empty stomach for lowest metabolic rate
- Resistance to low oxygen levels (better resistance to low oxygen = longer breath hold)
See more underwater Iara Mandyn videos.