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A freediving dicipline in which the diver tries to hold his breath for as long as he can, while floating motionless on water facing down.

Factors contributing to performance include:
  • Good aerobic fitness
    • Lower heart rate and general metabolism.
  • Tolerance to high levels of C02
    • CO2 partial pressure is the primary stimulus to the breathing reflex (urge to breath).
  • Strong diving reflex
    • The mammalian diving reflex is a phenomenon which results in lower heart rate, highened blood pressure and concentration of blood to vital orgins due to immersion in water and growing pressure.
  • Physiological changes
    • With correct training and diet the diver can highten his hemoglobin and myoglobin values, resulting in better O2 storing capacity.
  • Lung volume
    • It is quite obvious that bigger lung capacity helps. The effect is not as dramatic as one might think.
    • An accomplished freediver can pack as much as 4 liters of extra air into his lungs, by swallowing mouthfuls of air into his lungs (referred to as packing).
  • Mental training
    • Ability to concentrate and tolerate the breathing reflex allows the diver to push his limit.
    • Meditation can also reduce O2 consumption.
  • Ability to relax muscles
    • Results in lower O2 consumption.

    A typical dive starts with the breath up period. By slow, controlled and deep breaths the diver tries to highten the O2 saturation of his body and relax. The last few breaths are fast and deep to purge excess CO2 from the body. The diver then packs air into his lungs by forcing air into the lungs with his cheecks and controlling the epiglottis (also known as Buccal pumping). This can take up to 20 seconds and result in as much as 4L extra air in the lungs.

    The first few minutes of the dive are quite comfortable and relaxing, even euphoric. The duration of the comfortable phase varies from person to person, lasting usually around 3-5 minutes. As the CO2 level raises the diver starts to feel more discomfortable and starts to experince contractions of the diaphragm and towards the ends struggles with the feeling of discomfort.

    Training for the comfort phase is mainly physiological and the discomfort phase is lengthened mainly with mental training and conditioning to discomfort.

    The official world record is 8 minutes 47 seconds, held by Tom Sietas of Germany.

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