Free-diving

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Image:Freediver.jpg Free-diving refers to various aquatic activities that share the practice of breath-hold diving. Examples include breathhold spearfishing, freedive photography, Apnea competitions and, to a degree, snorkeling. The activity that garners the public's attention is Competitive Apnea, considered an extreme sport, where divers attempt to reach great depths on a single breath and without direct assistance of breathing apparatus.

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Description

Competitive free diving, often referred to as "apnea", is generally broken down into three categories; static, dynamic, and depth, with male and female records recognized in each category:

  • Static Apnea is timed breath holding and is usually attempted in a pool.
  • Dynamic Apnea is underwater swimming for distance and has sub-categories for swimming with and without fins. This competition is usually held in a pool.

The depth category has four sub-sections:

  • Constant Weight competition is for self-propelled maximum depth, no weights or lines are allowed. This category is also divided into sections for fins or without fins.
  • Free Immersion competition is for self-propelled ascent and descent along a line and is for maximum depth.
  • Variable Weight competition uses a weighted sled for descent and divers ascend by pulling themselves up along a line.
  • No Limits competition allows the diver to descend with a weighted sled and ascend with a buoyancy control device, usually an air filled bag with a tether. The world record for the "No Limits" category of competitive free diving is held by Belgian diver Patrick Musimu. On 30 June 2005 he dived to a depth of 209 m (686 feet), in Egypt, in Red Sea; surpassing the previous record set by Loic Leferme by 38 meters. The current women's record is held by Tanya Streeter, who dived to 160 m (525 feet) on 17 August 2002. The unofficial record is held by the late Audrey Mestre (170 m) wife of legend Francisco “Pipin” Ferreras; she drowned whilst trying to set a world record of 171 m (561 feet).

Competitive free-diving featured heavily in the 1988 Luc Besson film Le Grand bleu (The Big Blue).

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Physiology of Free-diving

The human body has several adaptations under diving conditions, which stem from mammalian diving reflex. These adaptations enable the human body to endure depth and lack of oxygen far beyond what one would expect. One explanation for the presence of these adaptations is given by the anthropologists' aquatic ape theory.

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

  • Bradycardia: Drop in heart pulse 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 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.
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Training

Training for free diving can take many forms, many of them out of water.

One example is the apnea walk. This consists of a preparation "breathe-up", followed by a short (typically 1 minute) breath hold taken at rest. Without breaking the hold, the participant then initiates a walk for as far as they can, until it becomes necessary to breathe again.

This form of training is good for accustoming muscles to work under anaerobic conditions, and for tolerance to CO2 build-up in the circulation. It is also easy to gauge progress, as increasing distance can be measured.

Before diving, untrained free divers may hyperventilate, resulting in a lower level of CO2 in their lungs and bloodstream. This postpones the start of stimulation to the breathing centre of the brain, and thus delays the warning signals of running out of air. As the oxygen level of the blood is not increased by hyperventilation, this is very dangerous and may result in drowning. (For more detail refer to the articles shallow water blackout and deep water blackout.) Trained freedivers are well aware of this and will limit their immediate pre-dive breathing, typically to a maximum of two or three breaths taken slowly and deeply so as to maximize oxygen saturation whilst not depressing blood CO2 levels. However this does not, of itself, eliminate the risk of deep or shallow water blackout and diving with a 'buddy' who remains observing at the surface is the standard practice.

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Official World Records as of 2006-03-29 (AIDA)

Constant Weight, women: Natalia Molchanova (Russia), -86 meter.

Constant Weight, men: Carlos Coste (Venezuela), -105 meter.

Constant Weight, women, without fins: Natalia Molchanova (Russia), -55 meter.

Constant Weight, men, without fins: Martin Štìpánek (Czech Republic), -80 meter.

Static Apnea, women: Natalia Molchanova (Russia), 7m16s.

Static Apnea, men: Tom Sietas (Germany), 8m58s.

Dynamic Apnea, women: Natalia Molchanova (Russia), 178 meter.

Dynamic Apnea, men: Tom Sietas (Germany), 212 meter.

Dynamic Apnea, women, without fins: Natalia Molchanova (Russia), 131 meter.

Dynamic Apnea, men, without fins: Tom Sietas (Germany), 180 meter.

Variable Weight, women: Tanya Streeter (USA), -122 meter.

Variable Weight, men: Martin Štìpánek (Czech Republic), -136 meter.

No limit, women: Tanya Streeter (USA), -160 meter.

No limit, men: Herbert Nitsch (Austria), -172 meter.

Free Immersion, women: Natalia Molchanova (Russia), -78 meter.

Free Immersion, men: Martin Štìpánek (Czech Republic), -102 meter.

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Some famous Competitive Apnea Divers

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See also

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External links

de:Apnoetauchen fr:Apnée (sport) id:Selam bebas nl:Vrijduiken ja:フリーダイビング pl:Freediving ru:Фри-дайвинг sk:Nádychové potápanie fi:Vapaasukellus sv:Fridykning

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