Freediving

The Basics of Apnoea- and Freediving!

Freediving is any of various aquatic activities that share the practice of breath-hold underwater diving. Examples include breath hold spear fishing, freedive photography, apnea competitions and, to a degree, snorkeling. The activity that garners the most public attention is competitive apnea, an extreme sport, in which competitors attempt to attain great depths, times or distances on a single breath without direct assistance of an underwater breathing apparatus. Breathing rates; the average breathing rate in a calmly position per time unit.

Age Breathing rate/min
Adult 12-15
Teenager 16-18
School kid 20
Toddler 25
Baby 30
Infant 40-50

The Tidal volume of a human
The tidal volume per Breath is about 1,0 liters.
The Minute Volume
The minute Volume Vmin is the product of  fmin and tidal Volume Vtidal:
 Vmin = fmin  x Vtidal
Example: 10 breath/min and 1l air per tidal breath
10 (tidal)/min x 1l = 5l/min

Overview

Freediving is a technique used with various aquatic activities. While in general all aquatic activities that include breath-hold diving might be classified as a part of freediving, some sports are more accepted than others. Examples of recognized freediving activities are (non-) competitive freediving, (non-) competitive spear fishing, freedive photography and mermaid shows. Less recognized examples of freediving include, but are not limited to, synchronized swimming, underwater rugby, underwater hockey, underwater hunting other than spear fishing and snorkeling.
The discussion remains whether freediving is only a synonym for breath-hold diving or whether it describes a specific group of underwater activities. Freediving is often strongly associated with competitive breath-hold diving or Competitive Apnea. It is a sport in which competitors attempt to attain great depths, times, or distances on a single breath and without the assistance of breathing apparatus like SCUBA.

Competitive freediving

Competitive freediving is currently governed by two world associations: AIDA International and CMAS. Most types of competitive freediving have in common that it is an individual sport based on the best individual achievement. An exception to this rule is the bi-annual World Championship for Teams, held by AIDA, where the combined score of the team members makes up the team’s total points. There are currently nine disciplines used by official governing bodies and a dozen disciplines that are only practiced locally. In this article, the recognized disciplines of AIDA and CMAS will be described. All disciplines can be done by both men and women and, while done outdoors, no differences in the environment between records are recognized any longer. The disciplines of AIDA can be done both in competition and as a record attempt, with the exception of Variable Weight and No limits, which are both only done as record attempts. The following official disciplines are recognized by AIDA, CMAS, or both.

Pool disciplines

Static Apnea is timed breath holding and is usually attempted in a pool (AIDA).Dynamic Apnea with fins: This is underwater swimming in a pool for distance. For this discipline the athlete can choose whether to use bi-fins or the monofin (AIDA), (CMAS).Dynamic Apnea without fins: This is underwater swimming in a pool for distance without any swimming aids like fins (AIDA).

Depth disciplines

For all AIDA disciplines, the depth the athlete will attempt is announced before the dive. This is accepted practice for both competitions and record attempts
Constant Weight with fins. The athlete has to dive to the depth following a guide line that he or she is not allowed to actively use during the dive. The ‘constant weight’ (“poids constant“) refers to the fact that the athlete is not allowed to drop the weights during the dive. Both bi-fins and mono-fin can be used during this discipline.

freediver_monoConstant Weight without fins follows the identical rules as Constant Weight with fins, except no swimming aids such as fins are allowed. This discipline is the youngest discipline within competitive freediving and is recognized by AIDA International since 2003.

freediver_slideFree Immersion is the discipline in which the athlete uses the guideline to pull him or herself down to depth and back to the surface. It is known for its ease compared with the Constant Weight disciplines, while the athlete is still not allowed to release weights

Variable Weight is a record discipline that uses a weighted sled for descent. Athletes return to the surface by pulling themselves up along a line or swimming while using their fins.

No Limits is a record discipline that allows the athlete to use any means of breath-hold diving to depth and return to the surface as long as a guideline is used to measure the distance. Most divers use a weighted sled to dive down and use an air-filled bag to return to the surface.
“The Cube” is also known as “Jump Blue” and is a discipline in which an athlete has to descend to 15 meters and swim as far as possible in a cubic form of 15 x 10 meters (CMAS only).
Each organization has its own rules on recognizing an attempt. These can be found on the website from the respective organizations.

Recreational

Freediving is also an intriguing recreational sport, celebrated as a relaxing, liberating, and unique experience. Many snorkelers may technically be freediving if they perform any sort of breath hold diving-it is important to stress the importance of training and supervision when making this association. Like other water sports, freediving is associated with therapeutic properties. The experience of freedom in an underwater environment makes freediving somewhat of a personal and spiritual journey for many. Yoga is used by many practitioners to increase focus, breath, and overall performance. The ‘art’ of freediving and the practice outside the athletic and competitive sphere goes beyond the scope of this article.

Physiology of freediving

The human body has several adaptations under diving conditions, which stem from the mammalian diving reflex.The mammalian diving reflex optimizes mammals respiration to stay underwater for a long time. It is exhibited strongly in aquatic mammals (seals, otters, dolphins, etc.), but exists in a weaker version in other mammals, humans included. Diving birds, such as penguins, have a similar diving reflex.

Every animal’s diving reflex is triggered specifically by cold water contacting the face — water that is warmer than 21 °C (70 °F) won’t cause the reflex, and neither will submersion of body parts other than the face. Also, the reflex is always exhibited more dramatically, and thus can grant longer survival, in young people and animals.

Upon initiation of the reflex, three changes happen to the body, in this order:

  • Bradycardia is the first response to submersion. Immediately upon facial contact with cold water, the human heart rate slows down 10-25%. In the seal the changes are even more dramatic, going from about 125 beats per minute to as low as 10 on an extended dives. Slowing the heart rate lessens the need for bloodstream oxygen, leaving more to be used by other organs.
  • Next, peripheral vasoconstriction sets in. When under high pressure induced by deep diving, capillaries in the extremities start closing off, stopping blood circulation to those areas. Note that vasoconstriction usually applies to arterioles, but in this case is completely an effect of the capillaries. Toes and fingers close off first, then hands and feet, and ultimately arms and legs stop allowing blood circulation, leaving more blood for use by the heart and brain. Human musculature accounts for only 12% of the body’s total oxygen storage, and our muscles tend to cramp up during this phase. Aquatic mammals have as much as 25 to 30% of their oxygen storage in muscle, and thus they can keep working long after capillary blood supply is stopped.
  • Finally, and arguably most interestingly, is the blood shift that occurs only during very deep dives. When this happens, organ and circulatory walls allow plasma/water to pass freely throughout the thoracic cavity, so its pressure stays constant and the organs aren’t crushed. In this stage, the lungs’ alveoli fill up with blood plasma, which is reabsorbed when the animal leaves the pressurized environment. This stage of the diving reflex has been observed in humans (such as world champion freediver Martin Štěpánek) during extremely deep (300’+) freedives.

Thus, both a conscious and an unconscious person can survive longer without oxygen under water than in a comparable situation on dry land. Children tend to survive longer than adults when deprived of oxygen underwater.

When the face is submerged, receptors that are sensitive to water within the nasal cavity and other areas of the face supplied by cranial nerve V (trigeminal) relay the information to the brain and then innervate cranial nerve X, which is part of the autonomic nervous system. This causes bradycardia and peripheral vasoconstriction. Blood is removed from the limbs and all organs but the heart and the brain, creating a heart-brain circuit and allowing the mammal to conserve oxygen.

In humans, the mammalian diving reflex is not induced when limbs are introduced to cold water. Mild bradycardia is caused by the subject holding his breath without submerging the face within water. When breathing with face submerged this causes a diving reflex which increases proportionally to decreasing water temperature. However the greatest bradycardia effect is induced when the subject is holding breath with face submerged.

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:

  • 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 plasma fills up blood vessels in the lung and reduces residual volume. Basically it is a protection of our lungs.

spaghettiA simple example is a Whale; the whale is breathing out when it is descending, we breathe in, a whales chest works like a Spaghetti nipper the Whales don´t have a chest bone, so the chest of a whale can easily shrink together without damaging lungs, even up to 1000 m of depth, no problem for them.

chest_boneCompare to our Chest, its only slightly flexible. For non professionals depths greater than 30 meters can cause a “Blood Shift”. The human lung shrinks, and wraps into its walls, the lung alveolus fill up with blood plasma to protect itself can cause permanent damage. We can train our lungs to reach more but

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. Athletes can do close to 400 meters in training this way.

This form of training is good for accustoming muscles to work under anaerobic conditions.
Anaerobic is a technical word which literally means without air (where “air” is generally used to mean oxygen), as opposed to aerobic. 
Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments as dissolved oxygen (DO; molecular oxygen dissolved in the water) becomes reduced in concentration to a point detrimental to aquatic organisms living in the system. Dissolved oxygen is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity (both of which affect the solubility of oxygen in water; see oxygen saturation and underwater). An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic; a system with low DO concentration—in the range between 1 and 30% DO saturation—is called hypoxic. Most fish cannot live below 30% DO saturation. A “healthy” aquatic environment should seldom experience DO less than 80%. 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, most performance oriented free divers hyperventilate to a certain degree, resulting in a lower level of CO2 in their lungs and bloodstream.
In medicine, hyperventilation (or over-breathing) is the state of breathing faster and/or deeper than necessary, thereby reducing the carbon dioxide concentration of the blood below normal.

Hyperventilation can, but does not necessarily always cause symptoms such as numbness or tingling in the hands, feet and lips, lightheadedness, dizziness, headache, chest pain, slurred speech and sometimes fainting, particularly when accompanied by the Valsalva maneuver. Sometimes hyperventilation is induced for these same effects.
In medicine, the Valsalva maneuver is performed by forcibly exhaling against a closed glottis (a closed airway). This maneuver with slight modifications can be used as a test of cardiac function and autonomic nervous control of the heart or to ‘clear’ the ears and sinuses (equalize pressure) when ambient pressure changes, as in diving or aviation.
The technique is named for Antonio Maria Valsalva, the 17th Century physician and anatomist from Bologna, whose principal scientific interest was the human ear. He described the Eustachian tube and the maneuver to test its patency (openness).

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, called shallow water blackout and deep water blackout.
Trained freedivers are well aware of this and will only dive under strict and first aid competent supervision. However this does not, of itself, eliminate the risk of deep or shallow water blackout. All safe free divers have a ‘buddy’ who accompanies them, observing from within the water at the surface. Due to the nature of the sport, safety is an integral part of freediving, requiring participants to be adept in rescue and resuscitation. Without proper training and supervision, freediving/apnea/breath-hold diving is extremely dangerous.

History

The Ama divers of Japan, use free-diving for the collection of pearls in a practice that is estimated to date back over 2000 years.
The sport is generally acknowledged as the invention of the Bottom Scratchers, a diving club in San Diego, California in the 1930s.

Official world records as of April, 2008 (AIDA)

  • Static Apnea
    • women: Natalia Molchanova (Russia), 8m00s
    • men: Tom Sietas (Germany), 9m15s
  • Dynamic Apnea
    • women: Natalia Molchanova (Russia), 205 metres
    • men: Dave Mullins (New Zealand), 244 metres
  • Dynamic Apnea, without fins
    • women: Natalia Molchanova (Russia), 149 metres
    • men: Stig Severinsen (Denmark), 186 metres
  • Constant Weight
    • women: Sara Campbell (UK), -90 meters
    • men: Herbert Nitsch (Austria), -112 metres
  • Constant Weight without fins
    • women: Natalia Avseenko (Russia), -57 meters
    • men: William Trubridge (New Zealand), -86 meters
  • Free Immersion
    • women: Sara Campbell (UK), -81 meters
    • men: William Trubridge (New Zealand), -108 meters
  • Variable Weight
    • women: Tanya Streeter (Cayman Islands), -122 meters
    • men: Carlos Coste (Venezuela), -140 metres
  • No limits
    • women: Tanya Streeter (Cayman Islands), -160 meters
    • men: Herbert Nitsch (Austria), -214 meters

Literature References

Praxis des Tauchens
(Kromp, Roggenbach…..)
Ehm, Safer Diving
Diving Medicine
Apnoetauchen. Grundlagen, Trainingstipps, Praxis
from Dagmar Andres-Brümmer (Autor), Dagmar Andres- Brümmer (Autor)
Manual Of Freediving: Underwater On A Single Breath (Freediving)
from Umberto Pelizzari (Autor), Stefano Tovaglieri (Autor)
Apnoe. Mit einem Atemzug in blaue Tiefen
from Robert Margaillan (Autor)
Tauchen ohne Angst. Mental-Tipps. Atemtechnik. Übungen (Taschenbuch) 
from Monika Rahimi (Autor)