Freediving

In this section we will discuss the sport of free-diving (competitive apnea) which is considered to be an extreme sport. The aim of free diving is to reach great depths, distances or times on a single breath without assistance from an underwater breathing apparatus. The body has several adaptations it goes under when free diving which stem from the mammalian diving reflex.

Competitive free diving can be divided into two kinds

Pool disciplines

Static apnea
timed breath hold usually done in a pool.

Dynamic apnea with fins
this involves the free-diver swimming underwater in a pool with fins.

Dynamic apnea without fins
This is involves the free-diver swimming underwater in a pool without fins

Depth Disciplines

Constant weight with fins
The free-diver dives to a set depth following a guide line that they are not allowed to touch where the diver grabs a tag at the bottom.

Constant weight without fins
The same as above but without fins.

Free Immersion
The free-diver uses the guideline to pull themselves down to grab a tag.

Variable weight
The free-diver is allowed to use a weighted sled for descent however they must swim back to the surface.

No limits
The free-diver may use any means of breath hold diving to reach set depth and return to the surface.

Diving adaptations

Bradycardia
Dropping of heart pulse rate

Vasoconstriction
Shrinking of blood vessels blood directed away from limbs for the benefit of heart, lungs an brain

Splenic contraction
Releases red blood cells carrying oxygen

Blood shift
Blood plasma fills blood vessels in the lungs and reduces residual volume, making it safe to dive deeper than 30meters.

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