Here is food for thought.
In June 2002, I spent 10 days in Turkey doing experiments and discussions with Trevor Hutton. We spent hours each day, discussing previous experiences, good and bad, trying to figure out 'why.'
The conclusion was simple, and incredible:
- The diving reflex is something which is supposed to happen DURING THE DIVE
The is OPPOSITE to the usual method of 'activating the diving reflex' by various warmups BEFORE THE DIVE (or breath-hold).
In all marine mammals, the diving reflex happens DURING THE DIVE. The seal is suntanning on the surface. His spleen is not contracted, his heart is beating rapidly, oxygenating all parts of his body. When he starts the dive, his heart slows, and eventually his spleen contracts.
Notice that the seal didn't do any warmups, negative pressure dives, or other tricks to slow his heart or contract his spleen BEFORE he started the dive.
This is what Trevor and I discovered after countless hours of talking & experiments. Trevor's decades of freediving experiences were instrumental in this discovery.
At the time, we were not quite certain WHY this conclusion should be true, but one of the answers came some time later, from Sebastien Murat.
Sebastien reminded me that when the spleen contracts at the end of the dive/breath-hold, the fresh, oxygenated blood of the spleen feeds only the critical organs and brain, because by then, the whole body is so vasoconstricted that blood is not feeding the extremities.
This 'optimizes' the use of the 'splenic' energy reserve (spleen blood).
If, on the other hand, you contract your spleen BEFORE THE DIVE, this will make you feel much better in the early stages of the dive, because you have all this extra oxygen in your blood, and more blood to buffer CO2. It makes you feel like you are doing great, that you have 'lots of air left.' But, this oxygen is feeding your arms and legs, because you are not vasoconstricted yet.
When the end of the breath-hold comes and your brain needs oxygen, there is no energy left, because all that 'reserve' was burned by your arms and legs, since the reserve was available to your whole body, even before you were vasoconstricted.
In the no-warm up system of diving, you shouldn't 'feel good' at all in the early stages of the dive. You should feel like you are running out of air early, allowing the spleen to contract DURING THE DIVE.
However, keep in mind that it takes training and adaptation to have a spleen which can contract in only a short time. A beginner will probably not reach 'full' spleen contraction if the spleen tries to contract during the breath-hold. So this is a diving method which must be practiced.
To teach the spleen to contract faster, the 'no-warm up' method must be practiced at 100% effort frequently. Theoretically, this method would also DRAMATICALLY INCREASE THE SIZE OF THE SPLEEN.
Humans have about 4-6 litres of blood. Elephant seals store 24L of blood in their SPLEEN ALONE!
Recall the conclusion:
- The diving reflex is something which is supposed to happen DURING THE DIVE
Another reason this may be true is that when breathing up for your apnea (or just relaxing), you want blood to oxygenate every cell, even in your arms and legs. If you are already vasoconstricted from warm-up dives/breath-holds, then not much blood will pump to your arms and legs. This means that your arms and legs will be O2 deficient BEFORE YOU EVEN START THE DIVE.
Keep in mind that when we say:
- The diving reflex is something which is supposed to happen DURING THE DIVE
We also mean just the 'apnea reflex', i.e. the response to holding your breath, because it is still unclear if all the effects (vasoconstriction, spleen contraction) are happening due to apnea or immersion/diving, but it doesn't matter, the conclusion is still the same.
So, the challenge to all divers is:
- Practice 100% effort apnea on the 1st attempt
- Give your body time to 'reverse' the diving/apnea reflex (perhaps 20 minutes)
- Then you can practice 100% effort apnea on the 1st attempt again, because you are almost starting from scratch
- Once you have practiced for weeks or months, your spleen should be able to fully contract on the duration of one apnea
- Then, attempt to do 100% effort apnea to the point of reaching samba/BO on the 1st attempt. You will probably find that you must reach an insanely long time to do it (but use SAFETY if you are in the water, of course)
Your spleen is not the only thing which must learn to contract quickly. Your arms and legs must learn to vasoconstrict very fast, during the 1st breath-hold/dive. This must also happen through training.
Many expert divers are able to get in the water, and dive to their maximum on the 1st or 2nd dive, without any warm up. In my early days of diving, I would need to dive ALL DAY to even start to have good dives. Now it only takes one or two dives to reach my maximum. BUT, if I dive WITHOUT A WETSUIT in cold water, the cold water speeds up the vasoconstriction, so I can do my max on the 1ST DIVE, with no warm up. HOWEVER, given the strong vasoconstriction, I must NOT do any warm ups, because my arms and legs are so vasoconstricted from the cold water that they will NEVER FULLY RE-OXYGENATE if I do a warm up......