Something that a few recent discussions, both on DB and in person, have lead me to question a lot of what we claim about the dangers and risks surrounding hyperventilation.
So yes, I agree with the science around the Bohr effect, that high levels CO2 can improve dive response, and that hyperventilation is potentially very very dangerous as it, especially with beginner untrained freedivers, lead to blackouts without any warning what so ever.
As an Instructor I am a firm believer that you should never ever hyperventilate before a dive, but as an athlete I am not at all convinced.
This all started with a very interesting dry static experience 2 years ago. One day I was listening to wim hoff on the joe rogan experience podcast while he talked about his method for healing through breathing & breath holding I decided to dive it a try and on hold #3 I managed, after breathing until I couldn't feel my face arms, and feet, 4:37 FRC dry (mostly static). My HR started at 75 beats/min (30 beats faster than resting) but at 2 minutes my rate was 32. This dropped further to 30 measured from 3:30 -4:00. At 4:00 I ran up 2 floors from the basement to the 2nd floor bathroom so I could see the colour of my lips. I stopped with pink lips at first contraction, did 2 recovery breaths and made lunch thinking "that was interesting". The next day I tried a normal ventilated FRC static aiming for 5:00. Starting HR 40. At 2:00 my HR was 43, and at 3:48 I had a small LMC. Then depth training started and I kinda forgot about the whole thing as I was afraid to over breath.
~2 Years later (7 weeks ago) I was doing some packed 4:00 statics for stretching and I got hold of a mediocre pulse-oxi. Similar experience.. With normal breathup 4:00 ended with around 60 beats/min, and around 85% O2. Extreme hyperventilation 4:00 ended with 50 beats/min and around 95% O2.
In both cases evidence suggests that my dive response is better over the breath hold with hyperventilation, despite a much higher starting HR. This also seemed to greatly reduce O2 consumption or if you look into it, Improve O2 storage.
Could increasing the Bohr effect actually help us? Theoretically we cannot increase Arterial blood O2 but what about the veins. "sticky" alkaline blood might help us oxygenate the veins. As time goes on and we build up CO2 though the breath hold eventually we reach normal acidity levels allowing us to use the extra oxygen.
Is it possible that CO2 is not the main/only trigger for dive response. On dry breathholds with no other stimulus for DR common freediver knowledge suggests that CO2 is the only thing that will tell our body to save O2. This, at least in my case, seems to be false as my biggest drops in HR and lowest ending HR come with extremely low levels of CO2. What else triggers the "dive response" bradycardia mainly? could high alkalinity play a roll more significant (maybe for different reasons) than high acidity does.
I have similar experiences with deep (55m bi-fins) dives. My most difficult dives in terms of recovery are (normal CO2, normal neutral buoyancy (1/3 target depth), normal freefall (1/2 target depth). My best results in terms of recovery are (very low CO2, deep neutral buoyancy (1/2 target), and no freefall). My thoughts are that I store extra O2 in the veins, and due to not freefalling I can build up back to normal levels of CO2 to use the extra oxygen for the end of my dive (stop bohr effect and limit shallow water BO). I would like to do the comparisons with HR, dive time, and O2 levels as up until now I've been basing this all on feeling.
most of my tests however have been 3:00+ dives to 20m which also seem to be much better with less CO2, not in terms of urge to breath but in terms of the colour of my lips and number of possible reps. With normal CO2 2x is my maximum before performance starts falling off, with very Low CO2 I can do 3-4 reps.
I would be very interested in hearing some thoughts on this and maybe some ideas on how to test what's going on a little more scientifically.
Please, before anyone yells at me for being "unsafe", I dive around 5 times per week ( I know my sensations), with the same 3-4 dive buddies who are all aware of exactly what I'm doing and who know my diving very well. I make only very small changes at a time to limit unknown variables. And Finally, even with face numbing low levels of CO2, at around 2:45 dive time on the slow 20m dives, I get the strong urge to breath so 3:30+ doesn't sneak up on me resulting in any BOs. A little FYI, I've never had even an LMC in depth and I haven't been any closer since I've tried any of this, I actually feel (buddy feedback supports) that I'm actually farther away from it.
Lastly and probably most importantly: Anyone reading this, who hasn't been diving as much as possible for 5 years, who doesn't have 5-7 days per week to make tiny adjustments over time, and doesn't have consistent buddies, do not start breathing like crazy hoping for good results. Potentially loosing the urge to breath is very dangerous, especially in depth and results are going to vary a lot, person to person. With any experimentation, start with dry holds and if you change anything in the water it should always be done as controlled as possible changing only 1 variable at a time.
Preferably let someone else do it (me) and when I eventually get around to properly testing these things I'll let ya know..
So yes, I agree with the science around the Bohr effect, that high levels CO2 can improve dive response, and that hyperventilation is potentially very very dangerous as it, especially with beginner untrained freedivers, lead to blackouts without any warning what so ever.
As an Instructor I am a firm believer that you should never ever hyperventilate before a dive, but as an athlete I am not at all convinced.
This all started with a very interesting dry static experience 2 years ago. One day I was listening to wim hoff on the joe rogan experience podcast while he talked about his method for healing through breathing & breath holding I decided to dive it a try and on hold #3 I managed, after breathing until I couldn't feel my face arms, and feet, 4:37 FRC dry (mostly static). My HR started at 75 beats/min (30 beats faster than resting) but at 2 minutes my rate was 32. This dropped further to 30 measured from 3:30 -4:00. At 4:00 I ran up 2 floors from the basement to the 2nd floor bathroom so I could see the colour of my lips. I stopped with pink lips at first contraction, did 2 recovery breaths and made lunch thinking "that was interesting". The next day I tried a normal ventilated FRC static aiming for 5:00. Starting HR 40. At 2:00 my HR was 43, and at 3:48 I had a small LMC. Then depth training started and I kinda forgot about the whole thing as I was afraid to over breath.
~2 Years later (7 weeks ago) I was doing some packed 4:00 statics for stretching and I got hold of a mediocre pulse-oxi. Similar experience.. With normal breathup 4:00 ended with around 60 beats/min, and around 85% O2. Extreme hyperventilation 4:00 ended with 50 beats/min and around 95% O2.
In both cases evidence suggests that my dive response is better over the breath hold with hyperventilation, despite a much higher starting HR. This also seemed to greatly reduce O2 consumption or if you look into it, Improve O2 storage.
Could increasing the Bohr effect actually help us? Theoretically we cannot increase Arterial blood O2 but what about the veins. "sticky" alkaline blood might help us oxygenate the veins. As time goes on and we build up CO2 though the breath hold eventually we reach normal acidity levels allowing us to use the extra oxygen.
Is it possible that CO2 is not the main/only trigger for dive response. On dry breathholds with no other stimulus for DR common freediver knowledge suggests that CO2 is the only thing that will tell our body to save O2. This, at least in my case, seems to be false as my biggest drops in HR and lowest ending HR come with extremely low levels of CO2. What else triggers the "dive response" bradycardia mainly? could high alkalinity play a roll more significant (maybe for different reasons) than high acidity does.
I have similar experiences with deep (55m bi-fins) dives. My most difficult dives in terms of recovery are (normal CO2, normal neutral buoyancy (1/3 target depth), normal freefall (1/2 target depth). My best results in terms of recovery are (very low CO2, deep neutral buoyancy (1/2 target), and no freefall). My thoughts are that I store extra O2 in the veins, and due to not freefalling I can build up back to normal levels of CO2 to use the extra oxygen for the end of my dive (stop bohr effect and limit shallow water BO). I would like to do the comparisons with HR, dive time, and O2 levels as up until now I've been basing this all on feeling.
most of my tests however have been 3:00+ dives to 20m which also seem to be much better with less CO2, not in terms of urge to breath but in terms of the colour of my lips and number of possible reps. With normal CO2 2x is my maximum before performance starts falling off, with very Low CO2 I can do 3-4 reps.
I would be very interested in hearing some thoughts on this and maybe some ideas on how to test what's going on a little more scientifically.
Please, before anyone yells at me for being "unsafe", I dive around 5 times per week ( I know my sensations), with the same 3-4 dive buddies who are all aware of exactly what I'm doing and who know my diving very well. I make only very small changes at a time to limit unknown variables. And Finally, even with face numbing low levels of CO2, at around 2:45 dive time on the slow 20m dives, I get the strong urge to breath so 3:30+ doesn't sneak up on me resulting in any BOs. A little FYI, I've never had even an LMC in depth and I haven't been any closer since I've tried any of this, I actually feel (buddy feedback supports) that I'm actually farther away from it.
Lastly and probably most importantly: Anyone reading this, who hasn't been diving as much as possible for 5 years, who doesn't have 5-7 days per week to make tiny adjustments over time, and doesn't have consistent buddies, do not start breathing like crazy hoping for good results. Potentially loosing the urge to breath is very dangerous, especially in depth and results are going to vary a lot, person to person. With any experimentation, start with dry holds and if you change anything in the water it should always be done as controlled as possible changing only 1 variable at a time.
Preferably let someone else do it (me) and when I eventually get around to properly testing these things I'll let ya know..