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Can the Dive Reflex ruin your static performance?

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ADR

Well-Known Member
Jan 21, 2004
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Is the dive reflex "all good" for static performance?

If we look at each of the elements of the dive reflex I'm a little confused about the benefits of vasoconstriction particularly as it relates to the bodies ability to absorb and buffer CO2. Whenever I see comments on vasoconstriction relating to the dive reflex they usually talk about the benefits of reducing blood flow to the muscles and concentrating O2 stores at the core for heart, lungs and brain. In terms of remaining conscious for as long as possible in apnea this makes sense.......but doesn't the same also apply for CO2? ie If the vasoconstriction concentrates the O2 in the core won't it also concentrate the CO2 at the core and potentially the stronger the dive reflex the more CO2 concentration at the core you will get. Effectively this would reduce the comfort phase of the static compared with no vasoconstriction? How do we best balance these competing needs of concentrating O2 at the core but allowing CO2 to diffuse throughout the body?

Andy
 
Looking at the flip side of any concept can make for some interesting and fun analysis. Thanks for the question and I'll take a shot at the answer.

In this case,vasoconstriction prevents the large muscles from sending co2 back to the core. The big o2 users in the core should be the gut, heart and brain, and I expect blood flow to the gut also slows down, leaving only two major users. The question becomes: do the brain and heart turn more o2 into co2 than the large muscles during a static. Good question; in static, they very well might. However, if I understand dive reflex induced vasoconstriction correctly, blood flow to the extremities not only slows down, blood pools in the core, ie drains from the legs and arms. If that is true, the dive reflex is a gain in static because there is much more blood in the core to dilute the co2 even if the brain and heart use more o2 than the large muscles.

I think that's right. Anybody else got an opinion?

Connor
 
Hi Connor,

yep that does make sense for the blood in isolation but what about the muscles themselves as I thought they were great store of CO2 themselves. With out the blood flow to the muscles they are removed from taking on CO2 from the blood via partial pressure differences and thus the blood becomes the main store. Again I think we have a dilemma as we want vasoconstriction and localised blood stores for efficient use of O2 during a static but we then are stuck with the CO2 concentrations increasing in that same "store" when really it would be great to send the CO2 off to the extremities (muscle etc) and keep the O2 for the core?

.....perhaps I'm off track here.

regards

Andy
 
Last edited:
I see your point. Is the answer simply getting used to very high levels of co2?

Connor
 
co2 and o2 are both stored in the blood. How would one accomplish the seperation of co2 containing blood from o2 containing blood? If you could seperate them, wouldn't the local acidity of the co2 portion become a problem? Are vasoconstriction and pooling of blood in the core equivalent? If not what specificly triggers these two potentially different reactions?
 
It is true that vasoconstriction decreases your CO2 buffering ability. This is why doing static while vasoconstricted often results in earlier contractions. As an example of this, the latest I have ever had a first contraction in dry static is 6'22", while the latest I have ever had a contraction in wet static is about 5'30". Both examples are with maximum hyperventilation (i.e. not resulting in the longest ultimate static time, just delaying the first contraction for as long as possible).

However, despite the earlier contractions, you do save in other ways. In particular, the extremeties are prevented from consuming O2 from the blood.

A weird side effect of the smaller CO2 buffering capacity is that hyperventilation has a faster effect. In that sense, many people have found that the same level of hyperventilation makes them hypocapnic much faster in the water, than on dry land. Thus, many divers use a less aggressive breathing pattern in the water. The exception is once you get cold. Once you get cold, thermogenesis and decreased CO2 solubility make things complicated.
 
I have noticed that hyperventilation has a much greater effect in water than on land, but I thought it was only because of being cold. It is good to know that maybe things are better than I thought!

Lucia
 
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