Dive Reflex - Inhale Vs Exhale

[Phil C]

I have noticed a huge difference in how my DR comes on in an exhale hold compared to an inhale. I'm interested to hear about other people's experience (and opinions of course!).

The difference is well illustrated for me when doing uphill apnea walks:
I find that within 15 steps on a passive exhale my arms are tingling, my legs start aching and I start to feel lightheaded. At about 20 steps my thighs/hip area are developing a strong 'lactic burn'. If I break the apnea there and carry on walking the burn increases, reaching a peak at about 25 steps with me almost stumbling from leg fatigue. Repeats are less intense.

Doing the same thing on an inhale invokes minimal sensation.

Similar experience with dynamics. Exhale 25 DNF (done with an unweighted wetsuit to be neutral) can give me burn but I rarely get any lactic feeling on an inhale dynamic (even maximal).

Psychologically I struggle with exhales and so I have wondered if this stress is what makes the difference, however the last time I experienced a lactic burn doing a maximal inhale I was having a very relaxed swim.

How to replicate this (what I presume is) rapid and widepread peripheral vasoconstriction, but on an inhale dive?

I think that may be (for me) the BIG question.

PS - I am starting all these holds without any (conscious) hyperventilation, all the maximal inhales referred to are without warm up.

 

[cebaztian]

So What is the dive repsonse?

And what is it that you feel?

I guess you are mostly feeling the effects of low O2 and high CO2.

Put on a heartrate monitor and compare and then tell us.

Sebastian

 

[cdavis]

A heart rate monitor is a great tool. If DR is coming on faster on exhale, you should see a much faster drop in heart rate than you would on inhale. Sometimes, if your heart rate is very low to start with, it may not drop much even though DR is happening. A good clue is to watch it sky rocket after you start breathing again. That's what happens with me.

Something else is also going on, by taking down less o2 and having less room to store c02, you will feel the first urge to breath faster and it might directly affect how you legs feel during walks, outside of DR. It also helps kick in the DR faster, contributing to what you are trying to do.

How to get the same response on inhale? Now that's a good question. Part of the fast onset on DR is directly related to smaller lung volume and less space to store c02, so you won't ever get the full effect of exhale on an inhale dive. However, the more you inhale, the longer it will be to the first urge to breathe. My experiments in the pool show the DR starts setting in BEFORE the first urge to breathe. It should be possible to find the optimal place between FRC and a full inhale, the optimum mix of DR onset and O2/c02 storage, that will give you the optimum comfortable (safe) dive. That will differ between divers and type of diving. I'm working on that now in the pool and have increased my "real" diving time substantially as a result. Caveate: I'm interested in serial recreational dives to moderate depths(30 m or less). What is best for max dives could be quite different.

If you are diving shallow, increasing your weighting to lower effort on descent can compensate for increased inhale. Less effort going down helps the DR kick in early. Probably doesn't work for deeper dives, too much work coming up.

On FRC walks, are you pausing before you walk (until the first urge to breathe)? That gives time for the DR to set in.

Keep us posted on your results.

Connor

 

[hteas]

Phil,
I've always noticed the same thing. The reflex hits fast and hard when doing negatives. It should include slowed HR, skyrocketing blood pressure (normal for breathholds) and the burn and weakness. Not everyone agrees, but I think it's a great training technique.
Howard

 

[Phil C]

I agree, a more scientific approach is required. Maybe if I switch to a stationary bike on high resistance I can replicate. That would make it easier to read HR and (if I can lay my hands on an automatic machine) get some measurements of BP. (plus I will not look like a complete idiot sitting on a stationary bike in a bike helmet).

I'm interested in BP because I have a theory that the rapid change may be what gives me the lightheaded feeling.

Although not directly relevant, when I do an exhale dry static with HR monitor my rate drops very slowly untill about 80-90% through the hold (1:45-2:00 ish) where it drops to about 50-60% resting (30-35BPM)

I don't do a static at the start of the negatives (a'la Seb M) I just start walking, when I get to a hill I think 'time for some negatives'.

The rapidity and intensity of the sensations are a function of the workload. The hill that gives the strongest response is like going up stairs 2 steps at a time. I don't get the same response on level ground.

Reading back through the original post I thought some clarification required on what I am calling an 'exhale'. It is an exhale without negative packing or crunching but with maybe one or two gentle diaphragm lifts.