Exhaling during dynamics

[jimbodiver]

Just curious what other people's experience has been, (and recommendations regarding) blowing off some air during the last 10-15% of distance in dynamics. I sometimes find myself wanting to exhale some of my air as I approach the end of a dynamic run, and feel more comfortable doing so. However, I have no idea why this should be the case, or if it's even beneficial, or advisable. Could it even be "bad" in terms of reducing my distance potential? As background, I currently routinely only do 50 yards dynamic, with PB being about 65-68 yards (est). I cover this distance in about 50-58 seconds, depending on the actual distance covered in this range. My typical wet statics are only 1'45", with PB being just over 2 min....with contractions every 7-10 sec by the time I decide I've had enough.

That said, I realize I have a ton of room to improve on everything...I'm just getting back into shape, and am planning to take one of Kirk's courses soon, so expect to learn a ton of new things I can apply to improve my times, distance, etc.

In the mean time, I'm wondering if this is a good or bad thing I'm doing when I exhale as I push thru the last portion of a dynamic. If it's okay, at what point is it best to begin doing this? Thanks!

[DeepThought]

You feel more comfertable because the strong breathing stimulus comes from a high level of CO2 and not from a low level of O2. You are giving up O2 storage when exhaling and also reducing your breathing reflex therefore increasing your risk to blackout (and there are alos some blood pressure changes that might contribute to the issue) I suggest you'll stop doing that.
I hope you have a capable partner with you.

[loopy]

Nice avatar Micky

I agree though - basically you're blowing off a bunch of CO2, which makes you feel like you can go forever. You're also blowing out a bit of O2 though, which will limit you a fair bit. Getting used to that feeling at the end of a big dynamic/static and learning to relax through it will dramatically increase your times/distances.

[jimbodiver]

thanks guys....BTW, I never feel the urge to dump like that when doing statics, just during dynamics, and only at the last bit of the distance.

Since I'm not changing depth on the dynamics (okay, maybe 18 inches max) as I come up, I didn't think there was that much risk of a BO, esp if I'm not pushing for a PB...new distance. Is there still a big (or bigger) risk of BO due to my exhaling a bit during the last 10% of distance?

Also, it does make sense what you say about gaining some improvement in distance (dyn) and time (stat) if I'm able to resist exhaling this way. I'll see if I can try to resist more. As it turns out, in today's session my dynamic was full 50 yards without any exhale at the end, and I felt like I could have gone a bit more (but not that much, with turn-at-wall included!). Not wanting to push things (no buddy walking with me...just the usual absent-minded lifeguards hanging around), I just stopped at the distance I knew I could do repeatedly, without risk of samba, much less BO.

I seem to remember Eric F. posting something a while back about it being fine (maybe even preferable) to exhale some in the last ~10 feet of ascent on a CW dive...and that doing so might even DECREASE the risk of SWBO. Do I remember this correctly? If so, how does this advice change (or does it) when doing horizontal swims (dynamics in pool)?

[quasimoto]

jim:

you are right exhaling during the last 10 feet or so or a cw dive is fine and can reduce the risk of shallow water blackout. At the performance freediving clinic they had us practice doing that because as the lungs re-expand it starts to draw oxygen back out of the blood. If you exhale the vacuum effect on your blood will be lesened.

[ADR]

Loopy & Deepthought,

If your approach(don't exhale) applies to dynamics then doesn't it also apply to statics as there is little to no lung re-expansion on both events?

If you watch any of the videos or DVDs from comps you will see a number of people(some of the best) exhaling through the last 20-30secs of a static......On my PFD advanced course I was taught to do this at the end of every static. There is potentially more going on than simply the o2 and co2 levels and partial pressures at the end of dynamics and statics and we need to be careful we don't over simplify the situation......I don't have the answer but just have some doubts about the theories raised.

regards

Andy

[sebastien murat]

This issue of exhaling on ascent has always troubled me as I don't believe its clear-cut or even simple. My understanding:
From the ideal gas law,

PV=nRT

As the ambient pressure drops during the ascent there are two available options:

(1). expand lung volume -> reduced rate of of O2 diffusion from lungs to blood or reversal -> reduced arterial pO2 -> increased risk of BO/samba

(2). reduce n, the number of gas molecules in the lungs to keep the lung volume ~ constant/small. You do this by exahling into the surrounding water. But this has the same effect on arterial pO2 as (1). Wheter the lungs expand or not in this particular case the effect is the same, the gas has got to go somewhere.

There is no escape from a BO/samba by this reasoning except that the latter option may be the lesser of two evils since a reduced intrathoracic pressure associated with the latter method may facilitate venous return and maintain cerebral blood flow.

The bottom line: the best option is still to start off with a smaller lung volume.


Thoughts anyone ..... Ben, Eric

Cheers,
Seb

[Ben Gowland]

I think this is getting off the topic of exhaling in dynamics. A week or two back there was a thread on the issues of exhaling in the last 5 or so meters of ascent:

http://forums.deeperblue.net/showthr...threadid=53994

I agree with Seb in that in neither case can you have a large effect on whether you black out or not, but I would certainly say that (2) is the lesser of the two 'evils'. The thread above discussed why. FRV/exhale diving certainly seems a good way of reducing this sudden hypoxia of ascent - but again that is going off topic a bit.

WRT exhaling on dynamics (or statics), to be honest I haven't given it a lot of thought. One thing to note - from your description that you only do it in the very last phase of the dynamic suggests that rather than a CO2 effect, this may be due to the sudden and rapid oxygen desaturation that occurs in dynamics where the urge to breathe ramps up considerably.

Like with the ascent; if you are only swimming another 5m or so, i can't see that it would make much difference. If you are doing another 20m or so - I'd be inclined to hold the breath in in order to maintain stable blood pressure and keep as much of the little oxygen you have left available to your blood.

Ben

[DeepThought]

For safety I still hold my position regarding exhaling during dynamics (a 'no').

BUT on the other hand, what if someone is at his PB (dynamic or static), and things are getting dark?
Starting to exhale slowly will increase the venous return from the lungs to the heart with oxygenated blood (assuming there's still a higher O2 concentration in the lungs) and would also increase cerebral blood pressure, might this person still be able to stay conscious or even gain some of his senses back?

This should be an easy experiment for those who can stretch themselves to BO/LMC.... good luck.

[Aquagenic]

Ben,
Didn't you suggest on that previous thread that the effect of exhaling would not even reach the brain until about 3-10 seconds
later? If that is so wouldn't the same hold true for dynamic? In that case you would just have to watch black out AFTER surfacing, this could improve the safety, if only marginally.

Here's the quote:

"By the way - an extra hard kick at the end will have no effect on blackout or not as the deoxygenation of the blood in the muscle as a result of that kick will take at least 15 seconds (more like 2 minutes!) to make it's way back to the heart and then another 3-10 seconds before it gets to the brain."

~Picksmith

[Ben Gowland]

Close but not quite - blood takes that amount of time to go from heart-aorta-carotid-brain but blood pressure can be changed faster via arterio-constriction.

When on the verge of blacking out a shift in blood pressure could effectively become a brain on/off switch!

[DeepThought]

Originally posted by picksmither
Here's the quote:

"By the way - an extra hard kick at the end will have no effect on blackout or not as the deoxygenation of the blood in the muscle as a result of that kick will take at least 15 seconds (more like 2 minutes!) to make it's way back to the heart and then another 3-10 seconds before it gets to the brain."

Well, this is not exactly the same compared with testimonials I heard form other people regarding max performance.

Been told that many people at max performance get to a state where everything is black for a few seconds when they end their performance, and that in that instance, if they'll do the slightest move they know they'll pay for it with a LMC/BO, so they just stand still and wait for the newly gain O2 to do it's reviving job...

20 second AIDA rule shadow cruising?

[Ben Gowland]

I'm not quite sure what you are getting at here.

I've heard such 'testimonials' before but O2 consumption in static calf or thigh muscles could not account for 'pushing you over the edge', but the act of standing up can reduce blood pressure in the brain and make you black out. I.E. some 'efforts' do have a physiological impact on PaO2 in the brain and some do not.

Hope that clarifies what I was saying better.

The 1 minute (well 30 secs) rule is unnecessarily long IMHBPSO*. 10 secs to recover, OK, remove mask and 20 secs for decision, again IMHBPSO*.

Cheers,

Ben

*IMHbut-physiologically-sensibleO

[jimbodiver]

Wow...thanks for all the feedback guys....lots to think about.

In today's pool session I was able to easily do my normal dynamic (not pushing it), and completed distance withouth any exhale.....probably could have pushed for another 10-20 yards if I wasn't a wimp.

Then after resting a few minutes and not even really "breathing up" beforehand, I did about 18% above my previous PB for a wet static...and I wasn't even trying for PB....just finally decided the contractions were getting uncomfortable and I was ready to come up...had more in me. The watch reading surprised me. Go figure.

So, I'm guessing I was just a lot more relaxed that time, NOT having done as many minutes of deep breathing just prior....just was relaxing, then did 2-3 fairly deep ones (not packed), and started the static. Hmm. Guess I'll learn a LOT at the adv PFD course coming up. Thanks again for all the great comments in this forum!

[Walrus]

Hi all,
The PFD clinics now teach NOT to exhale underwater for statics. Martin said it feels good because it reduces the contractions but it doesn't buy you any extra time. They used to teach exhale the last 5 seconds or so before you come up and also to use Hook breathing. They have also now sugested not to use hook breathing for static because your blood pressure is already extremely high at the end of a static. I still do the exhale because it feels good and contractions stop. I don't think there are many people breathing out underwater for 20-30 seconds at the end of a static. I've never seen it anyway. Most people I've seen do something closer to the 5 second mark, maybe 10 seconds max.

Cheers,
Wal