DCI and freediving

[sebastien murat]

for empty, read frc not full exhale. I've watched seb playing around, doing exhales in 15-20m, handsfree eq with a mask all the way and very much relaxed with it.

i'd imagine wet eq would give better DR than covering face with a mask though, whether on full or empty lungs, both from stress and from water contact.

No mask....just nose plug, but you can do that on water also.
Also compared full vs. empty to about 35m weight assisted/no swimming and got DR difference, but not as pronounced as graph above. Also compared cost of transport, in terms of end-dive exhaled PO2, to 20m and straight back to surface, with higher PO2 after exhale. The pattern is the same over many trials, but only if you can keep it aerobic. Once you have an elevated post-dive metabolic rate from a fatiguing (anaerobic) dive, the difference narrows, and you may never be able to overcome the conflict with the exercise and dive responses.

 

[sebastien murat]

The BIG misunderstanding in comparing F vs E is overlooking the work of descending and ascending. For example, you experience greater buoyancy losses on F. Bottom line, it may not work for everyone as there are several factors to consider. In the end you just have to dive a lot with both and under different conditions to know if it will work for you or not. If you dive a lot, you'll know what will work and what wont. I don' t believe you can reduce it to a theoretical discussion as it takes experience and time in water to know.

 

[Fondueset]

Regarding the guy who is getting Sambas on short swims. I know this is really basic - but relaxation/exertion is the biggest culprit. I've been explaining to the the lifeguards at my pool that they should not measure the special forces and coast guard guys underwater practice against mine. Those guys combine aerobic swimming with apnea and when they do dedicated apnea they use quite a lot of force. Instead of relaxing when the urge to breathe hits, they tend to swim harder. Hard exertion seems to block a lot of the sensations associated with hypoxia - not to mention making for abrupt blackouts.

 

[sebastien murat]

There's no problem, in my experience, swimming harder/sprinting, once a sufficient DR is established, i.e., provided its is substantial and established. I think that many can attest to that. The problem with this approach is if you have a reversal or a poor DR, because the DR can't counteract an already elevated metabolic rate, then your muscles will rob you and that will precipitate hypoxia/BO. Doing lots of trials (once again), and I don't mean one or two, and using a HR monitor you can work all this out for yourself.

 

[no bubbles]

How about Fred Sessa who's going continue kikcs all the way. That's impressive, he must have a good DR and good lactic resistance

 

[Fondueset]

Agreed. It never gets the chance to kick in (assuming the potential is there).
During some open water dives yesterday I experimented a little with diving on a full (not exhaustive - but definite) exhale. It was made necessary by trying to get photographs in shallow water.

What was interesting was the duration, relative to breathe-up, and how clean and easy the dives felt. My HR definitely dropped more than on inhale - though I have no monitor and couldn't quantify it.

There's no problem, in my experience, swimming harder/sprinting, once a sufficient DR is established, i.e., provided its is substantial and established. I think that many can attest to that. The problem with this approach is if you have a reversal or a poor DR, because the DR can't counteract an already elevated metabolic rate, then your muscles will rob you and that will precipitate hypoxia/BO. Doing lots of trials (once again), and I don't mean one or two, and using a HR monitor you can work all this out for yourself.

 

[growingupninja]

Regarding the guy who is getting Sambas on short swims. I know this is really basic - but relaxation/exertion is the biggest culprit. I've been explaining to the the lifeguards at my pool that they should not measure the special forces and coast guard guys underwater practice against mine. Those guys combine aerobic swimming with apnea and when they do dedicated apnea they use quite a lot of force. Instead of relaxing when the urge to breathe hits, they tend to swim harder. Hard exertion seems to block a lot of the sensations associated with hypoxia - not to mention making for abrupt blackouts.

In my experience--ancedotal in the water since I don't have a HR monitor I can dive with but something I regularly monitor doing dry dynamics--I have to agree with Seb. In my case, on dry land, once low O2 DR is established (real peripheral vasoconstriction and bradycardia), my level of exertion does not change rate of bradycardia or seem to signficantly increase O2 consumption. HR continues to drop even if I increase rate of exertion, although lactic acid is inescapable and currently my limiting factor on dynamic swims. I should probably videotape the readout on my monitor sometime so I can have a fully objective measurement.

This is the ancedotal part--low O2 DR happens independent of exertion, but in my case I feel like exertion reduces cold water DR. In the ocean off the coast of LA (which is usually 54-66F at the surface and colder under the thermocline), beginning a dive with a very low level of exertion and high state of relaxation--for me a conscious slow down--seems to really help a comfortable DR start well before I am actually hypoxic (low O2 DR for me is not 'comfortable' and it takes a while to get there on a full lung). Ascent I also keep very slow, everything in the same slow rhythm, and on surfacing frequently experience the sensation I associate with release of vasoconstriction. This dive profile gives me by far the best bottom times and feels easier than a 'quicker' dive to the same depth, even if the quicker dive is still aerobic (ie not a sprint where I'm incurring a lactic debt or high CO2). These are serial 20M-ish drops, maybe a little bit of lateral movement on the bottom but not much.

Seb's observations on rising HR during ascent phase is very interesting and not something I have considered but will be thinking about. Because of our water temp and my response to it, out here I feel like empty lung diving is less practical than full, unless when used to counteract suit bouyancy when navigating kelp. However, when I travel, I am typically diving deeper in warmer waters and so reduced DR from warmer conditions becomes a greater safety concern, and for the record I am not in a situation where pre-dive anxiety/stress would prevent me from relaxing before the dive. I will probably repeat my cold water face dunk experiment and videotape my pulse O2 meter, now that I have one, and pay attention to pre and post immersion response, and try a couple different water temps. Again it is ancedotal, but other California divers I know say that diving in warmer water feels 'harder' for them, even if we do appreciate 100' tropical viz.

 

[sebastien murat]

How about Fred Sessa who's going continue kikcs all the way. That's impressive, he must have a good DR and good lactic resistance

Don't know his specs, so can't say. But I know of people with really consistantly pronounced DRs. Maybe he's one of them. Does he do warm-up swims? What's his BMR? Is he an anaerobic power house? What's his O2 storage capacity? See my point!

 

[trux]

Fred is indeed an anerobic power house (ex-swimmer). I am not quite sure about his DR, but his static times used to be quite miserable for long time - although he reached the 200m within around 6 months after starting with freediving, hist static times were around 4 minutes. In the meantime it changed, but his DYN style is still very similar - he is probably the fastest elite freediver. He sprints from the start to the end. I remember seing him at his first big competition in 2008, where he did 200m DYN and over 160m DNF, both without any neckweight, and in incredible tempo.

 

[sebastien murat]

The best measure of whether there's a difference in whether you can swim faster with no penalty compared to slow is the time difference. For me, static E in water vs. static + dynamic E there's no time difference at max effort.

 

[sebastien murat]

The best measure of whether there's a difference in whether you can swim faster with no penalty compared to slow is the time difference. For me, static E in water vs. static + dynamic E there's no time difference at max effort.

 

[rddk]

For those who has asked about full lungs and wet equalization, when i was in France, with seb we tested the HR of full and empty going down with and withouth mask with same conditions: dept, temperature etc, i was going down on freeimmersion style to 10 m and the difference between full and empty was amazing somthing like 10 beat at minutes, the DR on empty and withouth mask was a lot stronger even on me and as him i experienced low HR after surfacing for 20 second than it started going back up.

 

[rddk]

I was doing wet equalization in both cases: full and empty and the differences between the two was really significant, even considering that for me was a really bad day cuz was really tired and was starving.

 

[growingupninja]

I was doing wet equalization in both cases: full and empty and the differences between the two was really significant, even considering that for me was a really bad day cuz was really tired and was starving.

Okay, thanks. That is helpful for me to know. I don't doubt that difference between HR was significant as I have played with different lung states in all my pool training. This is all very helpful as more and more I have been trying calibrate a sweet spot for the way I dive (and water temps I dive) which balances safety, depth, ease, and sustainability.

One other variable in the full vs empty discussion--at least in my book--is chest compression. Is there any thought on that aspect? I know that this is another area where medicine hasn't entirely 'caught up', but most freedivers agree that chest compression due to depth causes DR that is independent of O2 level. Makes me wonder chicken or the egg. No doubt many many factors at work.

 

[sebastien murat]

Fred is indeed an anerobic power house (ex-swimmer). I am not quite sure about his DR, but his static times used to be quite miserable for long time - although he reached the 200m within around 6 months after starting with freediving, hist static times were around 4 minutes. In the meantime it changed, but his DYN style is still very similar - he is probably the fastest elite freediver. He sprints from the start to the end. I remember seing him at his first big competition in 2008, where he did 200m DYN and over 160m DNF, both without any neckweight, and in incredible tempo.

Sounds like he tackles freediving like a swimmer....stuck in speed mode. Meaning, he could be even better.

 

[sebastien murat]

Here's another set of graphs. The 45m one is on full, the one to 25m on empty. Both are weight-assisted/no swimming/fast descent/ascent/same system/same temperature/same preparation (e.g., ventilation). The dives are with the Galileo. Note the HR profiles: lowest HR during dive and HR trend post-dive. These dives are not at all stressful, should you be thinking that perhaps I was more stressed on empty to 25m or hypoxic 30" into the dive. Indeed, I'm 20m deeper on full. The HR on the full is so high that it's even questionable whether I have a significant DR and, therefore, any significant ascent tachycardia, since its already highly elevated. You'll note my previous suggestion as to why it may be best to wait or very much slow down the first 20-30 seconds, at leasr till the DR is established before dropping so quickly to depth (think pressure gradient and N2 loading). If I wasn't able to establish a substantial DR on full, as exemplified by this 45m, I would have picked-up so much N2, I'd probably be screwed if continued to great depth, or I'd have to deco. Anyway, my particularities and thoughts, if you're interested.

 

[Bill]

Can anyone re-post this in a Mac friendly file? Please.

 

[Simos]

Can anyone re-post this in a Mac friendly file? Please.

I am on my phone so can't do it but if you install Open Office, you'll be able to open it - it's free.

 

[trux]

Here you go:

 

[growingupninja]

Here's another set of graphs. The 45m one is on full, the one to 25m on empty. Both are weight-assisted/no swimming/fast descent/ascent/same system/same temperature/same preparation (e.g., ventilation). The dives are with the Galileo. Note the HR profiles: lowest HR during dive and HR trend post-dive. These dives are not at all stressful, should you be thinking that perhaps I was more stressed on empty to 25m or hypoxic 30" into the dive. Indeed, I'm 20m deeper on full. The HR on the full is so high that it's even questionable whether I have a significant DR and, therefore, any significant ascent tachycardia, since its already highly elevated. You'll note my previous suggestion as to why it may be best to wait or very much slow down the first 20-30 seconds, at leasr till the DR is established before dropping so quickly to depth (think pressure gradient and N2 loading). If I wasn't able to establish a substantial DR on full, as exemplified by this 45m, I would have picked-up so much N2, I'd probably be screwed if continued to great depth, or I'd have to deco. Anyway, my particularities and thoughts, if you're interested.

This would speak to chest compression as I imagine the amount of compression between 45M full and 25M passive exhale is comparable. Makes sense that for a full lung attempt, a stop on the way down to establish DR--if the diver responds to that trigger--might be advantageous.

From my peanut gallery perspective, I redid cold water tests (52F - 44F) on myself, videotaping my pulse O2 meter, and ultimately got the same amount of bradycardia despite full/empty. Nothing remotely hypoxic or extraordinary; holds to between 60-80 secs. Meter read 47-49 BPM on one day (I had trained that morning). Empty lung the drop just happened faster and held longer after finishing the hold. The next morning I did the test and it was 43 BPM on a full lung after 80 secs and did not test further as I was in a hurry to get in the ocean. I had done the test before with just pulse from wrist and thought I had lower values but while it is certainly possible it could also have been vasoconstriction--I remember having a really hard time finding my pulse, and the arrhythmiaas as it dropped made it very hard to measure. Watching the pulse graph on my meter, vasoconstriction seemed to happen faster than bradycardia. Also did some deep squats on a full lung with face immersed to see if exertion would 'break' the cold water DR. It didn't, but I would want to try exertion at the beginning of the hold, which from ancedontal experience does, I think, prevent my cold water DR from kicking in properly. I also want to start with cold water but warm it up after DR has started and see what happens (ie, coming up from below thermocline into warmer water). Low O2 DR happens for me regardless of exertion or water temp (or even water) but is not a state I consider 'recreational'.