• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Remember my thread about sleeping after diving?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.


New Member
Aug 9, 2002
My preliminary information is sketchy at best, but from what I am hearing, there are "micro-bubbles" in the blood after diving, and these affect the neurological system in the body causing sleep and a few other disorders.

This could be the cause that makes some of us real sleepy after a few hours of diving. I spoke to a guy who brought up this subject who claimed to know a little about this stuff. He claims that this is on the cutting edge of diving research. I have no way of verifying the truth , but he says that Duke University and the US Navy are researching this right now.
I thought this was a well known phenomenon. It's called non-clinical DCS, and it always makes scuba divers sleepy after diving.

I've gone on many trips with scuba divers, where I was the only freediver, and they all dozed off after the dive, and I was wide awake.

Eric Fattah
BC, Canada

Eric maybe its cos your super fit, and they were lazy asses.

Sub-clinical DCS can be caused by incorrect or incomplete decompression.
I can remember being totally wiped out after deep diving in the old days of US Navy tables and deep air diving. I would sleep all the way home on the boat and then need another nap in the middle of the afternoon when I got home.

Since I have switched to mix for my sucba dives AND incorperated deep stops on ALL of my dives I no longer have the same post-dive fatigue that I used to.

After a deep dive where I utilize nitrox and 02 for my deco I feel like I could go right to the gym and work out for a couple of hours. I actually feel better, more energized, after the dive.

Now, I noitce that I get tired after a full day of freedivng. Of course, I am in the water about 10 times as long as scuba diving, and the water tends to be little bit more on the cold side around here, so I imagine that I am just burning through a lot more calories on those days.

The divers I was with who were all tired were diving nitrox on air tables, so it still sounds odd.

Eric Fattah
BC, Canada
It can still make a difference on how they did their safety stops and which set of air tables the were using.

If I use deep stops, I can come out of my air dives feeling better than If I dove nitrox and didn't use them. Making sure that the bubbles never get a chance to form in the first place makes a difference in your deco obligations and your post dive fatigue.

Of course, it could be realted to exposure protection.
If their diving cold water in wetsuits they will get a lot colder than if they dive in drysuits.

I know that we all use wetsuits in freedivg, but they are warmer than scuba suits. Also,when we are on the surface they are fully expanded to keep us extra warm. Bubble blowers are down on the bottom the whole time with their suits squeezed thin as paper.
People wonder how I dive the great lakes in the summer with just a 3mm. The trick is that only the bottom water is in the 40's. The surface water can be almost 70 degrees (F)- in August. You can afford to dip down to 40's quite a bit if your surface interval is spent in 65 degree water. :D


so this sleepy thing, bubbles or whatever does not affect freedivers?


My vague theory about sleepiness after freediving is that it has something to do with the intense chemistry going in relation to recovery from anerobic metabolism.

I began to think this after observing a friend training up for a free immersion record. He's an extremely fit and powerful athlete, yet, after the daily open water training session involving no more than 2-3 warm up dives and one (1) target dive in the 80 - 90 meter range, he would fall stone cold asleep in my (very noisy and very hot, un-airconditioned) car on the way home from the marina.

Since he had not really exerted himself all that much, and had not spent more than 5-6 minutes total at any serious depth, we figured that what was going on was that his very sharp blood shunt was leaving his legs unoxygenated, thus foricing the tissues there to go make their living anerobically for a couple of minutes, thus incurring a large "debt" in the form of undone biochemical assets, the rebuilding of which is very energy intensive.

I often notice that I am very sleepy - sleepy, rather than tired - after low-intensity / long-duration apnea activities like safety spotting for a group of clinic students.

Eric ? Anything to this notion ?

Now that you mentioned it! I too get sleepy after 45 min static or beter after a max attempt.
But i never asked myself why.

Hi Paul

During hyperbaric testing (Tanya Streeter and I), we have experienced what you are talking about.

Between 1 and 4 hours after deep dives (more than 60m), the following symptoms appear: tiredness, dehydration, raise of the body temperature.

After investigations, we have discovered that some of the red blood cells were damaged, involving a lower oxygen supply.
The physicians from the hyperbaric center have compared the symptoms and effect to HPNS that deep saturation divers are experiencing.....

After the tests (2 times 1 week in 2 years),we have determined that a 48 to 72 hours interval between deep dives should be observed to have a good recovery.

It doesn't surprise me that a fit freediver like the one you are talking about falls asleep in your car......

The guy I spoke to called it "non clinical DCS".

I wanted to blame the blood shunt, but I figured that since I wasn't doing dives deeper than 12ft, it wasn't that. I do negatives to 12 though... I wonder if that has anything to do with it?

So they related your symptoms to HPNS....hmmm. HPNS isn't known for making you sleepy. Usually nausea, tremors, loss of dexterity are your main indicators. There are some more serious side effects, but none of them "sleepy". (that I know of. I get my info from a book written in 1993. things change.)
I've never heard of non-clinical dcs, but it must be another term for sub-clinical. I double checked with someother friends, who had never heard of it either, but assumed that it must be the same. Tomato/ tamoto

I have to agree with TM about it not sounding like HPNS.

Have any of you been tested for a PFO? They have caused some incidents of unearned dcs in the bubble blowing comunity.

from what i understand here is that 'non-clinical DCS' makes you sleepy after diving, which isn't necessary a DCS symptom. on the other hand a PFO causes DCS with clear DCS symptoms.

as for DCS symptoms: according to 2 doctors i know and some books "extreme" fatigue/tiredness after a dive can be a sign for DCS.

i know of one diver who got bent on a 15m dive with a rapid ascent after 20 minutes. The hyperbaric doctor found PFO to have been the reason.

i personally don't experience sleepyness after shallow dives, but i do get sleepy after deep (40+m) dives.
The difference in symptoms is the difference between sub-clinical and a full blown case. If it's mild fatigue then you may have some microbubbling going on. If it's extreme fatigue you have a higher chance of developing a full blown case of DCS.

Just because you don't end up in the chamber doesn't mean that nothing happened.

Over a long period of time, repeated sub-clinical DCS can build up into other things like aseptic bone necrosis, arthritis and other nasties.

In scuba diving I have virtually elminated my own post dive fatigue with the proper use of deep stops ( or Pyle stops as some others might call them). I actually have more energy after a 60m dive with proper deco than shallower dives where I am donign repeated ascents all day long.
Freediving is another story. Since my freedives are less than 100', and I always stay on the surface for double my bottom time (gotta love a D-3 for that feature), I have assumed that mine were caused by the cold. I am sure that I would be tired after just swimming around on the surface for 6-8 hours in cold water.;)

Freediving to 60m+ puts all of the DCS stuff back into play. When you have freedivers pulling off 90m dives (not me) with total bottom times of 3 minutes, or more, I am sure that there is some bubbling going on.

There have also been instructors bent in shallow water doing training dives all day long. The repeated out-of-air assents can take a toll over time. So can not being properly hydrated.

so when you stop freediving that day and you are dead tired where you can't stay awake while driving home, should you head for a chamber? When does this form of DCS become dangerous? Just wondering.
I think that it has more to do with prevention than treatment at the sub-clinical level.

Fred said that they found improvement by spacing deep dives out 48-72 hours apart.

Kirk talked about taking your bottom time and doubling that time for your surface interval to help avoid the bends.

I believe that Freediver magazine has published soem tables (where they Spainish?:confused: ) that recommended certain surfce intervals for specific depths.

I just read the NAUI freediving book and they mentioned specific numbers of times that you can decend in a single day to specific depths fo rspecified amounts of bottom times- not quite sure if I trust the NAUI guidelines.

Keeping properly hydrated and resonably warm can also play important roles.

PFO test are done in tech diving, I wonder if anyone has start to usetilize them in freediving?

I have noticed a sleepy feeling after deep dives, especially multiple deep dives.

I know the rule about double the dive time to get the surface interval, but surely it cannot hold for deeper dives. I once got the sleepy feeling after I did two dives to 71m (around 2'20 - 2'30), with 12 minutes in between. I actually wanted to make the 2nd dive after 8 minutes, but I thought I should delay it in case of DCS. I checked a scuba model later and found that I was probably right on the edge of DCS, so I probably got non-clinical DCS (and sleepy). Same thing might have happened to Martin; could it also be a residual narcosis effect?

I had the same problem in Summer 2002 when I started doing training for long hangs at 20m-30m. We started doing hangs at 30m, but the hang times became so long that we were afraid of DCS, so we dropped it to 20m; but that famous first experiment on freediving DCS was done in 20m, so even then it can happen. I would really like to know what the interval needs to be. For example, 20m 4'30, 9 minute rest, 20m 4'30, 9 minute rest... etc... is this enough? Or what about 30m 4'00, 8 minute rest, 30m 4'00, 8 minute rest... or 37m 3'45, 7'30 rest, 37m 3'45, 7'30 rest etc...

I'd rather be safe than sorry. If anyone knows the surface interval needed please come forward.

Eric Fattah
BC, Canada
What about getting your own doppler bubble detector and start to put together some of your data into your own personal table?

I know that Wings Stock, a California tech instructor, had his own doppler unit about 10 years ago that he used after his deep dives to adjust his deco programs- at least that was the story he told me.

I am sure that you could find, or make, one to do the same tests on yourself.

Actually, it might be neat to get DAN involved and have them attend one of Kirk's, or other's, clinics and take data after a morning of diving. I know that they have done this in the recreational scuba arena.

What kind of surface intervals are Tanya, Loic, Pipin, Umberto and others using on their sled dives?

DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing


ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.