What depth/frequency is a concern for pushing the "bent" limit?

[Noah]

As I push deeper, longer spearfishing... I am curious of the facts.

Thankyou for your time, Noah Metzger

 

[Rik]

That depends how frequent you dive to an certain depth. You can get badly bend in just 20 meters of water due repetitive diving during three or four hours. For deeper depths, this would be earlier.

 

[cdavis]

Efattah knows more about that that most anybody and has posted some specific detail in the last 6 months. Sorry don't remember the detail, beyound my ability, but if you search all his posts for the last 6 months, you will find what you seek.

Connor

 

[Noah]

Rik... you're not making me feel any better Haha...

Thanks Connor, you still fooling with that half breath diving stuff?

 

[Moana]

As I recall in the PFI course we spent at least twice as long on surface intervals than we did underwater. This was for shallow depths like 20 meters or less. Going deeper, I recall more like 4:1. This is just recollection and could use verification by someone who knows for certain or has recently taken the course.

 

[cdavis]

HI Noah. Half lung is wonderful stuff. I'm a permanent convert. I can even do reasonable depth with it, 30 m+, as long as I train regular.

Connor

 

[Moana]

I confirmed with my friend who is a PFI instructor. This is their surface interval recommendation.

2:1 <25m
8min 25m-40m
40m+ not sure, but a long time, plus O2 for 5min if possible

JD

 

[growingupninja]

That depends how frequent you dive to an certain depth. You can get badly bend in just 20 meters of water due repetitive diving during three or four hours. For deeper depths, this would be earlier.

As I learn I am beginning to realize that I have been mildly bent from spearing in past; last summer Ihad some marked confussion and vertigo after a a day of diving which I just wrote off as exhaustion but I realize now was mild tarvanna. 3rd day in a row of spearing (3-6 hours per day, dives from 50-90', mostly about 70'). My elbow is jacked right now and I have been worried it is bent. I hurt it a few weeks ago, but it wasn't too bad and I didn't need to rest it much and I continued training/diving. A week later I dove again and was doing 40'-60', long bottom times, short surface intervals. Probably in the water for about 3 hours. Within an hour of getting out my elbow was was in a lot of pain. That as 10 days ago and I have been resting it but it is not much improved. It comes and goes, sharp pain, dull ache, sometimes a tingle. It feels like a sprain and maybe it is but it does worry me. I am actually planning to do an in water scuba deco hang at the end of the day next time I am fishing deep from a boat; I am much fitter now and know I will be well within the risk range.

I think I would be at a greater risk but as I mostly shoredive in california and I don't do much surface swimming, I usually do progressively shallower dives as I come back shore. Times when I suspect I might have been bent I was diving from a boat so it was just the deep end the whole session.

 

[Noah]

Spooky stuff, never really thought about it much... Good info Moana, thanks!

I'm primarily spearfishing, usually all day... as hard and deep as I can haha.... been gradually pushing past the 30m mark the last few years, and with a new boat on the horizon... ... it's looking like I'm gonna be able to hit it real hard this year...

... hence why I'm finally researching this DCS/freediving stuff... suprised I've not had any issues yet honestly!

 

[EARL1220i]

nice topic guys got dcs bad freediving experience but i change my dive habbits after that its just 25m but after that i have gone deeper and more relax bout my bottom time and consious to the surface interval the longer the better twice or more than the bottom time dive safe guys

 

[Mullins]

As I learn I am beginning to realize that I have been mildly bent from spearing in past; last summer Ihad some marked confussion and vertigo after a a day of diving which I just wrote off as exhaustion but I realize now was mild tarvanna. 3rd day in a row of spearing (3-6 hours per day, dives from 50-90', mostly about 70')

More likely to be dehydration I would say. If that kind of diving was likely to result in DCS there wouldn't be many freedivers or spearos left alive. I reckon people are a bit quick to jump to the conclusion they have DCS because it's cool - means they must have been diving really deep.

 

[growingupninja]

More likely to be dehydration I would say. If that kind of diving was likely to result in DCS there wouldn't be many freedivers or spearos left alive. I reckon people are a bit quick to jump to the conclusion they have DCS because it's cool - means they must have been diving really deep.

Perhaps it was exhaustion; it was easily the hardest day of diving I had ever done. I doubt it was dehydration or electrolytes as I was drinking water and taking vitamins, etc, and still pissing like a racehorse when we got back to the launch ramp... and I have been all kinds of dehydrated and exhausted and beat-up from other sports in the past but it wasn't like this. Besides mild vertigo what was strange was that on the ride back to the house I was really confused for a bit and I thought we were riding in my mom's car... I started to ask my dad about it--I couldn't understand how he was towing the boat with my mom's car. And then I realized I we weren't in my mother's car. Perhaps all the shots to the head I have taken in my life caught up to me in that moment.

Granted I think my elbow is just hypochondria and me going crazy because the white sea bass are running in the kelp 45 minutes from my house, 200 yards offshore, and I am stuck with dry dynamics and reading internet forums.

 

[Bill]

There have been a few tables posted here over the years. I have a note, with no reference, that discusses similar dives. Three minute dives to thirty meters with one and a half minutes on the bottom and two minutes on the surface will put you over in less than two hours. It also means your the best diver that ever chased White Sea Bass. If you use a surface interval of five minutes, you can do it for eight hours and not go over the red line. Note the restriction though. Thirty-five meters per minute. Surfacing in twenty seconds will change things big time.

 

[Mullins]

Those numbers seem pretty close to reality i.e. the very best spearos sometimes find themselves in DCS territory.

G.U.N. - that'd drive anybody mad.

 

[efattah]

It depends a lot on your susceptibility to DCS. It also depends on how fast you ascend in the last 15m.

Since you don't know your susceptibility in advance, you must assume you are susceptible. In that case Bill's profiles will kill you way faster than advertised.

3-6 hours at 70 feet (22m) can definitely cause DCS if you are susceptible. Luckier divers might get away with it. A few long dives to 40m can already stuff you up if you're unlucky.

I would ignore the PFI rules since I got bent many times while following the 8min interval after 30-40m dives (Herbert too).

The problem with surface interval 'rules of thumb' is that the surface interval you need to take keeps increasing dramatically after each repetition. As an example, dive to 40m, rest for 2 minutes on the surface. Now, after each 40m dive, increase the surface interval by 50% compared to the last dive. So the surface interval would be 2, 3, 4.5, 6.75, 10.1, 15.2, 22.8min, and so on. This is not itself perfect science either but that is similar to what you will get if you use a freediving computer like the Xen.

You can download a fully functional Xen simulator that you can run on your PC. You can play with it and see what your real surface interval would need to be after a series of dives. It should be online in the next day or two.

 

[growingupninja]

Thanks very much for the info, Bill, Mullins, and Eric. The incident last summer was in Florida while snapper fishing; I definitely wasn't hitting the numbers Bill described but I was doing a number of shorter dives over a much longer period. In California our depths are relatively shallow, especially for WSB but to get halibut year round we go a little deeper. Since I have started training regularly my bottom times and 'all day' depths out here have gone up much faster than my surface intervals but winter temperatures have been limiting my total dive sessions, maybe for the better.

I will study the charts and try out the Xen program. I got lucky on a lot of fronts for diving but don't know what my DCS threshhold is.

 

[Moana]

The problem with surface interval 'rules of thumb' is that the surface interval you need to take keeps increasing dramatically after each repetition.

Agree. This makes perfect sense when you look at scuba tables too. During your surface interval, you eliminate some nitrogen, but not all. It's still accumulating each dive. I think PFI rules work fine for target dives since we generally would not do more than a handful of dives and certainly not more than a dozen dives in a session. However, when I spearfish in an area where you dive deep repetitively, I might do 40-50 dives.....flirting with danger I suppose.

 

[azapa]

It may be me and the fact that I don't do deep spearing (its hard in a 7mm suit) regularly, but when I do it is always completely exhausting and not, as far as I know, DCS.

I normally spear between 12 a 17m for 3 hours, about 20 to 25 dives in that time with very little fatigue. Last time I went deep spearing in warmer waters, from 25 to 32m I was dead that evening. The bottom times were 1:30 to 2:00 and the surface times at least 5 or 6 mins (we were diving in a group of three, one diving two watching/resting). The dive session was about 3 hours, but with the boat moving between points, I am sure I only did 15 drops in total.

I make this point because DCS and the fatigue of deep repeated diving may be confused?

 

[growingupninja]

It may be me and the fact that I don't do deep spearing (its hard in a 7mm suit) regularly, but when I do it is always completely exhausting and not, as far as I know, DCS.

I normally spear between 12 a 17m for 3 hours, about 20 to 25 dives in that time with very little fatigue. Last time I went deep spearing in warmer waters, from 25 to 32m I was dead that evening. The bottom times were 1:30 to 2:00 and the surface times at least 5 or 6 mins (we were diving in a group of three, one diving two watching/resting). The dive session was about 3 hours, but with the boat moving between points, I am sure I only did 15 drops in total.

I make this point because DCS and the fatigue of deep repeated diving may be confused?

It would seem so... I think I read a study where divers were medically examined after long sessions it seems they were prone to confuse fatigue and DCS--thinking that they were really fatigued when in actuality they were showing symptoms of DCS, and it would follow that paranoid spearos would confuse fatigue with DCS . Given that information though I don't know how many spearos would modify their diving that much unless the DCS was severe.

It's good to be aware though. EFattah's info on rate of ascent is helpful; I usually go slow on all aspects of a dive since it makes bottom times better for me but if ascending vertically, I do ascend faster than 1m/sec.

I had my elbow xrayed and the doctor said it was probably bursitis. I had taken a lot of blunt force from a fall on some rocks that split the skin under the wetsuit. It hurt and stayed swollen but didn't really slow me down--still training and playing hard, then a week later when I went diving again and after that it was 2 weeks of excruciating pain. I obviously didn't let the initial injury heal and then I think cramming a swollen injured elbow into a tight wetsuit for three and a half hours caused massive irritation to the nerves and tissues. It's getting better finally.

 

[RPGgrenade]

isn't there someplace where there's a strange mathematical equations where X is depth, Y is time diving and Z is interval rest time? (or maybe more complex than that, but you know what i mean)