Exercise and bends

[pescador775]

Summary of ariticle published recently in a popular science magazine:

Zeljko Dujik, physiologist at the University of Split School of Medicine in Coatia says the secret to avoiding bends may be exercise. Dujic's team subjected 12 divers to an intense 40 minute workout on a treadmill. Twenty four hours later, the divers sat in a pressure chamber simulating conditions 60 feet underwater. After 80 minutes, the chamber pressure quickly returned to surface levels. Echo cardiograms showed one-fourth as many nitrogen bubbles in their hearts compared with readings in similar tests that were not preceded by heavy workouts. Dujic theorizes that nitric oxide in the body, produced during exercise, destroys most of the tiny 'bubble nuclei' around which larger bubbles form. He is not yet prepared to recommend exercise in place of other methods of dealing with the bends. But there seems no harm in working out a day before you slip into a wet suit.

 

[pescador775]

Raising the NO

Well, the possibility that the surface tension of the blood could be raised (?), or that micronuclei could be suppressed, and that the arterial passages could be (temporily) dilated, without arm waving, should suggest something to someone. Maybe not.

Other than some obvious prescription drugs there have been reports that nitric oxide levels can be increased by oral doses of L-arginine (arginine). Some proprietary mixtures of arginine and citrulline have been promoted by sports clubs. It seems that increasing NO levels is of some interest to serious athletes. Thus, this sort of product is available in various permutations.

 

[DocVikingo]

From the May '04 issue of "Undercurrent"
http://www.undercurrent.org :

"More About Exercise Before Diving and a pill to prevent DCS?

The investigators speculate that it may be possible to develop a drug for divers that would imitate the effects of general physical fitness.

In the March issue of Undercurrent, we examined the DCS risk posed by exercise before, during, and after scuba diving. We
concluded that strenuous exercise four hours before and six hours after diving should be avoided. We did not, however, address the possible effects of exercising well before the first dive, a topic that has received a flurry of interest in the wake of recent studies from the Norwegian University of Science and Technology.

While research conducted in the early 1990s suggested that
exercising the day before a dive suppresses inert gas bubble production and reduces the incidence of DCS, this line of inquiry was not given much attention until the present Norwegian investigations. These studies have shown that a
single episode of high-intensity aerobic exercise 24 hours before a chamber dive decreases the number of bubbles more than fourfold and cuts the maximum bubble size in half.

Interestingly, other studies by members of this research group
have shown that heavy exercise suppressed bubble formation and reduced DCI-related deaths in rats when performed 20 hours prior to a chamber dive but had no meaningful effect at 48, 10, or five hours prior. High-intensity exercise half an hour before a dive actually increased bubble formation.

Also investigated were the effects of a drug known to release
nitric oxide within the body — not to be confused nitrous oxide, the “laughing gas.” When given to rats for five days and then 20 hours before a chamber dive, or when nitric oxide itself was administered 30 minutes prior, both bubble formation and death were significantly diminished.

Why particular regimens of exercise interfere with inert gas bubble formation is unclear. However, this later study has generated the hypothesis that high-intensity exercise may enhance the production of nitric oxide, a compound that relaxes capillary walls, allowing them to expand. This change might allow micronuclei generated by exercise to be more readily eliminated, thereby inhibiting the growth of bubbles of
sufficient size to cause DCS.

Many experts have suggested that physically fit divers are at less risk for DCS because of healthier and more numerous capillary systems to efficiently eliminate inert gases. If so, nitric oxide’s capacity to enlarge capillaries transiently, and perhaps render their surfaces less sticky and less likely to trap particles like microbubbles, may mimic the effects of fitness — improved capillary blood flow and filtration.

These findings don’t contradict our earlier advice regarding
minimizing exertion before, during, or after a dive. However, if vigorous activity is undertaken, it might best be done around 24 hours before diving. And, once you start getting wet on a dive vacation, the simplest and safest approach is it to delay the weight lifting and marathon training until after returning home.

As for a magic pill, the Norwegian investigators speculate that within a decade it may be possible to develop a nitric oxide releasing drug for divers that would imitate the effects of general physical fitness. However, there are many questions to be addressed, including whether indeed nitric
oxide is a major player.

So, given the uncertainties and the research to be done, speculation that a pill will allow divers to stay down longer without increased risk of DCS reminds us of the always sound scuba advice — when in a difficult spot, remain hopeful and don’t hold your breath. — Doc Vikingo"

Best regards.

DocVikingo

 

[Dr Deco]

Hello Readers:

Exercise and Medicines

Divers – as is true of many others – are always looking for a shortcut with regard to health. I know, it is true with me also. We would like to find a pill to help us loose weight. And probably by processing it differently rather than by reducing the eating of “goodies.” Such gustatory treasures are only a small component of the Elixir of Life. In this case, the Elixir promises “bends-free” diving.
It is clear from all of the investigators that the protective effect does not occur if exercise is performed shortly before the dive. They knew this when they started and were investigating the question of nuclei lifetimes as described in the Dervay paper [Dervay JP, Powell MR, Butler B, Fife CE. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude. Aviat Space Environ Med. 2002; 73(1): 22-7]. Thus, any effect probably would be negated by exercise immediately preceding a dive.

That kind of activity is always a trouble maker. :no

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[pescador775]

That is a bit patronizing, is it not. It is more apparent than ever that blood chemistry is a crucial component of bends resistance. It seems to me that there is something about the chemistry of whales and pinipeds that suppresses bubble formation, ex explosive sound waves . Thanks submariners, for that.

The reason that divers do not get relief from some of these risk factors is the lack of research in the area of blood chemistry and nitrogen susceptibility. For too long, we have dwelt on the negative, scoffing at futuristic advances. Divers are programmed to buy more gadgets while ignoring the idea that we shouldn't be in this fix in the first place. We buy accident insurance while, for far less money, important research could be conducted to ameliorate this problem or, at least, modify it significantly. The danger lies in complacency.

Hello Readers:

Exercise and Medicines

Divers – as is true of many others – are always looking for a shortcut with regard to health. I know, it is true with me also. We would like to find a pill to help us loose weight. And probably by processing it differently rather than by reducing the eating of “goodies.” Such gustatory treasures are only a small component of the Elixir of Life. In this case, the Elixir promises “bends-free” diving.
It is clear from all of the investigators that the protective effect does not occur if exercise is performed shortly before the dive. They knew this when they started and were investigating the question of nuclei lifetimes as described in the Dervay paper [Dervay JP, Powell MR, Butler B, Fife CE. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude. Aviat Space Environ Med. 2002; 73(1): 22-7]. Thus, any effect probably would be negated by exercise immediately preceding a dive.

That kind of activity is always a trouble maker. :no

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[Dr Deco]

Hello Readers:

Blood Chemistry

I suspect that some aspect of the body’s physiology plays a role in DCS. Blood chemistry has been extensively investigated since the mid 1960s. In fact, for a couple decades, bubbles were believed by many (not me, however) to not cause DCS but rather be only a “trigger” that set into play some biochemical mechanism. The fact that pressure immediately relieves DCS (in its early stage), and a biochemical mechanism could not be pressure sensitive, made little regard. It was a fad in science.

Many (but not all) diving scientists believe today that there is an innate variability in DCS proneness. That is, it makes a big difference whether you dive one hundred divers once versus one diver 100 times. At one time, this was not thought to be true. [I am one who helped to dispel this notion.] I believe that this variability is traceable to some aspect of the body. It is by no means certain, however, that this variation lies in the blood is by no means a certainty.

Whales and DCS

It seems to be true that diving mammals do not get DCS in the course of their normal daily diving. This might be the result of small gas loads in breath-hold diving, it might be a result of minimal stress assisted nucleation in neutrally buoyant animals, and it might be a biochemical factor.

Research

It is true that some research in this area is neglected. Some of this is because individual variation is not a current topic in diving science. Part of it is because the proposals have not been funded. It is a sad commentary on science to realize the number of proposals I have submitted in the area of activity, individual variation, and DCS. All were rejected because of “lack of operational importance and interest.” And you would be shocked to see the ideas in the proposals that come to me for review!

I am now about to retire in a couple of years and no longer will be doing lab work in this area.

The problem can be greatly ameliorated by slower ascents and less strenuous activity on deck. That does not appear to be too hard. If one wanted to elicit DCS in laboratory subjects, I would simply dive the US Navy tables and do the opposite of what is suggested here. It is that simple - and you got it “for free” from NASA- government sponsored research.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[Coogeeman]

Hi DocVikingo

When you say that "strenuous exercise four hours before and six hours after diving should be avoided" would you class lifting weights as strenuous exersise or are you talking about cardio vascular exersise?

Thanks

Coogeeman

 

[Dr Deco]

Hello coogeeman:

Intervals

These numbers were derived by me a couple of years ago and posted in the FORUM. They are based on the lifetime of micronuclei formed by stress-assisted mechanisms and the washout of dissolved nitrogen from the longest tissue of consequence to recreational scuba divers.

Based on the research performed by me at NASA over the past 13 years, “exercise” would include both cardiovascular (running) and strength training (weights over 10 pounds). As on can see, this would certainly include climbing ladders, beach volleyball and the carrying of scuba cylinders.:sprite10:

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[DocVikingo]

I would class both lifting weights and cardiovascular exersise that stresses joints or leads to a potentially dangerously accelerated inert gas elimination rate as strenuous.

You may wish to read the following for a more indepth treatment of the issues--->

Exercise Before, During, and After Diving

http://www.undercurrent.org/UCnow/articles/Exercise200403.shtml

Best regards,

DocVikingo