New exercise + diving article

[ericdiver]

I saw this abstract referenced on the scubadiver.com forum and looked it up, couldn't find the full article however (not yet published 10 days after epub?).

Anyway, has anyone heard of this or seen the article (or are any of the authors on scubaboard)? Of course it's only one article, with 24 subjects and 2 dives each, but still very interesting for those of us who dive and make a serious effort to maintain fitness (which of course requires regular exercise which can conflict with regular diving). These results certainly seem different from the common recommendation of waiting 24 hours before or after diving to exercise.

The hydration/dehydration sideline is interesting too.


The abstract:

Eur J Appl Physiol. 2010 Nov 24. [Epub ahead of print]
Endurance exercise immediately before sea diving reduces bubble formation in scuba divers.
Castagna O, Brisswalter J, Vallee N, Blatteau JE.

Biomedical Research Institute of the Army (IRBA), Naval Medical Institute (IMNSSA-Toulon), Departments of Operational Environment and Marine and Underwater Research, BP 20548, 83049, Toulon Cedex 9, France, castagna.olivier@gmail.com.
Abstract
Previous studies have observed that a single bout of exercise can reduce the formation of circulating bubbles on decompression but, according to different authors, several hours delay were considered necessary between the end of exercise and the beginning of the dive. The objective of this study was to evaluate the effect of a single bout of exercise taken immediately before a dive on bubble formation. 24 trained divers performed open-sea dives to 30 msw depth for 30 min followed by a 3 min stop at 3 msw, under two conditions: (1) a control dive without exercise before (No-Ex), (2) an experimental condition in which subjects performed an exercise before diving (Ex). In the Ex condition, divers began running on a treadmill for 45 min at a speed corresponding to their own ventilatory threshold 1 h before immersion. Body weight, total body fluid volume, core temperature, and volume of consumed water were measured. Circulating bubbles were graded according to the Spencer scale using a precordial Doppler every 30 min for 90 min after surfacing. A single sub-maximal exercise performed immediately before immersion significantly reduces bubble grades (p < 0.001). This reduction was correlated not only to sweat dehydration, but also to the volume of water drunk at the end of the exercise. Moderate dehydration seems to be beneficial at the start of the dive whereas restoring the hydration balance should be given priority during decompression. This suggests a biphasic effect of the hydration status on bubble formation.


A link to the pubmed listing of the abstract (which I've copied above): Endurance exercise immediately before sea diving r... [Eur J Appl Physiol. 2010] - PubMed result

Eric

 

[ninjadoc47]

Hi Eric, I will read the article, that is very interesting. Somehow between the robust ideals of the 50's,60's & 70's , it has become the easy light hearted times of the 80's, 90's and beyond. It is great that more folks are into scuba, it is essential for divers to strive to attain better fitess.Its just common sense, it seems there has not been long term studies of whether our more adventureous forefathers of yesteryear were any less accident/incident prone as we are today bu tit'll a good thing to study.Who are the better participants in any sport ,those who more closely resemble the icons of the sport they are following or those who are more like the michelin man.I'm not saying you have to be a Navy Seal , but to more inline with veterans like Karl Shreeves, Tom Mount, Joe Dituri, Steve Bogaerts, who range from Kung Fu masters, to guys you can tell engage in a regular regimen but not built like Daniel Craig or Vin Diesal, it helps to have that to be a more effective breather,m efficient diver, and all around able diver , whether divung easy or a deep tech dive. Like Dr Tom Mount said" Training(all around) ,equipment(which includes a fitness routine and clothes) and Attitude( mindset to be the best diver you can be ). Cheers

 

[DocVikingo]

The exercise regimen described in this research was at each subject's "own ventilatory threshold."

The ventilatory threshold is that point at which ventilation increases above and beyond the increase in oxygen uptake. It corresponds to the lactate threshold, where maximal sustained breathing about balances production. By definition it is near the upper limit of aerobic performance. 45-mins of this type of running likely is beyond the endurance capacity of the average recreational diver (at least most of the ones I see), not to mention having the stamina to dive safely just 1-hr afterwards.

Regards,

DocVikingo

 

[Duke Dive Medicine]

It looks like the abstract was publicized ahead of publication... I can't see the full text on PubMed yet. I'd like to take a closer look at their protocols before drawing any conclusions on this.

 

[Dr Deco]

Hello Eric:

Exercise and Diving

Exercise comes in three types.

[1] The first is exercise conducted during all the months and years of one’s life. The goals are cardiovascular fitness, weight loss, reduction of depression, and muscle strength. This paper does not refer to this type.

[2] Another is exercise that is performed during the decompression phase of the dive [ascent and topside]; this is when the tissues are supersaturated. It is not addressed in this paper. This is the type that I investigated at NASA [for EVA] and have written about on SCUBA BOARD for the past decade. It is not good to do but is seldom discussed in the diving literature. It has the biggest effect on decompression outcome , I believe, after inert gas loading [i.e., bottom time and depth]. I attribute the effect to the formation [or enlargement] of tissue micronuclei. [Exercise during the bottom phase is also not good and has been addressed in research studies for many decades.]

[3] The third is exercise performed prior to the bottom phase. This has been related to nitric oxide formation, although this has not yet proved. This type of exercise is the object of this study. The study employs a cross-over design, my favorite. One hour predive, the subjects exercise for 45 minutes and then enter the water after 15 minutes.

They find that this scheduling of exercise is beneficial [with respect to formation of Doppler-detectable bubbles, anyway]. [Any micronuclei formed prior to exposure to the bottom pressure appear to be compressed and dissolve.] There is no indication of how large was the reduction in Doppler bubbles, and likewise no indication of whether this was consistent with all of the test subjects.

There clearly appears to be some biochemical involvement. It occurs rapidly, and it does not persist for hours following the activity.

Take-home Lesson

Physical fitness is good – for everyone! Exercise, such as hauling dive gear, before the dive actually appears to be protective with respect to DCS based on this one study, anyway.

As I have written for years, do not undertake strenuous physical activity for a couple of hours post dive while the tissues are supersaturated.

Dr Deco :doctor:

 

[ninjadoc47]

I t is a interesting article, I no longer train the way I did in the Navy, I still train prtty hard, I know I do not feel goo whne I have not exercised in awhile especially prior to diving

 

[Duke Dive Medicine]

Finally got the hard copy of this article and read it. Their methodology was interesting - Dr Deco, I'd love to hear your take on this if you've read it. For now, here's what I got from the article:

1. Based on the results of their study, the authors theorize that the dehydration induced by exercise reduces nitrogen uptake during a dive by reducing blood volume and thus cardiac output and blood flow past the lungs.
2. By having their subjects drink water immediately after exercise but before diving, the authors further theorize that, by the time the dive is complete and the divers are ready to decompress, the water has gone into the subjects' bloodstreams enough to rehydrate them and thus mitigate the negative effects of dehydration on decompression.
3. They concluded this because they found fewer doppler bubbles in the divers who exercised pre-dive than those who did not.

I'm not sure how much of this can be applied to practical diving, for several reasons:

1. These test subjects were all relatively young men in good physical condition diving in warm (77-82 degree) water after exercising and rehydrating under controlled conditions.
2. A diver in the "real world" would not be able judge his/her own level of hydration and rate of fluid absorption well enough to take advantage of this phenomena, if indeed the authors' conclusions are correct. I would submit that playing with one's hydration level on a dive boat would be inviting problems since dehydration is a well-known risk factor for DCS.
3. There were two variables: exercise and hydration level. To really conclude what they did, the authors would have had to have at least one more control group: one which was dehydrated by some other means besides exercise. That way, they could determine whether dehydration alone played a role.
4. There is controversy as to whether pre-dive exercise reduces venous gas emboli. In one recent study, exercise prior to diving had the opposite effect (http://archive.rubicon-foundation.org/dspace/handle/123456789/7793). Note that this is a meeting abstract only, so the full study protocol isn't available for review.

All in all, I don't think that this paper has much practical value for divers. Anybody else get anything different?

Cheers,
DDM

 

[ericdiver]

I agree that one study like this in and of itself is of limited value. It does of course in combination with other studies help provide guidance, although the fact that there were two variables does seem to make it hard to see what was going on in this particular study. It is interesting how seemingly-small changes in the study conditions can make a large and non-intuitive change in outcome.

My interest in this stems from the apparent conflict between being an fairly active diver (not to mention an instructor or divemaster who is hopefully diving multiple days per week) and the basics of developing and maintaining fitness. Even a basic aerobic routine involves running (or something) 4 or 5 days a week, plus one or two strength/resistance training days: the much recommended but rarely followed "most days of the week" approach to training. But this doesn't leave many open days for diving if we follow a 24-hour separation rule.

Dialing in an increased "personal factor" on one's dive computer to compensate for having gone for a run or ride a couple hours before a dive seems like a tempting solution but it doesn't look like the research is there to back it up. Has there been a study looking at how much shorter or swallower a "post-exercise dive" needs to be to achieve similar bubble counts to a "not-post-exercise dive"?

Thanks again,
Eric

 

[Duke Dive Medicine]

I agree that one study like this in and of itself is of limited value. It does of course in combination with other studies help provide guidance, although the fact that there were two variables does seem to make it hard to see what was going on in this particular study. It is interesting how seemingly-small changes in the study conditions can make a large and non-intuitive change in outcome.

My interest in this stems from the apparent conflict between being an fairly active diver (not to mention an instructor or divemaster who is hopefully diving multiple days per week) and the basics of developing and maintaining fitness. Even a basic aerobic routine involves running (or something) 4 or 5 days a week, plus one or two strength/resistance training days: the much recommended but rarely followed "most days of the week" approach to training. But this doesn't leave many open days for diving if we follow a 24-hour separation rule.

Dialing in an increased "personal factor" on one's dive computer to compensate for having gone for a run or ride a couple hours before a dive seems like a tempting solution but it doesn't look like the research is there to back it up. Has there been a study looking at how much shorter or swallower a "post-exercise dive" needs to be to achieve similar bubble counts to a "not-post-exercise dive"?

Thanks again,
Eric

Hi Eric,

There are a couple of other considerations:

1. Most studies that involve exercise and diving use VGE (venous gas emboli, or Doppler bubbles) to measure decompression stress. However, the presence of VGE is just that, a measure of decompression stress. VGE do not indicate the presence of decompression sickness, and there's only a small correlation between VGE and DCS related to diving. Although higher grades of VGE were detected in the "no-exercise" group in this study, none of the divers experienced DCS. Here's another study:

Rubicon Research Repository: Item 123456789/6938

In brief, it's a DAN study from 2000 that looked at 281 dives in 67 test subjects. Many VGE were detected, some as high as Grade III (IV is the highest), but no divers experienced DCS.

2. Another article: Aviat Space Environ Med. 2005 Jul;76(7):666-9.
Aerobic exercise 2 hours before a dive to 30 msw decreases bubble formation after decompression. Blatteau JE, Gempp E, Galland FM, Pontier JM, Sainty JM, Robinet C.
I couldn't access the entire article, but this one suggests that exercise 2 hours prior to a dive may reduce post-dive VGE. It's one of the references from the original study you asked about. The study was only 16 military divers performing intense aerobic exercise so is probably not applicable to all divers in all situations, but it's another piece of the puzzle.

As you asked, how do you apply all this research to your own diving and exercise routine, especially when some if it is conflicting? You've already figured out how difficult it is to make individual decisions based on the available research. I'm not aware of any studies that indicate how much shorter or shallower a post-exercise dive needs to be to reduce VGE (and thus the presumed risk of DCS), but once again, this question assumes that pre-dive exercise INCREASES risk of VGE, and there IS research that disputes that assumption.

From a medical standpoint, a conservative approach is best. I think that your idea of adding an increased personal factor on your computer after a regular maintenance run or bike ride is very reasonable. Beyond that, you're going to have to be the judge of what's conservative based on your knowledge of your own level of fitness, recovery time, and exercise routine. For example, are you planning on making a series of deep technical dives three hours after pounding out a max set of bench presses or going for a personal record 10 K time? Might not be not such a good idea.

I'm riding on Dr. Powell's coattails here because he's already said this, but overall physical fitness is GOOD, and you sound like a pretty fit guy. I also think it's worthwhile to mention the fact that most working military divers exercise strenuously on a daily basis. Physical conditioning has been demonstrated to have a protective effect, and I think that by being conservative and mindful of your own physiology, your risk of DCS post-exercise will be mitigated by your overall level of fitness.

Best regards,
DDM

 

[ninjadoc47]

TOTALLY AGREE, the studies are great, a diver I hope and pray, takes anything they read and have the sense to dial in their own personal paremeters(ie, experience, fitnss, health hx, diet and etc.) and function
safely, effectively and efficiently in the u/w realm. Its a matter of making sure to accept personal responsibility to your self assessment (your ultimate dive team mate) to mitigate risks of injury when diving.