New insights into exercise before diving

[Diver0001]

The local dive rag has an article in their September number about new insights into excercising before diving. Their conclusion was along the lines of:

- More research is needed becuase the test subjects were all well trained military personnel and the researchers didn't make any recommendations regarding the duration or intensity or how diver should apply this knowledge.

BUT

- ASSUMING you drink enough fluids to replenish what you lost from your excercise then EVERYTHING we were ever told about not excercising right before a dive is false and that excercising before a dive is, in fact, GOOD, not bad.

In typical journalistic style they don't cite or analyse their sources and the go on for pages about how excercise works and how we should all be come young, fit and happy like the picutres of young fit happy people they printed.....

Which all left me wondering what (if anything) can be made of this......

Dr. Deco, Are you aware of any recent excercise-before-diving studies and can you give us your take on what they're suggesting?

thx.
R..

 

[T-Dog]

There was a good presentation on "DCS Risk Factors" by Dr David Doolette at the NSS-CDS workshop last spring, which includes a section on exercise.
It was also presented at the 2008 DAN Technical Conference, and is available free to DAN members.
Just log-in to down load the presentation.
DAN Divers Alert Network

 

[Wayan]

There has a some study by DRDC (I believe from memory), results not conclusive however there are some indications that some light exercise before the dive may not be a big issue. The tests were vibration analysis tests to where the participants stood a vibration machine.

 

[jagfish]

There was a good presentation on "DCS Risk Factors" by Dr David Doolette at the NSS-CDS workshop last spring, which includes a section on exercise.
It was also presented at the 2008 DAN Technical Conference, and is available free to DAN members.
Just log-in to down load the presentation.
DAN Divers Alert Network

Crap, I'm a member of DAN Japan...no access....

 

[Dr Deco]

Hi Diver0001:

Exercise before a dive - if not very strenuous - appears to be OK.

In times past, I thought that exercise would create tissue micronuclei and contribute to DCS. It appears that whatever is generated is crushed by the dive and is of no consequence. There might even be beneficial effects of [supposed] nitric oxide.

I have list a few recent publications on this topic. If I were top go back further, you would find several more studies.


Dr Deco :doctor:


References :read:

[1] Dujic Z, Valic Z, Brubakk AO. Beneficial role of exercise on scuba diving. Exerc Sport Sci Rev. 2008 Jan;36(1):38-42.

Exercising before, during, or after diving is proscribed because of the
assumption that it would increase incidence of decompression sickness. Our
findings show that exercise performed in a timely fashion before diving or during
decompression will reduce the number of venous gas bubbles formed. Exercise after diving did not increase the number of bubbles. Nitric oxide seems to play a
protective role.


[2] Blatteau JE, Boussuges A, Gempp E et al. Haemodynamic changes induced by submaximal exercise before a dive and its consequences on bubble formation. Br J Sports Med. 2007 Jun;41(6):375-9. Epub 2006 Nov 30.

OBJECTIVES: To evaluate the effects of a submaximal exercise performed 2 h before a simulated dive on bubble formation and to observe the haemodynamic changes and their influence on bubble formation. PARTICIPANTS AND METHODS: 16 trained divers were compressed in a hyperbaric chamber for 30 . Circulating bubbles were detected with a precordial Doppler at 30, 60 and 90 min after surfacing. Haemodynamic changes were evaluated with Doppler echocardiography. RESULTS: A single bout of strenuous exercise 2 h before a simulated dive significantly reduced circulating bubbles. CONCLUSION: A single bout of strenuous exercise 2 h before a dive significantly reduced the number of bubbles in the right heart of divers and protected them from decompression sickness. Declining stroke volume and moderate dehydration induced by a pre-dive exercise might influence inert gas load and bubble formation.


[3] L?et A Jr, Mlerlken A, Berge V, Wislf U, Brubakk AO. Post-dive bubble formation in rats: effects of exercise 24 h ahead repeated 30 min before the dive. Aviat Space Environ Med. 2006 Sep;77(9):905-8.

INTRODUCTION: Recent studies have shown that a nitric oxide releasing agent or a single bout of high-intensity exercise 20-24 h before a dive can prevent bubble formation following decompression. The aim of this study was to determine whether high-intensity exercise immediately prior to a dive eliminates the protective effect of a single bout of high-intensity exercise 24 h before the dive. METHODS: Twelve female Sprague-Dawley rats were randomly divided into two equal groups. Group 1 performed 90 min of exercise twice, beginning 24.5 h and again 2.0 h before compression. Group 2 performed 90 min of exercise beginning at 25.5 h before compression.. All rats were exposed to a pressure of 7 ATA for 45 min in a dry hyperbaric chamber followed by
decompression to the surface at 1 ATA breathing air. RESULTS: Bubble formation was significantly higher in rats that had exercised 24 h AND 30 min prior to dive than rats that had ONLY exercised 24 h prior to the dive (median bubble grade 4.5 vs. 0.5).CONCLUSION: This study demonstrated that acute exercise prior to a dive eliminated the protection against bubble formation found 24 h after high-intensity exercise in rats.

 

[HBO MD]

Exercise has been controversial in relation to DCS. However, the references sited by Dr Deco ( thanks!) implicate nitric oxide, a potent vasodilator ; in other words, a compound which opens blood vessels. As such it enhances blood flow through tissues which would predispose to enhanced delivery and removal of gas in active tissues. Nitric oxide has had tremendous implications in the treatment of diseases of blood vessels, shock states and organ injury and remains the target of intense investigation.
Other factors also effect gas exchange locally in the presence of exercize; eg, the development of acidosis and it's effects on O2 delivery/offloading (increased), local tissue injury ( the so-called cause of autocthonous/heterocthonous bubble formation), the underlying fitness of the subject, the physiological reserve ( ie, the capacity to deal with the stress of exercize), etc.

Unfortunately, we lack the practical instrumentation to measure alteration in the "micro-environment " of local tissues. However there is much promise with such technology as Near Infra Red Spectroscopy, which measures tissue oxygen dynamics non invasively.

So is there any recommendation that can emerge from all this? Probably no definitive one and to consider that the protective benefits of exercise in terms of DCS remain speculative at present.

Just my 2 cents

Safe diving guys.

 

[NiclasG]

Take a Viagra before the dive?
but it wouldn't be comfortable after dressing!

Niclas