New Research on Pre-Dive Exercise and DCS

[CameronMartz]

I post this information here as it has much in common with research that Dr. Deco has publshed on exercise and decompression to altititude.

Just last month, two new studies were published examining the effect of pre-dive exercise on resistance to DCS.

http://www.ncbi.nlm.nih.gov/entrez/...d&dopt=Abstract&list_uids=16018350&query_hl=5
Aerobic exercise 2 hours before a dive to 30msw decreases bubble formation after decompression. (Blatteau et al, 2005)

In this study, 16 military divers performed 45 minutes of aerobic exercise 2 hours before being compressed to 30msw in a dry chamber. They ascended at a rate of 30ft/min with a 3 minute safety stop at 10ft. The reduction of post-dive bubbles during exercise trials was judged to be "highly significant."

http://www.ncbi.nlm.nih.gov/entrez/...d&dopt=Abstract&list_uids=15828630&query_hl=5
Exercise ending 30 min pre-dive has no effect on bubble formation in the rat. (Berge et al, 2005)

Rats were exercised for 90 minutes up to 90% VO2max, then 30 min afterwards, dived to 200ft on air. There was no difference in bubbling or mortality between the exercise and control group.

What does this mean for us? The evidence that getting a workout in the morning before diving is at worst, not harmful, and at best, beneficial, is accumulating. Though certainly there is room for additional understanding before making outright claims that pre-dive exercise will reduce your chance of getting bent, it seems that divers who choose to go for a moderate run, etc., the morning before a dive are not incurring the same risk as they would if they were instead to be decompressed to altitude.

Dr. Powell, what are your thoughts on this?

Cameron

 

[pants!]

Rats were exercised for 90 minutes up to 90% VO2max, then 30 min afterwards, dived to 200ft on air.

And I thought I was pretty cool way back when I first went below 100 feet. Geez.

Besides, didn't anyone tell these rats that deep air isn't in vogue anymore??

 

[dbulmer]

Cameron,
Don't mean to interrupt your question but I noticed that the divers were military trained divers who in general would be extremely fit compared to the vast majority of the diving fraternity. Have any studies been done showing similar results performed on a more representative sample (BTW I appreciate the difficulty there might be in defining the representative sample)?

And wasn't there a similar survey done in Norway last year which concluded the same?

 

[rcohn]

Any information as to what exercises were used? There might be a difference between say, swimming and running up stairs in terms of tyhe number of nuceli generated in the joints.

Ralph

 

[CameronMartz]

Cameron,
Don't mean to interrupt your question but I noticed that the divers were military trained divers who in general would be extremely fit compared to the vast majority of the diving fraternity. Have any studies been done showing similar results performed on a more representative sample (BTW I appreciate the difficulty there might be in defining the representative sample)?

And wasn't there a similar survey done in Norway last year which concluded the same?

No average joes, but keep in mind that they were looking at post-dive bubbling, not cases of DCS. Though DCS is accompanied by bubbles, bubbles can be measured long before they develop into DCS. The lungs act as a great filter, preventing veinous bubbles from entering arteries, where they can cause problems.

So, these subjects were probably in above-average shape, but that just means that the bubbles that formed were less likely to result in DCS. While less fit divers might be more prone to getting bent in the first place, it is unlikely that baseline fitness will affect the benefit of pre-dive exercise when measured relative to baseline risk of DCS.

The study in Norway, which is mentioned in the quoted abstract, examined exercise done 24 hours before diving. This is the first human study to look at exercise so close to the beginning of an otherwise recreational profile.

Cameron

 

[CameronMartz]

Any information as to what exercises were used? There might be a difference between say, swimming and running up stairs in terms of tyhe number of nuceli generated in the joints.

Ralph

Straight from the abstract found at the link above:

"...running for 45 min at 60-80% of maximum heart rate (estimated as 220 - age)."

Cameron

 

[dbulmer]

Cameron,
Thanks - for some reason I didn't read the second link.

 

[Dr Deco]

Hello readers:

Pre-dive Exercise and Nuclei

I was not planning to comment on the exercise/dive study until someone posed a question. However, we now have the web link to research on exercise and a deep dive.

It has been suspected for a couple of decades that a deep dive would remove many of the tissue micronuclei. The study referenced here indicates that this is true. This would be true, I suspect, for fit and unfit individuals, men and women, and independent of the type of exercise.

Post Dive Nuclei

If one is very active during the dive itself , nuclei will be regenerated. If there are strong currents, the situation can be very bad with respect to exercise intensity.

Likewise, on board the boat , activity that is strenuous will generate nuclei or cause those formed to grow bigger.

Nuclei Research

I am very pleased to see how much work has been performed over the past decade. The interest in nuclei springs from my work at NASA on the formation and control of these little tissue entities.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology is September 10 – 11, 2005 :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[CameronMartz]

It has been suspected for a couple of decades that a deep dive would remove many of the tissue micronuclei. The study referenced here indicates that this is true. This would be true, I suspect, for fit and unfit individuals, men and women, and independent of the type of exercise.

What is most interesting is that pre-dive exercise *reduced* post-dive bubbles compared to the control group. So, there must be something else at work here in addition to the "treatment effect" of diving on micronuclei generated at the surface.

Could there be a latent effect from increased perfusion of the peripheral tissues or even a biochemical effect, as has been presented by other researchers?

Cameron

 

[Dr Deco]

Yes, exercise preformed 24 hours before a dive seems to produce fewer bubbles compared to rest 24 hours before. That could well be a perfusion [blood flow] situation.