Cardio 20 hours before diving reduces venous bubble formation in humans

[ChillyWaters]

This DAN posting is several years old- in fact, Dr. Thalmann unfortunately died since this was posted. It predates the studies performed in the past several years that actually looked at exercise before diving rather than exercise before decompressing to altitude (Dr. Powell's, aka "Dr. Deco," NASA studies). They are two different animals, and fortunately, our knowledge in this area continues to grow.

I wish DAN would update this.

Cameron

Roughly how has it changed?

- ChillyWaters

 

[CameronMartz]

What does the floating safety stop do? Cool the muscles before exerting oneself on the exit?

- ChillyWaters

Actually, nothing different than any other deco stop. When you break the surface, you have once again reduced the ambient pressure, allowing bubble nuclei to grow. Off-gassing is non-linear- you do the most decompression in the first few minutes at a new pressure, and you're just waiting at your new "deco stop" to take advantage of this.

Another way of putting it, by waiting a few minutes on the surface, you are (theoretically) allowing many of these bubbles to get cleared by your lungs before causing another bubble shower climbing the steps or ladder or whatever.

Cameron

 

[CameronMartz]

Roughly how has it changed?

- ChillyWaters

We've actually looked at exercise before diving. This DAN post was written when all we knew about pre-decompression exercise came from the NASA studies, showing that exercise before decompression to altitude increased risk of DCS. Keep in mind that the NASA studies more accurately represent exertion at depth during a saturation dive prior to surfacing.

When we actually look at exercise before a *dive*, we do not see the problems found in the altitude studies. In fact, some studies found a protective benefit, as mentioned in other posts in this thread.

Cameron

 

[*Floater*]

Dr. Doolette's personal take on all of the pre-dive exercise research was that it merely says that there is no reason to change what you are doing. If you already exercise before diving and have no problems, then don't worry about stopping. If you don't currently exercise before diving, the evidence isn't yet strong enough to make the recommendation that you should.

Hi Cameron, by exercise above do you mean cardio or also weight training? would you advice against the latter several hours before a dive?

 

[CameronMartz]

Hi Cameron, by exercise above do you mean cardio or also weight training? would you advice against the latter several hours before a dive?

All of the studies on pre-dive exercise focused on cardiovascular activity. Some of the NASA studies focused on deep knee bends and the like (more akin to strength training), but as previously mentioned, the protocols in these studies do not resemble exercise on the surface before a dive.

One thing to keep coming back to is that nobody that I have asked, no online resource, no book on diving, no nothing I have been able to find lists a single case of DCS directly attributed to any form of pre-dive exercise- cardiovascular or strength training. This says a lot, since there are certainly plenty of divers out there, and if even only a microscopic percentage have strength trained before diving, there are probably many potential episodes of this.

Another thing to note is that the "microtrauma" theory on muscle conditioning has been called into doubt. It doesn't appear that so-called "tiny tears" are taking place, or if they do indeed take place, they are not the trigger for strength gains.

It is not a given that strength training is therefore more risky before diving than going for a run, for example. Mind you, the protocols used in some of the pre-dive studies involved fairly intense interval training, not a Sunday jog- the muscles are definitely getting stressed in these studies.

That said, there is a very big reason to be mindful of strength training before a dive. Post-exercise soreness can mimic symptoms of DCS. This can cause you grief in two ways: 1. You actually are bent but attribute your symptoms to your workout, not your diving, or 2. You don't get bent but worry that you might be because something is unusually sore after your dive.

There is not enough information to safely make a recommendation on what to do. However, as Dr. Doolette said, there isn't anything that suggests you should change what you already are doing successfully with your pre-dive routine.

Cameron

 

[Vayu]

There is enough information on diving related injuries, however, to justify treating the whole thing with a large amount of respect. Whatever you choose to do, make sure you do it well hydrated and are in the proper mindset for the type and number of dives you plan to make on any particular day.