A clear answer to your question doesn't exist, but the interplay of exercise physiology and DCS risk in the context of diving is certainly interesting.
It was observed several decades ago that vigorous physical activity during decompression from a dive seemed to correlate with a higher probability of DCS. (Citation: Van der Aue et al. The effect of exercise during decompression from increased barometric pressure on the incidence of decompression sickness in man. Panama City: Navy Experimental Diving Unit, NEDU Report, 1949, p. 8-49.)
Since then, other scientists have extended this work to demonstrate that physical exercise after diving increases venous "bubbling" (measured via Doppler ultrasound detectors). It has been
hypothesized that this elevation in venous "bubbling" is related to an increase in micronuclei formation due to mechanical joint forces (and possibly other processes). Feel free to do a search on the
Rubicon Foundation Repository.
On a related note, research also shows that greater aerobic fitness of a diver can lower post-dive bubbling.
Recently several groups have investigated the effect of timing of strenuous exercise on venous bubbling in scuba divers. Interestingly, one group reported that a single bout of vigorous exercise 24 hours
before a dive actually decreases venous bubbling (protective effect!). In contrast, strenuous workouts conducted 48 hours or 10 hours before a dive caused no significant change in post-dive bubbling. It is thought that the "protective" effect of pre-dive exercise
in the appropriate time window might involve nitric oxide signaling. [N.B.: Although bubble formation does not guarantee DCS, it may point to increased risk.]
Neal Pollock wrote a nice article on exercise that's posted on the DAN website.
The take-home messages are:
- Being in good aerobic shape decreases DCS risk, so having a regular workout regimen is a good thing.
- Strenuous exercise 24 hours before a dive might be protective against DCS.
- In the 24 hour pre-dive window, it's best to limit vigorous physical activity.
- During the dive, it's probably best not to exert yourself maximally for DCS and other safety considerations.
- In the 24 hour post-dive window, it's best to limit vigorous physical activity.
To sum up, although we have empirical evidence that post-dive exercise increases DCS risk, we don't really know "why" exercising after diving is bad. Some would say it's related to increased micronuclei formation, but I don't believe any hard evidence for this exists.
Perhaps
Dr. Deco might have a better answer.
So I'd love an excuse to get drunk, but why no exercising?
