The impact of exercise before diving is an area of current research. Do a search here on SB, and you should find several posts referencing the relevant research, but in summary, it appears that pre-dive cardiovascular activity is not only *not* harmful, but might actually be beneficial. However, there is much more research that needs to be done here. Keep in mind that the NASA research mentioned in the DAN article is more akin to exercise at depth on a saturation dive, then decompressing to lesser pressure (it is also a very old article, published before much of the best research on pre-DIVE exercise). Exercising at depth is not what we're talking about here- it is a known bender.
There has also been an increase in research on post-dive cardiovascular activity, with the most recent findings suggesting that it might also reduce risk of DCS. However, there are several other studies and much real-world diver experience showing that post-dive activity can bend you, too (especially strenuous lifting, stair climbing, etc.). It comes down to a competition between the heightened cardiovascular activity accelerating off-gassing versus free phase bubbles cavitated out of solution from joint movement. We have no way to know where the balance falls, though, so no one is suggesting that divers hop on a stationary bike after surfacing to reduce their chance of DCS. <g> It is especially important to limit heavy lifting for some time after diving.
As I have said here and elsewhere before, in years of doing research for my book and since, I have found only two clinical cases of DCS attributed to pre-dive exercise in any way, and both cases involved signficant levels of dehydration. In other words, it wasn't the activity itself blamed for the DCS, but the dehydration that resulted.
At this point, the best advice I've heard directly from a NEDU researcher is, if you currently exercise before diving and don't have any problems, then there doesn't seem to be any reason to stop. However, research isn't far enough along to where it makes sense to recommend that divers *should* exercise before diving for its possible protective benefits.
Keep in mind, as others have alluded to, you must consider your hydration level and your fatigue before diving, just as you would if you didn't exercise beforehand. Also, muscle and joint soreness caused by training (or hauling heavy dive gear) can mimic the symptoms of DCS. This might mean that you seek treatment when none is needed, or worse, ignore actual DCS thinking that you're "just sore."
Cameron
