Diving post-strenuous exercise?

[DevonDiver]

Had an email from a potential customer, who wants to go scuba diving following (immediately/same day?) completing a marathon.

Am hoping someone could provide some professional/medical advice on the medical implications of doing that, particularly with regards to DCI, but not limited to that issue.

I'm disinclined to permit the dives, but I don't want to penalise someone because of my lack of in-depth understanding of the issues.

Cheers,
Andy

[DocVikingo]

Hi Andy,

This recent article of mine may prove useful:


“Exercise and Diving -- pre-dive workouts can protect against decompression sickness

from the October, 2011 issue of Undercurrent

In the March and May 2004 issues of Undercurrent, I examined the estimated risk of decompression sickness (DCS) posed by exercise before, during and after scuba diving. My conclusion: Based on the research at hand, divers should avoid strenuous exercise four hours before and six hours after diving. I also reviewed research showing that a single episode of high-intensity aerobic exercise 24 hours before a chamber dive decreased the number of circulating gas bubbles in humans more than fourfold, and reduced the maximum bubble size by a half. Studies on rats showed that strenuous exercise 20 hours before a chamber dive suppressed bubble formation and reduced decompression illness-related deaths in rats, but had no meaningful effect at 48, 10, or five hours prior. This line of inquiry suggests that vigorous exercise many hours before diving may reduce the already tiny incidence of DCS.

Since then, new findings suggest exercising much closer to diving substantially reduces circulating gas bubbles, and thus may have a protective effect against DCS. Clearly, these studies have implications for our prior recommendations regarding wait time between exercise and diving.

For example, in July 2005, researchers in France reported in the journal Aviation, Space and Environmental Medicine on 16 divers compressed in a hyperbaric chamber following 45 minutes of running two hours before their chamber ride. Each diver performed two dives three days apart, one without exercise and the other with exercise before the dive. Similar to doing exercised 24 hours ahead of a dive, it was found that running two hours before a dive decreased bubble formation after diving.

Other researchers followed up with a June 2011 study published in the European Journal of Applied Physiology that examined the effect on bubble formation of a single bout of exercise one hour before a dive. Twenty four divers did open water dives to 100-foot depths for 30 minutes, followed by a three- minute stop at 10 feet. These divers first did a control dive without exercise beforehand, then three days later, they made a second dive after vigorous (but below-maximum effort) running on a treadmill for 45 minutes one hour before immersion. Circulating bubbles were then graded every 30 minutes for 90 minutes after surfacing. Again, the exercising divers showed significantly reduced bubble grades.

Why exercise hinders inert gas bubble formation is unknown, but there are two favored hypotheses. One is exercise increases nitric oxide, which induces relaxation and expansion of capillary walls, making their linings less sticky, so gas bubbles are off-gassed more quickly and efficiently. The second hypothesis is that, rather than altering the nitrogen elimination rate, exercise may reduce the population of gaseous nuclei from which inert gas bubbles form.

The newer findings modify my earlier advice about minimizing strenuous exertion before a dive. Specifically, semi-vigorous exercise up to one hour before may have a protective effect against DCS. In any event, such exercise appears unlikely to be harmful.

As regards high-intensity activity during and after a dive, my advice has not changed. Micobubbles present at those times can only be problematic, i.e., they expand upon ascent, and in sufficient number and/or size, they can precipitate DCS.

In closing, don't forget that this guidance only refers to exercise at the start of each new dive day. Once a dive has been made, exercise before, during or after that dive would be exercise following a previous dive, and not recommended. Also, this guidance does not advocate the avoidance of post-dive activity of all kind. Vigorous, joint-jarring exercise decidedly is a bad idea, and so is taking a nap. Your best protection is mild, gentle-on-the-joints activity, such as an easy swim or walk, following a dive. - - DocVikingo”


Of course, a marathon is a rather different level of exercise than has been researched by the studies above and I would offer that dehydration and possible musculoskeletal injury are concerns with marathoning soon before diving.

An arbitrary but not capricious wait period between running a marathon and diving would be on the order of 24-hours, provided that no injuries were sustained, full rehydration has occurred, and the diver feels mentally and physically up for SCUBA.

Regards,

DocVikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.

[Bubbletrubble]

Of course, a marathon is a rather different level of exercise than has been researched by the studies above and I would offer that dehydration and possible musculoskeletal injury are concerns with marathoning soon before diving.

An arbitrary but not capricious wait period between running a marathon and diving would be on the order of 24-hours, provided that no injuries were sustained, full rehydration has occurred, and the diver feels mentally and physically up for SCUBA.

DocVikingo pointed out the important issues of hydration status and being otherwise injury-free (with respect to joints/muscles). I would hope that the marathoner has paid attention to normalizing electrolyte balance and getting enough nutrition as well. Moreover, there are the potential issues of being absolutely exhausted and having increased inflammation throughout the body (effect on DCI pathogenesis?). Separate from the issue of DCI risk, I would think a diver would want to have a nice "energy reserve" while diving in case an emergency occurred and a burst of energy was required. Obviously, marathoners deplete such energy reserves during the course of a long race.

I'd like to add another concern for a person post-marathon: subclinical exertional rhabdomyolysis. This could potentially harm kidney function and may alter molecular mediators of DCI pathophysiology.

To be clear, DCI has not been studied in people recently finishing a marathon, so these are all merely theoretical concerns.

With respect to DocVikingo's quoted article on the DCS protective effects of pre-dive exercise, I think we can all agree that a marathon is far more strenuous than the exercise regimens employed in the published scientific experiments suggesting that pre-dive exercise may lower DCS risk. Perhaps bubble scores follow an inverted bell shape (x-axis: amt. of exercise, y-axis: bubble score)...and with extreme pre-dive exercise (e.g., running a marathon), post-dive bubbles increase in number and size. We really don't know. There's a danger in extrapolating the findings of a science experiment beyond the testing parameters.

On a side note, I'd have to say that your potential customer is a little bit nutty (and I mean this in a nice way) if he thinks that running a marathon in the heat and humidity of the Philippines and then going diving later on the same day is a good idea. Why put your body through so much stress in one day?

[bleeb]

Of course, a marathon is a rather different level of exercise than has been researched by the studies above and I would offer that dehydration and possible musculoskeletal injury are concerns with marathoning soon before diving.

I am NOT a medical or dive professional, but I am a marathoner, so if I might offer some food for thought: If someone sweats at all significantly, they'll be dehydrated after a marathon no matter how much they drink. Even with drinking a lot during the run, basic replenishment can take hours and like diving, some parts of the body can take 12-24 hours to re-equilibrate. Clues as to whether dehydration is possibly an issue include a temperature above 10-15C/50-60F (assuming they're from a temperate part of the world), high ambient humidity, sunny conditions, or a finishing time below about 4.5-5 hours, especially in males who tend to sweat more, or larger people. An experienced long distance runner may know their sweat rate, but basically above a certain temperature and work load, your digestive system can't absorb fast enough to make up the losses. There may also be significant electrolyte losses to make up, mainly sodium. Leg and foot cramps are more likely, from the combination of electrolyte looses, exhaustion of specific muscles and maybe micro-damage.

If this is his or her first attempt at this distance, there's a pretty good chance they'll be pretty exhausted until after a good nights rest, and possibly pretty stiff the day after.

Less than next day may be debatable, but I'd definitely question diving anything less than 6-12 hours later (which probably means a night dive), and that's assuming a slow, easy and cool marathon, and a very low effort dive. Anything more significant run or dive-wise would be at least the next day, and for a first time marathoner, their might surprise them by being non-cooperative even then.