This brings up a totally different consideration. I too got tired of sitting on my butt and started fast jogging a couple mails a day. I've always heard no strenuous exercise after diving. Is a 12 hour hiatus acceptable or should it be more or can I get by with less.
My sac is generally 0.65, I wish I could get it to 0.40.
Your nitrogen loading on recreational dives in most cases should be clear in 12 hours.
Maybe I wasn't paying attention in the past, but I don't remember ever hearing that! I'll keep that in mind now...Good excuse for a full on week vacation from running?
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Cali_Alli: During a dive vacation where a person is doing repetitive multi-day diving, it is highly likely that some nitrogen loading will persist beyond 12 hours after any given dive.
Current research indicates that it's not good to schedule strenuous exercise immediately after a dive or in the 4 hour post-dive period. Doing so will increase the risk of decompression sickness (DCS).
If strenuous exercise is part of the plan, the general recommendation is to try to schedule it 24 hours prior to a dive. As a bonus, there may even be a protective effect (lower DCS risk) by scheduling activities in this way...at least that's what some studies suggest.
That being said, adhering to such recommendations would be nearly impossible on a dive vacation featuring
repetitive multi-day diving.
When it comes to planning a vacation filled with both strenuous exercise and diving, it's probably best to try to limit your nitrogen loading on dives (use nitrox, take generous surface intervals, limit bottom time, limit max depth, extend deep/safety stops, etc.) and tone down your workouts a little.
For example, you may want to take off a day from diving halfway through your trip. You also might not want to do any of your weekly long runs, i.e., the ones you might be doing during marathon training. DCS risk has not been studied in divers doing long runs (18-22 mile sessions) as part of marathon training. And, FWIW, DCS risk shouldn't be your only concern. (A few years ago, one of my college roommates was trying to do too much too soon in getting back into shape and got hit with rhabdomyolysis, putting him into the early stages of acute renal failure. Not good.) Pay attention to hydration and nutrition. Recovery is important. Not all types of diving are "effortless," so that complicates fitting diving in during a recovery period.
Anecdotally speaking...
A couple of my dive buddies are avid marathoners (one is now doing triathlons). In the few weeks prior to one of their marathons, we took a weekend dive vacation to Catalina Island where we did 10 dives over 3 days. Typical dives were at a max depth of 80-90 fsw with a run time of 70-80 minutes. The dive profiles were multi-level in nature with long stays at safety stop depth (10-15 minutes). Our group tends not to move around too much underwater because many of us like taking pictures. Everyone was diving air (not nitrox). The runners woke up early on Saturday (after 2 dives on Friday afternoon/evening) and did a 16 mile run before the rest of us had gotten up. Both of them did all of the dives our group had planned. Neither reported any symptoms indicative of DCS.
These guys are experienced divers (700+ lifetime dives each) and extremely fit individuals with experience doing multiple marathons. I wouldn't recommend what they did to anyone who is either an inexperienced diver or runner.
In the end, the level of risk is probably associated with how fit you are and the duration/pace of your regular workouts. If you run only 3-4 miles 2 or 3 times per week at home, you might want to abstain from running during your scuba vacation. If you run 5+ miles everyday at home, you'd probably be OK fitting in a series of easy 2-4 milers while on a dive vacation. Listen to your body, though...and do your best to stay
properly hydrated (before and after both runs and dives).
Have fun on your vacation...
