Hello,
Actually, no disrespect to Neal who is an old friend, extremely knowledgeable in the area, and trying to provide easy non-nuanced rules of thumb, I think your advice is more reflective of the current state of the literature. I am not sure when Neal wrote his DAN article, but there are three later human studies [1-3] in which aerobic exercise much closer to the dive (one [ref 3] and two hours prior [refs 1,2]) than the one he quotes (24 hours prior) [4] was also associated with significant reductions in post dive bubble formation. In case there is any confusion, the two Blatteau studies look very similar, but the write up for the second one [ref 2] suggests that they are separate experiments.
None of this is hard proof of anything with respect to DCS prevention, but there is strong evidence that pre-dive exercise quite close to diving reduces bubble formation. In respect of the OPs original question I would not consider it unwise to run in the morning, followed by a three hour drive to a dive site during which time he could rehydrate and then dive. I do agree that ridiculous amounts of exercise followed by diving are probably unwise on the basis of fatigue, but the general plan articulated by the OP is not unreasonable. Obviously there are never any guarantees, no matter what the circumstances in diving that DCS will not occur.
Everybody has commented accurately on the likelihood that exercise after diving increases risk. I would not recommend that. Interestingly, (and for balance) there is one human study that showed a
reduction in bubbling
during vigorous cycling early after a dive. [5] However, cycling is non-weight bearing exercise and things might be quite different with exercise like running, or especially exercise that involves lifting or straining and that might promote right to left shunting across a PFO when there are venous bubbles present in the right heart.
Simon M
1. Blatteau J-E et al. Aerobic exercise 2 hours before a dive to 30 msw decreases bubble formation after decompression.
Aviat Space Environ Med. 2005;76:666-9.
2. Blatteau J-E et al. Haemodynamic changes induced by submaximal exercise before a dive and its consequences on bubble formation.
Br J Sports Med 2007;41:375-9.
3. Castagna O et al. Endurance exercise immediately before sea diving reduces bubble formation in scuba divers.
Eur J Appl Physiol. 2011;111:1047-54.
4. Dujic Z et al. Aerobic exercise before diving reduces venous gas bubble formation in humans.
J Physiol. 2004;555:637-42.
5. Dujic Z et al. Venous bubble count declines during strenuous exercise after an open sea dive to 30m.
Aviat Space Environ Med. 2006;77:592-6.
