Posted by Kendall Raine on March 10, 2004 at 14:41:42:
A recent study published in The Journal of Physiology notes significantly lower post dive bubble scores in divers who did strenuous areobic excercise the day before the dive.
The abstract, which follows, suggests no mechanism. It's interesting to note that this goes against the standard recommendation of not excercising even a full day before a dive. The thinking was that tribonucleation resulting from excercise would increase microgas nuclei into which inert gas could more readily diffuse during decompression. I suspect the time scale (24 hours pre-dive) is a critical factor.
Aerobic exercise before diving reduce venous gas bubbles formation in human
eljko Duji1*, Darko Duplani2, Ivana Marinovi-Terzi1, Darija Bakovi1, Vladimir Ivanev1, Zoran Vali1, Davor Eterovi1, Nadan Petri3, Urlik Wisløff4, and Alf O Brubakk5
1 University of Split School of Medicine
2 University Hospital Split
3 Naval Medical Institute Split
4 St. Olavs Hospital
5 Norwegian University of Science and Technology
* To whom correspondence should be addressed. E-mail: firstname.lastname@example.org.
We have previously shown in a rat model that a single bout of high intensity aerobic exercise 20 hours before a simulated dive reduces bubble formation and after dive protects from lethal decompression sickness. The present study investigates the importance of these findings in man. Twelve healthy male divers were compressed in a hyperbaric chamber to 280 kPa at a rate of 100 kPa · min-1 breathing air and remaining at pressure for 80 minutes. The ascent rate was 9 m · min-1 with a seven-minute stop at 130 kPa. Each diver underwent two randomly assigned simulated dives, with or without preceding exercise. A single interval exercise performed 24 hours before the dive consisted of treadmill running at 90% of maximum heart rate for three minutes, followed by exercise at 50% of maximum heart rate for two minutes; this was repeated eight times for a total exercise period of 40 minutes. Venous gas bubbles were monitored with an ultrasonic scanner every 20 minutes for 80 minutes after reaching surface pressure. The study demonstrated that a single bout of strenuous exercise 24 hours before a dive to 18 meters of seawater significantly reduced the average number of bubbles in the pulmonary artery from 0.98 to 0.22 bubbles · cm-2 (p = 0.006) compared to dives without preceding exercise. The maximum bubble grade decreased from 3 to 1.5 (p = 0.002) by pre-dive exercise, thereby increasing safety. This is the first report to indicate that pre dive exercise may form the basis for a novel approach to prevent serious decompression sickness.
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