06 September 2005

Health Article: Exercise before scuba diving

A single bout of aerobic exercise 24 h before a dive significantly reduces the formation of circulating venous gas emboli (VGE) on decompression.

The purpose of this investigation was to determine the effect of aerobic exercise 2 h before a dive.

There were 16 trained military divers who were compressed to 30 msw (400 kPa) for 30 min breathing air in a dry hyperbaric chamber at rest, then decompressed at a rate of 10 m x min(-1) with a 9-min stop at 3 msw.

Each diver performed two dives 3 d apart, one with and one without exercise that consisted of running for 45 min at 60-80% of maximum heart rate (estimated as 220 - age).

VGE were graded according to the Spencer scale using a pulsed Doppler detector on the precordium at 30 min (T30) and 60 min (T60) after surfacing. RESULTS: Mean bubble grades at T60 were 1.25 for control dives and 0.44 for dives preceded by exercise, the difference being highly significant. None of the divers showed an increase in venous bubble grade after exercise.

Like exercise 24 h ahead, 45 min of running 2 h before a dive decreases bubble formation after diving, suggesting a protective effect of aerobic exercise against DCS. The threshold of exercise intensity and duration necessary to change venous circulating bubbles is unknown.

Mechanisms underlying the protective effect of exercise remain unclear. Rather than altering the nitrogen elimination rate, exercise may affect the population of gaseous nuclei from which bubbles form.

Source: www.ncbi.nlm.nih.gov


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