Exercise effects during diving and decompression on postdive venous gas emboli

BACKGROUND: Exercise and diving have generally been associated with an increased risk of decompression sickness (DCS), thus accounting for the lack of studies involving exercise during decompression. However, theoretical and observational evidence contrary to this association motivated the present investigation on the effects of moderate, intermittent exercise during diving and/or during decompression on venous gas emboli (VGE) activity following a dive. HYPOTHESIS: VGE observed at both the precordium and subclavian vein sites after diving should be reduced if moderate exercise is performed during decompression vs. remaining inactive. METHODS: In a water-filled hyperbaric chamber, 39 healthy male subjects were compressed to a pressure of 450 kPa (45 msw) for 30 min followed by 55 min of staged decompression. Subjects were either active or inactive at the bottom phase (450 kPa) and/or during the decompression. Activity comprised three 5-min intervals of moderate arm or leg exercise at the bottom and five such intervals during decompression. After decompression, VGE were monitored at the precordium and subclavian vein sites using Doppler detection. Bubble activity scores were converted to various indices and analyzed using non-parametric statistics. RESULTS: VGE activity was invariant as to whether subjects were active or sedentary during the bottom phase of the dive. However, it was significantly lower for all indices examined (p < 0.05) after dives in which exercise was performed during decompression vs. inactive decompression. CONCLUSION: Moderate, intermittent physical activity during decompression decreases VGE activity after diving.