Aerobic exercise 2 hours before a dive to 30 msw decreases bubble formation after decompression

Area of Science:

• Diving Medicine
• Exercise Physiology
• Decompression Physiology

Background:

• A single bout of aerobic exercise 24 hours prior to a dive significantly reduces circulating venous gas emboli (VGE) formation upon decompression.
• The impact of exercise performed closer to the dive, specifically 2 hours before, on VGE formation remained to be investigated.

Purpose of the Study:

• To determine the effect of aerobic exercise conducted 2 hours before a dive on the formation of venous gas emboli (VGE).

Main Methods:

• Sixteen trained military divers underwent two simulated dives to 30 msw for 30 minutes breathing air.
• One dive condition included 45 minutes of running at 60-80% maximum heart rate 2 hours prior; the other served as a control.
• Venous gas emboli (VGE) were quantified using Doppler ultrasound and graded post-dive at 30 and 60 minutes.

Main Results:

• Mean venous gas emboli (VGE) grades at 60 minutes post-dive were significantly lower (0.44) in the exercise condition compared to the control (1.25).
• No divers exhibited an increase in venous bubble grade following the pre-dive exercise bout.

Conclusions:

• Aerobic exercise, including 45 minutes of running 2 hours before a dive, effectively decreases post-dive bubble formation, indicating a protective effect against decompression sickness (DCS).
• The precise intensity and duration thresholds for exercise to influence circulating bubbles are unknown.
• Mechanisms may involve altering gaseous nuclei populations rather than nitrogen elimination rates.