Aerobic exercise before diving reduces venous gas bubble formation in humans

We have previously shown in a rat model that a single bout of high-intensity aerobic exercise 20h before a simulated dive reduces bubble formation and after the dive protects from lethal decompression sickness. The present study investigated the importance of these findings in man. Twelve healthy male divers were compressed in a hyperbaric chamber to 280kPa at a rate of 100kPamin⁻¹ breathing air and remaining at pressure for 80min. The ascent rate was 9mmin⁻¹ with a 7min stop at 130kPa. Each diver underwent two randomly assigned simulated dives, with or without preceding exercise. A single interval exercise performed 24h before the dive consisted of treadmill running at 90% of maximum heart rate for 3min, followed by exercise at 50% of maximum heart rate for 2min; this was repeated eight times for a total exercise period of 40min. Venous gas bubbles were monitored with an ultrasonic scanner every 20min for 80min after reaching surface pressure. The study demonstrated that a single bout of strenuous exercise 24h before a dive to 18 m 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 was 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 new way of preventing serious decompression sickness.