Impact of Hyperbaric Oxygen Exposure on Exercise Performance in the Diving Population

Background: Diving operations frequently require personnel to be submerged for extended periods of time, breathing either compressed air or oxygen (100% O2). In addition, these operations may require repeated days of diving. Combining these factors may impact exercise performance immediately following diving. Methods and Results: In order to determine ideal diving conditions for maximal exercise performance, healthy divers (N=8) completed a single 6-hr dive (OSD) then repetitive resting dives (ODW; 5 consecutive 6-hr dives with 18-hr surface intervals) while breathing 100% O2 at 1.35 ata PO2. Dynamic exercise performance (EP; time-to-fatigue on treadmill at 85% of VO2 max) was assessed before and the day immediately after OSD and ODW. Repetitive diving was found to produce greater dynamic exercise decrements than the single dive (-26% vs. -5%, p<0.003). Based on these findings, we sought to determine if these decrements could be attenuated by breathing compressed air. Healthy divers completed a similar dive week while resting and breathing oxygen (OD; N=10) or air (AD; N=10). EP decreased more following OD than AD (-25% vs. -17%, p<0.05). Finally, a SD (DSD) and DW (DDW) was performed by healthy divers (N=12) in a dry chamber breathing 100% O2, removing the variable of water immersion. Repetitive dry dives significantly reduced EP (DSD +6% vs. DDW -38%, p<0.01). Conclusion: Repeated exposure to hyperbaric O2, independent of water immersion, adversely affects dynamic exercise performance. Future research may be directed at the mechanism behind the performance decrements, or altering gas composition to attenuate performance losses.