Endurance Exercise Performance Is Reduced after 6-h Dives at 1.35 ATA When Breathing 100% Oxygen Compared with Air.

Introduction: Long-duration dives on consecutive days reduces muscular performance, potentially affecting military personnel. However, a paucity of data exists on how breathing gases affect endurance performance. This study examined the influence of long-duration diving with different breathing gases on aerobic endurance and handgrip performance.

Methods: Twenty-three military divers completed a single 6-h dive (single dive [SD]) and five 6-h dives over consecutive days (dive week [DW]) with 30-min cycling intervals using air (AIR, n = 13) or 100% oxygen (OXY, n = 10). Before and after SD and DW, subjects completed a maximum handgrip strength test, a handgrip endurance test at 40% maximal strength, and a time to exhaustion run.

Results: Handgrip endurance decreased after DW in OXY (SD, 1.9 ± 0.0 vs 1.4 ± 0.3 min) compared with AIR (1.8 ± 0.0 vs 1.8 ± 0.2 min) ( P < 0.001). Run time decreased after SD (Pre, 20.7 ± 10.4 min; Post, 16.6 ± 7.6 min; P = 0.039) and DW (Pre, 21.6 ± 9.0 min; Post, 11.2 ± 4.0 min; P < 0.001) in OXY and after overall diving in AIR (Pre, 26.5 ± 10.2 min; Post, 22.3 ± 7.5 min; P = 0.025). V̇O 2 decreased after diving only in AIR (Pre, 42.6 ± 3.4 mL·kg -1 ⋅min -1 ; Post, 40.4 ± 3.7 mL·kg -1 ⋅min -1 ; P = 0.010). There were no other significant effects.

Conclusions: Breathing 100% oxygen during long-duration dives on consecutive days may exacerbate decreases in aerobic endurance and impairs handgrip endurance compared with air. Additional research is needed to elucidate mechanisms of action and possible mitigation strategies.