Hyperbaric oxygen and muscle performance in maximal sustained muscle contraction.

PURPOSE The purpose of this study was to examine the effects of hyperbaric oxygenation (HBO2) on sustained maximal muscle contraction. METHODS Fifty-two healthy volunteers participated in the study. Thirty-four experimental subjects breathing 100% oxygen at 253kPa (2.5ATA) in a multiplace hyperbaric chamber performed a maximal grip contraction for one minute (initial grip) followed by a 30-second rest period and another one-minute maximal contraction (recovery grip). The protocol was repeated one week later inside the chamber while subjects were breathing normobaric air. A control group of 18 subjects completed the same two-week protocol but breathing normobaric air during both sessions to assess any changes due to learning effect. RESULTS Exposure to HBO2 significantly increased force production for initial maximal grip, recovery maximal grip and total one-minute effort. Time to decrease to 50% of initial contraction was shorter with HBO2 for both initial grip and recovery grip, but force production remained higher throughout the effort with HBO2. CONCLUSIONS These data suggest that when performing sustained maximal contractions during acute exposure to HBO2, overall contractile force may be significantly increased compared with breathing normobaric air. Initial rate of fatigue is higher with HBO2, perhaps due to increased extravascular compression with the initial greater force production.