ObjectiveTo determine whether hyperbaric oxygen (HBO) therapy could accelerate recovery from exercise-induced muscle damage in humans.DesignPretest–posttest design with random assignment to either a treatment (HBO) or placebo control (sham) group.SettingUniversity of Alberta and Misericordia Hospital, Edmonton.Participants12 healthy male students (24.2 ± 3.2 years) who were unaccustomed to strenuous eccentric exercise of the calf muscles.InterventionsAll subjects performed a strenuous eccentric exercise protocol designed to elicit muscle damage within the right gastrocnemius muscle. Subjects subsequently received either HBO (100% oxygen at 253 kPa [2.5 ATA] for 60 min; n = 6) or sham (atmospheric air at 132 kPa [1.3 ATA] for 60 min; n = 6) treatment conditions. The first treatment was administered 3–4 hours after damage, with a second and third at 24 and 48 hours after the first, respectively.Main Outcome MeasuresDependent variables included peak torque at 0.52 radians/s, peak isometric torque, and muscular endurance using isokinetic dynamometry; muscle cross-sectional area using magnetic resonance imaging; inorganic phosphate levels and T2relaxation time using31P and1H magnetic resonance spectroscopy; pain sensation and unpleasantness using the Descriptor Differential Scale. These variables were assessed at baseline and until day 5 postdamage.ResultsThere was little evidence of a difference in recovery rate between the HBO and sham groups. Faster recovery was observed in the HBO group only for isometric peak torque and pain sensation and unpleasantness.ConclusionsHBO cannot be recommended as an effective method of treatment of this form of muscle injury.