title: Effects of pre-exposure to hyperbaric hyperoxia on high-intensity exercise performance.
abstract: This study comprised 2 main experiments: one was to determine the oxidative DNA damage under hyperbaric hyperoxia (HBO), and the other was to evaluate the effects of pre-exposure to HBO on high-intensity exercise performance. Healthy subjects (n = 8) inspired 100% O2 in an experimental chamber at a pressure of 1.3 atmospheres absolute (ATA) for 50 minutes once per week for 2 weeks. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) was measured as a marker of DNA oxidative damage on day 0 and on days 1, 3, and 5 after each HBO exposure. To investigate the effects of pre-exposure to HBO on high-intensity exercise performance, subjects (n = 6) performed maximal isometric knee extensor exercise (30 repetitions x 2 sets) with and without HBO pre-exposure (100% O2 at 1.3 ATA for 50 minutes). Urinary 8-OHdG did not show any significant change after HBO exposure. Isometric knee extensor torque was significantly lower during the first half of the first set of exercises after HBO pre-exposure compared with the normobaric normoxia (NBO) trial. The decreased torque was associated with the lower integrated electromyography with respect to time. Changes in the degree of ischemia-reperfusion in the vastus lateralis muscle during exercise were larger in the HBO pre-exposure trial than in the NBO trial. Muscle fatigue index, serum lactate concentration, heart rate, and systolic blood pressure showed no differences between the 2 trials. These results indicated that HBO exposure was harmless to DNA, and HBO pre-exposure did not enhance high-intensity exercise performance. As a practical application, athletes who require maximal muscle strength should not inspire high-concentration of O2 just before their competitions because it might, as the case may be, impair their performance.
authors.affiliation: The Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Chiba Prefecture, Japan. kawada@k.u-tokyo.ac.jp
authors.forename: Shigeo
authors.initials: S
authors.lastname: Kawada
authors.forename: Kohei
authors.initials: K
authors.lastname: Fukaya
authors.forename: Masaru
authors.initials: M
authors.lastname: Ohtani
authors.forename: Kando
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Chiho
authors.initials: C
authors.lastname: Fukusaki
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D015331:Cohort Studies; D004249:DNA Damage / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006931:Hyperbaric Oxygenation; D018496:Hyperoxia / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology; D005082:Physical Exertion; D011336:Probability; D012016:Reference Values; D012680:Sensitivity and Specificity