Author(s): PINTO, A., AUGUSTO, D., FEBRA, C., REIS, J.F., MONTEIRO BENTO, C., MORAIS FERNANDES, T., BRITO, J. , Institution: FACULDADE DE MOTRICIDADE HUMANA, Country: PORTUGAL, Abstract-ID: 872

INTRODUCTION:
As physical demands of sports have increased, optimizing recovery has become an essential step to perform better. Mild hyperbaric oxygen therapy (mHBOT) is a potential recovery modality, and it operates at pressures 1.3-1.5 ATA with 95% oxygen-enriched air. However, further scientific evidence is required to understand the effects of mHBOT. The objective is to explore the effects of a single mild hyperbaric oxygen session on hematological, autonomic and perceptual recovery following a running fatigue protocol.
METHODS:
Eleven recreational runners (mean ± SD, age: 31.3 ± 5.3 years; height: 177.7 ± 2.3 cm; body mass: 78.2 ± 3.6 kg) with a minimum of two training sessions per week in the preceding three months were invited to participate in this randomized crossover pilot study. First, the participants performed an incremental treadmill test to determine maximal aerobic speed (MAS: 15.6 ± 1.1 km/h) and maximal heart rate (192 ± 9 bpm). On different days (washout period < 7 days), the participants performed a running fatigue protocol (including 8-min warm-up at 9 km/h, 30-min continuous running at 80% MAS, followed by 10×30-s sprints at 100% MAS with a 30-s passive recovery). Immediately post-exercise, the participants underwent either mild hyperbaric exposure (95% oxygen-enriched air at 1.5 ATA) or a sham condition (ambient air at 1.1 ATA) for 60 min in an individual hard-shell chamber. Hemoglobin concentration and heart rate variability indices (RMSSD, SDNN, RR) from 5-min recordings were analyzed at pre-, post-protocol, and the early morning of the following day. Wellness data (sleep, fatigue, stress, mood, muscle soreness; scale 1-7) were collected before the protocol and the early morning of the following day. Hemoglobin concentration was determined by Drabkin’s method. Data were analyzed using linear mixed models with participants treated as random effect.
RESULTS:
Five participants fully completed both experimental conditions. Hemoglobin concentration showed no significant differences between conditions on the early morning of the following day (p = 0.373), nor between baseline and the early morning of the following day between conditions (p = 0.699). RMSSD (p = 0.458), SDNN (p = 0.416) and RR (p = 0.371) did not differ between pre-exercise and the early morning of the following day between conditions. No significant differences were observed in wellness parameters between pre and the early morning of the following day across conditions [sleep (p = 0.842), mood (p = 0.646), stress (p = 0.477), fatigue (p = 0.845), muscle soreness (p = 0.249) and Hooper Index (p = 0.829)].
CONCLUSION:
These results suggest that a single 60-min mild hyperbaric session at 1.5 ATA with 95% oxygen-enriched air did not produce significant changes in hematological, autonomic, or perceptual recovery markers following a running fatigue protocol.