Cognitive Processing Efficiency (Throughput) Improves with Aerobic Exercise and Is Independent of the Environmental...

Aerobic exercise with eicosapentaenoic acid (EPA) may enhance cognition via cerebrovascular pathways. We tested whether mild hyperbaric oxygen (HBO; 1.41 atmospheres absolute [ATA], approximately 30% O₂) adds to gains in cognitive processing capacity (throughput) versus normobaric normoxia (1.0 ATA, approximately 21% [20.9%] O₂). Healthy young adults (n = 16) performed cycling exercise at 60-70% VO_2peak for 60 min, twice weekly, for 4 weeks per environment with a 1-week washout; EPA (2170 mg·day^-1) was taken during each 4-week training phase (total 8 weeks) and was paused during the washout. An EPA-only control (n = 8) was included for supplementary analysis. The primary outcome was throughput (correct·min^-1; T1-T4); secondary outcomes were interference indices (I1: stroop interference, I2: reverse-stroop interference). Effects were estimated using linear mixed models [environment, time, environment × time; AR(1), REML] and Hedges' g_av; accuracy used generalized estimating equations. Throughput improved mainly with time (T1-T2 p < 0.001; T4 p = 0.017; T3 p = 0.055), with no environment or interaction effects. I1/I2 showed no significant change, and one task exhibited an accuracy ceiling. Under safe, feasible conditions (≤1.41 ATA), aerobic exercise improved processing capacity (throughput) independently of environmental oxygenation level. The absence of detectable additive effects should be interpreted cautiously under conservative settings.