Fig. 4

End tidal gas measures throughout CPET-1 and CPET-2 for ME/CFS and controls. Changes in measures related to end tidal gases across rest, ventilatory/anaerobic threshold (VAT), and peak exercise in ME/CFS (n = 84) and controls (CTL; n = 71) and VO₂peak-matched pairs (n = 55). Measures were colleged during cardiopulmonary exercise tests (CPET) across day 1 (CPET-1) and day 2 (CPET-2) and include end tidal O₂ (A, B) and end tidal CO₂ (C, D). Data were analyzed using 2-way repeated measures ANOVA and are presented as mean ± SD. *denotes p ≤ 0.05 between CPETs, **p ≤ 0.01 between CPETs, ^ap ≤ 0.05 between groups for CPET-1, ^aap ≤ 0.01 between groups for CPET-1, ^bp ≤ 0.05 between groups for CPET-2, ^bbp ≤ 0.01 between groups for CPET-2