Figure 2: No detectable PaCO2 rise above the normal range during exercise even when frequently sampled. (a) Mean breathing. (b) Mean ± se change in brachial PaCO2 from resting values (PaCO2) and mean change in pHa (pHa) during rest followed by the 6 min exercise period (average values for the 8 subjects displayed in 10 s time bins) with cycling at ~0.6 kW (80% of their lactic acidosis threshold), ~0.9 kW, and ~1.1 kW (mean max. was 3.6 L O2 min−1 = 1.2 kW) in 8 subjects. (c) Mean ± se PaCO2 during the first minute only. * rest (repeated measures ANOVA). Reproduced with permission from Stringer et al. .