Baseline performance and response to NAC treatment of healthy subjects with different plasma redox states (study D). The design of this study has been described in detail.37 The total group of 38 volunteers has been subdivided into quartiles according to their baseline cystine/thiol ratio (upper left panel). The data for VO₂max, bcm index, and plasma lactate after exercise to exhaustion (see ref 37) indicate the mean ± SEM of the two treatment groups in the four quartiles. The lower two panels show the relative changes of bcm and total intracellular glutathione in PBMC during the 5-week observation period including 4-week anaerobic physical exercise and treatment with NAC or placebo. The significance between the indicated groups has been determined by the t-test for independent samples.