Fig. 6. Time-course of the muscular exercise response in (A) normoxia and (B) hypoxia. Untrained male subjects exercised for 30 min at the aerobic threshold on a bicycle ergometer while breathing normoxic (21% O₂) or hypoxic air (13% O₂, N=6/group). Biopsies were harvested during the time-course of recovery from this single bout of exercise. Total RNA was isolated and subjected to expression profiling using custom-made microarrays (Fluck et al., 2005a; Schmutz et al., 2006). Transcript signals were related to the internal 28S rRNA reference and analyzed for statistical significance using a Friedman ANOVA. The significant changes of selected transcripts related to the oxidative pathway, such as fatty acid transport, beta oxidation and mitochondrial respiration, are shown in A and B. Significantly altered mRNA levels throughout the time-course of recovery are underlined. Unaffected transcript levels of the main cytoskeletal factors titin and desmin demonstrate the specificity of effect.