DOI 10.1007/s00421-013-2783-8 ORIGINAL ARTICLE Hypoxia refines plasticity of mitochondrial respiration to repeated muscle work

© The Author(s) 2013. This article is published with open access at Springerlink.com vastus lateralis muscle, collected pre and post a single exercise bout, and training, were assessed for levels of tran-scripts and proteins being associated with mitochondrial metabolism. Results Hypoxia specifically lowered the training-induced expression of markers of respiratory complex II and IV (i.e. SDHA and isoform 1 of COX-4; COX4I1) and preserved fibre cross-sectional area. Concomitantly, trends (p < 0.10) were found for a hypoxia-specific reduction in the basal oxygen consumption rate, and improvements in oxygen repletion, and aerobic performance in hypoxia. Repeated exercise in hypoxia promoted the biogenesis of subsar-colemmal mitochondria and this was co-related to expres-sion of isoform 2 of COX-4 with higher oxygen affinity after single exercise, de-oxygenation time and myoglobin content (r ≥ 0.75). Conversely, expression in COX4I1 with training correlated negatively with changes of subsarcolem-mal mitochondria (r < −0.82). Conclusion Hypoxia-modulated adjustments of aerobic performance with repeated muscle work are reflected by expressional adaptations within the respiratory chain and modified muscle oxygen metabolism