Environmental hypoxia favors myoblast differentiation and fast phenotype but blunts activation of protein synthesis after resistance exercise in human skeletal muscle

We hypothesized that a single session of resistance exercise performed in moderate hypoxic (FiO ₂ : 14%) environmental conditions would potentiate the anabolic response during the recovery period spent in normoxia.Twenty subjects performed a 1-leg knee extension session in normoxic or hypoxic conditions.Muscle biopsieswere taken 15 min and4hafter exercise in thevastus lateralis of the exercisedandthenonexercised legs.Bloodandsaliva samplesweretaken at regular intervals before, during, and after the exercise session. The muscle fractional-protein synthetic rate was determined by deuterium incorporation into proteins, and the protein-degradation ratewas determined by methylhistidine releasefromskeletalmuscle.Wefoundthat:1)hypoxiablunted theactivationofprotein synthesis after resistance exercise; 2) hypoxia down-regulated the transcriptional program of autophagy; 3) hypoxia regulated the expression of genes involved in glucose metabolism at rest and the genes involved in myoblast differentiation and fusion and in muscle contractionmachinery after exercise; and 4) the hypoxia-inducible factor-1a pathwaywas not activated at the time points studied. Contrary to our hypothesis, environmental hypoxia did not potentiate the short-term anabolic response after resistance exercise, but it initiated transcriptional regulations that could potentially translate into satellite cell incorporation and higher force production in the long term.