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

What is it about?

Hypoxic resistance training has become popular amongst athletes as it is thought to favor muscle accretion. Indeed, previous observations suggest that muscle hypertrophy can be optimized when resistance training is performed in an environment with a reduced oxygen level, namely in hypoxia. However, the molecular mechanisms are largely unknown. Here, we hypothesized that a single session of resistance exercise performed in moderate environmental hypoxic conditions would potentiate the anabolic response during the recovery period. Twenty subjects performed a one-leg knee extension session in normoxic or hypoxic conditions. Muscle samples were taken 15min and 4h after exercise in the quadriceps of the exercised and the non-exercised legs as well as blood samples to determine protein synthesis and protein breakdown. Additional analyses were performed to determine the molecular mechanisms potentially activated by hypoxic resistance training in skeletal muscle. We found that hypoxia blunted the activation of protein synthesis after resistance exercise. In addition, hypoxia regulated the expression of genes involved in glucose metabolism at rest, and genes involved in cellular differentiation and fusion, and in muscle contraction machinery after exercise. In conclusion, contrary to our hypothesis, environmental hypoxia did not potentiate the short-term anabolic response after resistance exercise, but it initiated molecular regulations that could potentially translate into higher force production on the long-term.

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