Influence of the terrestrial vs. simulated normobaric hypoxia on biomolecular anabolic signaling response to resistance exercise

BACKGROUND: The aim of this study was to compare the myokine/miRNA response to a traditional hypertrophy session (RT) under moderate terrestrial (hypobaric) vs. simulated (normobaric) hypoxia. METHODS: Two groups of active men (hypobaric hypoxia, HH: 2320 m asl; vs. normobaric hypoxia, NH: FiO2 of 15.9%) completed the same RT session at the corresponding hypoxia condition. Circulating blood lactate, growth hormone (GH), myokines (irisin and myostatin) and miRNAs (miR-378, miR-206, and miR-29c) were measured before and throughout the 30 min post-RT exercise. RESULTS: RT did not affect the mechanical capacity in any environmental condition. Recovery displayed a moderate increase in circulating GH and blood lactate favoring the NH (ES=-0.92; P=0.274) and HH (ES=1.19; P=0.103) conditions, respectively. The exercise revealed a moderate decrement of irisin in HH as compared to NH (ES=-1.16; P=0.068). Both kinds of hypoxia exposure reduced circulating myostatin after exercise (ES>0.11; P>0.156). An increment in miR-378 and miR-29c was detected in both hypoxic conditions. Compared to HH, a moderate to large rise in miR-29c and miR-206 was found in NH (ES>0.96; P<0.134). CONCLUSIONS: Our results suggest that the type of hypoxia mainly affects the circulating metabolic, hormone, and miRNA responses after the same RT exercise, which could indicate potential differences in muscle signaling pathway activation linked to muscle hypertrophy. Overexpression of miR-206 under NH conditions could imply a muscle preservation tendency, which probably interferes with muscle growth after longer training periods.