Skeletal muscle is key in the maintenance of homeostasis in humans. Atrophy of muscle has negative health effects. Atrophy is due to decreased synthesis, increased degradation, or impaired proliferation of precursor myoblasts. One poorly understood inducer of muscle atrophy is hypoxia. Exposure to altitude has been linked to atrophy and a catabolic state in humans and rats (Hoppeler et al., 1990, Preedy et al., 1985) and increases in pro-inflammatory cytokine regulator NF-κB (Rius et al., 2008) . In humans exposed to 2 hours of 12% O2, basal muscle protein synthesis is not altered (Etheridge et al., 2011), suggesting that elevated degradation or impaired myoblast proliferation and migration underlies atrophy. Myotubes treated with cobalt chloride (a hypoxia mimicking agent) show elevated myostatin expression (Hayot et al., 2010), key as myostatin has been shown to increase degradation and decrease proliferation. We therefore aimed to explore the result of hypoxic exposure on migration of immature myoblasts and atrophy of mature myotubes. We also aimed to examine the role of inflammation in hypoxia effects. C2C12 myoblasts were grown to confluence in 6-well plates or 10cm dishes. 6-well plates were scratched, photographed (2.5X zoom) and exposed to control (21%O2) or hypoxic (1%O2) conditions in the presence of the NF-κB inhibitor PS1145 (10 µM in PBS) or blank (PBS only). After 16 hours, cells were photographed and scratch closure quantified using ImageJ. 10cm dishes were differentiated as standard (DMEM with 2% horse serum, pen/strep) into mature myotubes, then treated with control (21%O2) or hypoxia (1%O2). Hypoxic myotubes were further treated with PS-1145 (10 µM in PBS) or hypoxic control (PBS only). Myotubes were stimulated for 2, 24 or 48 hours. Cells were photographed by light microscopy (10X zoom, phase contrast), lysed and supernatant frozen for future analysis. Control plates showed significant closure of 63.7% 16 hours post scratch (p<0.05), PS1145 had no further effect on closure. Hypoxic plates showed reduced closure (39.6%) relative to control conditions. Stimulation of hypoxic myoblasts with PS1145 showed trends towards increased closure. Incubation of myotubes in 1% hypoxia reduced myotube diameter at 2 hours that was further reduced at 24 and 48 hours (14.2%, 36.9% and 34.2%, respectively). Atrophy in response to hypoxia was prevented by co-incubation with PS1145 at 2 hours (p<0.05) and showed trends towards offsetting atrophy at 24 and 48 hours. Expression of myostatin was unaltered by hypoxia or PS1145 exposure. Here we report that hypoxia directly regulates both myotube size and myoblast migration. These effects appear in part to be via NF-κB. Counter to previous reports (Hayot et al., 2010), we did not see increased myostatin expression in response to hypoxic exposure.