Low‐Intensity Pulsed Ultrasound Prevents Hypoxia‐Induced Skeletal Muscle Atrophy in Association with HIF ‐1α Suppression

Objectives Hypoxia is a known contributor to muscle atrophy. While low‐intensity pulsed ultrasound (LIPUS) has been shown to promote myogenic cell proliferation and differentiation, its effect on hypoxia‐induced muscle atrophy remains unclear. This study aimed to investigate whether LIPUS can alleviate hypoxia‐induced muscle atrophy and to elucidate the underlying molecular mechanisms. Methods In vitro, C2C12 myoblasts were exposed to chemical hypoxia (CoCl 2 ) and treated with LIPUS at varying intensities to determine the optimal parameter. In vivo, mice were housed in a 10% hypoxic chamber and received 30 mW/cm 2 LIPUS irradiation on quadriceps (anterior thigh) and the triceps surae (posterior calf muscles). Muscle mass, cross‐sectional area, strength, and molecular markers (HIF‐1α, MSTN, AKT/mTOR, mitochondrial dynamics) were assessed. Pharmacologic inhibition of HIF‐1α was used to verify its regulatory role in MSTN expression. Results LIPUS at 30 mW/cm 2 was identified as the most effective intensity for reversing chemical hypoxia induced inhibition of myoblast proliferation. In physically hypoxic mice, LIPUS significantly attenuated the reduction in muscle fiber cross‐sectional area, muscle mass, and strength. Mechanistically, LIPUS suppressed HIF‐1α and MSTN expression, reduced mitochondrial fission proteins while increasing fusion proteins, and upregulated the AKT/mTOR anabolic pathway. In vitro, graded inhibition of HIF‐1α led to a corresponding reduction in MSTN expression. Notably, correlation analysis revealed a significant positive association between HIF‐1α and MSTN protein levels, further supporting their correlative relationship under chemically hypoxic conditions. Conclusions LIPUS ameliorates hypoxia‐induced muscle atrophy, along with the downregulation of HIF‐1α, which coordinately regulates mitochondrial dynamics‐related proteins and the AKT/mTOR pathway. These findings provide experimental evidence for LIPUS as a potential noninvasive physical therapy for hypoxia‐related muscle atrophy.