Abstract
[Purpose] This study examined the effects of therapeutic ultrasound on the inhibition of disuse atrophy progression in rat gastrocnemius muscles. [Subjects and Methods] Male Wistar rats were randomly divided into control, ultrasound (US) and sham treatment groups. In the US and sham group, bilateral ankle joints of each rat were fixed in full plantar flexion with a plaster cast over a 2-week period. Continuous ultrasonic energy (frequency, 1 MHz; intensity, 1.0 W/cm2) was delivered to the gastrocnemius muscle of the US group over a 2-week immobilization period. [Results] In the US and sham groups, type IIa and IIb mean muscle fiber diameters decreased significantly relative to the control group. In the US group, muscle fiber diameters of all fiber types were markedly larger than those of the sham group. Heat shock protein 70 (HSP70) content of the US group increased significantly in comparison with the sham group. The levels of basic fibroblast growth factor were substantially higher in the US group relative to the control and sham groups. However, meaningful differences in insulin-like growth factor I level were not evident between the groups. [Conclusion] Continuous therapeutic ultrasound inhibits the progression of disuse muscle atrophy via elevation of HSP70 levels in skeletal muscle.
