NON-THERMAL ULTRASOUND AND EXERCISE IN SKELETAL MUSCLE REGENERATION

Background: Both non-thermal ultrasound and exercise are commonly prescribed treatment modalities in acute muscle injuries, but few data on the effects of healing of these modalities at microscopic level exist.

Research question/s: Does continuous non-thermal therapeutic ultrasound (US) and low-intensity exercise (Ex) improve skeletal muscle regeneration after a contusion injury in an animal model?

Methodology:Experimental animals: 20 male Wistar rats (age, 8 months) (40 gastrocnemius muscles).

Experimental procedure:All the animals were subjected to a bilateral contusion injury to the gastrocnemius muscles (n = 40) while 10 gastrocnemius muscles from five non-injured, non-treated rats were controls (CON). Following injury, muscles were randomised into four treatment groups: Ultrasound (US) (continuous, 3MHz, 0.1W/cm², 5 min/day, duty cycle - 100% started within 24 hrs), Exercise (EX) (20 min/day, low-intensity treadmill walking at 14 m/min), no treatment (NT), or exercise and ultrasound (EX+US). Animals were sacrificed at 4 days post-injury (96 hours) and muscles were analysed for evidence of muscle regeneration.

Measures of outcome:Muscle mass, contractile protein concentration, fiber cross-sectional area, number of nuclei per fiber (indicator of muscle regeneration), and myonuclear density.

Main finding/s: Muscle mass, % of contractile protein, mean fiber cross sectional area, and fiber cross-sectional area per myonuclear number were not significantly different between treatment groups at day 4.

Conclusion/s: In an animal muscle contusion model, ultrasound treatment, exercise (at …