A Randomized Trial of Therapeutic Ultrasound on Pain, Tenderness, and Muscle Stiffness Using a High and Low Intensity Model of Delayed Onset Muscle Soreness

Abstract

Purpose: This study evaluated ultrasound (US) effectiveness in an experimental model of soft tissue injury, and examined the model, delayed onset muscle soreness (DOMS), as a variable in the outcome. Methods: One hundred and twenty females completed 30 repetitions (low-DOMS) or 70 repetitions (high-DOMS) of eccentric contractions of biceps brachii muscles and received one of four protocols: no US (control), placebo US, or 3 MHz US, pulsed 20% duty cycle, at either 0.6 W/cm2, spatial-average temporal-peak intensity (SATP) (0.12 W/cm2, spatial-average temporal-average intensity (SATA)) or 1.0 W/cm2, SATP (0.2 W/cm2 SATA). A further 60 females completed a low-DOMS protocol and received one of three protocols: placebo US, or continuous wave 3 MHz US at either 0.2 or 0.4 W/cm2, SATP/SATA. US was applied to biceps muscles for 5 minutes on days 1 to 3. Muscle soreness, tenderness, and stiffness were measured pre-DOMS induction and at 24, 48, and 72 hours post-induction. Results: Pulsed US, 20% duty cycle, at 0.6 W/cm2, SATP, (0.12 W/cm2, SATA) reduced muscle soreness in a low-DOMS but not in a high-DOMS protocol. Continuous wave US at 0.4 W/cm2, SATP/SATA reduced tenderness. Continuous US at 0.2 W/cm2, SATP/SATA was marginally effective on stiffness and tenderness. Conclusion: The results have implications for US management of acute soft tissue injury and the use of DOMS as an experimental model for soft tissue inflammation.