Continuous Therapeutic Ultrasound Decreases Pain Perception and Increases Pain Threshold After Muscle Damage

Objective: Therapeutic ultrasound (TUS) is one of the most common treatment modalities used in the management of symptoms associated with delayed onset muscle soreness (DOMS). However, due to the lack of adequate research and poor study designs the ability to accurately determine if there is an effect on the perception of pain using continuous therapeutic ultrasound is not possible. Therefore, we conducted a randomized, double blind trial to try and determine the effect of repetitive continuous therapeutic ultrasound for the treatment of pain caused by muscle damage in the biceps brachii. Methods: Twenty young healthy participants (mean age, 24.05 ± 3.71) were randomly assigned to a control group (sham treatment) or TUS group (treatment). All subjects performed 50 maximal eccentric contractions in both arms on a Biodex dynamometer, but only the non-dominate arm was measured. Criterion measures of isometric force production and serum creatine kinase activity were measured at baseline and peak damage. Muscle soreness and pain were assessed at baseline before damage, 24 h post damage, 48 h post damage, and every other day until day 8. Muscle soreness/pain was assessed with a battery of tests: Visual Analog Scale (VAS), Short-form McGill Pain Questionnaire-2 (SF-MPQ-2), joint angle, and mechanical pressure threshold measured with an algometer. Results: Significant changes in the VAS (p=0.01) and algometer (p=0.015) were found after the third treatment of ultrasound in the distal region of the biceps. Significance (p=0.036) was seen in the overall timepoints of the distal region of the biceps at rest in the VAS scale, as well as significant change in mechanical pressure threshold (p=0.045) in the overall timepoints of the distal region. The means of the treatment group showed greater improvement from baseline than the placebo group for most variables at each measured time point. Conclusion: Continuous therapeutic ultrasound reduced perception of pain and increased mechanical pressure threshold in the biceps brachii after muscle damage was induced