Long Duration Ultrasound

Long duration ultrasound was initially studied as a technique that uses ultrasonic waves with frequencies at 3 MHz to warm and mechanically stimulate tissue, reducing pain and improving function.^1,2 Recent advances in ultrasound transducer design and temperature monitoring have led to the development of wearable long duration ultrasound devices. These devices can correctly dose injuries with up to 18,000 J of energy without damaging the tissue, a significant increase compared to conventional therapeutic ultrasound.³ Similar to other interventions, such as non steroidal anti-inflammatory drugs (NSAIDs) or acetaminophen, matching the dosage of the treatment to the patient’s condition is crucial to ensure the patient sees benefits without having off-target effects, such as excess tissue heating leading to thermal damage. Long duration ultrasound (e.g., sustained acoustic medicine [SAM]) provides up to 4 hours of continuous ultrasound treatment to treat back pain, knee osteoarthritis, and musculoskeletal injuries.^3–7 Treatment benefits are seen after 1-2 weeks, potentially leading to faster return-to-play.⁸  With fewer contraindications than traditional ultrasound, long duration ultrasound is an effective treatment option for athletic trainers to consider.        

“Intramuscular Heating Characteristics of Multihour Low-Intensity Therapeutic Ultrasound” Rigby et al. 2015. Therapeutic ultrasound demonstrated prolonged increases in deep and surface triceps tissue temperatures after 3 hours of treatment. This sustained heating of the triceps could prolong physiological benefits of ultrasound therapy by increasing the acoustic energy applied to the tissues.

     

“Sustained Acoustic Medicine Increases Local Circulation with a Diclofenac Delivery Patch: A Randomized Placebo Controlled Study.” Scanzuso et al. 2025. This study examined the diathermic effects of SAM when used with a topical NSAID, diclofenac. Sixty-four healthy participants were given active or placebo SAM with or without 2.5% diclofenac for 1 hour. The SAM device was placed on their elbows, and changes in blood flow and temperature were measured for the full treatment duration. For subjects receiving active SAM treatment, there was a significant increase in tissue temperature compared to placebo after 20 minutes of treatment, but the blood flow significantly increased compared to placebo after only 10 minutes of treatment. The addition of diclofenac did not significantly change the increase in temperature or blood flow from typical SAM treatment. 

  

“Evaluation of Sustained Acoustic Medicine for Treating Musculoskeletal Injuries in Military and Sports Medicine.” Walters et al. 2023. The authors surveyed 97 ATs and formed a panel of 142 ATs to expand on the survey answers. The survey results showed most participants used SAM for tendon and ligament injuries, followed by joints, large muscles, and bones. A significant majority of ATs said that at least half of their patients used less medication while using SAM. Over 80% of athletes were completely or mostly receptive to using SAM, and nearly 70% saw clinical improvement in under 2 weeks. The panel discussion corroborated the results of the survey, with ATs agreeing that treatment benefits are very clear after 1-2 weeks of treatment and that patients receiving SAM heal 50% faster than people who don’t. 

  

“Sustained Acoustic Medicine for the Treatment of Musculoskeletal Injuries: A Systematic Review and Meta-Analysis.” Winkler et al. 2021. The authors conducted a meta-analysis of clinical research studies on SAM, selecting 13 studies with a total of 372 participants for their analysis. Injuries included in the meta-analysis spanned neck and back myofascial pain and injury, knee osteoarthritis, and generalized elbow, shoulder, back, and ankle soft-tissue injuries. For neck and back myofascial pain and injury, two studies showed a significant reduction in pain compared to placebo. For the knee, patients that received SAM showed a decrease in pain and an increase in function. For soft-tissue injuries, there was a significant increase in ultrasound diathermy tissue heating with SAM compared to placebo. Overall, SAM was found to be effective across a variety of musculoskeletal injury types.

  

“Efficacy of Sustained Acoustic Medicine as an Add-on to Traditional Therapy in Treating Sport-related Injuries: Case Reports.” Draper et al. 2020. This study reports 18 athletes who showed little or no improvement with traditional therapy options including physical therapy, muscle activation, ice, or heat. These athletes were given SAM (ZetrOZ Systems LLC, Trumbull, CT) as an add-on for daily home use at 3MHz, 0.132W/cm2, 1.3W, each delivering a total of 18720 Joules over 4 hours of treatment. The injuries in the athletes included arm/shoulder injuries, upper leg/glutes/hip injuries, knee injuries, back injuries, and foot/ankle injuries. All athletes reported improvements in pain, 16 of the athletes indicated improvements in their range of motion, and 10 of the athletes were able to return to sports after ~2.25 weeks of treatment.

          

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