Background Ultrasound (US) is “one of the most frequently used electrophysical agents with over 60 years of clinical use” (Robertson & Baker 2001). The concept of US is based upon the application of acoustical vibrations at high frequencies that are capable of producing mechanical effects (thermal and non-thermal). The most common frequency ranges for therapeutic ultrasound are 1 MHz and 3 MHz. Ultrasound is dependent on a crystal in the sound head to create the energy with application of an Alternating Current (AC) crossing with a specific polarity: This generates the current frequency, which is known as a Reverse Piezoelectric Effect to produce ultrasound. Thermal ultrasound is a common therapeutic modality used for treating “soft tissue
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Non-Thermal Effects are applied with less than 20% duty cycle and are beneficial to apply during the acute phase of injury because it promotes cell permeability and vascular permeability to promote movement of fluids. Where as Thermal effects are achieved with continuous (100% duty cycle) to promote blood flow and tissue extensibility to promote a decrease in pain and often can help regain ROM by “decreased joint stiffness through increased collagen extensibility” (Merrick & Bernard et. al. 2003). The concept of heating from US is also incorporated with the idea of a stretching window as well. One study believes that applying a heating agent to “static stretching alters the viscoelastic properties of connective tissue: Making it more extensible, thereby potentiating the effects of stretching” (Reed, Ashikaga et. al 2000). The therapeutic frequencies also play a significant part in the effects of US. For example, it is proven that 1MHz heats at a slower rate yet it is capable of penetrating deeper into the skin (2-5 cm) where as 3MHz heats at a quicker rate but cannot penetrate as deep (2-3cm) therefore targets superficial tissues …show more content…
The application of the US was 3MHz with an intensity of 1.25 W/cm^2 for 2.5 minutes and the control was 0 W/cm^2 for the same time and same location on the medial knee. The 3MHz was chosen because of the superficial tissue target and the intensity was based on the tissue temperature increase desired (2-3 deg. C): “Enough to alter dense connective tissue viscoelastic properties” (Reed & Ashikaga et. al 2000). The authors hypothesized that stretching alone was less likely to be effective compared to stretching and US treatment but from this study they found very little difference in
Non-Thermal Effects are applied with less than 20% duty cycle and are beneficial to apply during the acute phase of injury because it promotes cell permeability and vascular permeability to promote movement of fluids. Where as Thermal effects are achieved with continuous (100% duty cycle) to promote blood flow and tissue extensibility to promote a decrease in pain and often can help regain ROM by “decreased joint stiffness through increased collagen extensibility” (Merrick & Bernard et. al. 2003). The concept of heating from US is also incorporated with the idea of a stretching window as well. One study believes that applying a heating agent to “static stretching alters the viscoelastic properties of connective tissue: Making it more extensible, thereby potentiating the effects of stretching” (Reed, Ashikaga et. al 2000). The therapeutic frequencies also play a significant part in the effects of US. For example, it is proven that 1MHz heats at a slower rate yet it is capable of penetrating deeper into the skin (2-5 cm) where as 3MHz heats at a quicker rate but cannot penetrate as deep (2-3cm) therefore targets superficial tissues …show more content…
The application of the US was 3MHz with an intensity of 1.25 W/cm^2 for 2.5 minutes and the control was 0 W/cm^2 for the same time and same location on the medial knee. The 3MHz was chosen because of the superficial tissue target and the intensity was based on the tissue temperature increase desired (2-3 deg. C): “Enough to alter dense connective tissue viscoelastic properties” (Reed & Ashikaga et. al 2000). The authors hypothesized that stretching alone was less likely to be effective compared to stretching and US treatment but from this study they found very little difference in