Electrical stimulation has also been employed in the treatment of UI, especially in Europe. The mechanism of action of electrostimulation is still unclear, but it probably serves to provide a kind of muscular training similar to that of pelvic floor exercise. In this regard, Green and Laycock (1990) demonstrated that interferential currents produce increases in muscle activity as indicated by pressure probes at the perivaginal and abdominal areas. It is also conceivable that electrical stimulation may improve re-innervation of partially damaged pelvic floor muscles by enhancing the sprouting of sensory motor axons. Additionally, repeated stimulation of the pelvic floor musculature may also help to strengthen the supporting ligaments. Examples of electrical stimulation devices include the Innova and Minnova systems (Empi, Inc., St. Paul, MN). An assessment of nonsurgical treatments for urinary incontinence prepared for the Agency for Healthcare Research and Quality (AHRQ) (Shamliyan, et al., 2012) found that intravaginal electrical stimulation increased continence rates and improved stress urinary incontinence more often than sham stimulation. The AHRQ assessment stated that a high level of evidence suggests increased continence rates and improvement in UI with electrical stimulation. This conclusion was based upon nine studies that examined intravaginal electrical stimulation. The studies included women with predominant urgency UI, clinical or urodynamic stress UI, or urodynamic mixed UI. Electrical stimulation was described with different levels of detail and had variable stimulation parameters, depending on the UI type being treated, including the use of 4 Hz, 10 Hz, 20 Hz, or 50 Hz frequency for 4 weeks, 7 to 8 weeks, 12 weeks, or 15 weeks.