Interferential vs TENS

As i dabbled on in earlier posts, neuromuscular stimulation (NMES) has been shown to be effective in the treatment of USI. (Dumoulin et al. 1995) Activation of the PFM and a subsequent increase in urethral closing pressure has been shown to effectively stimulate the pudendal nerve at frequencies between 20-50 HZ (Dumoulin et al. 1995).
In addition to this NMES can increase conscious awareness of the action of our PFM, ultimately increasing our ability to perform a voluntary muscle contraction.  Treating the primary weakness of in most cases of USI.

Different methods compared

Several electrical methods have been used to stimulate the PFM; these include low frequency faradic currents and medium frequency interferential currents.

The use of interferential, medium frequency currents are used in order to effectively stimulate the deep structures without the need of more invasive techniques

This has commonly been a problem with TENS, as it predominately stimulates the more superficial structures. In technical terms, has been found that the resistance of tissues increases inversely to the current frequency (Fall & Lindstrom 1991). Therefore higher frequencies are required to penetrate deeper structures, which can be very uncomfortable.

Traditionally intravaginal electrodes have been used with tens so direct stimulation of the PFM could occur.  This method is highly invasive and is not well tolerated by the user, with an example machine shown below:

http://www.medwest.com.au/index.php?cPath=2_14&&page=5

Bi and quadripolar interferential currents decrease the surface reactance, decreasing the overall tissue resistance and enabling the stimulation of deep structures such as the pelvic floor (Dumoulin et al. 1995, Yamanishi & Yasuda, 1998).

REFERENCES:

Baessler, K., Schussler, B., Burgio, K., Moore, K., Norton, P. & Stanton, S. (2008). Pelvic Floor Re-education. Springer. London.

Fall, M. & Lindstrom, S. (1991) Electrical stimulation. Urologist Clinical North America. 18: 393-407.

Yamanishi, T. & Yasuda, K. (1998). Electrical stimulation of stress incontinence. International Urogynecology Journal and Pelvic Floor Dysfunction. 9: 281-290.