Shortwave Therapy

Thermal Effects

How does shortwave work using thermal effects?

It heats the tissues producing:

  • Vasodilatation
  • Reduction in muscle spasm
  • Acceleration of cellular metabolism
  • Increased soft tissue extensibility
  • Cellular healing with heat shock proteins
  • Elevation of pain threshold
    • (Kitchen et al. 1992; Shields et al. 2002; Masiero et al. 2020).

Theory:

In the past to get thermal effects from shortwave it was generally understood you needed to use continuous short-wave (often referred to as diathermy for heat)

Pulsed short-wave (PSW) was generally used for it’s for athermal effects.

Recent studies have demonstrated that PSW may also induce an elevation of tissue temperature that is dependent on the total average power delivered and pulse rate (Murray and Kitchen 2000, Al Mandeel and Watson 2010).

Laufer and Dar (2012) in a review article on shortwave use in the knee suggested that the clinical effects of PSW are mainly related to increased temperature.

There are many articles going back to the 1940’s showing shortwaves increase temperature:

    • Bennett 1941
    • Kottke et al. 1949
    • Lehmann, DeLateur, Stonebridge 1969
    • Weber, Zák, Malec, 1969
    • Kovach 1973
    • Valtonen, Lilius, Svinhufvud 1973
    • Ilja, Neninger, Maria 1974
    • Verrier, Falconer, Crawford  1977
    • Davies 1979
    • Yang & Wang  1979
    • Auda, Steinert , Elias, 1980
    • Griffiths et al. 1984
    • James et al. 1988.
    • Jan & Lin 1990
    • Bricknell , Watson  1995
    • Draper et al. 1999
    • Garrett, Draper, Knight 2000
    • Murray & Kitchen 2000
    • Draper et al. 2013
    • Hawkes et al. 2013
    • Kumaran & Watson 2015
    • Hafen et al. 2019
    • Masiero et al. 2020

So why are we interested in increasing the temperature? Well according to Lehman (1982) a 1 degree (C) temperature increase gives a 13% increased metabolism in cells which increases healing and recovery.

Increased healing with heating?

According to Masiero et al. (2020) cellular healing processes can be accelerated with the use of shortwave by producing an overexpression of heat shock proteins (HSP), which contribute to intracellular protein repair. High levels of HSP increase the speed of healing of cells and tissues and may be important in preventing skeletal muscle breakdown during exercise (Terauchi et al. 2003; Costantino et al. 2005; McCarthy et al. 2006).

Kumaran (2017) showed temperature increase using various types of radio frequency, including pulsed shortwave (continuous shortwave is high RF)

Here we can see High RF (continuous shortwave) and pulsed shortwave both increased temperature post treatment compared to placebo and control groups. 

Reduction of pain with shortwave?

Reduction in pain is one of the stated effects of diathermy, although the physiological basis is poorly understood.

  • Vasodilatation and efflux from the affected tissue of pain mediators, e.g., bradykinin, serotonin, and prostaglandins (Masiero et al. 2020)
  • Inhibition of nociceptive transmission by activation of A-alpha and A-beta fibers (Melzack et al. 1977)
  • Stimulation of the cutaneous thermoreceptors; this mechanism, known as gate control, blocks the transmission of pain as it enters the spinal cord (Goats 1989)
  • Reduction of muscle spasm (Goats 1989)