Physical treatment modalities Pulsed electromagnetic (short-wave) energy therapy

Therapy using pulsed electromagnetic energy is now used widely in the UK and many claims are made regarding its clinical effectiveness. The technique developed about 40 years ago from that of continuous short-wave diathermy, to which it is similar in many respects. There are, however, certain important differences between these therapies that influence significantly their clinical application. Continuous short-wave diathermy (SWD) is described fully elsewhere' ' and relies principally for its therapeutic effect upon the pattern of heating generated deep within the tissues of the patient by a strong oscillating electromagnetic field. Heat is generated by the movement of ions and distortion of molecules and crystal lattices within the field, and by eddy currents induced within the tissues. The electromagnetic field oscillates at a frequency of 27.12 MHz. More energy enters the tissue than is transported away in the circulation and tissue easily achieves temperatures within the therapeutic range of 40-450C3. This technique is thus accurately described as diathermy. Pulsed electromagnetic energy therapy (PEMET) cannot correctly be called a diathermy because little or no heating of the tissue occurs. The apparatus operates at the same frequency as continuous SWD but the output is delivered as a train of pulses5. The intense electromagnetic field is thus established only briefly, and during the subsequent period of nil output, any heat produced is dissipated by the circulation6. This technique allows the use of a very high peak power output without the risk of an undesirable increase in tissue temperature. Peak power output appears to be more significant biologically than mean output . The therapeutic effects of PEMET appear to depend more upon subtle interactions between the electric and magnetic field and biological tissue than upon heating. These processes are as yet poorly understood, although investigations are continuing. This paper will attempt to describe the apparatus, biophysics and physiological and therapeutic effects of PEMET with reference to the types of condition encountered frequently in sports medicine.