What are the difference between the two main types of Shortwave Diathermy applications? Capacitive Plates versus Inductive Coils

While the goal of both methods is the same—to generate therapeutic heat deep within the body—shortwave diathermy uses two fundamentally different ways of delivering the high-frequency electromagnetic energy: capacitive plates and inductive coils.

The choice of applicator depends on the type of tissue you want to target and the size of the area being treated.

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SWD Application Methods: Capacitive vs. Inductive

Feature	Capacitive Plate Method	Inductive Coil Method
Applicator	Two insulated metal plates (or pads) are positioned on opposite sides of the body part (e.g., the front and back of the knee).	A coiled, heavy, insulated cable or a specialized drum applicator is placed over the treatment area.
Mechanism	The body part acts as a dielectric material (an insulator) between the two plates. The electromagnetic field generates heat primarily through the rapid oscillation of charged molecules (like water) in the tissues.	The coiled wire acts like an antenna, creating a strong magnetic field that passes through the tissues. This field generates heat via eddy currents (small electrical currents) induced in the tissues.
Primary Target	The primary target includes tissues with low conductivity but high water content, including fat, skin, and superficial joints. The field concentrates heat in the most resistive layers.	High conductivity tissues include muscle tissue and synovial fluid due to their high electrolyte content.
Treatment Area	It is utilized for treating smaller, superficial joints and areas where precise placement is feasible.	Used to treat large muscle masses (e.g., thigh, calf, back) and large joints where deeper, more uniform heating of muscle tissue is needed.

 

Summary of Differences

• Capacitive: Creates an electric field between two plates. The tissues act as an electrical capacitor, heating the most resistive layers.

• Inductive: Creates a magnetic field using a coil/drum. The magnetic field generates currents in the tissues, primarily heating the highly conductive muscle and fluid layers.

The inductive coil method is generally preferred in sports medicine and physical therapy when the target is a large, deep muscle or tendon structure.