References / Physics and formulas
The body is transparent to the magnetic field
Established physicsThe report describes a device's reach as how far the field stays above a usable level. That reach comes from the coil's size and the strength of the pulse, not from the field pushing through a tissue barrier.
Where it appears in the report: Penetration Depth, Peak Field Strength
The evidence
At the low frequencies a PEMF device uses, skin, muscle, and bone barely absorb or block the magnetic field. The whole practice of non-invasive magnetic stimulation depends on that. Since the field passes through, its reach comes down to the coil's geometry and the strength of the pulse. A higher peak, or a larger coil, keeps the field above a usable level farther from the surface. That's greater reach, not deeper absorption.
Primary sources
- Barker AT. An introduction to the basic principles of magnetic nerve stimulation. J Clin Neurophysiol. 1991;8(1):26-37. view
- Hallett M. Transcranial Magnetic Stimulation: A Primer. Neuron. 2007;55(2):187-199. view
- Wagner T, Valero-Cabre A, Pascual-Leone A. Noninvasive Human Brain Stimulation. Annu Rev Biomed Eng. 2007;9:527-565. view