Human subjects exposed to a specific pulsed extremely low frequency magnetic field: Effects on standing balance

Abstract

Extremely low frequency pulsed magnetic fields (±200 μT, ∼400 mT/s, 0–1 kHz) may produce electric currents similar to action potentials, which in turn would be expected to produce detectable physiological or behavioral effects in human subjects. This thesis reports on the effects of pulsed extremely low frequency magnetic fields (ELFMFs) on human standing balance by measurement of postural sway on a force platform utilizing a double blind protocol with four randomly assigned 2 min exposure conditions (eyes open/closed, sham/ELFMF) within each subject's session. Historically, and in current research by others, normal postural sway has been well characterized. Standing balance in humans is a largely automatic behavior and with “eyes open” is a robust behavior not easily disrupted by small perturbations. However, with “eyes closed” standing balance becomes very sensitive to perturbation by a wide variety of stimuli. Since we have shown that ELFMF perturbs human postural sway, measurements of standing balance may be an ideal method of investigating bioelectromagnetic coupling mechanisms in humans (i.e., peripheral versus central nervous system mechanisms). Ideal because, being under automatic control, standing balance is an objective measure not subject to placebo effects. The coupling mechanisms can be studied by examining the effects related to different anatomical location of ELFMF exposure, or studying patients with different pathology. This thesis has established that normal standing balance is perturbed by weak ELFMF for both eyes open/eyes closed conditions. Also, it has been established that this human assay may indeed be appropriate to study coupling mechanisms, since the ability of ELFMF to affect sway varies between patients with diseases affecting different anatomical and physiological centers. © 2001, American Association of Physicists in Medicine. All rights reserved.