Modern blood vessel measurements test belief that magnetic fields can influence blood flow

April 09, 2003

San Diego, CA - April 9, 2003 -- Some 2,000 years, the Chinese first advocated the use of magnetic therapy. In the Middle Ages, Paracelsus (1493-1543), a physician and alchemist, came to the conclusion that since magnets have the power to attract iron, perhaps they can also attract diseases and leach them from the body.

Even in the 21st century, the magnetic therapy industry generates approximately $500 million in income, in part, as a result of aggressive marketing strategies that use professional athletes to promote the healing effects of magnetic therapy products. Supporters of this alternative medicine cite anecdotal evidence that this treatment is effective; however, scientific evidence supporting the efficacy of magnetic therapy is somewhat lacking.

There is, however, growing evidence that magnetic field therapy can influence physiological processes such as bone formation, action potential generation, edema formation, and tumor apoptosis. Studies have also suggested that magnetic field application can influence cutaneous circulation and blood pressure in rats, but little information is available regarding the impact of magnetic fields on microvascular blood flow in general, and resistance arterioles in skeletal muscle in particular. Changes in microvascular tone have been implicated as net effects of magnetic field application and although study models have included in vitro, in vivo and clinical trials, no direct measurement of blood vessel diameter in skeletal muscle in vivo has been completed to date.

A New Study

Researchers from the University of Virginia set out to demonstrate the effects, if any, of a static magnetic field exposure on microvascular tone in skeletal muscle in vivo via direct measurement of microvascular diameters. The authors of "Magnet Therapy - The Power to Heal" are Thomas Skalak, PhD, and Cassandra Morris, both from the Department of Biomedical Engineering at the University of Virginia, Charlottesville, VA. Their findings are being presented at Experimental Biology 2003, a meeting sponsored by the American Physiological Society, being held April 11-15, 2003, at the San Diego Convention Center, San Diego, CA.

Key to the research study is the notion that local and overall blood flow and function can be directly related to blood vessel diameter based upon changes in flow resistance. Claims have been made that magnet therapy can increase blood flow to the site of injury, relieving inflammation, edema and other pathophysiological conditions related to either excess or insufficient blood flow. Accordingly, these experiments were designed to determine the direct effect of static magnetic fields (SMF) on blood vessel diameter, and therefore the overall influence on network resistance and subsequent effect on localized blood flow.

Methodology

Changes in microvessel diameters in response to the magnetic field were measured in intact skeletal muscle in vivo. The spinotrapezius muscle of female Sprague-Dawley rats was exteriorized and exposed to a localized SMF for 15 minutes. Images were taken before exposure, after exposure and 15 and 30 minutes post-exposure or "recovery." These images were later digitized and arteriolar vessel diameters measured.

Additionally, a pharmacological stimulus was topically applied to establish near maximal dilation of the microvasculature. This data was used to generate reference diameters for calculation of microvascular tone. Comparison of the calculated tone values between timepoints facilitated analysis of the overall response to the magnetic field.

Results

The results indicate that the initial, resting tone of the microvasculature can dictate the overall response of the skeletal muscle microvasculature to application of a static magnetic field. Microvessels that are initially dilated respond to the magnetic field by constricting, and microvessels that are initially constricted respond by dilating. This response is regarded as a biphasic response to the field application. Interestingly, it was found that this biphasic response was dependent upon the initial size or diameter of the vessel. The entirety of the response was manifested in microvessels with initial diameters less than 30mm. These size vessels generally encompass the terminal arterioles, which are thought to be intimately involved in the alteration of network flow resistance because they are situated in a position to directly regulate capillary blood flow. Relatively small changes in vessel diameter can influence the network resistance and lead to substantial changes in tissue perfusion. While no direct measurements of flow were acquired in the present study, the results support the conclusion that SMF exposure can have a significant impact on blood flow as well as microvascular tone.

Conclusions

From this study, it can be concluded that a 700G static magnetic field exposure has a restorative, biphasic effect on microvascular tone in skeletal muscle acting to normalize the tone following exposure. This effect is primarily mediated by the smaller resistance arterioles. These results suggest that application of this field to ischemic (vasoconstricted microvascular state) or edematous (vasodilated microvascular state) soft tissue injuries would result in modulation of tissue perfusion, thus acting as an alternative or additional therapy for these conditions.
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The American Physiological Society (APS) is one of the world's most prestigious organizations for physiological scientists. These researchers specialize in understanding the processes and functions underlying human health and disease. Founded in 1887 the Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals each year.

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