April 9, 2003 (San Diego, CA) -- 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 micro vascular blood flow in general, and resistance arterioles in skeletal
muscle in particular.
Changes in micro vascular 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 micro vascular tone in skeletal
muscle in vivo via direct measurement of micro vascular 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 path physiological
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 micro vessel 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 micro vascular tone. Comparison of the
calculated tone values between time points 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. Micro vessels that are initially dilated
respond to the magnetic field by constricting, and micro vessels 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 micro vessels 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 micro
vascular tone.
Conclusions
From this study, it can be concluded that a 700G static magnetic field exposure
has a restorative, biphasic effect on micro vascular 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 (vasoconstrictor micro vascular state) or edematous
(vasodilator micro vascular state) soft tissue injuries would result in modulation
of tissue perfusion, thus acting as an alternative or additional therapy for
these conditions.
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.