Magnetic Therapy (MT) may have had its historical origins in China, as healing properties were claimed for the lodestone in some early Chinese medical literatures. In the West, however, it was not until 1530, at the University of Basel , that Paracelsus reported on the first medical treatments utilizing magnetic fields.
Thanks to work by Franklin, Lavoisier, Galvani, and Volta, and their understanding of electro-magnetism and magnetic-field medicine, things began to develop. Their investigations laid the foundations for comprehension of the piezo-electric effect on bones and connective tissue, as well as the biophysical explanation for nerve and muscle function. Michael Faraday's work on electro-magnetic induction , and in determining the magnetic properties of oxygen, provided further scientific explanations for the observed effects of MT.
Life on this planet developed under the influence of the Earth's magnetic field . The relationship is more than accidental. The importance of the magnetic field for life functioning, has been shown many times. Electrical activity of the brain, neuromuscular function and the pathways of the nervous system show the influence of the magnetic field. About twenty different effects of weak magnetic fields on biological systems were listed in 1964. Specific  natural electro-magnetic frequencies around 10 Hz trigger endogenous biological rhythms .
Experimental shielding of plants and animals from the terrestrial magnetic field leads to many health problems including loss of calcium and stunted growth in mammals. Though basic electro-muscular phenomena were discovered as early as the beginning of the Eighteenth Century, the mechanisms of cell regulation and communication are little understood. Biologists have expressed life processes in terms of biochemistry and electron transfer.  Electrical potentials have been measured across many biological membranes . There is a constant migration of ions across these membranes and the movement of these electrical charges produces electrical and magnetic fields.
In fact, the health of our bodily cells depends on the maintenance of a delicate electro-magnetic balance, and when this balance is disturbed, illness occurs.
Toward the end of the 1960's serious investigation was taken a step furthur into the possible effects of magnetic fields on the human organism. This was given added impetus with the substantial financial and research facilities of NASA and the Soviet space research centers. Astronauts loss of calcium from bone has now been blamed on the weaker magnetic fields found in space. This in turn led to further investigations in prominent European research centers. To date, about four thousand scientific papers have been published worldwide, on the biophysical effects of magnetic fields.
The primary cause of numerous critical illnesses will doubtless be more often attributed to deficiencies in the cells of the body than has been the case in the past. Irregular fluctuation in the voltage across the cell membrane can be found with most illnesses. Such disturbance contributes to the slowing down of the metabolism, with subsequent reduction in oxygen efficiency.
The aim of MT is to help to restore the cells, by affecting their normal operating voltage, therefore re-establishing the cell's normal metabolism.

Further information, consult:
1) Barnoth, Biological Effects of Magnetic Fields. Plenum Press, New York (1974).
2) Wever, Neuroscience Research Program Bulletin. 15, 1, 39 (1976).
3) Van Dike, Halpern, Cited in Space, Biomagnetics Space Life Science, 1. (1976).
4) Ardenne, Stimulation of the metabolism of cells as a weapon against illnesses. Published in
    W-Germany, (1973)
5) Popp, Being ill, when cells no longer talk to one another. Bild der Wissenschaft, No.8/77 pp.90-97

The magnetosphere shields the surface of the Earth from the charged particles of the solar wind

Antoine Lavoisier 1743-1794
Father of modern chemestry

Luigi Galvani, Italy
1737-1798

Allesandro Volta, Italy
1745-1827

Michael Faraday
1791-1867

Magnetic Therapy influences neuromuscular function and loss of calcium in bones of  Astronauts