雅思阅读的真题机经：磁疗

　　Magnet Therapy

　　Magnet therapy, magnetic therapy, or magnotherapy is an alternative medicine practice involving the use of static magnetic fields. Practitioners claim that subjecting certain parts of the body to magnetostatic fields produced by permanent magnets has beneficial health effects. These pseudoscientific physical and biological claims are unproven and no effects on health or healing have been established. Although hemoglobin, the blood protein that carries oxygen, is weakly diamagnetic and is repulsed by magnetic fields, the magnets used in magnetic therapy are many orders of magnitude too weak to have any measurable effect on blood flow.

　　Methods of application

　　Magnet therapy is the application of the magnetic field of electromagnetic devices or permanent static magnets to the body for purported health benefits. Some practitioners assign different effects based on the orientation of the magnet; under the laws of physics, magnetic poles are symmetric.

　　Products include magnetic bracelets and jewelry; magnetic straps for wrists, ankles, knees, and the back; shoe insoles; mattresses; magnetic blankets ; magnetic creams; magnetic supplements; plasters/patches and water that has been magnetized. Application is usually performed by the patient.

　　Purported mechanisms of action

　　Perhaps the most common suggested mechanism is that magnets might improve blood flow in underlying tissues. The field surrounding magnet therapy devices is far too weak and falls off with distance far too quickly to appreciably affect hemoglobin, other blood components, muscle tissue, bones, blood vessels, or organs. A 1991 study on humans of static field strengths up to 1 T found no effect on local blood flow. Tissue oxygenation is similarly unaffected. Some practitioners claim that the magnets can restore the bodys theorized electromagnetic energy balance, but no such balance is medically recognized. Even in the magnetic fields used in magnetic resonance imaging, which are many times stronger, none of the claimed effects are observed.

　　Efficacy

　　Several studies have been conducted in recent years to investigate what, if any, role static magnetic fields may play in health and healing. Unbiased studies of magnetic therapy are problematic, since magnetisation can be easily detected, for instance, by the attraction forces on ferrous objects; because of this, effective blinding of studies is difficult. Incomplete or insufficient blinding tends to exaggerate treatment effects, particularly where any such effects are small. Health claims such as longevity and cancer treatment are implausible and unsupported by any research. More mundane health claims, most commonly pain relief, also lack any credible proposed mechanism, and clinical research is not promising.

　　Pain

　　Effects of magnet therapy on pain relief beyond non-specific placebo response have not been adequately demonstrated. A 2008 systematic review of magnet therapy for all indications found no evidence of an effect for pain relief. It reported that small sample sizes, inadequate randomization, and difficulty with allocation concealment all tend to bias studies positively and limit the strength of any conclusions. In 2009 the results of a randomized double-blind placebo-controlled crossover trial on the use of magnetic wrist straps for osteoarthritis were published, addressing a gap in the earlier systematic review. This trial showed that magnetic wrist straps are ineffective in the management of pain, stiffness and physical function in osteoarthritis. The authors concluded that reported benefits are most likely attributable to non-specific placebo effects.

　　The History of Magnets.

　　Historically it is reported that magnets have been around for an extremely long time. Magnets were first documented around 2500-3000 years BC. Their origins are first noted in Asia Minor in a vast land called Magnesia. The earth there was enriched with iron oxide which attracted metals to it. The locals named it Magnetite

　　Magnets have been used in Chinese medicine from around 2000 BC in-conjunction with reflexology and acupuncture. It is still used today as a first line treatment for many common complaints.

　　3,500 years after they were first discovered, magnets have gained popularity in Europe and the USA. In the 15th century a Swiss physician Paracelsus recognised the therapeutic powers of magnets. He wrote medical papers on the influence of magnets on the inflammatory processes within the body.

　　How Do Magnets Work?

　　The human body is not based simply on biochemical reactions, but also electromagnetic interactions. Biological processes, like smooth muscle contractions and nerve signals, are controlled by the balance and movement of chemical ions. These are biochemicals that have a positive or negative electric charge. They can be influenced chemically, as with drugs, as well as by external electrical and magnetic fields.

　　Based on more current studies, researchers believe magnets may make it easier for ions to shift and move through membrances , triggering biological processes more efficiently. For example, the body uses calcium ions as a messenger system, causing the smooth muscle walls of capillary blood vessels to either relax or constrict. This increases or decreases the amount of blood flow.

　　Researchers from Japan, and more recently, the University of Virginia, have observed that when exposing an injured area to a strong magnetic field, changes in blood flow happened much faster. Interestingly, magnetic fields were able to both decrease blood flow to reduce swelling quicker, and later increase blood flow for faster healing. This means the magnets were not causing changes directly, but rather improving the bodys own ability to regulate blood flow - likely by improving the ion signal process.

　　Separating magnet therapy from almost every other form of alternative or mainstream medicine, both doctors and researchers agree that magnets are safe and do not cause side effects when used properly. This is because instead of changing processes chemically, biomagnetics enhance the bodys own abilities to heal itself after injury and reduce pain signals. For this reason, people with chronic conditions, like arthritis, tendonitis and fibromyalgia, are turning to magnets as a safer form of pain relief.

　　Use Around the World

　　Today, magnet therapy is used in Germany, France, Britain, India, Japan, China, Italy, Israel and about 40 other countries. A number of government health systems, such as Japans Ministry of Health, Labour and Welfare, officially recognize magnet therapy as a safe, viable and cost-effective treatment option. Britain is the most recent to adopt magnetic therapy, where doctors are prescribing magnets to both heal and help prevent the development of leg ulcers - reducing the time and costs of patient care.

　　While magnet therapy is not fully understood, millions of people have benefited from its use for pain relief, improved healing, and better sleep. Of all forms of alternative medicine, magnetic therapy is both the safest and easiest to use. It offers the best opportunity for sustainable, long-term pain relief and better quality of life, without the worry of side effects. This alone makes magnets the ideal first choice for arthritis and chronic pain management, before trying other options.

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