The most award winning
healthcare information source.
TRUSTED FOR FOUR DECADES.
September 2001; Volume 1; 13-24
By Dónal P. O’Mathúna, PhD
In the first part of this monograph, attention was focused on the dietary supplements and herbal remedies used to enhance athletic performance.1 The second part of the monograph will focus on the integrative medicine approach to the treatment of sports-related injuries. Estimates in the early 1990s suggested that in the United States there were 100 million regular swimmers, 75 million cyclists, and 25 million runners and joggers.2 In spite of the many benefits of these various forms of exercise, between 45% and 70% of those who regularly exercise are likely to suffer from an injury during the course of a year.3 Highly competitive athletes always walk a fine line between intense and appropriate exercise and over-training and subsequent injury.
When injuries strike, recreational and competitive athletes alike seek whatever methods will assist in their recovery. Competitive athletes resort to whatever they think will return them to full fitness in the shortest time. The British sports medicine community reacted with astonishment when the coach of the English national soccer team recruited a faith healer to care for his athletes during the World Cup.3 The injuries themselves and the required recovery periods often result in relatively rapid loss of muscle strength along with muscle stiffness and soreness. If athletes perceive that conventional medicine is not treating them adequately or rapidly enough, they often turn to complementary and alternative therapies.
Little evidence exists to help physicians, coaches, and athletes make decisions about those alternative therapies that might treat sports injuries. Stories spread rapidly among athletes about a particular complementary therapy that provides complete pain relief or returned a well-known champion to a full training regimen in record time. The problem with such anecdotal evidence is that a myriad of other factors could have contributed to the results attributed to the therapy. Only high-quality, controlled studies can demonstrate with reliability if a putative therapy is both safe and effective. Unfortunately, many of the most popular alternative therapies used for sports injuries have very little scientific data to support their efficacy, or are believed to work via some controversial mechanism of action.4
The treatment of muscle strains is extremely important because of the long-term negative effects of repeated injuries. Muscles that have had minor strains are more susceptible to subsequent major strains.5 If rehabilitation is attempted too rapidly, more serious injuries may result. Medications taken or injected for local pain relief can bring short-term benefits, but may lead to further long-term damage. Animal studies have shown that using anti-inflammatory medications after muscle strains allowed greater activity on the day after injury.6 However, in the following seven days, the animals receiving medication had more serious tissue damage as seen in histological studies. Similarly, care must be taken with alternative therapies to ensure they are not just masking the symptoms of a minor underlying injury or biomechanical problem that may go untreated or may end in a serious injury. Ineffective or inappropriate therapies, whether conventional or alternative, may cause further damage in addition to slower healing; sports injuries should be treated with the most effective therapies available.
Acupuncture is an integral part of traditional Chinese medicine (TCM) and has been growing in popularity within conventional medicine. Approximately 10,000 acupuncturists practice in the United States, one-third of whom are physicians.7 Although acupuncture is used for a wide variety of ailments, some scientific evidence supports its effectiveness in relieving pain.8 Acupuncture most often is used by athletes for the relief of pain, especially pain associated with tendonitis.
One of the areas of controversy surrounding acupuncture involves its proposed mechanism of action. TCM is based upon the belief in a nonphysical "life energy" called qi (pronounced "chee") that circulates throughout the body via invisible channels called meridians.7 Health is said to require a balanced flow of qi, or energy. Illness or pain results when the flow of qi is obstructed or unbalanced. Acupuncture needles are inserted into the skin at specific locations on the body (acupuncture points). TCM practitioners believe this restores normal flow of qi through the meridians. Other physiological changes are elicited by needle insertion which conventional medicine believes underlie any benefits acupuncture may have. Needle insertion has been shown to release endorphins and serotonin which may account for an analgesic effect.9 Acupuncture also may have an anti-inflammatory effect by causing the release of endogenous corticosteroids.10
In Western societies, acupuncture has two schools of practice: classical and formula.11 (See Table 1 for a list of the different types of acupuncture and acupressure.) Classical acupuncturists are TCM practitioners who evaluate patients individually and vary acupuncture points for the same condition between patients. This school views acupuncture as inseparable from other elements of TCM, such as pulse diagnosis, yoga, and herbal remedies. The formula school uses standard acupuncture points for specific disorders and isolates acupuncture from other TCM therapies. This approach makes possible the design of randomized controlled trials (RCTs), although classical acupuncturists criticize this as a "recipe book" form of acupuncture, unrelated to real practice.11 This controversy hinders any attempt to objectively demonstrate whether acupuncture is effective by conventional standards.
|Table 1: Types of acupuncture and acupressure|
|Acupuncture: The use of fine needles at specific points on the body to balance or correct the imbalance or circulation of energy flow (qi).|
|Moxibustion: The burning of an herb or needle at an acupuncture point.|
|Electroacupuncture: The use of electric stimulation at acupuncture points.|
|French Energetic Acupuncture: The use of needles as electrodes to release blockage of electrolytes.|
|Five Element Acupuncture: The use of wood, fire, metal, water, and earth as five basic qualities to describe personality and organ dysfunction and aid in the choice of acupuncture points.|
|Auricular Acupuncture: A French tradition of using ear acupoints.|
|Myofascial Acupuncture: The palpation for tender points along meridians (energy pathways), which signify a blockage of energy flow.|
|Acupressure: The use of deep fingertip pressure massage along meridians.|
|Korean Hand Acupressure/Acupuncture: The use of needles or pressure on pressure points of the hands and feet.|
|Shoni Shin: A Japanese system of acupuncture that uses small tools such as tapping needles, press needles, and round edged rakes instead of more traditional acupuncture needles.|
|Source: Nicholson S. Alternative medicine: Acupuncture. Clinician Reviews 1999;9:87-92.|
Nevertheless, several RCTs have been conducted using formula acupuncture for sports-induced tendonitis. Tennis elbow (or lateral epicondylitis) is a relatively common form of tendonitis. Half of all tennis players experience prolonged pain and disability from this injury, which also affects almost 1% of industrial workers.12 Many therapies have been studied for treating this type of tendonitis, of which acupuncture is a commonly recommended alternative. A total of 48 patients who experienced tennis elbow pain for 15 months, on average, were randomly assigned to receive true acupuncture or sham acupuncture.9 After one treatment, 79.2% of the true acupuncture group experienced at least a 50% reduction in pain, compared to 25% of the control group (P < 0.01). Most patients who benefited from acupuncture reported 70% relief that lasted 20 hours, on average. The relief experienced from the placebo lasted 1.4 hours, which was significantly less (P < 0.001).
Conventional therapy for tennis elbow generally consists of steroid injections, which often are effective. However, some people are refractory to steroids, or receive only short-lived relief. In a study of 34 patients for whom steroid injections had previously been of little benefit, acupuncture brought complete relief of pain for 21 patients.13 Treatment consisted of five to eight acupuncture needles around the elbow and was given on average six times over four weeks. When compared to a control group of 26 patients who received steroid therapy, the acupuncture group did significantly better (P < 0.005). Four patients receiving steroid therapy reported worsening of their condition, while none receiving acupuncture reported worsening. The duration of pain relief was the same for both groups.
Other forms of tendonitis also have been treated with acupuncture. One study used a different form of placebo therapy consisting of a specially designed blunt needle that gave the patient the sensation of pricking the skin, but did not penetrate the skin.14 Fifty-two patients with rotator cuff tendonitis were randomly assigned to true or sham acupuncture groups. Patients received eight treatments over four weeks using TCM acupuncture points. Those receiving true acupuncture reported significantly less pain using the Constant-Murley rating system (P = 0.014). A similar number of patients in both groups reported adverse effects such as fainting, headaches, dizziness, increased muscle tension, and loss of strength in the legs.
In conclusion, although only a limited number of studies have examined the use of acupuncture for tendonitis, the results generally have been favorable. The analgesic effect of acupuncture is among its better-established indications, although controversy undoubtedly will continue until its mechanism of action can be better elucidated. Especially when conventional therapy for sports tendonitis proves ineffective, a trial with acupuncture appears warranted. Acupuncture is relatively free of serious adverse effects, although classical acupuncturists warn that symptoms may become worse before they improve. In a review of 16 acupuncture studies, 23 of the 320 subjects (7%) reported side effects such as fainting, earache, mild nausea, and dizziness.11 Case reports of more serious adverse effects have been published, although these typically involve the use of unsterilized needles or pneumothorax from needle insertion to the chest wall.15 Caution should be exercised in choosing a practitioner since great variability exists in the training and experience of acupuncture practitioners. (See Table 2 for a list of acupuncture organizations.)
|Table 2: Acupuncture organizations|
|National Acupuncture and Oriental Medicine Alliance, 638 Prospect Ave., Hartford, CT 06105-4298. Telephone: (203) 586-7509.|
|American Association of Acupuncture and Oriental Medicine, 433 Front St., Catasauqua, PA 18032. Telephone: (610) 266-1433.|
|American Acupuncture Association, 4262 Kissena Blvd., Flushing, NY 11355. Telephone: (718) 886-4431.|
|American Academy of Medical Acupuncture, 4929 Wilshire Blvd., Suite 428, Los Angeles, CA 90010. Telephone: (323) 937-5514.|
A chiropractor named George Goodheart noted in 1964 that weaknesses in certain muscles could be corrected by massaging seemingly unrelated muscles. Various muscle groups are believed to be connected to other muscles and organs through interconnected "energy circuits" similar in concept to the meridians found in traditional Chinese medicine. This led to associations between each muscle and acupuncture points. In addition, applied kinesiology holds that each muscle is associated with a specific nutrient. (Applied kinesiology should not be confused with kinesiology, which is the scientific study of the principles of human movement.) Thus, of particular relevance for athletes, a muscular weakness may be traced by a practitioner of applied kinesiology to dysfunction in an organ or gland, which may be related to a nutritional deficiency.16 Table 3 provides some examples of the relationships proposed by applied kinesiology to exist between various muscles and nutrients, organs or glands, the nervous system (for spinal manipulation), and acupuncture points. Applied kinesiology claims that these connections apply in only one direction. Thus, localized injury to a muscle will not affect its associated gland or organ.
|Table 3: Applied kinesiology relationships|
|Abdominal muscles||L-glutamine||small intestine||T5-12||SI 3, 19|
|Deltoids||vitamin C||lungs||C5, 6||LU 9|
|Gastrocnemius||vitamin C, pantothenic acid||adrenals||S1, 2||CX 9|
|Hamstrings||vitamin E||rectum||L5-S||LI 11, 20|
|Quadriceps||L-glutamine||small intestine||L2-4||SI 3, 9|
|Tricepts brachii||vitamin A, chromium||pancreas||C7, 8||SP 2, 3|
If an athlete were concerned about muscular weakness, applied kinesiology would involve the application of various challenges and muscle testing. These terms have specific meanings in applied kinesiology that differ from those in conventional medicine. The challenges are better known for their role in the diagnosis of allergies and dietary insufficiencies. Patients are asked to hold their arms out straight and practitioners apply firm but gentle pressure with their fingers to the patients’ arms. If the resistance to this pressure feels normal to the practitioner, the patient’s systems related to that arm muscle is considered normal. However, a dysfunction would be indicated if the patient’s muscle feels weak to the practitioner. Further tests then are carried out on other muscles to pinpoint the problem.
Once a dysfunction is identified, the second phase is to determine the source of the problem. According to applied kinesiology theory, the etiology lies in either a dysfunctional organ or a nutritional imbalance. The muscle testing is repeated, except this time the patient holds or tastes a sample of various nutrients or minerals. Changes in the detected muscle strength from the earlier muscle testing help identify the role of that nutrient in the dysfunction. Three outcomes are viewed as possible:16
• If the initial test revealed muscle weakness, and the subsequent test with the nutrient restored the strength to normal, that nutrient would benefit the patient.
• If the muscle strength was normal in the initial test, and now became weaker with the nutrient, the patient should not use it as a supplement.
• If no change in muscle strength occurs, the nutrient is benign and others should be tested.
The result of this approach is a highly individualized regimen of recommended and discouraged nutrients and supplements. This individualized attention is well received by many. The approach also is holistic.
Another aspect of applied kinesiology involves the use of emotional and mental challenges. The testing procedures are similar, except that instead of using nutrients, certain words or images are used to elicit responses. If the athlete thinks of a certain situation or person, and the practitioner detects weakening of the muscles, alternative thoughts or images are suggested until the muscle strength returns to normal.16 Thus, the replacing of one thought or image by another is believed to restore normal muscular function and permit maximal athletic performance.
Although the general approach to applied kinesiology forms a consistent viewpoint, very little if any of the theory has been verified scientifically. No compelling scientific evidence has been published demonstrating that applied kinesiology works for diagnosing or treating any health problems. While anecdotal successes are reported, a search of MEDLINE revealed no controlled studies of the effectiveness of diagnosing or treating muscular weakness with applied kinesiology. A major problem with the approach is the subjective nature of the muscle testing. The outcomes have been shown to vary depending on the amount of pressure applied to the muscle, the angle at which pressure is exerted, and whether the patient or the practitioner pushes first. Practitioners have attempted to develop instruments to standardize the muscle-testing method, with no success.
One published study assessed the consistency between different practitioners.17 Three practitioners, all with at least 10 years of experience using applied kinesiology, participated in two separate trials. In the first, they tested 32 healthy individuals for the strength or weakness of their piriformis and hamstring muscles. The practitioners demonstrated significant agreement with the piriformis muscles, but not with either of the hamstring muscles. In the second part, 53 subjects were examined for the strength or weakness of their pectoralis and tensor fascia lata muscles. Again, significant agreement occurred with the diagnoses for one muscle (pectoralis), but not for the other. This study demonstrated the problems with lack of consistency among even experienced practitioners.
Another study demonstrated more significant limitations with this therapy. Eleven subjects were evaluated for their nutritional status regarding thiamin, zinc, vitamin A, and ascorbic acid.18 Three experienced practitioners examined all subjects, who also were evaluated using standard laboratory tests for those nutrients. No statistically significant correlation was found among the results of the three practitioners, nor between their results and those of the lab tests. A computerized isometric muscle testing apparatus also revealed no correlation between its results and those of the applied kinesiology muscle testing. Finally, the subjects were randomly assigned to receive supplements of whichever nutrients applied kinesiology determined they lacked or a placebo. No statistically significant differences were found between those who received the placebo and those who received the actual nutrient. The authors concluded that applied kinesiology was no more reliable than random guessing.
Applied kinesiology is a complicated system that involves much personal attention. When athletes are unable to understand their poor performance, applied kinesiology holds out some hope for identifying a cause that can be corrected with relative ease. However, the small number of scientific studies that have been published on this therapy offer very little support for its effectiveness or reliability. Although the therapy is relatively benign, following the recommendations may lead to inaccurate nutritional advice. Some nutrients, which the athlete actually needs, may be discouraged, and others may be taken in amounts beyond what is necessary. There is no scientific evidence to recommend the use of applied kinesiology for any problem athletes may have.
Chiropractic manipulation is based on the theory developed by Daniel David Palmer during the 1890s. His primary assumption was that all illness has its origins in how well the spine and joints are aligned. Palmer was initially interested in magnetic healing, but is reported to have manipulated the spine of a man who had been deaf for 17 years and completely restored his hearing. Although Palmer coined the term chiropractic from the Greek words cheerio and prakrios, which mean "done by hand" or "manipulation," the general approach is said to be traceable to Hippocrates who stated, "Look well to the spine for the cause of disease."
Although chiropractic manipulation has been controversial throughout the twentieth century, it has grown in popularity and acceptability (see Table 4). Chiropractors are licensed in all 50 states of the United States, and 45 states have mandated benefits for chiropractic services.19 One of the more controversial aspects of chiropractic care relates to its proposed explanation for musculoskeletal pain and discomfort. The underlying causes are believed to be mechanical lesions on the spine and peripheral articulations that interfere with the normal activity of the nervous system.16 This interference can lead to physical, chemical, or emotional dysfunction. These lesions generally are called "subluxations" and can be felt manually by the trained practitioner. Whereas in conventional medicine a subluxation refers to a partial or incomplete dislocation, a chiropractic subluxation refers to any form of dysfunction within a joint’s normal range of motion.16 The subluxation also can be referred to as a spinal joint strain or sprain, which results in local and referred pain, muscle spasm, and reduced motion or misalignment at the affected joint.19
|Table 4: Alternative therapies most commonly reimbursed by health insurance organizations|
|Source: Albertson D. Alternative medicine benefits on the rise. Employee Benefit News 2000;14:60.|
The dysfunction can be treated by either of two approaches, called adjustments or manipulations. A long-lever manipulation uses high-velocity forces on a part of the body that is relatively far from the dysfunction. The short-lever technique applies high-velocity thrusts directly onto the area of dysfunction. Both techniques result in the characteristic popping or cracking sounds of chiropractic adjustments. A procedure related to manipulation is called mobilization, in which pressure is applied to the joint but without the application of the chiropractic thrust.
Hundreds of studies have examined the efficacy and safety of chiropractic manipulation, and these have resulted in more than 50 systematic research reviews. However, little attention has been given to the use of chiropractic specifically for sports-related injuries, in spite of the growing use of chiropractic by athletes.19 The best-supported uses of chiropractic are for low back and neck pain, but not necessarily pain resulting from sports injuries. However, reviews have consistently pointed out that many of the primary research studies have significant methodological flaws that make overall conclusions very difficult. In spite of this, there is growing consensus that chiropractic manipulations are effective in relieving at least some forms of low back pain.20
When compared to treatment by primary care physicians, physical therapists, or neurosurgeons, little difference has been noted in their relative effectiveness or speed of recovery, although patients generally report being more satisfied with chiropractors. One study found no significant differences between physical therapy and chiropractic manipulation on all measured outcomes of relief of low back pain.21 The benefits of either therapy were only marginally better than that experienced when patients were simply provided an educational booklet. However, the cost of the booklet was about one-third of the cost of either therapy (which cost practically the same).
The evidence for chiropractic treatment of neck and shoulder pain is much less convincing than that for low back pain.22 In addition, one review found 32 case reports of death following manipulation of the cervical spine.23 While the risk of serious injury from chiropractic manipulation cannot be estimated because of the unknown number of total manipulations, there appears to be greater risk of adverse effects when manipulation is carried out higher on the spine. Mobilization, as opposed to manipulation, seems to carry lower risks, but also may be less effective.19
Many professional, collegiate, and amateur teams now incorporate chiropractic care into their sports medicine programs.16 Athletes involved in contact sports and those that include jarring movements are particularly susceptible to back and joint problems that can be very painful. Many report effective, rapid relief from chiropractic manipulation. Controlled clinical trials have not been conducted for many of the ways chiropractic care is used by athletes.
One recent study did find that chiropractic manipulation of the ankle after inversion sprains produced significantly greater improvement than ultrasound therapy.24 Both groups showed improvements in pain reduction, ankle range of motion, and ankle function. Thirty patients were randomly assigned to either treatment; because of the intervention, the study was not blinded.
Studies on the long-term effectiveness and safety of chiropractic care are needed, especially because athletes often receive on-going manipulation for the musculoskeletal and joint pain associated with their sports. Although the short-term relief is welcome, the long-term effects should be investigated.
Magnet therapy is based on the belief that permanent magnets have healing properties. The concept dates back to Paracelsus, the physician and alchemist who lived in the 1500s. He reasoned that since magnets attract iron, they also might attract toxins or diseases and remove them from the body. At the same time, though, he wrote that while the course of a disease could be influenced by many factors, "The imagination produces the effect." Probably the best-known proponent of magnetic healing was Franz Mesmer, an 18th-century Austrian doctor. Mesmer claimed that all illness had its origin in problems related to the flow of "animal magnetism." He moved magnets around a patient’s body, allegedly to correct the flow of this magnetic energy. However, Mesmer later modified his therapy, believing that the magnets were not essential and developing a form of hypnosis (from which we get the term "mesmerized").
Mesmer moved to Paris to practice his form of hypnotism and magnetic healing, and soon attracted professional attention. At the urging of King Louis XVI, the French Royal Academy of Medicine appointed a committee to evaluate Mesmer’s claims. The report produced by this committee (with Benjamin Franklin as the committee’s chairperson) describes some of the first documented "blinded" tests. These involved groups of women who literally were blindfolded. When the women could see they were being treated with "magnetic energy," they reported sensing the energy. When they were blindfolded, there was no correlation between when they thought they were being treated and when they actually were being treated.
The committee concluded that the patients believed the therapy worked because of a complicated set of conditions that today would be grouped under the placebo effect. The report stated that any observed effects were explained better "by the touches of the operator (i.e., therapist), the excited imagination of the patient, and by the involuntary instinct of imitation."25 Although not without limitations compared to modern clinical tests, these studies formed the beginnings of what would later be called the single-blind method in clinical research.26 Many agreed with Thomas Jefferson, who declared, upon reading the commission’s report, "Animal magnetism is dead, ridiculed."
Yet since that time, magnetic therapy has gone through cycles of ridicule followed by resurgence in interest. Currently, we are in the midst of a phase of popularity. Developments in magnet engineering have allowed permanent magnets to be made in many shapes and sizes. This allows magnets to be molded to fit onto various parts of the body, or shaped into insoles for insertion into shoes. A huge industry has materialized selling magnets in mattresses to promote sleep and ease back pain, in insoles to prevent tiredness from walking or standing, and in jewelry for promoting general health. Athletes are attracted to magnets for all of these purported benefits. One particular company increased its annual U.S. sales of magnets from $3 million in 1989 to $150 million in 1997.27
The form of magnet therapy that places permanent magnets next to the body must be clearly distinguished from pulsating electromagnetic field (PEMF) therapy, which will be described in a subsequent section. The pulsing of the magnetic field is essential for this effect and thus is completely different from a permanent magnet. However, promotional materials for permanent magnets sometimes inappropriately cite the promising results of PEMF therapy to support their approach to magnet therapy.
Permanent magnets are believed to act therapeutically by promoting blood flow to the injured tissues. Some claim this is due to attraction of iron in red blood cells, but this is highly unlikely because of the way individual iron atoms are held within hemoglobin in the blood.28 Also, with the advantage of newer permanent magnets being thin and malleable comes a significant limitation: The magnetic field drops off rapidly. This can be seen in the way refrigerator magnets can hold very few sheets of paper. The magnetic field of many magnets used in therapy would barely penetrate clothes or skin.27 This makes the influence of magnets on blood flow or any other metabolic process very questionable. Nevertheless, even if the mechanism of action is not understood, a therapy’s effectiveness still can be tested in clinical trials.
Athletes use magnets primarily to relieve the aches and pains of exercise and competition. Interest among golfers has been particularly high. This popularity received a major boost when a well-controlled study was published in a mainstream medical journal in 1997.29 This study reported better pain relief from magnets than from a placebo in patients with chronic postpolio pain of a muscular or arthritis-like type. The 50 patients were randomly assigned to active or control groups, and a device was placed over a pain trigger point for 45 minutes. Patients in both groups reported significant pain relief, but the group treated with permanent magnets had significantly greater relief than the control group (P < 0.0001). This benefit contrasts with the results of most other studies.
One of the few earlier double-blind studies involved 101 subjects with shoulder and neck pain.30 The patients were randomly assigned to wear either a magnetic necklace or a control necklace. Patients wore the necklace 24 hours per day for three weeks. At that time, both groups of patients reported decreased frequency and intensity of pain, but there was no statistically significant difference between the magnetic necklace and the nonmagnetic necklace.
A more recent randomized, double-blind study examined 20 patients with chronic low back pain.31 Permanent magnets or a similar placebo were worn for six hours per day, three days a week, for one week. After a wash-out period, subjects crossed over to use the other device. No statistically significant differences were found between the two groups.
Another popular use of magnets is in insoles for the relief of foot and heel pain, and to relieve generalized fatigue. A double-blind study randomly assigned 34 patients with heel pain to wear either a magnetic or nonmagnetic insole.32 Sixty percent of the patients in both groups reported improvement, with no statistically significant differences between the two groups.
A preliminary report has been published in which magnetic insoles showed some benefit in treating older adults with postural instability.33 Twenty-eight adults, 14 older and 14 younger, were randomly assigned to wear magnetic insoles for a single test, and nonmagnetic insoles in another test. Only the older adults showed a significant reduction in swaying when wearing the magnetic insoles.
The popularity of magnets for many types of healing has waxed and waned over the centuries. Many people, including many athletes, are convinced that magnets are effective in relieving a variety of conditions, especially generalized aches and pains. The result has been an industry with annual sales of more than $5 billion. However, simply wearing a belt, pad, or insert may be enough to produce a beneficial effect, especially since many of the conditions for which magnets are recommended are strongly influenced by the placebo effect. Nevertheless, at least one study has found magnets more effective than placebo. However, given the lack of a plausible mechanism of action and the results of several studies finding magnets no more effective than placebo, skepticism toward the numerous claims made regarding magnet therapy is warranted until the one positive study is replicated and confirmed.
Massage therapy has long been a part of sport, both prior to competition as part of an athlete’s warm-up and after exercise for the prevention or treatment of muscle soreness and injury. Among British athletes at the 1996 Olympic Games in Atlanta, 47% of all the treatments given to athletes from all sports consisted of massage.34 The role of massage in medicine has long been recognized, with Hippocrates having written, "The physician must be experienced in many things, but assuredly in rubbing."
Athletes use several types of massage, with effleurage, petrissage, and tapotement being the most common techniques.35 (See Table 5 for a list of the different types of massage.) Effleurage involves long, gliding strokes along the length of the muscles, and can be either superficial or deep. Petrissage is the name given to the kneading or muscle rolling aspects of massage. Tapotement involves light, rapid blows to the muscle using the therapist’s relaxed hands, and is the most common technique used in pre-competition massage.
|Table 5: Types of massage|
|Cranio-Sacral: is a technique for finding and correcting cerebral and spinal imbalances of blockages that may cause sensory, motor, or intellectual dysfunction.|
|Deep Tissue: releases the chronic patterns of tension in the body through slow strokes and deep finger pressure on the contracted areas, either following or going across the grain of muscles, tendons, and fascia. It is called deep tissue, because it also focuses on the deeper layers of muscle tissue.|
|Effleurage: is a stroke generally used in Swedish massage treatment. This smooth, gliding stroke is used to relax soft tissue and is applied using both hands.|
|Friction: is the deepest of Swedish massage strokes. This stroke encompasses deep, circular movements applied to soft tissue causing the underlying layers of tissue to rub against each other. The result causes an increase in blood flow to the massaged area.|
|Myofascial Release: is a form of bodywork that is manipulative in nature and seeks to rebalance the body by releasing tension in the fascia. Long, stretching strokes are utilized to release muscular tension.|
|Petrissage (also called kneading): involves squeezing, rolling, and kneading the muscles and usually follows effleurage during Swedish massage.|
|Reflexology: is based around a system of points in the hands and feet thought to correspond, or "reflex," to all areas of the body.|
|Rosen Method: utilizes gentle touch and verbal communication to help clients release suppressed emotions and subsequently muscular tension.|
|Shiatsu and Acupressure: are Oriental-based systems of finger pressure that treat special points along acupuncture meridians (the invisible channels of energy flow in the body).|
|Sports Massage: focuses on muscle systems relevant to a particular sport.|
|Swedish Massage: is a system of long strokes, kneading, and friction techniques on the more superficial layers of the muscles, combined with active and passive movements of the joints.|
|Tapotement: is executed with cupped hands, fingers, or the edge of the hand with short, alternating taps to the client.|
|Trigger Point Therapy (also known as Myotherapy or Neuromuscular Therapy): applies concentrated finger pressure to "trigger points" (painful irritated ares in muscles) to break cycles of spasm and pain.|
|Source: American Massage Therapy Association. Available at: www.amtamassage.org/about/terms.htm.|
Massage is reported to assist in recovery from muscle injuries through some combination of increased blood and lymph flow, reduced muscle tension, release of biochemical healing factors, pain relief, and stimulation of the immune system.16 In spite of the widely held belief that massage increases muscle blood flow, recent ultrasound and radiotracer studies have not confirmed this claim.36 The same result was found regardless of the massage technique used or the size of the muscle involved. Instead, light exercise was found to increase blood flow more significantly, and therefore was recommended over massage for pre-exercise warm-up or post-exercise muscle recovery.
Similar types of studies have failed to demonstrate that massage increases lymph flow, although this measurement is difficult to make accurately.35 In fact, very little evidence supports the belief that massage helps eliminate the biochemicals most commonly associated with muscle soreness and damage. For example, several studies have failed to demonstrate that massage increases the rate of removal of lactate from muscles after exercise. One study found that 10 minutes of post-exercise massage was no more effective at removing lactate than passive rest, and light exercise was significantly more effective than both at reducing blood lactate levels.37
One of the symptoms of muscle damage is prolonged loss of strength, which can exist even before soreness is noted and persist after soreness diminishes.38 Massage is reported to be beneficial in aiding recovery from damage related to muscle strength loss. However, reviews of the controlled research in this area have found contradictory results. Some studies have found massage beneficial, some found no effect, and others found it slowed recovery.39
Massage often is recommended for athletes to prevent post-exercise soreness and to shorten the recovery period after intense exercise. A study using underwater jets of warm water to massage athletes’ legs has received considerable attention because of its beneficial results.40 Fourteen elite track and field athletes underwent five days of intense training during which their performances were expected to decline due to fatigue and muscle soreness. The athletes were randomly assigned to two groups; one group received warm-water massage after each training session and the other group did not. The groups were then crossed over. No significant difference was found in the levels of muscle soreness, but the athletes showed significantly less performance deterioration during the weeks they received the warm-water massage (P < 0.05). However, this technique differs significantly from manual massage, and the benefits may have been due to the higher temperature of the water, or to being immersed in water.
Delayed-onset muscle soreness is a significant problem for athletes, leading to slight stiffness or even debilitating pain. Biomechanical changes undertaken to compensate for the soreness may lead to other injuries. This soreness tends to appear between eight and 24 hours after exercise, peaks at around 48 hours, and dissipates over the course of the next few days.41 Several studies administering massage immediately after exercise, or 24-48 hours later, have found it ineffective in reducing muscle soreness. However, a study using massage two hours after exercise found significantly less soreness in those treated compared to the control group (P = 0.0477).41 Biochemical markers for tissue damage also were higher in the control group.
A recent review of this application of massage found seven controlled trials.42 Most of the studies had serious methodological flaws. All but one had fewer than 20 subjects. The results were variable, although there did seem to be a pattern indicating massage was effective in reducing muscle soreness. However, the review concluded that "its effectiveness has not been demonstrated convincingly." Although not limited to athletes, massage as a treatment for low back pain has gained much popularity. Again, the controlled research available to support this use is scant and of poor methodological quality.43
In contrast to the lack of conclusive evidence for massage’s effect on muscle healing and recovery, a growing body of evidence supports its benefit for connective-tissue, tendon, and collagen healing.35 A recent animal study has demonstrated beneficial effects on tendonitis using a form of massage called augmented soft-tissue mobilization (ASTM).44 This technique uses specially designed solid instruments to apply considerable pressure to the injured tissue. This study showed significantly more fibroblasts in the injured tissues treated by ASTM (P < 0.05). Also, greater response was seen when the pressure applied was greater. If this finding is confirmed in athletes, it may explain the variability found in massage studies as the applied pressure varies considerably among therapists.
In conclusion, massage is likely to remain popular among athletes. It is primarily used to prepare for competition and prevent muscle soreness and injury. These uses are more firmly based on anecdotal evidence and tradition, rather than scientific studies. However, massage has a relaxing effect that can be of clear benefit in preparation for competition and in facilitating healing in general. Meanwhile, controlled studies are revealing that a form of high-pressure massage (ASTM) may have more clear-cut benefits in treating tendonitis and other connective-tissue injuries. Given that the popularity of massage among athletes is unlikely to wane, better studies are needed to ensure that the best forms of massage are used for specific muscle or tendon conditions. (See Table 6 for a guide to choosing a massage therapist.)
|Table 6: Choosing a massage therapist|
|When selecting a massage therapist, the American Massage Therapy Association (AMTA) recommends asking the following questions:|
|•||Where did you receive your massage therapy training?|
|•||Are you a graduate of a training program accredited by the Commission on Massage Therapy Accreditation or that is a member of the AMTA Council of Schools?|
|•||Are you certified by the National Certification Board of Therapeutic Massage and Bodywork?|
|•||Do you have advanced training in any specific massage techniques?|
|•||Are you currently licensed as a massage therapist in this state (if applicable)?|
|•||Are you a member of the American Massage Therapy Association?|
|Source: American Massage Therapy Association. Available at: www.amtamassage.org/news/presskit.pdf.|
Pulsed Electromagnetic Field Therapy
Pulsed electromagnetic field (PEMF) therapy is based on the well-established fact that biological structures contain electric dipoles. All living organisms contain endogenous electric, magnetic, and electromagnetic fields that may be affected by externally applied fields.45 The endogenous fields play an important role in tissue growth and repair, which has led to much speculation, and some experimentation, concerning the potential benefits of electromagnetic fields in healing.
Although some would question the inclusion of this therapy within complementary and alternative medicine, many aspects of this approach have not yet become widely accepted within conventional medicine.46 An understanding of developments within this field is important because of the frequent mention of "energy fields" among proponents of alternative medicine. The developments with electromagnetic field therapy are sometimes cited to support the efficacy of other therapies.28 If these other therapies involve nonphysical "life energies" or static magnetic forces, these associations are unwarranted. Clear distinctions should be drawn between therapies based on electromagnetic fields and forces and those based on unrelated fields and forces.
Pulsed electromagnetic fields can be generated at different frequencies and power outputs. PEMF therapy must be clearly distinguished from the use of static magnets, which have been considered in an earlier section. The pulsed field is believed to alter the cell membrane potential that influences the flux of ions in and out of the cells.45 Repair of damaged tissues involves much proliferation and migration of many cells, all of which could be influenced by these changes.46 The apparatus used in PEMF therapy consists of copper wires twisted into a coil that is then shaped to fit the area of treatment. Straps hold the coiled wire in place, which usually is used for several hours each day for a number of weeks. The wires are connected to a pulse generator that is set to deliver the appropriate frequency and power output. Much variability occurs in the frequency, power output, and duration of treatment recommended.
One of the first applications of PEMF was its use in promoting the healing of bone fractures, especially those that were slow to respond to conventional care. A substantial body of literature has examined the role of PEMF in calcium metabolism and bone healing. A multicenter, randomized, double-blind trial involved 45 patients with delayed bone union.47 All were immobilized in plaster casts; 20 received PEMF units and 25 received control units. Healing was assessed using x-rays read by a blinded radiologist and an orthopedic surgeon. After 12 weeks, nine of the 20 PEMF fractures showed union, whereas only three of the 25 control fractures showed union. This difference was statistically significant (P = 0.02).
A review of the controlled trials of PEMF with delayed or non-uniting bone fractures showed it to be essentially equivalent to surgical repair.48 Many of these studies had high success rates for PEMF with fractures that had previously been treated unsuccessfully by surgery. Overall, PEMF had an 81% success rate, compared to 82% for surgery. However, PEMF is non-invasive and thus spares patients the risks of surgery and the additional healing time.
PEMF therapy has been examined with a number of specifically sports-related conditions, but few studies are available for any one condition. Rotator cuff tendonitis is a very common form of shoulder injury. A double-blind study was conducted with 29 patients whose rotator cuff tendonitis was refractory to conventional therapy, including steroid injections.49 After four weeks, the patients receiving PEMF reported significant improvements in pain levels compared to the control group (P < 0.02). For a subsequent four weeks, both groups were given PEMF, and there was no significant difference in pain levels between the two groups.
Another double-blind study examined the impact of PEMF on 30 patients with chronic tennis elbow.50 Pain levels were measured using various lifting and twisting procedures every two weeks for eight weeks. Statistically significant differences were found in favor of PEMF at six weeks only (P < 0.05), and not at the conclusion of the study. A more recent animal study found beneficial effects from PEMF on experimentally induced Achilles tendonitis.45 The tendons of those animals treated with a pulsed magnetic field (PMF) had less inflammation and were more histologically normal. PMF and PEMF are believed to produce similar effects. This study also used different field frequencies, with PMF 17 Hz being the most beneficial, PEMF 46 Hz showing better results later in the study, and PMF 50 Hz being most beneficial during the acute phase of inflammation.
The latter results show how much is yet to be learned about PEMF therapy before it can be widely recommended. More research is needed to determine the best frequency to use, and whether this should be varied over the course of treatment. The most effective duration of exposure to the field also is poorly understood. There may be differences in the responses of various tissues and types of injuries to the various fields. Until more is known, PEMF may be useful on an experimental basis when sports injuries are refractory to conventional therapy.
Water is the most important natural substance that athletes need to ingest. Yet its importance often is overlooked even by professional athletes, which then can lead to a variety of injuries, including death. Water plays many roles in the body, but for athletes, one of its most crucial ones is in heat regulation. Working muscles generate much heat, which must be eliminated. Sweating dissipates some of this heat, but the fluids lost this way then must be replaced. If fluid consumption is not adequate, the risk of dehydration increases. (Table 7 lists the most common symptoms of dehydration.)
|Table 7: Common symptoms of dehydration|
|•||Thirst, dry mouth|
|•||Reduced performance, weakness, fatigue, headache|
|•||Increased breathing and pulse rate|
|•||Increased body temperature|
|•||Muscle spasms, dizziness, delirium|
|•||Poor circulation, failing kidney function|
|•||Heat stroke: thermoregulatory failure; dry, hot skin; lack of sweat|
Athletes can lose 2-3 liters of water per hour if exercising vigorously in hot weather. As the body dehydrates, blood volume drops, requiring the heart to pump faster to get oxygen around the body. Body temperature increases further, the athlete begins feeling more tired and performance starts to deteriorate. More severe dehydration can lead to heat exhaustion and to heat stroke, which can be fatal (see Table 8).
Heat-stress index for evaluating risk of heat injury51
|Air Temperature (°F)|
|Heat Sensation (°F)|
|Heat Sensation||Risk of Heat Injury|
|90-105||Possibility of heat cramps|
|105-130||Heat cramps or heat exhaustion likely; heat stroke possible|
|130+||Heat stroke a definite risk|
For normal sedentary adults, eight to ten 8-ounce glasses of fluids per day are commonly recommended to replace normal water loss. Athletes require much more, especially when exercising in warm weather. Fluids should be consumed prior to, during, and after exercising, although adequate consumption during exercise can be awkward, if not impossible, during some sports. For endurance events, fluid loss can be 2 L/hr, while maximal stomach emptying averages 1 L/hr.
The following general guidelines can be helpful:51
• About 20 minutes before exercising, drink 12-20 ounces of fluids.
• During exercise, drink 4-8 ounces every 20 minutes.
• After exercising, athletes should consume about 20 ounces of fluids for every pound of body weight lost. Every pound lost represents a loss of 15 fluid ounces.
Athletes should not use their thirst level to indicate whether or not they are adequately hydrated. Calculating how much water is lost on average and drinking the needed replacement fluids in the hours following exercise is a more reliable guide to adequate rehydration.
Injury Prevention Strategies
Scientific research into the prevention of sports injuries is still in its infancy. However, some patterns are beginning to emerge. Stretching prior to exercise appears to have some benefit in preventing muscle strains. However, two cautions are needed here. Stretching must be limited, as muscle injury experiments in animal models have demonstrated. When muscles were stretched 10 times to 50% of their maximum, strains were less prevalent.5 However, when the muscles were stretched to 70% of maximum, strains occurred more frequently. Recent research is establishing that the stretching itself may not be what is most important, but the way stretching contributes to warming up.52 When stretching is the only component of a warm-up, the incidence of muscle strains is unchanged. But when stretching is one component of an overall warm-up prior to vigorous exercise, muscle strains were reduced. Exactly what leads to an effective warm-up is still a matter of some debate, although it seems to involve increasing muscle temperature and stretching only within certain limits.5
An important aspect of preventing injuries is to avoid common training errors.2 Continuous, high-intensity training can lead to overuse injuries, as can the failure to alternate hard training days with easy (recovery) days. Another error is to increase the training intensity too rapidly. Among runners, for example, a 10% rule is commonly cited: A week’s mileage should not increase by any more than 10% of the previous week’s mileage.2 A similar rule of thumb could be developed for other sports. When competitive athletes are recovering from injury, however, this schedule can be too prolonged, resulting in further loss of fitness. Nonetheless, the risk of re-injury warrants patience and close monitoring during recovery.
At the same time, remedial exercise with pain-free stretching and strengthening should be started as soon as possible to avoid unnecessary muscle atrophy.12 Cross-training may be helpful here, where losses in cardiovascular fitness can be minimized by exercising muscles that are not injured. Physicians who call on injured athletes to cease exercising completely may end up losing their opportunity to help the athlete. Some athletes avoid physicians when injured, on the assumption the physicians will just tell them to rest and take pain pills. Among 364 runners who competed in the Montreal International Marathon, 21% suffered an injury while training for the event.53 Of those injured, 69% consulted a physician and almost half of these were told to stop running. More than one-third disregarded this advice, on the belief that the doctor "knew nothing about running." However, 36% of those who suffered injury while training were still injured on the day of the race, and competed anyway.
Clearly, telling injured athletes to stop training may not always be the best advice, either physiologically or psychologically. The advice often may be ignored anyway, leading to further breakdown in communication between physician and athlete. If your patients include athletes, keeping them active and staying apprised of developments in the treatment of common sports injuries will be beneficial for all involved.
Athletes also are susceptible to other, less-common training errors, including the use of inadequate or worn-out equipment, training on inappropriate surfaces, or poor technique.2 Although attention often is focused on training, an athlete’s performance also is influenced by the general activities in his or her life. Athletes must ensure they get adequate nutrition, hydration, and rest if they are to avoid injury and perform at the maximum of their potential.
Unfortunately, accidents happen and injuries will occur. Informed physicians can help athletes receive the care they need. When reduction in training is needed, the goal of returning the athlete to full training should, if possible, be clearly expressed. Although conventional medicine has much to offer the injured athlete, care must be taken to avoid simply masking the symptoms. Getting at the underlying causes will be essential to a full recovery. Some complementary and alternative therapies have little scientific evidence to support their use; others are demonstrating that they can play a role in helping injured athletes recover. Much more basic research is needed in this interesting area. To promote their best interests in the long run, athletes should be treated with therapies that are demonstrated to be effective and safe.
Dr. O’Mathúna is Professor of Bioethics and Chemistry at Mount Carmel College of Nursing in Columbus, OH.
1. O’Mathúna DP. Complementary and alternative medicine for athletes. Part 1: Ergogenic aids—dietary supplements and herbal remedies. Altern Med Reports 2001;1:1-12.
2. O’Toole ML. Prevention and treatment of injuries to runners. Med Sci Sports Exerc 1992;24(Suppl 9):S360-S363.
3. Ernst E. The "Hoddle Muddle": Using faith healers and other complementary therapists in sports medicine. Br J Sports Med 1998;32:195.
4. Tiidus PM. Alternative medicine interventions in sport: Introduction to the symposium. Can J Appl Physiol 1999;24: 232-233.
5. Garrett, Jr WE. Muscle strain injuries. Am J Sports Med 1996;24(6 Suppl):S2-S8.
6. Obremsky WT, et al. Biomechanical and histological assessment of a controlled muscle strain injury treated with piroxicam. Am J Sports Med 1994;22:558-561.
7. Cadwell V. A primer on acupuncture. J Emerg Nurs 1998;24: 514-517.
8. NIH Consensus Conference. Acupuncture. JAMA 1998;280: 1518-1524.
9. Molsberger A, Hille E. The analgesic effect of acupuncture in chronic tennis elbow pain. Br J Rheumatol 1994;33:1162-1165.
10. Tashkin DP, et al. A controlled trial of real and simulated acupuncture in the management of chronic asthma. J Allergy Clin Immunol 1985;76:855-864.
11. Jobst KA. Acupuncture in asthma and pulmonary disease: An analysis of efficacy and safety. J Altern Complement Med 1996;2:179-206.
12. Sevier TL, Wilson JK. Treating lateral epicondylitis. Sports Med 1999;28:375-380.
13. Brattberg G. Acupuncture therapy for tennis elbow. Pain 1983; 16:285-288.
14. Kleinhenz J, et al. Randomised clinical trial comparing the effects of acupuncture and a newly designed placebo needle in rotator cuff tendonitis. Pain 1999;83:235-241.
15. Peuker ET, et al. Traumatic complications of acupuncture. Therapists need to know human anatomy. Arch Fam Med 1999;8:553-558.
16. Maffetone P. Complementary Sports Medicine: Balancing Traditional and Nontraditional Treatments. Champaign, IL: Human Kinetics; 1999.
17. Lawson A, Calderon L. Interexaminer agreement for applied kinesiology manual muscle testing. Percept Mot Skills 1997; 84:539-546.
18. Kenney JJ, et al. Applied kinesiology unreliable for assessing nutritient status. J Am Diet Assoc 1988;88:698-704.
19. Crawford JP. Chiropractic intervention in the treatment of joint and soft tissue disorders. Can J Appl Physiol 1999;24:279-289.
20. Ernst E, Assendelft WJ. Chiropractic for low back pain. BMJ 1998;317:160.
21. Cherkin DC, et al. A comparison of physical therapy, chiropractic manipulation, and provision of an educational booklet for the treatment of patients with low back pain. N Engl J Med 1998;339:1021-1029.
22. Hurwitz EL, et al. Manipulation and mobilization of the cervical spine. A systematic review of the literature. Spine 1996;21: 1746-1760.
23. Di Fabio RP. Manipulation of the cervical spine: Risks and benefits. Phys Ther 1999;79:50-65.
24. Pellow JE, Brantingham JW. The efficacy of adjusting the ankle in the treatment of subacute and chronic grade I and grade II ankle inversion sprains. J Manipulative Physiol Ther 2001;24:17-24.
25. Podmore F. From Mesmer to Christian Science: A Short History of Mental Healing. New Hyde Park, NY: University Books; 1963.
26. Kaptchuk TJ. Intentional ignorance: A history of blind assessment and placebo controls in medicine. Bull Hist Med 1998; 72:389-433.
27. Livingston JD. Magnetic therapy: Plausible attraction? Skeptical Inquirer 1998;22:25-30, 58.
28. Ramey DW. Magnetic and electromagnetic therapy. Sci Rev Altern Med 1998;2:13-19.
29. Vallbona C, et al. Response of pain to static magnetic fields in postpolio patients: A double-blind pilot study. Arch Phys Med Rehabil 1997;78:1200-1203.
30. Hong CZ, et al. Magnetic necklace: Its therapeutic effectiveness on neck and shoulder pain. Arch Phys Med Rehabil 1982;63:462-466.
31. Collacott EA, et al. Bipolar permanent magnets for the treatment of chronic low back pain: A pilot study. JAMA 2000; 283:1322-1325.
32. Caselli MA, et al. Evaluation of magnetic foil and PPT Insoles in the treatment of heel pain. J Am Podiatr Med Assoc 1997; 87:11-16.
33. Suomi R, Koceja DM. Effect of magnetic insoles on postural sway measures in men and women during a static balance test. Percept Mot Skills 2001;92:469-476.
34. Callaghan M. Commentary. Br J Sports Med 1998;32:214.
35. Tiidus PM. Massage and ultrasound as therapeutic modalities in exercise-induced muscle damage. Can J Appl Physiol 1999; 24:267-278.
36. Shoemaker JK, et al. Failure of manual massage to alter limb blood-flow: Measures by Doppler ultrasound. Med Sci Sports Exerc 1997;29:610-614.
37. Gupta S, et al. Comparative study of lactate removal in short term massage of extremities, active recovery and passive recovery period after supramaximal exercise sessions. Int J Sports Med 1996;17:106-110.
38. Clarkson PM, Sayers SP. Etiology of exercise-induced muscle damage. Can J Appl Physiol 1999;24:234-248.
39. Callaghan MJ. The role of massage in the management of the athlete: A review. Br J Sports Med 1993;27:28-33.
40. Viitasalo JT, et al. Warm underwater water-jet massage improves recovery from intense physical exercise. Eur J Appl Physiol Occup Physiol 1995;71:431-438.
41. Smith LL, et al. The effects of athletic massage on delayed onset muscle soreness, creatine kinase, and neutrophil count: A preliminary report. J Orthop Sports Phys Ther 1994;19:93-99.
42. Ernst E. Does post-exercise massage treatment reduce delayed onset muscle soreness? A systematic review. Br J Sports Med 1998;32:212-214.
43. Ernst E. Massage therapy for low back pain: A systematic review. J Pain Symptom Manage 1999;17:65-69.
44. Gehlsen GM, et al. Fibroblast responses to variation in soft tissue mobilization pressure. Med Sci Sports Exerc 1999;31: 531-535.
45. Lee EWC, et al. Pulsed magnetic and electromagnetic fields in experimental Achilles tendonitis in the rat: A prospective randomized study. Arch Phys Med Rehabil 1997;78:399-404.
46. Bassett CA. Beneficial effects of electromagnetic fields. J Cell Biochem 1993;51:387-393.
47. Sharrard WJ. A double-blind trial of pulsed electromagnetic fields for delayed union of tibial fractures. J Bone Joint Surg Br 1990;72:347-355.
48. Gossling HR, et al. Treatment of ununited tibial fractures: A comparison of surgery and pulsed electromagnetic fields (PEMF). Orthopedics 1992;15:711-719.
49. Binder A, et al. Pulsed electromagnetic field therapy of persistent rotator cuff tendonitis: A double-blind controlled assessment. Lancet 1984;1:695-698.
50. Devereaux MD, et al. Chronic lateral humeral epicondylitis— a double-blind controlled assessment of pulsed electromagnetic field therapy. Clin Exp Rheumatol 1985;3:333-336.
51. McArdle WD, et al. Sports & Exercise Nutrition. Philadelphia, PA: Lippincott Williams & Wilkins; 1999.
52. Shrier I. Stretching before exercise: An evidence based approach. Br J Sports Med 2000;34:324-325.
53. Thibault G, et al. Utilization of ergogenic aids and the attitude toward safety in marathon runners. In Katch FI, ed. Sport, Health, and Nutrition. Champaign, IL: Human Kinetics; 1986.