There are various kinds of back aches, as well as various causes for these aches; for most of them,  massage therapy, exercise, and posture modifications are the most efficient way to get relief.

1. 1. Various types of lower back pain.

Lumbagos, chronic lower back pain and emergencies are 3 categories in which lower back pains can be classified [1].

• Acute lower back pain.

Acute lower back pain, or lumbago,  is a sudden, intense pain of the lumbar region. Its intensity makes it impossible to move for several days; however, the pain then recedes completely and there is no residual pain or loss of movement after that episode. A lower back pain is considered acute if it lasts less than 3 months.

• Chronic lower back pain.

Chronic lower back pain is a low intensity pain that lasts more than 3 months [1]. It can increase with some movements or positions, and usually decreases with rest. Chronic lower back pain often appears after several episodes of lumbagos [2]! This is why after a first episode of back pain, immediate preventive action should be taken (see the paragraph “Chronic pain and prevention of recurrence”).

• Radiculopathy (sciatica).

Lumbagos and chronic lower back pains can be accompanied by radiculopathy: the root of a nerve is affected causing neurological symptoms. For example, a  sciatica is a lower back pain accompanied by a shooting pain in the posterior part of the leg (photo B). This shooting pain, described as tingling or numbness, corresponds to the trajectory of the Sciatic nerve, meaning that the nerve is pinched or irritated by surrounding structures [3]. The Sciatic nerve can be pinched in between vertebras, or it can be compressed by a tight muscle (often the Piriformis muscle, which is deep inside the Gluteus muscles).

• Emergency!

Cauda equina syndrome, which causes progressive lower limbs weakness and/or bowel or bladder dysfunction, is an emergency and medical attention should be seeked immediately! [1]

The types of lower back pains have different causes.

1. 2. Causes for lower back pain.

Lower back pain can be caused by various factors, but for 90% of them, X-rays or MRIs don’t show any signs, the cause is unknown [1]. However, some clinical observations are often found in those suffering from lower back pain such as muscle weakness, misaligned spine or excessive pressure on spine [4].

• Common clinical observations linked to lower back pain.

-muscles:

Lower back pains are often accompanied by muscle spasms, a permanent and painful state of muscle contraction, or muscle knots. Muscles can also be weak, with insufficient core strength: this insufficiency means that the vertebras are not supported enough, making the back more vulnerable. Or muscles can have poor flexibility: their shortened state makes them pull on the vertebras, forcing them out of alignment.

-vertebral alignment:

The spine can appear straight, but a chiropractor’s expert touch might reveal small vertebral misalignments.

-pressure on lumbar disks:

Often, a posture analysis reveals that the lumbar disks, in between the vertebras, suffer from too much pressure: because of bad posture, overweight, repetitive movements…

All these risk factors can be decreased through massage therapy, exercise and posture modifications.

• Discernable causes for lower back pains

Only a small proportion of sufferers present discernable organic conditions such as: ante-spondylolisthesis (vertebras have slid forward), retro-spondylolisthesis (vertebras have slid backwards), malformations such as scoliosis, vertebral compression due to osteoporosis, fractures, cancer, infection… In these cases, a particular medical or surgical treatment is recommended; however, an accompanying treatment of massage therapy, exercise and posture education is always necessary as well as a preventive way to protect the lower back [12]. Moreover, even when a discernable cause is found, there is often also one or more of the three previous observations that coexist with the specific cause.

A thorough analysis of muscles, vertebral alignment and posture helps all lower back pain sufferers to find the causes and relieve some of the symptoms.

1. 3. A Clinical examination can reveal possible causes for lower back pain.

Knowing that there are risk factors for lower back pain, whenever clients comes to our massage practice complaining of back pains, we assess their muscles, vertebral alignment and posture, within our means.

• Muscle tone, strength and flexibility analysis

-muscle tone

To assess muscle tone, it is necessary to feel the muscles: this is generally done during a massage, more specifically, a deep tissue massage, so that even the deeper muscles can be analyzed for tightness or knots. The most common muscles that present tightness or knots are the spinal muscles, those longitudinal muscles that are the pillar of the spine (photo C).

-muscle strength

The muscles that support the spine are the extensors (Spinals and Gluteals), the flexors (Abdominals and Hip Flexors) and the Obliques,  often referred to as the core muscles, because together, they form a “belt” around the lower back [6]. Core strength can be assessed with the Sorensen and Shirado tests [5]. The Sorensen test is used to assess the spinal extensors (photo D). The person is positioned face down, at the top of the table, with the trunk bent forward hanging outside the table, while the therapist hold down the ankles firmly. The person then lifts up until the spine is straight, and holds the position for as long as possible. Healthy extensors allow to hold the position for at least 2 minutes.

The Shirado test is used to assess the spinal flexors (photo E). The person is positioned on the back, feet elevated on a chair so that the hips and the knees are bent at a right angle. The person then lifts the shoulders off the table and tries to maintain that position as long as possible. As for the previous test, healthy flexors allow to hold the position for at least 2 minutes.

-muscle flexibility

Muscle flexibility can also affect the lower back. Tight muscles that are inserted close to the spine, such as the hamstrings or the hip flexors (the Psoas, for example, see photo F), can pull on it and create pain.

An easy way to test the flexibility of the hamstrings and the back is to measure the distance from the fingers to the ground when the person bends forward (photo G) [7]. To test the hip flexors, the bent knee is pushed towards the chest, with the opposite leg straight (photo H).

• Morphostatic Analysis

A morphostatic analysis is an observation of the immobile standing form, from the side, and from the back [8].

-profile, standing:

A standing profile analysis should show 3 spinal curves: lumbar, thoracic and cervical (photo I-A). These curves can be accentuated (photo I-B) by overweight, pregnancy or megalomastia (large breasts).These curves can also be decreased (photo I-C) by sitting or standing with a rounded back, or because of scoliosis.

-back, standing:

A standing back analysis can also show imbalances. Standing straight, the hips and the shoulders should be horizontal and parallel, making the spine straight from this angle (photo J-A). If one hip or one shoulder is elevated, for instance from carrying a handbag on the same shoulder every day, the spine is no longer straight and suffers from unnatural curves (photo J-B).

In all cases, any unnatural curvature of the spine puts increased pressure on the intervertebral disks, resulting in lower back pain.

• Static or active Posture Analysis

A posture analysis can also be done for everyday activities. There is a proper way to position your spine whenever you are sitting, cooking, sleeping, walking, lifting weights…  If incorrectly positioned, the spine is once again put under additional pressure.  For example, when sitting straight, the spine must have the same curves that are present when standing (photo K-A). In an incorrect position, the cervical and thoracic curves are often accentuated while the lumbar curve is reversed (Photo K-B). Your therapist will assess those positions and movements that you do often to check and advise you on proper positioning. For instance, a golfer and office clerk will be asked to reproduce his golfing swing as well as his sitting position so that his therapist can assess any incorrect form.

• Vertebral mobility

The spine needs to be mobile in all its areas: if an area is less mobile, the areas around it will be overworked to compensate for this loss of mobility, and as a result there will be pain.

To test the spine’s range of movement, the basic tests are the following [9]:

-the forward bend (photo L) assesses the spine flexion

-the backward bend (photo M) assesses the spine extension

- the twist (photo N) assesses the spine rotation

- the sideway bend (photo O) assesses the spine inclination.

Each movement is observed and felt for different parts of the spine, to point out areas that may not move as well as others.

Once the back pain is analyzed, a treatment can be put in place.

1. 4. Treatments of lower back pain

• Treatment for non-specific causes:

The treatments differ for acute or chronic pains. But remember that an acute lower back pain can be a precursor for chronic pain: therefore, preventive treatment is necessary for all cases!

-acute pain

In the acute phase of a lower back pain, most people contact their primary physician and get pharmacological treatment: since the cause of the pain is non-specific, several different medications are tried, such as muscle relaxants, pain relievers, or anti-inflammatory medication [10]. Hot or cold therapies are natural physical agents that relax muscles (heat) and numb pain (cold). Massage therapy is also recommended in the acute phase for pain relief. No more than 3-4 days rest, lying on the back, on a hard surface, legs bent, is recommended (photo P). After that, being somewhat active makes recovery faster, and a preventive treatment can start [13].

-chronic pain and prevention of recurrence

For chronic pain or for prevention, there are three parts of treatment.

The first part consists of decreasing pain through massage therapy on the whole back, hot and cold therapy on the specific pain area, and/or topical pain relievers (photo Q) [12].

The second part consists of increasing muscle flexibility and vertebral mobility with a therapist [6]. Muscles that need stretching are: the hamstrings (photo R), the hip flexors, the Gluteus (photo S) and the Piriformis muscles, most importantly. Spine stretches are spine rotation, flexion, extension and inclination. Working with a therapist ensures that the specific muscles or spine areas are targeted, it allows for deeper stretches and increased gain of range of movement, and it is a preamble for the third part of the treatment which is integrating treatment in the everyday lifestyle.

The third part of treatment is change in habits through education of posture modification [11].

One has to learn exercises to reproduce on a regular basis at home or at the gym. These exercises target core strength, muscle and vertebral mobility, and are vary varied. For example, a healthy back regimen can consist of:

-core strengthening: do a straight plank (for the flexors and extensors – photo T)  for one minute, a side plank (for the Obliques – photo U) for 30 seconds on each side, the whole 2 minutes repeated 4 times.

-hamstring and adductor (inside thigh muscles) stretch: lie on the floor, the buttocks against a wall, and the legs straight up (photo V-A). Try to straighten your knees. Once they are straight, spread your legs and let the weight pull them downwards and stretch the muscles (photo V-B). Stay in that position for 5 minutes [1].

-hip flexor stretch: a deep lunge held 30 seconds on each side (photo W). [1]

-Piriformis stretch: lying on the floor, cross the left leg over the other, then grab your right leg and pull towards your chest. Hold 30 seconds then change sides and repeat (photo X) [1].

This series of exercises are repeated 3 times a week and can be complimentary of another physical activity. Ideally, these exercises are evaluated on a regular basis by a therapist, personal trainer or workout instructor to be adjusted as strength and range of motion increase and pain decreases.

One also has to correct their posture at work or during other pain causing activities. For example, a computer programmer might want to change his regular work chair for an ergonomic work chair or a medicine ball (photo Y).

One can also include a monthly session of massage therapy in their schedule to preventively detect tight back muscles and knots.

One can also team up with a dietician to lose weight to release pressure on the intervertebral disks.

The changes necessary differ for each individual and will be more effective and targeted with guidance from a therapist.

Back pains are very common in our society, and their non-specificity makes them difficult to treat in one unique way. Analyzing morphology, posture, muscle tone and flexibility can make possible causes for a back pain stand out, and therefore, allow for a treatment program to be developed. This can be done with a physician, physical therapist, massage therapist, personal trainer, dietician…: a life-long commitment to protect your back, with their help, will rid you of pain.

REFERENCES

[1] Ullrich P. F., Jr., MD, Lower Back Pain Symptoms and Treatment Options, http://www.spine-health.com/conditions/lower-back-pain/lower-back-pain-symptoms-and-treatment-options (retrieved 3/11/11)

[2] Biering-Sørensen F., A prospective study of low back pain in a general population. I. Occurrence, recurrence and aetiology, Scand J Rehabil Med. 1983;15(2):71-9., http://www.ncbi.nlm.nih.gov/pubmed/6223365 (retrieved 3/11/11)

[4] “National Institute of Neurological Disorders and Strokes” website, Low Back Pain Fact Sheet, http://www.ninds.nih.gov/disorders/backpain/detail_backpain.htm (retrieved 3/14/11)

[5] Rannou F., Poiraudeau S., Revel M., Les lombalgies communes., http://mediatheque.parisdescartes.fr/doc/racine/f/flandinf/107871SorensShirad.PDF (retrieved 3/13/11)

[6] HydeT. E., DC, Back Exercises and Abdominal Exercise Recommendations, http://www.spine-health.com/wellness/exercise/back-exercises (retrieved 3/11/11)

[7] Ruiz S., Evaluation musculaire du lombalgique:, 25 août 2006, http://osteopathe-montpellier.com/evaluation-musculaire-du-lombalgique (retrieved 3/13/11)

[8] Cohen J., Montagnon J., “Cours de kinesitherapie” website, Bilan scoliose, http://www.courskine.fr/scoliose_451.htm (retrieved 3/14/11)

[9] L’examen d’une lombalgie par le médecin de Médecine Manuelle – Ostéopathie

ANMSR Paris 2007, http://www.anmsr.asso.fr/2007/images/documents/8_l_examen_d_une_lombalgie_par_le_m_decin_de_mmo.pdf (retrieved 3/14/11)

[10] Stewart G. Eidelson, MD, Back Pain Treatment Option, http://www.spineuniverse.com/conditions/back-pain/back-pain-treatment-options (retrieved 3/11/11)

http://www.aafp.org/afp/20000315/1779.html (retrieved 3/11/11)

[12] Stewart G. Eidelson, MD, Back Pain Treatment Option, http://www.spineuniverse.com/conditions/back-pain/back-pain-treatment-options (retrieved 3/11/11)

[13] STEVEN J. ATLAS, MD, MPH, Nonpharmacological treatment for low back pain, The Journal of Musculoskeletal Medicine. Vol. 27 No. 1 , http://www.musculoskeletalnetwork.com/pain/content/article/1145622/1507555 (retrieved 3/11/11)

Indeed, exercising regularly increases the amount of Lactic Acid in muscles, creates muscle soreness, swelling, stiffness and fatigue, all of which can promote injury. Before injuries occur, having massages helps the muscles recover faster, be more flexible and less fatigued, through techniques such as stretching, PNF, Swedish and Deep tissue.  Overall, Massage Therapy helps improve performance and prevent injuries for all those interested in working out.

1. The side-effects of exercising and how massage counteracts them

Exercising is a necessary and beneficial part of a healthy lifestyle; but working out regularly can have some negative side-effects that slow down one’s efforts and promote injury if not tended to. Historically, athletes have used massage therapy to counteract these negative side-effects, and today, scientific research confirms that massage is effective. Even though the experiment of the University of Tennessee (High et al., 1989) concludes that pre-workout massages and stretching have no relieving effect on training pains, during or post-workout massages have measurable positive effects on performance: they facilitate muscle drainage and circulation, decrease muscle soreness and swelling, improve relaxation and range of motion, and decrease fatigue.

1.1 Lactic Acid builds up in muscles and massage facilitate its drainage

The accumulation of Lactic Acid in the muscles is a consequence of chemical reactions, necessary to fuel the muscles; massage facilitates its drainage. The Atlas de poche de Physiologie explains that ATP is the energy source for muscles: it is created, in part, directly in the muscle, through a series of chemical reactions that use Creatine Kinase, Glucose, Fatty acids and Oxygen as reactants. The products are ATP but also Carbonate Dioxide, Lactates and Hydrogen, the 2 latter combining to form the infamous Lactic Acid (Silbernagl, Despopoulos, 2004). However, Lactate isn’t bad: Brooks (1986) states that 20% of the Lactate produced in the muscle is converted to Glucose that can be reused in the muscle to create ATP, and the 80% remaining  are transported to the heart and liver where it is converted to Glucose for these other organs’ use. Consequently, Lactate is removed from the muscle quickly after a workout, and a massage isn’t necessary to push it out of them, as the Neuromuscular Research Laboratory of Pittsburg, PA has found in a study (Martin et al., 1998). Nevertheless, massage holds an indirect role in the muscle drainage of toxins and circulation: by promoting muscle relaxation and decrease in tonicity, the muscle can perform its own drainage better than if it stays in a state of contraction and hypertonicity (Vanderbilt, 2001).

1.2 Muscle soreness and muscle swelling are decreased by massage therapy

The vilified Lactate was also thought to be responsible for the muscle soreness felt days after exercising. But it isn’t the case: the lasting pain is caused by micro-traumatism in the muscle; having post-workout massages help decrease it. The muscle soreness, or DOMS (Delayed-Onset Muscle Soreness), is the pain that usually starts after 24 hours and decreases after 72 hours, in muscles that have been solicited during a new or a longer exercise than they are accustomed to. In his book, Skeletal muscle damage and repair, Tiidus (2008) says it corresponds to micro-traumatisms such as micro-tears of muscle fibers and connective tissue. DOMS can be accompanied by muscle swelling due to the inflammation that surrounds micro-traumatisms. A research experiment by Zainuddin and colleagues (2005), involving the repetition of elbow flexions, showed that the muscles that were massaged after the repetitions had less muscle soreness and presented decreased swelling. Other research by Hilbert and his colleagues (Hilbert et al., 2003), involving a series of hamstrings contractions, have yielded the same conclusions: post-workout massages decrease DOMS and muscle swelling, helping athletes recover faster and with less pain.

1.3 Muscle stiffness and inflexibility are improved by massages and stretching

Along with muscle soreness and swelling, another possible manifestation of training is post-workout stiffness: massage therapy and stretching help diminish this muscle hypertonicity and increase muscle flexibility. According to the works of Jones et al. (1987), stiffness corresponds to the “shortening of non-contractile elements” and can result in the apparition of “knots” inside the muscle. Thebodyworker.com explains that these “knots”, also called trigger points, are a cause of pain during movement and stretching, which results in a decrease in the range of motion. Moreover, they are tender when direct pressure is applied: the pain can be on the spot or in a referred area of the body (Trigger point therapy definitions). Around the muscle, hypertonicity has an effect on joints, that are put under stress by those pulling muscles, and arteries and veins that are compressed by the shortened muscles. During a massage therapy session, a lighter massage stimulates muscle relaxation, as Morelli and his team studied in their research (Morelli et al., 1990), while a deep massage helps loosen “knots”. Moreover, stretching techniques also participate in muscle relaxation and trigger point release, while they elongate shortened muscles.

1.4 Fatigue is decreased after a massage

Lastly, and quite simply, fatigue occurs during the workout or afterwards; fatigue is decreased by post-workout massages. The Atlas de poche de physiologie divides fatigue in two kinds. There is a peripheral fatigue, which happens when the muscles themselves are tired because they are running out of resources to create ATP. Measurements done by Ogai et al. (2008) during intensive cycle pedaling have shown that post-workout massages provoke a marked decrease in muscle fatigue. There is also a central fatigue. This affects the whole body, and the psyche. When exercise is intense, muscles are sore, joints too, the whole body and mind aches and there is a decrease in the motivation to continue (Silbernagl, Despopoulos, 2004).  The general relaxing and mood enhancing effects of massage are a way for the athlete to regain motivation and energy to continue his/her training. Both peripheric and central fatigue are decreased by massage, which means that it is possible for the athlete to do more and better workouts, which, ultimately, will help improve performance.

2. The sports massage techniques

The sports massage techniques, that counteract training side-effects and help prevent injury, are varied: they combine, among other methods, stretching, PNF (Proprioceptive neuromuscular facilitation), Swedish massage and Deep tissue massage. The techniques are determined by the Massage Therapist according to the needs and tolerance of the athlete: each massage is unique to the therapist, the athlete, and the particular session.

2.1 Stretching and PNF (Proprioceptive Neuromuscular Facilitation)

Stretching is a good way to start a sports massage session, as it elongates, relaxes and warms up the muscles. The massage therapist knows which position allows for the maximum elongation of a muscle according to its position and physiology. In this position, the therapist ensures that the stretch is localized by making sure no other joints than the one involved in the stretch move: this can be done by holding down body parts or by putting the athlete in a position that will not allow compensatory movements. The therapist is positioned to have a good lever and to use his/her body weight against the shortened muscle: that way, he/she is always stronger than the stiff muscles and doesn’t get tired. According to massage therapist Laura Allen (2010), PNF can be used to increase flexibility: “a muscle is stretched into resistance and then held for 10 seconds, followed by the client holding a [static] contraction for 5 seconds, and repeating the process several times” , until the maximum stretch position doesn’t move anymore. This is great for a deep and visible stretch

2.2 Swedish massage

After stretching, a few Swedish massage techniques are a good way to continue warming up and relaxing the muscles. After applying some oil or lotion on his hands, the therapist does effleurage, which is a gliding stroke. Petrissage, or kneading, can follow, which is pulling the muscle away from the bone and rolling it like cooking dough. If the therapist finds a knot, he can stay on that spot and create friction circular movements that are more localized. Friction can also be perpendicular to the muscle fibers, which is called cross-friction. Tapotement stimulates blood flow by tapping the muscle rapidly, alternating both hands, with the side of the hand.

2.3 Deep tissue massage

Once the muscles are warmed up, the therapist can go deeper, on the whole muscle or on the specific trigger points found on an individual. The principal of these techniques is the same: longitudinal strokes, cross-friction strokes and circular strokes, but the therapist goes much deeper to get to the deep muscle fibers of the superficial muscles or to get to the deeper layers of muscles. To do so, the therapist uses his/her thumbs, forearms and elbows assisted by his/her body weight. The pressure is as hard as the muscle can take without creating pain. Both the athlete and the massage therapist determine the level of comfort tolerable for the deep massage.

Exercising regularly and intensely is great for the body, but it has negative side-effects such as the creation of lactic acid, DOMS, swelling, muscle stiffness, decrease in range of motion, as well as prolonged fatigue, that can lead to injury if left untreated. Research has shown that massage helps the muscle drain their toxins, decrease muscle soreness and swelling, increase muscle relaxation and flexibility, and decrease fatigue. The sports massage techniques vary, and include stretching, PNF, Swedish massage and Deep tissue massage. These allow the athlete to recover faster in-between or during workouts, to prevent sports-related injuries, and to improve his/her general well-being.

References :

• Allen, L. (2010). Plain and simple guide to therapeutic massage and bodywork examinations. Lippincott Williams & Wilkins, Wolters Kluwer Health.
• Brooks, G.A. (1986). The lactate shuttle during exercise and recovery. Med Sci Sports Exerc. 1986 Jun;18(3):360-8.. (http://www.ncbi.nlm.nih.gov/pubmed/3523107 consulted on 08/10/10)
• High, D.M., Howley, E.T., Franks, B.D. (1986). The effects of static stretching and warm-up on prevention of delayed-onset muscle soreness. Res Q Exerc Sport. 1989 Dec;60(4):357-61.(http://www.ncbi.nlm.nih.gov/pubmed/2489863 consulted on 08/10/10)
• Hilbert, J.E., Sforzo, G.A., Swensen, T. (2003). The effects of massage on delayed onset muscle soreness. Br J Sports Med 2003;37:72-75 doi:10.1136/bjsm.37.1.72 (http://bjsm.bmj.com/content/37/1/72.full consulted on 08/11/10)
  • Jones, D.A., Newham, D.J., Clarkson, P.M. (1987) Skeletal muscle stiffness and pain following eccentric exercise of the elbow flexors. Pain. 1987 Aug;30(2):233-42. (http://www.ncbi.nlm.nih.gov/pubmed/3670875 consulted on 08/10/10)
  • Morelli, M., Seaborne, D.E., Sullivan, J. (1990) Changes in H-reflex amplitude during massage of triceps surae in healthy subjects. J Orthop Sports Phys Ther 1990;12:55–59. (http://www.ncbi.nlm.nih.gov/pubmed/18787257 consulted on 08/10/10)
  • Ogai, R., Yamane, M., Matsumoto, T., Kosaka, M. (2008). Effects of petrissage massage on fatigue and exercise performance following intensive cycle pedaling. Br J Sports Med. 2008 Apr 2 (http://www.ncbi.nlm.nih.gov/pubmed/18385196 consulted on 08/10/10)
  • Silbernagl, S.-Despopoulos, A. (2004). Atlas de poche de physiologie. Medecine-Sciences, Flammarion.
  • Tiidus, P. (2008). Skeletal muscle damage and repair. Human kinetics. (http://books.google.com/books?id=ueMh1x7kFjsC&pg=PA59#v=onepage&q&f=true consulted on 08/10/10)
  • Trigger point therapy definitions (http://www.thebodyworker.com/triggerpointdefinitions.html consulted on 08/10/10)
  • Vanderbilt, S. (2001). Sports Massage and Recovery Time, Re-examining the role of lactic acid. Massage & Bodywork magazine, October/November 2001. (http://www.massagetherapy.com/articles/index.php/article_id/541/Sports-Massage–Recovery-Time consulted on 08/10/10)
    • Zainuddin, Z., Newton, M., Sacco, P., Nosaka, K. (2005). Effects of massage on delayed-onset muscle soreness, swelling, and recovery of muscle function. J Athl Train. 2005 Jul-Sep;40(3):174-80. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1250256/ consulted on 08/10/10)

• Martin, N.A.,  Zoeller, R.F., Robertson, R.J., Lephart, S.M., (1998). The Comparative Effects of Sports Massage, Active Recovery, and Rest in Promoting Blood Lactate Clearance After Supramaximal Leg Exercise. J Athl Train. 1998 Jan–Mar; 33(1): 30-35 (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1320372/ consulted on 08/11/10)