RETHINKING OUR APPROACH TO PAIN #Chiropractic1st

 It’s time to change the way we approach pain. The services of doctors of chiropractic, along with other non-drug forms of pain management, can be an important part of the solution to the opioid epidemic gripping the United States. While medication may be necessary for some patients, there are cases—particularly those involving chronic pain—where a more conservative approach may alleviate pain and even lessen or eliminate the need for prescription painkillers.
The American Chiropractic Association (ACA) believes people in pain need better access to drug-free options such as chiropractic services. ACA has worked for years to raise awareness of conservative treatments such as chiropractic as a first line of defense against pain.
 A Problem of Epidemic Proportions
Inadequate pain management coupled with the epidemic of prescription opioid overuse and abuse has taken a severe toll on the lives of tens of thousands of people in the United States. According to the Centers for Disease Control and Prevention (CDC), as many as one in four patients who receive prescription opioids long term for non-cancer pain in primary care settings struggles with addiction. Every day, more than 1,000 people are treated in the ER for misusing prescription opioids.
Deaths involving opioids have quadrupled since 1999; in 2014 alone, more than 14,000 people died from overdoses involving the drugs. That same year, another 2 million people abused or were dependent on opioids.
Beyond the risks of addiction and overdose, prescription drugs that numb pain may convince a patient that a musculoskeletal condition is less severe than it is or that it has healed. This misunderstanding can lead to overexertion and a delay in the healing process…or even permanent injury.
The problem of prescription drug overuse and abuse reaches beyond the general population. New research suggests that the rising prevalence of chronic pain and opioid use by U.S. combat military personnel is cause for serious concern. The study, published online as a research letter in JAMA Internal Medicine, is accompanied by an editorial recommending that the goal should be nothing short of a “cultural transformation” in how pain is managed.
Dr. Dave Edenfield, "your Jacksonville Chiropractor", and Lakewood Chiropractic offers the most advanced treatments for back pain, sciatica, neck pain, whiplash and headaches. They also treat auto accident victims with state-of-the-art technologies. Now accepting VA patients. For more information visit:
Lakewood Chiropractic
Jacksonville, Florida 32217
904-733-7020
http://www.lakewoodchiropracticjax.com/
https://www.facebook.com/lakewoodchiropractic
https://twitter.com/AskDrEdenfield

Your Computer and You

A Healthy Workstation That Works

Setting-up your computer workstation to be a healthy environment is a key element in avoiding repetitive stress injuries. Monitor position, seat height, and elbow-wrist placement are the main elements of a ergonomically healthy design. Your chair seat height and the keyboard should be aligned so that when your hands are on the keyboard, your elbows are parallel to the floor. In other words, in an ergonomically efficient typing position, your elbows are neither above nor below the keyboard. Your wrists should be in a neutral position when typing, neither flexed nor extended. Chronic wrist flexion or extension will result in fatigue and overuse. Position your monitor or laptop display so your neck flexes slightly and your angle of gaze is directed downward about ten degrees. If you're using a mouse, it should be close to the keyboard, so that good elbow alignment is maintained. You should not have to reach for the mouse. It should be right there.

Windows and Mac users actually do have one thing in common - computer ergonomics issues, namely, pain.^1,2 Beyond the usual hardware and software gotchas we deal with on a daily basis, the real bottom-line question is, "how to play nice with my computer".

Doing computer work is a funny kind of work, a type of activity we're still getting used to. It's not physical work in the sense that there's no heavy lifting going on, no truck-driving, no emergency services heart-pounding decision-making.

But computer work is still an intensely physical activity, although the work is pretty subtle. In computer work it's the small muscles that are getting the workout, not the big muscles we're used to thinking about.

Wrist muscles, tendons, and ligaments. Finger muscles, tendons, and ligaments. Shoulder muscles, Neck muscles. All of these are involved in ongoing repetitive tasks when you sit at a computer and one hour turns into two, two hours turns into three, and suddenly half the day is gone and you notice you've got a killer stiff neck.

Or, one day the tendons on the back of your hand begin to hurt, feeling irritated and inflamed. Or your shoulders and upper back are tight and painful.

Your hands or shoulders feel better by the time you go to sleep. But the next day, as soon as you start to type they act up again.

This is all very uncomfortable, because you've got to do your work.

What's going on?

These various pain patterns in your hands, wrists, shoulders, and neck can be grouped together as a repetitive stress syndrome. Repetitive activities, done over a long period of time, can irritate and inflame the muscles, tendons, and ligaments that are involved in doing the work.

But computer work involves repetitive tasks. How can you avoid these painful problems?

The best approach is to prevent them in the first place.³ If such a syndrome does develop, relative rest is indicated. Reduced computer activity, in smaller intervals, is a good solution. A very useful work-around for right- or left-arm pain is to teach your non-dominant hand to use the mouse or touch pad. This training may take a few weeks - the valuable result is the ability to switch hands whenever you like, distributing the workload between the two sides. Much better.

The most important aspect of prevention is to take a quick, refreshing break once an hour. This is a critical habit to develop. Get out of your chair, walk around, get some fresh air if possible. Change your environment for a few minutes - talk to a co-worker for a moment, get a drink from the water-cooler down the hall, seek out a picture, wall-covering, or landscape you've never seen before.

These activities refresh your body AND your brain, and you're ready to do another hour of productive, creative, healthy work. You'll feel much better, you'll be avoiding repetitive injuries, and your workday will be more enjoyable.

Dr. Dave Edenfield and Lakewood Chiropractic offers the most advanced treatments for back pain, sciatica, neck pain, whiplash and headaches. They also treat auto accident victims with state-of-the-art technologies.  For more information visit:

http://www.lakewoodchiropracticjax.com/

https://www.facebook.com/lakewoodchiropractic

https://twitter.com/AskDrEdenfield

 ¹Keyserling WM, Chaffin DB: Occupational ergonomics - methods to evaluate physical stress on the job. Annu Rev Public Health 7:77-104, 1986.
²Computer Workstation Ergonomics. Centers for Disease Control and Prevention, 2000. http://www.cdc.gov/od/ohs/Ergonomics/compergo.htm
³Robertson MM, et al: Effects of a participatory ergonomics intervention computer workshop for university students. Work 18(3):305-314, 2002.

Strong Bones and Core Strengthening - Good Tips for a Healthy Lower Back

Strong Bones and Core Strengthening - Good Tips for a Healthy Lower Back

Core Strengthening

The benefits of core strengthening include support for your lower back, improved heart and lung function, and improved coordination and stability. This miracle set of exercises even helps reduce your waistline! A basic core exercise starts with you lying on your back on an exercise mat. Your arms are extended to the side, perpendicular to your torso. Your thighs are flexed - perpendicular to the floor, and your knees are bent so that your calves are parallel to the floor. Focusing on your deep abdominal muscles - visualizing these muscles working - gently lower your thighs to the floor on the right side. Your spine stays straight, maintaining contact with the floor, so the effect is that you're twisting your legs against the line of your trunk. Using your abdominals to initiate the movement, return your legs to center and gently lower them to the left side. You've now done one repetition. Start with six total reps, moving your legs gradually and making sure the movements originate in your abdominal muscles. Build up to 10 reps over a period of several weeks. You could include this valuable exercise into your regular pre-workout routine.

Strong bones are important for all of us, not only for the aging baby boomers about whom we're hearing so much lately. And, "strong bones" are much more than a marketing ploy cooked-up by the dairy industry and pharmaceutical companies.

Bones are incredibly dynamic, constantly reshaping themselves in response to physical forces. Bones provide structure for our bodies, and they carry our weight around as we move from place to place. Long bones such as the thigh bone act as factories to produce blood cells. So, bones are an important part of our overall health and well-being.

Lots can go wrong when your bones aren't strong. If you suddenly fall onto an outstretched arm, you'll probably be OK if your bones are healthy. If not, you'll probably be in a cast for four weeks to help repair a wrist or forearm fracture.

If an older person falls, hip fractures are the main concern. A fit, healthy person can usually walk away. With weakened bones, hip fractures can result in many other problems, both immediately and long-term.

Bones lose their strength due to a calcium imbalance and/or not enough physical exercise. For most of us, these factors can be corrected. The best approach, of course, is to be proactive and ensure enough calcium in the diet and regular exercise.

How much calcium and how much exercise? Recommended daily calcium requirements¹ vary, and 1000 mg per day is a good ballpark amount. Dairy products are the best natural source of calcium, and dark leafy greens such as spinach and broccoli, as well as dried beans, are also good sources. Vitamin/mineral supplements typically provide 25-50% of the daily calcium requirement.

Regarding exercise, both the American Heart Association² and the American College of Sports Medicine recommend 30 minutes of exercise, five days a week. This takes some effort and planning, particularly if regular exercise is a new addition to one's routine. By making the effort and spending the time, we're saying "yes" to health and wellness, empowering ourselves as well as our family and friends.

Importantly, regular exercise in combination with sufficient dietary calcium is the key. Taking calcium alone will not be effective in maintaining strong bones. Unless long bones are undergoing consistent mechanical stresses, as with exercise, there's no need for them to use the calcium that's available. Exercise plus calcium makes the difference!

Core strengthening³ is a hot topic in the world of fitness - Pilates training and its offshoots. But the principles of core strengthening have been around for many decades - dancers, gymnasts, boxers, and wrestlers have been doing these things all along. Only the term "core fitness" is new.

Core fitness turns out to be critically important for all of us. By adding a handful of core exercises - 10 minutes at most - to your regular routine, you will profoundly improve the mechanics of your lower back, hips, and pelvis. And, these remarkable exercises improve the efficiency of your heart and lungs. A very big "bang" for your exercise "buck"!

Your chiropractor will be able to provide expert advice and guidance on these nutritional- and exercise-related topics.
 http://www.lakewoodchiropracticjax.com/
¹Daly RM, et al. Long-term effects of calcium-vitamin-D3 fortified milk on bone geometry and strength in older men. Bone 39(4):946-953, 2006.
²Haskell WL, et al. Physical Activity and Public Health. Updated Recommendations for Adults from the American College of Sports Medicine and the American Heart Association. American Heart Association, 2007.
³Akuthota V, Nadler SF. Core strengthening. Arch Phys Med Rehabil 85(3 Suppl 1):S86-92, 2004.

When Is Back Pain More Than Back Pain?

Your First Chiropractic Office Visit

Your chiropractor's purpose on your first office visit is to make sure you're in the right place. He or she wants to make certain your back pain really is back pain - and treatable - rather than being a symptom of an underlying medical condition. Your chiropractor will take a complete history, learning the facts about your problem. How long you've had the pain, the nature and quality of the pain itself, whether the pain is localized or radiating, and whether the pain wakes you up at night are key elements in solving the puzzle. Following the history, your chiropractor will perform a complete orthopedic and neurologic exam, gathering all the information necessary to arrive at what's called a "working diagnosis". If your chiropractor concludes that treatment is appropriate, she will outline the anticipated stages of improvement and recovery, noting that further evaluation will be done if you're not getting better in a timely manner.

Out of the blue, your back starts to hurt. At first, it's just an annoyance. You can live with it. You've had lower back pain before and it went away on its own.

Now it's a few weeks later. You've got a low-grade pain that's not getting any better. You're actually worse, in fact, because your back hurts most of the time.

What to do?

You don't want to run to a doctor. After all, it's just back pain. Everybody has back pain. So you begin to solicit advice from your friends. And, of course, your friends have plenty of advice. "Do these exercises my doctor gave me." "Do these stretches - they worked for me." "Go to yoga class." "I know a great Pilates instructor. She'll get you in shape and your back will stop hurting." "Take vitamins and drink more water." "Meditate."

Your friends mean well and it's all very good advice. But none of it seems to work. Another month goes by and now the pain is increasing. It's even affecting your sleep.

It's time to see a doctor. But which one? For the most part, medical physicians are not experts on back pain. Typical recommendations include rest, moist heat, and anti-inflammatory medication.^1,2 But, really, you've done all that. You need more specific advice.

Choices might include doctors of chiropractic, orthopedic surgeons, and physical therapists.

Many orthopedic surgeons are spinal specialists, but what they do is surgery. This would be a last resort, typically, after other treatment options have failed.

Physical therapists are highly skilled practitioners who focus on exercise, rehabilitation, and re-training. They are not primary care providers, and typically patients are referred to physical therapists by family physicians, chiropractors, and orthopedic surgeons.

Doctors of chiropractic are spinal specialists, too, and what chiropractors have to offer is expert conservative therapy.³ Chiropractors treat back-related problems all day, every day, and are the right doctor to see first.

As spinal specialists, chiropractors receive extensive training in evaluating patients with back pain. Chiropractors consider all aspects of the problem, and develop sound treatment plans based on the facts. If a person does not respond as anticipated, their chiropractor has a "Plan B" in place for further evaluation and possible referral.

When choosing a doctor, you're allowed to ask questions and participate in the process. The strategy for follow-up is critically important.

First, if you're improving and doing well, how will can you help keep the problem from recurring? Will your chiropractor prescribe stretches, exercises, and other self-care action steps to help you keep yourself well?

And, what steps will be taken if your problem and pain are not improving? Where might you be referred for further tests and evaluation? Chiropractic treatment is a powerful tool in most cases of back pain. Symptoms should begin to improve quickly. Have your chiropractor outline the "Plan B" if you are, in fact, not getting better.

Your doctor of chiropractic will be able to answer these questions.
http://www.lakewoodchiropracticjax.com/

¹Zuhosky JP, et al: Industrial medicine and acute musculoskeletal rehabilitation. Arch Phys Med Rehabil 88(3 Suppl 1):S34-39, 2007.
²Cayea D, et al: Chronic low back pain in older adults. What physicians know, what they think they know, and what they should be taught. J Am Geriatr Soc 54(11):1772-1777, 2006.
³DeVocht JW: History and overview of theories and methods of chiropractic. Clin Orthop Relat Res 444:243-249, 2006.

Pregnancy, Parenting, and Lower Back Pain

How to Pick Up Your Kids

We're not talking minivan here. Moms and Dads spend a lot of time bending and lifting. We want to do this right, as much as possible, and not have a lot of down time while our injured back is healing. First, get as close to your child as possible. You want to have your arms right next to your body, not extended in front of you. Next, always bend your knees. Never bend over with straight legs. Next, suck in your stomach muscles. When you activate your abdominal muscles, you're taking a lot of potential strain off the lower back muscles. Your abdominal muscles are designed to carry the weight. Finally, straighten your legs, continuing to activate your stomach muscles, holding your child close to you. With a little practice, safe lifting will become a habit.

You're pregnant! Congratulations! Your body's changing-wondrously, marvelously. One unexpected and unwelcome change may be lower back pain. Recent studies suggest that two-thirds of pregnant women experience lower back pain.¹

These statistics seem reasonable. The weight of the growing baby, plus the weight of the placenta and amniotic fluid, create an unbalanced load in front of the lower back. The  result is irritation of spinal ligaments, muscles, and tendons, causing pain, muscle spasm, and loss of mobility.

Of course, some cases of pregnancy-related back pain have specific medical causes. Uncommon conditions such as pregnancy-associated osteoporosis, septic arthritis, and inflammatory arthritis may need to be considered.²

That said, the vast majority of cases of back pain in pregnancy are mechanical in origin.

Your doctor of chiropractic will perform a complete examination and determine the correct course of treatment, if appropriate. Once you're feeling better, you can begin

stretching and doing safe, gentle exercises that will help prevent recurrences of lower back pain. The goal is to strengthen your lower back and minimize the mechanical effects of pregnancy.

The best method of preventing back pain in the first place is being fit. This includes healthy nutrition, gaining a moderate amount of weight, and regular exercise. Your obstetrician will likely recommend vitamin and iron supplements and will monitor your weight. The average healthy woman gains between 25 and 35 pounds during the course of her pregnancy.³

Let's fast forward a few years. Your newborn is now a toddler. Parents know that if you have kids, stuff happens. You bend over to place a bulky car seat in your car. Then you place your child in it. And then, you bend over to remove the car seat from your car. If you've gone to the mall, kids want Daddy or Mommy to carry them. Pick them up, cart them around, put them down again.

What's a parent to do? It's not like you can avoid any of these activities. Your kids are kids - it's up to you to do stuff for them. The answer lies in regular exercise. "But how will I find time to exercise, when there already isn't enough time to do the things I need to do?"
That's a tough question, but if you recognize the benefits, you'll make the effort to make the time. Forty-five minutes or an hour per workout, three or four times a week, will be plenty. And, once you're in the habit of exercising, you'll notice it's easier to lift your kids, easier to bend over, easier to carry them. It's easier because you're

fitter and stronger. And healthier. And, surprisingly, you're having more fun.
http://www.lakewoodchiropracticjax.com/
¹Pennick VE, Young G: Interventions for preventing and treating pelvic and back pain in pregnancy. Cochrane Database Syst Rev 18(2):CD001139, 2007.
²Sax TW, Rosenbaum RB: Neuromuscular disorders in pregnancy. Muscle Nerve 34(5):559-571, 2006.
³Jain NJ, et al: Maternal obesity: can pregnancy weight gain modify risk of selected adverse pregnancy outcomes? Am J Perinatol 24(5):291-298, 2007.

Carpal Tunnel Syndrome or Repetitive Stress?

Carpal Tunnel Syndrome or Repetitive Stress?

Relative rest will give overused muscles and tendons a chance to heal. What's next is to pay attention to your posture and do exercises designed to strengthen your shoulder girdle, forearm, and wrist. To restore good posture, let your shoulder girdles rest on your rib cage. Your shoulders tend to ride upward during the course of a workday. Gently remind yourself to let go of these tight neck and upper back muscles, allowing the shoulders to assume a neutral position and rest on the upper rib cage. Shoulder shrugs are a useful isometric exercise that will help relieve painful trigger points. Sitting comfortably, lift both shoulders as high as they can go. Not forcing anything, just lifting. Hold at the highest position for a moment, then relax, gently returning the shoulders to a neutral position. Repeat three times.

You're getting ready to launch your new business. And, being a savvy entrepreneur, you've been spending a lot of time doing research on the Internet. Entering searches, following links, cutting-and-pasting, typing, mouse-clicking, dragging-and-dropping.

By the time you're ready to "go live" you've begun to notice a dull ache in your wrist (the one that does most of the mouse-ing). There's an annoying tingling sensation in your thumb and the tendons in your forearm hurt whenever you move your fingers.

"Oh, no," you think. "I've got carpal tunnel syndrome."

However, the news is probably not as bad as that. It's much more likely you've developed repetitive stress syndrome, which can be effectively treated by a chiropractor.

Repetitive stress syndrome is often misdiagnosed as carpal tunnel syndrome by family physicians, internists, and even many orthopedists. The doctor thinks, "wrist pain and thumb pain, must be carpal tunnel". This path of least resistance leads to much unnecessary neurologic testing, needless medication, and unwarranted surgeries.

Real carpal tunnel syndrome (CTS) is actually uncommon, usually associated with pregnancy, rheumatoid arthritis, or decreased thyroid activity.^1,2 Also, pain is more noticeable at night, rather than during activity. Finally, a quick test for CTS is to place the tips of your thumb and index finger together, forming a circle. Hold the circle closed while another person tries to pry your fingers apart. If your fingers are strong and can keep the circle closed, you probably don't have CTS.

The wrist, tendon, and forearm pain most of us experience after too much time at the computer is due to repetitive stress syndrome (RSS) - basically, too much of the same activity repeated frequently over too long a time. These new pains can be very uncomfortable and cause significant limitation and frustration.

The primary solution is rest and avoidance of the irritating activities. In practice, rest can mean relative rest.³ One key approach for computer-related repetitive stress is to begin using the opposite hand to do mouse or trackpad activities. This may take a while, but it's a highly effective method. And, once your non-dominant hand gets up to speed, you've got two hands that are smart, not only one!

What about chiropractic treatment? Several trouble spots may contribute to RSS, particularly tight shoulder and neck muscles. Your chiropractor will do a complete physical examination and determine the sources of the problem.

Treatment may include gentle chiropractic manipulation to improve the mobility of your neck and remove stress from that area of your spine. Trigger point therapy will relieve pain and relax tight muscular "knots" in your shoulder girdle and forearm.

Treatment combined with relative rest and rehabilitative exercises will likely result in rapid improvement - decreased pain, greater mobility, and a renewed focus on the work you want to get done, rather than the pain that is getting in your way!

Dr.’s Steven Warfield and Dr. Dave Edenfield offer the most advanced treatments for back pain, sciatica, neck pain, whiplash and headaches. They also treat auto accident, Veterans and Workers Compensation injuries with state-of-the-art technologies.
http://www.lakewoodchiropracticjax.com/


¹Source: National Institute of Neurological Disorders and Stroke - http://www.ninds.nih.gov/disorders/carpal_tunnel/detail_carpal_tunnel.htm.
²Piazzini DB, et al. A systematic review of conservative treatment of carpal tunnel syndrome. Clin Rehabil 21(4):299-314, 2007.
³Akuthota V, et al. Shoulder and elbow overuse injuries in sports. Arch Med Phys Rehabil 85(3 Suppl 1):S52-58, 2004.

Shoulder Pain - Heart Attack or Rotator Cuff Injury?

Rotator Cuff Rehabilitation

Basic rotator cuff rehabilitation addresses the loss of mobility. The two main activities are finger walking and pendulum swings. In finger walking, stand about 18 inches away from a wall, positioned, so your torso is perpendicular to the wall. Reach your arm out to the side and touch the wall with the tips of your fingers. Your elbow should be bent slightly. Slowly walk your fingers up the wall as high as you can go. Walk your fingers slowly all the way down the wall and repeat ten times. As you continue the exercise over days and weeks, your range of motion will improve. In pendulum swings, sit at the edge of a hard chair and bend your torso forward, supporting your weight by activating your stomach muscles and resting your non-working arm on the inner thigh. Let your working arm dangle to the side and, slowly and gently, begin to swing the arm in a small circle. The movement begins by a gentle swaying of your torso. Slowly increase the diameter of the circle to a maximum of about 18 inches. The whole routine should take about a minute.

The great TV classic ER helps teach armchair physicians to become amateur diagnosticians. He's in shock! She's got kidney stones! Rule-out pheochromocytoma!

But sometimes a little knowledge can be a dangerous thing.

You've learned somewhere - on the network news, in the Science section of The New York Times, or in a CPR class at your job - that shoulder pain can mean you have a heart attack. Now, seemingly out of the blue, your shoulder begins to ache and throb. Very concerned, you rush to the local emergency room.

The resident's first question, of course, is "where does it hurt"? You point to your right shoulder and blurt out, "Am I having a heart attack?" The resident smiles, gently reassuring. "A heart attack might give you pain in your left shoulder," she says. "Have you been to the gym lately? This might indicate a rotator cuff strain."

The resident knows that heart attack symptoms usually involve chest pain (in two-thirds of cases), and may include faintness, shortness of breath, sweating, and a feeling of impending doom.¹   Chest pain may spread to the back, jaw, and arms. Left arm pain may radiate to the inside of the forearm and the ring and little fingers. So, shoulder pain by itself probably doesn't suggest a heart attack.

She orders an MRI which shows mild damage to the right rotator cuff. What's going on? What exactly is the rotator cuff?

The rotator cuff is a muscular sheath that surrounds the head of the arm bone (the humerus) and the entire shoulder joint (really, two joints - the acromioclavicular and glenohumeral joints). The four muscles that comprise the rotator cuff help raise the arm to the front and the side and help turn the shoulder inward and outward.

If you're a sports fan, you know that rotator cuff injuries affect baseball pitchers, tennis players, swimmers, and football players. Such injuries are due to repetitive motion, and may also result from falling on the shoulder or arm or lifting heavy weights.

Rotator cuff injuries may also be slowly developing and chronic, related to arthritic and degenerative changes in the rotator cuff tendon and the two shoulder joints. Low-grade pain may develop, and the pain may become aching, throbbing, and chronic. Raising the arm may cause pain, and there may be a loss of mobility.²

In the above-40 population, lack of exercise and chronically poor posture may contribute to rotator cuff problems. Sitting at a desk all day, with the neck jutting forward and slumped shoulders, places long-term mechanical stress on the rotator cuff.

Chiropractic treatment may be very useful in helping to rehabilitate chronic rotator cuff injuries. The chiropractic physician is an expert in evaluating postural problems and associated spinal conditions. By providing effective treatment, postural corrections, and rehabilitative exercise, chiropractors offer a comprehensive therapeutic program to reduce pain, improve shoulder mobility, and regain function. 
Dr.’s Steven Warfield and Dr. Dave Edenfield offer the most advanced treatments for back pain, sciatica, neck pain, whiplash and headaches. They also treat auto accident, Veterans and Workers Compensation injuries with state-of-the-art technologies.

http://www.lakewoodchiropracticjax.com/

¹Source: Cedars-Sinai www.cedars-sinai.edu
²Baring T, et al.: Management of rotator cuff disease. Best Pract Res Clin Rheumatol 21(2):279-294, 2007.