by Paul Vessa, M.D.

Running has gained tremendous popularity in the United States. The current Generation-Xer's and baby boomers have embraced physical fitness with unprecedented enthusiasm. Running is probably one of the most basic physical exercises. Although controversial, it may be actually quite good for your health, as well as your back.

The repetitive stress to both the central aspects of your skeleton, that is your spine, as well as to the peripheral aspects of the skeleton, specifically the lower extremities, will usually result in increased bone/mineral content. Some studies have reported increases as great as 40% in bone/mineral content in runners. However, most people do not run because of the benefits to their skeleton, but rather the beneficial effects to the overall well being, weight control and increased muscular tone. Running, done properly, is not bad for your back; however, oftentimes people will run without proper preparation, training, etc. and create painful overuse syndromes of the lower back area. This can occur in the novice runner, as well as in the most experienced of runners. Many experienced runners have endured the frustration of increasing their mileage acutely, resulting in several days and even weeks of increased low back pain. However, most studies have indicated that only rarely are spine related injuries experienced by runners. Even x-rays taken of patients who all are experienced runners, in comparison to their non-running colleagues, fail to demonstrate any degenerative changes related to their running. Certain aspects of running, however, need to be specifically addressed to beginners in order to prevent injuries to the low back region.

Running, done well, actually enforces the protective mechanisms that our body has developed in order to dissipate stress across the lumbar spine. The lumbar protective mechanisms are the outer muscular envelope of our bodies, i.e. the abdominal and paraspinal musculature. Once these muscles are properly developed, their tone often reduces stress across the lumbosacral spine, throughout all aspects of our physical activity. Runners have been shown to have well toned abdominal and paraspinal muscles in order to serve as a protective mechanism. On the other hand, poorly trained runners, who either run sporadically or have never run at all and begin to run as part of a fitness program, will oftentimes stress their paraspinal and abdominal musculature, resulting in lumbar strain injuries. Therefore, an understanding of the biomechanics of running is necessary in order to properly train.

Running should be considered a repetitive loading exercise of the lumbosacral spine which can, depending on stride length and the nature of the terrain, increase the stress across the lumbosacral spine two to three times the individual's body weight. To give you an idea of the forces incurred during an average runner's work-out; if a 150-pound man would run for approximately one mile at a brisk pace something around eight or nine minutes, the forces that the lumbosacral spine would be exposed to would be in excess of 200 tons. Generally speaking, forces are distributed across the lumbosacral spine in various percentages.

The lumbosacral spine can be divided into the front or round portion of the vertebra where the disc connects one vertebra to another and the paired joints in the back of the vertebra called the facet joints. During repetitive stress such as running, 80% of the weight is generally borne through the vertebral body, across the disc space; while 20 to 25% of the weight is borne across the facet joints. However, running normally exerts an extension force; that is, runners extend backwards, and excessive stresses are then felt across the facet joints. Microtrauma that occurs across the facet joints often will leave experienced runners with a backache that is usually somewhat to the right or left of the midline, radiating down into the buttock region. This usually will occur between 18 and 24 hours from the time of the running event. This usually is best relieved with anti-inflammatory agents that are readily available over-the-counter. Part of the injury that can occur is actually more related to the vibratory forces that occur across the lumbar spine as the runner strikes the ground with each stride. Properly trained runners are able to use their ankles, knees, hips, paraspinal and abdominal musculature, in a way to diminish the vibratory forces across the lumbar spine and alleviate the stresses that occur at the time their feet strike the ground. This so-called kinetic chain diffuser is not something that results by reading about it, rather through the use of properly taught body mechanics and practice. The practice that is meant is beginning at reasonable distances and slowly, but progressively, increasing those distances. As the speed of the runner increases, generally speaking, the amount of hyperextension forces to the lumbar spine and especially the facet joints in the back of the spine will increase. Therefore, novice runners or runners who are in less than optimal condition, should start at a slower pace, so as not to increase the hyperextension and vibratory forces across the facet joints which, when irritated, have been shown to cause significant lumbar strain symptoms.

We have spent considerable time now discussing the back of the spine; that is the facet joints. However, as stated earlier, the majority of the forces that the spine encounters during running really are dissipated across the front of the vertebral body, where the full body is in contact with the vertebral body adjacent to it, across the disc space. The forces that are concentrated across this area are quite considerable, and it has been clearly shown there is a significant loss of disc height during running. This has been found in even the most experienced of runners. What has also been shown is that the position of the pelvis can alter the forces across the disc space, allowing the protective muscular envelope to dissipate those forces preventing repetitive Micro trauma. Additionally, the pistoning action across the disc space that occurs during running is actually quite healthy for the disc, as long as there is no underlying injury to the disc itself. Generally speaking, there is a reparative process that occurs in the disc with certain types of activities such as running. However, once the reparative process has become overwhelmed by excessive Microtrauma to the disc, inflammation will ensue and the patient will generally become symptomatic; that is, they will experience a backache. Most backaches attributed to running are self-limited in that they occur anywhere from 24 to 36 hours following the run and are generally resolved over the next 2 to 3 days, especially with the aid of anti-inflammatory agents. However, on a microscopic level, what the backache generally represents, is Micro trauma to both the disc complex, as well as, the facet joints. Degeneration of the disc complex has been discussed throughout this web page and I will not go into a lengthy discussion regarding this. However, with regard to the facet joints, these are joints that are called synovial joints and by definition, this means that they are lined with special cartilage, have a special capsule, special fluid that is placed in between the joints to act as a lubricant for the smooth transition of opposing joint surfaces. The micro trauma that occurs after an overuse run in an untrained individual alters the cartilage on a microscopic level. As the friction at the joint surface level increases, the articular cartilage gradually wears away. Over years, this process results in increased surface area across the joint as the body tries to dissipate the forces, increasing both surface area and effectively diminishing motion. Once the joints become totally deformed and nonfunctional, motion of any type can become quite painful. Therefore, prevention of injuries to the low back region while running is of utmost importance. These principles are the cornerstones of most preventive programs. Most injuries, as previously stated, are secondary to overuse. Generally speaking, the more one runs, the higher the frequency of an overuse injury. It is generally recommended for the recreational athlete that training of 2 to 3 times per week is sufficient. Additionally, total aggregate weekly miles should not exceed 30 miles. Clearly, there are those runners, who while training for marathons are of a more competitive nature, far exceed these limitations. However, in general, the recreational athlete should never work to exceed the mentioned frequency and aggregate weekly miles.

The 90s brought about a revolution in specific types of athletic training, specifically cross-training which involves the use of alternative exercise programs to enhance physical fitness and thus prevent overuse injuries. Popular cross-training regimens for runners have included the use of step machines; quadriceps and hamstrings strengthening exercises done in the gyms on variable resistance machines; anterior tibialis (the muscles in front of the leg), as well as, the gastrocsoleus complex (the muscles in back of the lower leg), variable resistance machines are done in the gymnasium setting. Additionally, most recreational runners run at a pace far below the aerobic burn of an all-out sprint. Cross-training involves occasional work-outs, where sprinting for short periods of time are performed on a repetitive basis. However, these types of workouts should be avoided by recreational athletes in that, without proper preparation, muscle strains are likely. The actual mechanics of running need to be understood in order to alter your stride and pace so as not to injure yourself. The "float" phase of running is that portion of the running phase where both feet are essentially off the ground. This is the definition of running, whereas in rapid walking; one foot is always in contact with the ground. Running is defined by the achievement of the "float" phase where both feet are essentially off the ground, the runner is "floating" in the air. The longer the "float" phase, the greater the impact when the leg strikes the ground As previously stated, it is this repetitive impact, where the cumulative stress of one's body weight across the spine has resulted in the greatest amount of injuries. By lengthening one's stride and thereby increasing the "float" phase, the heel strike impact increases. Additionally, running on uneven terrain or rising downhill, will likewise increase the impact at the time of heel strike. Various other factors are important. However, probably the two most important factors are the training shoe utilized, as well as the terrain on which one runs.

The 90s have seen the advent of the most sophisticated training shoes known to mankind. The training shoes now available are lighter, with space-age materials that allow for proper cushioning of the foot and dissipation of forces upon heel strike. Additionally, the shoes generally increase the surface area of the foot with the ground, which lessens the impact and increases the amount of push-off force that can be generated by tie gastrocsoleus complex, thereby making it easier to run. Most experienced runners have found that as the shoes wear and the cushioned heel surface is altered, the shoe no longer performs its designed functions and overuse injuries will ensue. Therefore, it is recommended that most runners running anywhere between 3 and 4 times per week, should change shoes every 3 to 4 months. The running surface on which one is doing the running is, likewise, as important. The best surfaces are cushioned surfaces such as grass, or the traditional loose granular tracks of years ago. Harder materials, such as the black-top of streets, teats, concrete, and rocky gravel surfaces, are more injurious because of the increase impact force to the lumbosacral spine. People should, if possible, therefore, run with high quality shoes on either track or grassy surfaces. Admittedly, this is often not possible; most runners run on the streets with shoes that are either of low quality, or sufficiently worn, thereby negating their designed protective cushioning effect. This is the setting in which most overuse injuries come into play.

Beginning runners should start at modest distances within the range of one-half to one mile, slowly progressing if there is no pain or stiffness. The cadence should be equivalent to a light jog. Clearly, pain or stiffness that follows any run within 24 to 36 hours, should be an indication that the level or performance is too great and the next work-out should be scaled back accordingly. There is no doubt that too low a baseline will slow the training process successively, and this is where most recreational athletes get into trouble. Generally speaking, increasing the baseline by 10% per week with consistent training is an acceptable target for most recreational runners. Those recreational athletes who would like to exercise on a more regular basis than 2 to 3 times per week can do so, and this is where cross-training becomes so important. On so-called off days, those days when a runner is not running, gym work or work using different muscle groups in different ways, such as on Stair-Master machines, bicycle machines, bicycles themselves, climbing machines, and upper extremity strengthening machines; will provide sufficient work-outs to speed up the training process and allow for more rapid achievement of the desired level of fitness. However, many patients will bring to running a previous injury to their low back region. Oftentimes, this will be a herniated disc which has resulted in an operative procedure or previous herniated disc that has been treated appropriately with anti-inflammatory agents, whether they are by mouth, or through epidural injections, and proper training technique. Clearly, these people with previous injuries to the low back region, should undergo at least 2 days a week of lumbar stabilization exercises. Specific exercises that encompass a lumbar stabilization program will not be discussed at this time. What these exercises serve to achieve is the enhancement of the lumbar protective mechanisms. As stated earlier, these specifically include the muscles surrounding the lumbosacral spine; that is the abdominal, paraspinal, gluteal and iliopsoas muscles which effect pelvic orientation. Besides the abdominal and paraspinal musculature, gluteal muscles, hamstrings, iliopsoas muscles, are other important muscles that serve to protect the lumbosacral spine and should be properly trained. The gluteal muscles are those muscles that make up our buttock, the hamstring muscles extend from the back of our buttock down to the back of our knee, the iliopsoas muscles are large hip flexor muscles reside alongside the lumbosacral spine attached down into our hip muscles. These highly specialized filet mignon muscles of our body are extremely important in runners' lumbar protective mechanisms. That is, the stress ordinarily placed on the lumbar spine needs to he transferred through the hips to the knees, by a coordinated effort of strong abdominal, paraspinal, gluteal, and hamstring muscles.

Rehabilitation
Rehabilitation of patients with previous spinal injuries, who either are former runners or would like to adopt running as part of an exercise regimen, require observation of the runner in action. Specifically, a person trained in the proper body mechanics should observe the patient running at slow jog, medium pace and a rapid pace, In this way, the lumbar protective mechanisms that when properly trained can stabilize the spine, can be worked on to allow for more ease and comfort while running. Additionally, a runner's tolerance to a specific cadence can be evaluated. Clearly, patients with frankly herniated discs will have pain that is so severe that they will be unable to perform any type of running activity and none is advised. However, patients that have had previous disc surgery and have properly convalesced according to their physician's recommendations and have been released from care, need to develop the skill necessary to accentuate the lumbosacral protective mechanism which will allow for pain-free activity.

Exercises designed to accentuate the lumbosacral stabilization mechanism specifically serve to increase the tone and strength of the abdominal, gluteal, and paraspinal muscles. Enough cannot be said about proper strengthening of the abdominal muscles, which will then allow for more pain-free running style. Additionally, as the strength and training endurance proceeds, people will shed pounds of weight, which effectively diminishes the axial loading forces to the disc space. Simple abdominal strengthening exercises, such as sit-ups, abdominal crunches, and the recently promoted abdominal roller machines, serve to isolate the abdominal musculature and strengthen the rectus abdominus muscles, which are those muscles that sit in the front of the torso. In well-trained individuals these are seen as ripping transverse bundles of muscle across the abdomen. The lateral transversis abdominis muscles, as well as the external obliques, are also important in providing a strong muscular envelope around the lumbosacral spine, thereby acting to defuse the forces across it.

Specific exercises for the obliques and transversis abdominis include traditional sit-up type exercises with the torso twisted. A note of caution, before any type of torso twisting exercises with flexion to the abdomen can be initiated, patients should, at least those with previous back pain, contact their doctors to determine whether or not there is any underlying pathology which can be easily be made worse with twisting and flexion type activities, specifically disc herniation or unstable lumbar segments.

Paraspinal muscle rehabilitation requires some special equipment that can be found in most gymnasiums. These are essentially the opposite of sit-ups, also known as back-ups, and they will, at least initially, require some assistance before the patient becomes comfortable with the exercise. Additionally, because most recreational athletes never train the paraspinal musculature properly, initial attempts will result in only several back ups being able to be completed properly. However, with practice and repetition, most should be able to perform sets of 20 or 30 back ups with some facility.

Once the paraspinal musculature and abdominal flues musculature are properly developed, greater ease with running will ensue. Additionally, the buttocks are the strong extensor muscles of the lower spine that traverse the hip joint. These muscles known as the gluteal muscles are, perhaps, the strongest muscles in our body. Generally speaking, this group of muscles is best stabilized with the advent of the stair stepper machine. A word of caution: the stair stepper machine, especially if done with a flexed posture, can oftentimes result in a mild backache. Therefore, proper positioning and posture while performing these exercises is critical in allowing for proper gluteal strengthening. In addition to strengthening exercises, flexibility exercises are of equal importance and some find them to be even more important than actual strengthening exercises. During flexibility an athlete is trying to increase the range of motion across joint spaces that are protected by those muscles and tendons intrinsic to that area. The classic muscle groups that become spasmed and tightened in runners with intermittent low back pain include the hamstrings and iliopsoas muscles. Initially, flexibility strengthening oftentimes will require the aid of a physical therapist, who can isolate the hamstrings and iliopsoas muscles with various stretching techniques. Once these are learned, it is advised that all runners perform these exercises for 15 to 20 minutes prior to starting their run and 15 to 20 minutes after the run has completed. Emphasis should be made on doing the flexibility exercises following the running in order to prevent overuse injuries. I personally believe that flexibility strengthening is the key to running both effortlessly and without pain.