Shin Splints vs. Exertional Compartment Syndrome in Runners

Introduction and Background

This paper details the personal experiences of the author in identifying the source of physiological symptoms triggered by sports and fitness activities involving running or extensive (i.e., fast-paced and/or long-distance) walking. The author experienced significant discomfort in a localized region of both shins associated with running as a physical fitness activity. Anecdotal information based on advice from more experienced runners suggested that the problem related to the early formation stages of "shin splints," a colloquial term for micro-fractures in the tibia caused by repetitive impact stress from running-type activity.

To resolve the problem, the author attempted to identify its cause. In connection with this, footwear was changed to address potential causes attributable to dampening the intensity of repetitive foot-fall impact. When the problem persisted, the author attempted to vary the running surface to further reduce any physiological stress that was a function of impact intensity with harder running surfaces.

The author conducted simultaneous research of scientific literature to confirm the initial assumptions about shin splints and to identify other possible causes in the event that the symptoms were associated with alternate physiological issues possibly requiring different solutions. In fact, the author determined that the source of the symptoms was more likely attributable to an alternate diagnosis: namely, the buildup of intramuscular pressure within the anterior lateral compartment of the tibialis muscles.

More specifically, the muscles involved in raising the foot at the conclusion of each individual stride run along the front of the shin bone. They are encased within a thin sheath composed of fascia tissue, as is typical of muscle systems and their attachments throughout the body. As in the case of other areas susceptible to Exertional Compartment Syndrome (ECS) — such as the muscles of the forearms — ECS in the tibial area is caused by insufficient space within the fascia sheath to allow for normal expansion of the muscle during strenuous athletic activity involving those muscle systems. The differentiation of shin splints and chronic ECS problems is crucial because they are distinct conditions with different mechanical causes and, therefore, substantially different methods of treatment most conducive to their resolution.

Methodology

In principle, the methodology consisted of a relatively long-term process of recording the author's symptoms in conjunction with a comparison of those symptoms against descriptions found in the literature pertaining to shin splints and ECS-related pathology. More particularly, the author recorded all apparent symptoms experienced during, immediately after, one day after, and several days after exercise sessions. Those symptoms were then compared to the detailed symptomatology provided within the scientific literature pertaining to shin splints, exertional compartment syndrome, and the established criteria for differentiating between the two different types of ailments commonly affecting runners and other athletes and fitness enthusiasts.

Initial Symptoms and Anecdotal Diagnosis

The author began running in the fall of 2009, initially on an outdoor running track. Almost immediately, acute pain was noticed in the front (anterior) outside (lateral) portion of the lower leg in the upper region of the tibial bone. The discomfort consisted of a dull ache that increased in intensity with continued running but subsided substantially afterwards. The symptoms were ignored at first, as they were believed to be simply a variation of ordinary aches and pains often caused by athletic activity, particularly in persons who are not accustomed to those activities.

Anecdotal information from more experienced runners suggested that the symptoms were functions of a phenomenon called "shin splints," a colloquial reference to small fractures developing in the tibial bone itself. Informal advice consisted of decreasing the distances run in each exercise session, increasing the rest and recuperation periods between successive sessions, and evaluating the quality and proper fit of running shoes.

Prior to conducting a search for scientific literature, the author attempted to follow the advice provided by experienced runners. Specifically, this involved cutting back on the duration and distance of individual running sessions, increasing rest periods between successive sessions, and investing in a higher-quality pair of running shoes. The sales staff at the athletic footwear store concurred with the experienced runners' suspicions and suggested that insufficient arch support, inadequate cushioning, and imprecise fit were contributing to excessive impact forces associated with each foot-fall of the running stride.

Additionally, the store personnel suggested that the choice of running surface might also be a contributing factor, noting that the asphalt-based outdoor running track was among the least forgiving surfaces because it absorbs very little of the energy of foot-fall impact. The salesman expressed optimism that the new running shoes would provide sufficient protection even on hard surfaces but simultaneously suggested that the author consider softer surfaces such as modern composite materials used on newer running tracks or natural surfaces such as grassy terrain.

In retrospect, the author should have conducted at least a preliminary search for available empirical research on shin splints before relying on information from any individual whose obvious self-interest — in this case, retail sales — could have accounted for potentially biased information. However, because the information provided by the retail sales personnel matched the anecdotal information supplied by the experienced runners (which presumably did not reflect any conflicts of self-interest), the author began implementing the advice prior to conducting a search for empirical research on the informal concurrent diagnosis of "shin splints" from two independent lay sources.

Realistically, the main impetus for conducting further research was the persistence of the problem despite implementing all of the elements of the informal solutions suggested by experienced runners and retailers. The author first tried changing running shoes, reducing exercise session duration and distance, and increasing the rest period from one or two days to three, then four and five days between sessions. Initially, the running surface variable was not changed, in the hope that the other implemented changes would be sufficient to resolve the symptoms without changing the exercise venue.

Survey of Empirical Research on Shin Splints

The changes in workout intensity, duration, and footwear seemed to help only very moderately — mainly, they delayed the onset of discomfort and delayed its escalation to the point of significant pain. After these initial attempts failed, the author began a search for empirical literature and other authoritative information on shin splints.

According to the available literature, "shin splints" actually refers to medial tibial stress syndrome, a condition with two principal causes: (1) micro-fractures within the tibial bone; and (2) irritation and inflammation of the periosteum tissue lining the tibia (AOS, 2009; NIH, 2007; Wilder & Sethi, 2004). Sports physiologists and orthopedic physicians report that runners vary considerably with respect to their physiology as well as the biomechanics of their running strides (AOS, 2009; NIH, 2007).

These variations can result in dramatically different exposure of various tissues to impact stress associated with running. In general, runners with poor biomechanics tend to achieve much higher vertical elevation in their strides compared to better biomechanical strides that minimize vertical clearance between the soles of the feet and the running surface. The excessive elevation of poor running strides results in much greater impact forces transmitted through the foot and into the tibia; those forces can produce momentary spikes equivalent to more than four times the runner's body weight at the point of impact between the sole of the foot and the running surface (Wilder & Sethi, 2004).

The repetitive trauma from kinetic energy produced by shock and compressive loading during the impact phase of the running stride produces micro-fractures of the tibial bone that are initially asymptomatic. Continued exposure to the same stresses before the bone has had the chance to repair itself through normal biological processes results in larger cracks caused by the extension of microscopic fractures into one another, ultimately resulting in medial tibial stress syndrome. The formation of periosteum irritation and inflammation is closely related to these processes, except that the affected area is closer to the surface of the tibia and primarily affects the periosteum (Schissel & Godwin, 1999; Wilder & Sethi, 2004).

The empirical research into factors responsible for both conditions identifies the following elements of running — either alone or in various combinations — as contributors to excessive repetitive trauma: (1) poor running mechanics; (2) excessive foot pronation; (3) insufficient padding in footwear; and (4) excessively hard running surfaces (AOS, 2009; NIH, 2007; Wilder & Sethi, 2004).

The author did not set out to determine specifically which contributing factor (or combination of factors) was most responsible for the symptoms. However, since the initial attempts to resolve the problem had incorporated changes to all external variables except running surface, the author immediately sought a softer surface and temporarily abandoned running on any hard surface that magnified the physiological trauma associated with running.

Because the empirical research also implicated poor stride mechanics and excessive vertical elevation, the author devoted considerable attention to the following specific changes: (1) shorter strides to minimize travel time while neither foot is in contact with the running surface; (2) conscious attempts to reduce vertical clearance to a minimum; and (3) increased surface contact of the sole in a manner designed to decrease the magnitude of the highest compressive load spike transmitted from the foot to the tibia on each foot-fall.

To reduce the risk of other injuries — such as ankle sprains — from uneven natural grass surfaces, the author found an asphalt outdoor running track surrounded by a well-manicured grass field suitable for running on a soft but uniform surface.

Unfortunately, none of these changes made a significant difference. Even substituting a much more forgiving natural running surface only further delayed the initial onset of symptoms and the increase of their intensity. The changes implemented were insufficient to allow running as a regular fitness activity, because ECS-related symptoms recurred too soon and too intensely.

As a last resort, the author tried another anecdotal suggestion: brisk walking or "power walking" on inclined surfaces such as naturally hilly terrain instead of running on flat surfaces. In principle, brisk uphill walking provides many of the same cardiovascular and physiological benefits of running but eliminates the excessive trauma associated with the relatively high impact of foot-fall during a running stride.

A running stride necessitates that the exerciser leave the ground entirely, so the high-impact nature of the activity cannot be eliminated — only reduced. Conversely, a walking stride allows one foot to remain in contact with the surface at all times and never requires either limb to bear the entire weight of the body without support from the opposite limb. Walking also dramatically reduces the mechanical loading and the intensity of the compression load spike associated with a running stride, where each foot and tibia must bear the mechanical equivalent of several times the body weight on each stride (AOS, 2007; NIH, 2009).

However, the author found that symptoms actually increased from power walking on an inclined surface rather than decreasing. As a result, additional searches for empirical research were initiated to identify other possible solutions and to consider the possibility that the symptoms could be associated with an alternate diagnosis. In fact, the author identified another major potential source of explanation for the physiological symptoms — one related to a completely different aspect of physiology and biomechanics: exertional compartment syndrome of the tibial fascia.

Conclusion

By adhering rigidly to the comprehensive formula for ECS symptom reduction described above, the author was able to run short distances without any recurrence of ECS symptoms. Very gradually, the duration and distance of running sessions could be increased before any ECS-related symptoms returned. On several occasions, the amount of exercise required to elicit symptoms was exceeded, and ECS symptoms returned more quickly during subsequent running sessions.

To a certain degree, the naturally occurring endorphins and adrenalin produced by aerobic exercise may have contributed to the failure to recognize ECS-related symptoms at the earliest possible opportunity.

The author also determined through trial and error that warm soaks immediately prior to running sessions were more helpful in terms of symptom reduction and delayed onset than topical over-the-counter products that merely produced the sensation of warmth. The topical products were subsequently abandoned. Also, instead of submerging the entire body in a whirlpool before exercise, the author began using the whirlpool only to submerge the lower legs for a few minutes prior to running sessions.

Generally, the pre-running regimen now consists of a short whirlpool treatment first, followed by a stretching session, and ending with a tissue massage in which the thumbs are used in moderately deep longitudinal downward strokes along the entire length of the anterior tibial muscles. A small amount of oil is used to reduce friction, minimize skin irritation, and transmit as much energy as possible from the massage directly into the targeted tissue area.

A similar post-exercise regimen has been developed consisting of the immediate application of ice packs to the entire anterior tibial compartment area, irrespective of whether or not ECS symptoms are present. Ordinarily, there are no symptoms because the author has been careful to maintain a precise log of running times in different situations before the onset of symptoms. That log has enabled the termination of running sessions before any recurrence of ECS symptoms, in the belief that avoiding acute inflammation over the long term may help maximize the duration and length of running sessions without symptom recurrence and without the need for invasive fasciotomy surgery.

Ultimately, it is the author's hope that continuation of this process will obviate any need for surgery in the long term. Presently, it is certain that ECS symptoms will return upon extended running sessions. Accordingly, the author has begun supplementing with alternative aerobic activities such as bicycling and the use of elliptical machines to maintain the highest level of cardiovascular conditioning in the meantime.

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