A Closer Look At Preventing Running Injuries

Noting a recent case involving a 36-year-old runner who presented with left lateral ankle pain with no obvious precipitating cause, these authors provide a comprehensive review of the literature on injury prevention in runners.

A 36 year-old female reported to the clinic with a chief complaint of left lateral ankle pain for the last 10 days without any traumatic injury or specific inciting event. The pain gradually worsened over the last week. She has been training for a marathon, which is in nine days. While she has already completed her longest training run, the patient is now starting to have pain with walking. She has pain along the peroneal tendons and with active strength testing. The patient also has mild pain to the lateral most aspect of her Achilles tendon at the insertion. She has been using supportive running shoes with a heat molded over-the-counter insert that she had for about the last year. Although her diagnosis is rather clearly and easily presenting as peroneal tendonitis and mild Achilles tendinitis from overuse, her question is much more difficult: “What did I do wrong?”

Reviewing her training log, it is typical for a marathon buildup with the replacement of shoes within a reasonable time, denial of running on uneven terrain, etc. Fortunately, with rest (aqua jogging allowed) and the addition of a small lateral wedge to her insole, her pain improved, she completed her marathon and continued to improve (more rest was actually prescribed). However, the question remains: can running injuries be prevented?

Unfortunately, this scenario is rather common. According to a systematic review, the incidence of any lower extremity injury in long distance runners reportedly ranges from 19 to 79 percent with a 32 percent incidence of foot injuries and a 9 percent incidence of lower leg injuries.¹ The wide range of incidence can be explained, in part, by the vague terms of both “injury” and “runners.” Injuries in some studies can be self-reported and rather minor, resulting in no or minimal loss of participation whereas others can lead to permanent cessation of running. The term “runner” can range from ultra-marathon participants to the novice. Not surprisingly, ultra-marathoners have a high incidence of injuries (65 percent in one systematic review) but in comparison to the novice runner, they have low rates of injury per exposure hours (7.2 injuries per 1,000 hours in the ultra-marathoners in comparison to 17.8 per 1,000 hours in the novice runner).^2,3 It is also important to note that the majority of running injuries are considered overuse injuries such as Achilles tendinitis, plantar fasciitis, stress fractures, etc.⁴

Considering the elevated rate of injury, one has to wonder if running is worth these risks. Looking at mortality data, it appears that the long-term benefits outweigh the short-term injury risks. Running, even at lower doses or slower speeds, is associated with a significant life expectancy benefit. In general, runners have a 25 to 40 percent reduced risk of premature mortality and live approximately three years longer than non-runners.⁵ More specifically, runners have a 30 percent lower adjusted risk of all-cause mortality and a 45 percent lower risk of cardiovascular mortality.⁶ Several studies have suggested slightly lower or no mortality benefit at higher doses of vigorous activity.^7-9 Other studies show a linear dose-response relation between running and the risk of cardiovascular disease with greater benefits at higher doses of running.^6,10-13

Running And Osteoarthritis: What You Should Know

Another concern is the possibility of developing early osteoarthritis. As we have already discussed, running puts individuals at an increased risk for trauma and injuries that are consequently risk factors for osteoarthritis.¹⁴ However, running promotes a lower body mass index, combating a known risk factor for osteoarthritis.^15-19 Exercise may also increase both articular cartilage volume and glycosaminoglycan content, and prevent the loss of proteoglycans.^20-23 Cartilage thinning and focal loss of proteoglycans are prominent features with osteoarthritis.^14,21,24

The notion that running may propagate osteoarthritis is controversial but the literature is heavily in favor of no causal relationship. Marti and colleagues found an association with running pace, and in a survey of physical activity that included running, Cheng and coworkers found an association in a subset of individuals less than 50 years old.^25,26 However, the majority of published work seems to find no difference and some even have found a possible protective effect.^27-30 In a recent meta-analysis, recreational runners had a lower risk of osteoarthritis in comparison to both competitive runners and sedentary individuals.³¹

Moderation once again appears to be essential. One concern with some of the studies is that runners who develop osteoarthritis become non-runners, creating a selection bias. However, many of the studies were longitudinal with long durations of follow-up to control for this concern. It appears quite unlikely that osteoarthritis is a consequence of running for most. Conversely, there is strong evidence that age, prior joint injury, greater body mass index, heavy manual labor and cutting sports are associated with the development of osteoarthritis.^27,32-38

Pertinent Insights On Stretching, Strength Training And Proprioception Training

Some of the most common advice runners will hear is to stretch. Although this advice seems logical, the data just does not support these claims. In a meta-analysis including 26 randomized trials of interventions to prevent sports injuries, stretching had no effect on injury rate whereas strength training and proprioception had a significant effect on lowering injury rates (relative risk of 0.3 and 0.55 for strength and proprioception respectively).³⁹

This should not be taken as evidence to stop stretching but merely to redirect the emphasis of stretching to other areas much more likely to impact the incidence of injury. One randomized study actually found an increase in rate of injury in runners who typically stretch and were randomized into the no stretch group.⁴⁰ Not only is it surprising that the meta-analysis from Lauersen and coworkers did not find stretching to impact injury rates but also the degree to which strength and proprioception training decreased injuries.³⁹ Certainly, clinicians should pay more attention to these two interventions. Of note, the meta-analysis by Lauersen and colleagues was not specific to runners but rather to multiple sports and nonspecific to injury location.³⁹ Thus, this data is extrapolated but extremely promising. There are registered trials underway.^41,42

How much, how often and what specific exercises are best is not entirely clear, but strength training is generally recommended at least two times a week. Decreased muscle strength to the plantar flexors of foot, quadriceps, hamstrings and hip abductors have all been associated with common running injuries.^43-46 Thus, strength training that incorporates these lower extremity muscle groups is often targeted. The advantages of strength training also appear to improve running performance  with running economy being a critical factor in long-distance running.^47-51 In a recent systematic review of strength training, Blagrove and coworkers found that the addition of strength training (heavy resistance, explosive resistance and plyometric training) on two to three occasions per week will likely improve middle- and long-distance running performance.⁴⁷ Informing runners of the dual benefit of reduction of injury risk and improved performance will likely result in higher adherence.

Proprioception training is closely related to strength training but incorporates functional movements in order to improve neuromuscular control. Often individuals are performing both in exercises such as single leg squats. Functional balance training for lower extremity strength reportedly increases muscle strength and equalizes muscular imbalances.^52,53 Isolated ankle exercises may also result in increased joint stability and reduce joint loading.⁵⁴ Combining these exercises with strength training is likely more convenient for the runner.

Do We Overemphasize The Role Of Running Shoes In Preventing Injuries?

As podiatrists, most of us have been questioned as to the best running shoe for an individual. Although this is the prevailing preconceived notion, data is rather weak for any specific shoe. Shoe technology has grown rapidly over the last 30 years but reported injury rates have been arguably unchanged during this time.⁵⁵ In 2011, a Cochrane review found no significant reduction in injuries with wearing running shoes based on foot shape in comparison to standard running shoes.⁵⁶

However, since 2011, two randomized trials from Malisoux and colleagues have suggested there may be some reductions with pronation support in pronators and lower heel drop heights in occasional runners, indicating that shoe design may, as previously believed, impact injury rates in subsets of populations.^57,58 Others have suggested that foot type may be an oversimplification and have suggested comfort may be important to an individual’s “preferred movement pathway.”⁵⁹

 Still others have advocated barefoot or minimalist running shoes. Frequently, the absence of data supporting that shoes reduce injury rates is used as an argument for minimalist shoes but here again, the same argument could be reversed. Transitioning to minimalist shoes can also be burdened by extremely high injury rates.⁶⁰ Forefoot striking patterns have decreased the demand on the knees and anterior compartment of the lower leg, but at the cost of increasing force to the ankle, Achilles and forefoot.^61,62 This tradeoff and the fact that the majority of injuries are overuse injuries suggests minimalist shoes will likely decrease injuries at certain locations and increase injuries at others. Thus, minimalist shoes may be much more inviting as a treatment for certain individuals (such as exertional anterior compartment syndrome) rather than the general population. Others have discussed the pros and cons in much more detail.⁶³

Customized inserts are also a closely related topic to shoes. Some have demonstrated a decrease in lower extremity injuries in military recruits with customized inserts in randomized trials whereas other studies have not demonstrated a difference.^64-66

When data are unconvincing in either direction, personal bias tends to prevail. In our opinion, as overuse is the predominant cause of running injuries, any shoe modification risk reduction could easily be overcome by increases in training. Thus, the runner is often left with a choice to titrate the level of support with an increased or decreased level in training that one can tolerate. Finally, often a runner comes in convinced the shoe gear is the vital component but if many attempts at finding the “right” shoe and insert do not provide success, one must consider that the underlying issue may not exist in the foot or be modifiable by shoe gear. This is not to say shoes and inserts do not matter but to simply state that shoes and inserts are more likely to need fine tuning as opposed to being the major underlying issue for many runners. However, there certainly can be shoe gear that exacerbates an underlying issue and thus be a wrong shoe for the individual.

Other Considerations With Potential Risk Factors

Common sense must prevail in other situations. A graduated increase in mileage does seem to have lower injury risk in some studies but the commonly stated “10 percent rule” is not actually supported by much evidence.^67-71 This is the recommendation to increase weekly mileage by no more than 10 percent. However, a sudden increase of three miles a week to 40 miles a week will undoubtedly end in an injury. For the novice, more regimented protocols may circumvent many training errors committed until more experience can provide a more intuitive understanding of training progression.

Other factors influence risk of injury but are less modifiable. In nearly every study the authors identified and was reported, history of previous injury appears to supersede effectiveness of an intervention.^4,72-77 Increase in body mass index increases risk as well as being inexperienced at running.^3,4,72,74,78 In both of these situations, the individual is likely actively attempting to overcome these factors. Women may also be at higher risk for stress fractures.^75,79

Final Notes

Understanding what can actually be determined from studies in the era of big data is once again important in running injury prevention as it is for other topics. Big data, such as data gleamed from meta-analyses and even large randomized trials, are not always relevant to the individual. This is a combination of populations and not necessarily predictive of any one individual’s response as there may be a special case that precludes the patient from obtaining a benefit from an intervention. In any study, there are individuals with positive responses and negative responses to an intervention but the overall average of all participants is used to determine the intervention success. Thus, as with any meta-analysis, one must be mindful that subsets of the population may not experience the same results. For example, although stretching does not benefit the average runner, there may be a subset (such as those that habitually stretch) that does benefit.

Second, the outcome of reduction of risk of injury may be at odds with the outcome of performance. For example, decreases in frequency and duration of running decreases rate of injury. These are not desirable interventions for the average runner training for a marathon. Strength training, on the other hand, appears to be beneficial for both performance and risk reduction.

Third, although experienced runners are at lower risk of injury, it is difficult to determine what it is that decreases this risk. Likely, there are understudied interventions or techniques that have an effect on injury rate. This may be a cumulative effect of learned knowledge (such as when to change shoes, how hard to push, when rest is necessary, what pain is okay to run through, etc). However, ethical restraints may also make the study of generally accepted knowledge difficult to prove. For example, the purposeful prospective study of a generally accepted training error (such as wearing shoes for 1,000 miles) to determine if it is in fact harmful would be rather concerning in our modern day society.

Runners are, in general, a very well informed group of individuals but are often inundated with a plethora of information from both reliable sources and marketing. Understanding the current state of literature may help you reduce the risk of injury of your patients and yourself as well as earn their respect. Currently, redirecting more emphasis on strength training and proprioception as opposed to stretching and, in many cases, one particular shoe, appears to be in order. Encourage runners to consider adding strength training with heavy resistance as well as plyometric and balance training exercises two times per week. However, authors caution against over-reliance on the current state of evidence as the review of the literature is not overwhelmingly convincing and many studies are warranted on subsets of the population of different runners.

Dr. Thorud is board-certified by the American Board of Podiatric Medicine, and is a Fellow of the American College of Foot and Ankle Surgeons. Dr. Thorud is affiliated with Mercy Health System in Illinois.

Joslin Seidel is a fourth-year medical student at the Kent State College of Podiatric Medicine.

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Additional References

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