EDITOR’S NOTE:
To mark the launch of our second e-learning course on the sports injury theme, the following is an excerpt from the opening of the newly launched course ‘Resolving Running-Related Injury’.
The course is something of a passion project that was a decade in the making (the original iteration dates back to 2012) and this greatly expanded and updated offering cites over 400 studies from the sports medicine literature but also draws on practical expertise as a performance track and field coach and personal experiences accrued over a number of years working with broken runners to return them to doing what they love. I very much look forward to hearing readers’ thoughts on this latest offering…
RESOLVING RUNNING-RELATED INJURY…
Running is an activity with vast participation. Running features prominently in sports and athletic events. Aside from athletes in running events, running is the primary mode of locomotion for the majority of field and court sports. Even when this is not the case, running often still features in the dryland training performed by athletes in ‘non-running’ sports. Beyond sport, we must also consider the enormous numbers of recreational runners and those for whom running is a popular form of exercise for health and fitness. Part of the popularity of running is its lack of barriers to participation: it is low cost and does not require any facilities or others to participate, so there is a low bar for entry.
Yet despite all this, we have a persisting problem in that despite being a ‘natural’ form of locomotion there are disproportionately high rates of injury associated with running in each of these populations. Injury is of course the nemesis of the professional athlete and for recreational runners the health and economic burden of running-related injuries is also significant (Hespanhol Junior, van Mechelen et al. 2016).
The quest to unravel the causes and contributory factors in order to come up with ways to solve the problem of running injuries is thus pertinent to vast numbers of people across the world. The significance of this quest also goes beyond financial concerns. For many, running is more than simply a leisure time activity or a means to remain fit and healthy. Running is an outlet for managing stress and a tool for bolstering mental health. The role of running in different facets of an individual’s life and its profound and positive influence on quality of life explains why runners are so reluctant to suspend their running routine even when experiencing pain (around 40% report continuing to run despite their injury) (Wiegand, Mercer et al. 2019).
The consequences of an enforced absence from running due to injury are accordingly profound in terms of the negative impact on mental healthy and quality of life. The degree of impact is somewhat related to the severity of the running-related injury but some of the most common complaints suffered by runners also encroach into daily life such that they are a constant nagging presence. Preliminary data to suggest that part of the psychological and emotional toll is the impact on the individual’s sense of self efficacy (Mihalko, Cox et al. 2021). It follows that part of our task when putting the runner back together is restoring their faith that they know what to do and providing them with a strong grasp of how to do it.
A BRIEF HISTORY OF RUNNING INJURIES…
Suffering some sort of running-related injury can seem to be an inevitability. Recreational runners will be very familiar with this phenomenon. Most will be able to recite an extensive injury history, or at least recall a recent injury. Even if they are not out injured at this moment, many are presently coping with some sort of minor injury or niggle.
But how did we get here?
As a species we evolved to engage in bipedal locomotion over long distances. Thanks to this evolutionary history we are specifically adapted for endurance running. Indeed for long periods in our evolution our extraordinary propensity for running over long distances for an extended time was critical to our survival (Bramble and Lieberman 2004).
So we have something of a paradox. On one hand we are evolved for running activity, yet still we continue to see an extraordinarily high incidence of running-related injuries.
Something that may help explain this paradox is that as a species we are also notable for having the longest period of infant dependency. We emerge from the womb helpless and we remain work in progress for an extended period. Our formative years are just that: this period is critical for developing the capabilities, or the software, to make best use of the hardware we are endowed with. Whilst we have the underlying coordinative structures, locomotion skills are not hardwired in humans – they are developed through motor learning and skill acquisition during the developmental years. Moreover, this learning and refining of movement skills and capabilities continues over the life span. Whilst young kids fare well with their slightly clumsy looking running gait, as we grow and become heavier we find this no longer works and so we need to come up with alternative solutions and refine our running technique to meet the changing mechanical demands of our larger mass and longer limbs (Hubel and Usherwood 2015).
This raises the distinct possibility that running is not in itself necessarily injurious, but it is rather an issue of proficiency.
HOW BAD IS THE PROBLEM?
Rates of injury reported among recreational and competitive runners are consistently in the range of 20-80% (van Gent, Siem et al. 2007). Perhaps the most striking illustration of the prevalence of running injuries is that during the course of a year somewhere between 30% and 70% of runners can expect to suffer some kind of running-related injury, based upon the findings of studies to date (Lieberman 2012).
Running injury also has a significant cost for the individual. Beyond the financial cost, running-related injuries can often lead to lengthy periods out of action. One investigation of novice runners reported that the median time to recover from a running injury was 71 days before they were able to return to running (Nielsen, Ronnow et al. 2014).
The lack of any significant impact on injury rates over the past 40 years despite increased awareness and a great deal of attention invested in countermeasures and interventions is clearly a cause for some consternation among sports medicine authorities. But the far greater toll continues to be paid by the many runners who must endure being trapped in a cycle of chronic or recurrent injury and being deprived of the activity that brings them joy and supports their mental and physical health.
EXPLANATIONS FOR WHY SO MANY RUNNERS BECOME INJURED…
A number of different explanations are proposed for the high prevalence running-related injury. Here are the common ones:
Fundamental fragility problem? (i.e. we aren’t cut out for this?)
On the contrary it has been pointed out that humans evolved to run, driven by survival pressures that specifically selected for the ability to sustain bipedal running locomotion over long distances. This is evident in a number of specialised anatomical features and is also reflected in our physiology (Bramble and Lieberman 2004). Evolutionary biologists would therefore content that the idea that we are simply not cut out to run without becoming injured is not a plausible explanation.
It worth noting, however, that this does not rule out that the running injury epidemic we see in industrialised nations could still be an epigenetic phenomenon. More on that later.
Injuries result from training errors – i.e. too much too soon? Not obeying 10% rule?
Common sense would suggest that this is a probable causal factor at least in some instances, however the association between weekly mileage and injury is far less clear cut than has been suggested. For instance, the 10% ‘rule’ is a misnomer, as investigations are still unclear on what the threshold might be for safe increases in weekly running volume. The findings of a recent prospective study suggests that keeping weekly increases below 20% might be more reasonable (Damsted, Parner et al. 2018). That said, a systematic review by the same authors did not find any difference between 10% and 24% weekly increments, suggesting the threshold could be higher still (Damsted, Glad et al. 2018).
The conventional wisdom on restricting changes and building weekly mileage gradually was thrown up in the air entirely by a recent prospective study that looked at the longitudinal training data of runners and their incidence of injury. As a primer, the acute:chronic workload ratio is used to express the relative magnitude of week-to-week changes in training volume in relation to the volumes accrued over the preceding weeks. The idea is that coaches and athletes should seek to avoid excessive spikes in volume, so this acute:chronic value is kept to a minimum or at least below a threshold to protect against injury. The findings of this particular study contradicted this idea, as those runners with the lowest values (i.e. only small increases in weekly mileage) suffered more running related injuries (Nakaoka, Barboza et al. 2021). Another unexpected finding of this study was that runners with the highest weekly increases in mileage had fewer injuries than other members of the group – i.e. the higher the acute:chronic workload ratio of the runners’ week-to-week mileage progression the lower their odds of running-related injury during the study period.
Clearly there are other factors at play in how runners respond to frequency and volume of running and there are marked individual differences in tolerance to progressions in weekly mileage. This is likely not a bug but a feature, and it begs the question why some runners respond favourably as running frequency and volume is increased, whereas others prove highly susceptible to breaking down under increased running volumes. How runners cope with increases in intensity (i.e. running velocity) is another question entirely – and one that is also unresolved (Ramskov, Rasmussen et al. 2018). All of which raises doubts on whether it is as simple as just a universal issue with training prescription.
Engineering problem? (our evolution hasn't equipped us to run on hard road surfaces)
If we just require extra cushioning to cope with hard road surfaces then we would expect advances in running shoe technology should solve this. Or at the very least modern running shoes should have make a significant dent in the rates of running-related injury over recent decades…
A BRIEF HISTORY OF RUNNING SHOES…
During the 1970s and 1980s the high rates of injury among runners at different levels was becoming increasingly well documented. Such reports prompted manufacturers of running shoes to develop and market various innovations in running shoe design. The sports shoe industry has expanded dramatically in the intervening years with different modifications in running shoe design to provide cushioning and shock absorption that are promoted as reducing impact forces and injuries when running.
Moreover sports shoe manufactures have devised a myriad of technological modifications to provide reinforced arch support and engineering features designed to control or attenuate torsion and pronation at the foot. Such design features are purported to address various aspects of foot and ankle mechanics occurring during foot strike and stance phase when running, and in turn help to prevent common running injuries. Indeed one of the typical recommendations that is advocated for avoiding running injuries is to select a running shoe that is matched to the runner’s individuals specifications. A micro-industry has sprung up within the sports shoe retail sector to provide appropriate ‘assessment’ and guidance to assist the customer in purchasing the particular running shoe that will meet their individual biomechanical requirements. Likewise, expertise in the area of ‘prescribing’ the appropriate running shoe is now considered a critical skill for sports medicine and physiotherapy practitioners, as part of their role in managing and preventing running injuries among their clients (Richards, Magin et al. 2009).
Despite technological advances in running shoe design, the myriad options available and the specialist advice commonly provided to assist runners in selecting the running shoes to best fit their needs, there is little indication that the advent of running shoes has had little if any (positive) impact on the overall prevalence of injuries among runners (Lopes, Hespanhol et al. 2012). For example, a systematic review of the literature spanning a period from 1982 to 2004 identified rates of running-related lower limb injury reported in studies ranging from 19.4% to 79.3%, without any apparent decline in running injury rates over that time period (van Gent, Siem et al. 2007).
Paradoxically there is some indication that the properties of some engineered running shoes can have adverse effects on the stresses incurred when running, and indirectly contributing to of lower limb injury risk when running. For instance, running in highly cushioned shoes prompts the runner to increase active lower limb stiffness, with the result that impact loading is ultimately greater (Kulmala, Kosonen et al. 2018). Design features that are customary with modern running shoes, such as the cushioned sole and elevated heel, can also effectively enable poor running mechanics. One example is that the cushioned sole and raised heel enables and encourages the runner to heel strike when running. This heel-first foot strike strategy tends to produce a double impact spike in ground reaction forces (Lieberman, Venkadesan et al. 2010), as such is associated with higher impact peak forces and vertical loading rates (Almeida, Davis et al. 2015, Napier, Cochrane et al. 2015). It has also been demonstrated that cushioned running shoes are not very effective when it comes to attenuating impact forces or loading rates when running (Malisoux, Delattre et al. 2020).
It should be noted that it is not simply the generic type of foot strike employed which determines stresses and mechanical efficiency, but also how it is executed. However, a related issue that again exemplifies the paradoxical effects of the added comfort afforded by modern running shoes is that the cushioning provided may effectively serve to reduce sensory feedback from cutaneous and joint receptors and proprioception during initial contact and stance, such that 'feel' and technical execution is impaired (Lieberman 2012).
Furthermore, the stiffened soles and externally provided arch support that are characteristic of many modern running shoes may over time lead to the runner developing weakness in the muscles and structures of the foot and lower leg. Such developed weakness and reduced activity of the intrinsic and extrinsic muscles of the foot may predispose the runner to various forms of running-related injury affecting the lower extremity, including exertional compartment or ‘biomechanical overload’ syndrome (Franklyn-Miller, Roberts et al. 2014).
A review of the relevant research literature similarly concluded that there was no conclusive evidence that the design features of modern running shoes are in fact effective in serving the functions ascribed to them or preventing running injury (Richards, Magin et al. 2009). In general, the data has not supported the contention that these design features have any consistent effect in reducing rates of injury (Ryan, Valiant et al. 2011). Despite the purported benefits of ‘stability’ or ‘pronation control’ shoe design features, the data from prospective studies with extended follow up indicate a neutral shoe appears to be most appropriate, even for novice runners identified as having a pronated foot posture during initial screening (Nielsen, Buist et al. 2014). It would therefore appear that the real-world efficacy of the standard practice of ‘prescribing’ particular running shoes to address the individual biomechanical requirements of the runner is highly questionable based on the evidence (Richards, Magin et al. 2009).
THE (BRIEF) ADVENT OF ‘MINIMALIST’ RUNNING SHOES…
The apparent failure of cushioned and engineered running shoes to solve the running injury epidemic has prompted increased interest in barefoot running over recent years. The rationale for barefoot running is that humans have been walking and running without shoes for millions of years, and human running gait has therefore evolved accordingly (Lieberman 2012). As such, it is argued that humans should be well suited to running barefoot without undue risk of injury. By extension it is argued that running in a ‘barefoot style’ might also avoid the potentially injurious biomechanics that may be facilitated by running in cushioned running shoes, and in turn favour the development of more mechanically sound running technique (Warne and Gruber 2017).
Following this trend a host of shoe manufacturers were prompted to offer ‘minimalist’ running shoes which are marketed as mimicking running barefoot whilst offering some protection to the foot (Squadrone and Gallozzi 2009). Unfortunately for many runners who make this switch having habitually worn highly supportive and cushioned running shoes over a number of years, this change can prove too dramatic when not managed appropriately and accompanied with instruction to support gait retraining. As with barefoot running, the acute transition period when switching to minimalist running shoes is typically accompanied by transient pain and soreness. Increased rates of injury may also be reported during the initial period following the transition from conventional to minimalist shoes (Warne and Gruber 2017), likely in part due to bone and soft tissue structures having insufficient time to adapt.
Another problem is that the effect of switching to a ‘barefoot running style’ does not necessarily attenuate initial loading rates in the short term. Vertical loading rates observed when habitually shod runners first attempt to run barefoot may in fact increase (Tam, Darragh et al. 2017), particularly in habitual rearfoot strike runners (Hashish, Samarawickrame et al. 2016). Many of the same trends are observed when runners switch from conventional to minimalist running shoes. Favourable changes in running kinetics may not be evident in the short term, and participants often report pain and soreness during the transition period, particularly with relatively higher weekly mileage (Warne and Gruber 2017). Some studies report an increase in injury, albeit injury incidence differs between studies.
Due in part to these issues the trend for minimalist running shoes has proven somewhat short-lived. The pendulum appears to have swung in the opposite direction and many manufacturers have returned to producing cushioned and supported running shoes to meet popular demand, even introducing ‘maximalist’ running shoes at the opposite end of the spectrum (Napier and Willy 2018).
It should however be recognised that fundamentally the protective effect of sound running technique with respect to reducing the risk of running-related injury will apply whether or not an individual is running barefoot, shod in minimalist running shoes or wearing any other form of running shoe. In the words of Daniel Lieberman:
“How one runs probably is more important than is what is on one’s feet (but what is on one’s feet may affect how one runs)”
Those interested in learning about the consulting services we provide to organisations and support we offer to individuals can find more via the What We Do section on the site. You are also welcome to reach out via the Contact page.
Found this a worthwhile read? Subscribe to get Informed Blog posts direct to your email inbox and free to share with anybody in your network who might find value. When you subscribe you will receive a link to access a course entitled Fundamentals of Physical Preparation for free.
Also check out the Books section for a host of resources that take a deeper dive on various topics relating to human performance, coaching, athletic preparation and sports injury. The recent release Prepared: Unlocking Human Performance with Lessons from Elite Sport is now available worldwide (feedback and reviews always very welcome).
Finally, the new e-learning courses Comprehensive ACL Rehabilitation and Return to Performance and Resolving Running-Related Injury are both now available for practitioners interested in better supporting injured athletes on the journey back to sport following injury and stacking the odds in the athlete’s favour when they return.
