Biomechanics of Running – Implications for Running-Related Injuries and Future Areas for Research

For many years now, running has been counted among the most popular sports worldwide. According to current estimates, nearly 18 million people run regularly in Germany. In addition to the joy of movement and nature, most runners report improvement in fitness and health as their motivation. An increase in exercise capacity also is in the foreground for many runners and continuously high numbers of participants and finishers are seen in running events, such as the large City Marathons in Berlin, Frankfurt and Hamburg.

In addition to the numerous and well-researched advantages of running on general health, high rates of running-related injuries are also reported. Depending on the population and time period examined, the prevalence rate varies between 20 and 80% (20). The most frequent diagnoses are iliotibial ligament syndrome, tendinopathies of the Achilles tendon and plantar fasciae, patellofemoral pain syndromes and stress fractures of the tibia and metatarsus (17).

The etiology of running-related injuries is multifactorial and risk factors can be grouped into modifiable and non-modifiable (13). In addition to good evidence of a high running load (>60 km/week) and a history of running-related injuries as individual risk factors, there are numerous studies on anthropometric, anatomical and training-related parameters which could stand in connection to running-related injury (13). Biomechanical parameters are also a topic of many scientific studies, whereby the general evidence has not yet been adequately clarified (3).

Running shoes have been in the focus of biomechanical research not only thanks to the first marathon run in less than 2 hours by Eliud Kiechoe on 12. October 2019 under laboratory-like conditions. In addition to current discussion of the advantages offered by the influence of shoes on running economy and performance (11, 12, 16), running shoes are also central to the debate on running-related injuries. Although numerous innovations, such as new shock-absorbing systems or pronation elements have been on the market since the 1970s, no reduction in the number of injuries could be observed (20). Nigg et al. (2015) (20) thus proposed a paradigm switch away from greater cushioning, corrective shoe elements and general provision of innersoles to a “natural” and self-selected exercise pattern. Since the article by Lieberman and his colleagues  on Kenian barefoot runners, published in the journal “Nature” (15), numerous scientific articles have addressed the topic of (simulated) barefoot running over the last 10 years and there are now many models marketed by various manufacturers which are supposed to replicate the biomechanics of barefoot running (4, 6, 21). A focus of current research in this area addresses the potential of altered kinematics in the upper ankle (forefoot touchdown) and a reduced cadence with associated lower ground reaction forces (10, 24). These have been suspected for years to be related to certain injuries, even though the current evidence situation is still inadequate (3, 5). Future research in this area must address the long-term effects of (simulated) barefoot running and prospective studies are needed (9).

Current technical developments in the area of wearables (23) now enable the examination of biomechanical variables outside the biomechanics laboratories, which often had to be conducted at great technical and personnel costs. Using “Inertial Measurement Units (IMUs)”, which contain acceleration, torque rates and magnetic sensors, continuous kinematic data can, for example, be measured during a training session or a competition (7, 8, 14). Moreover, forces which arise can be estimated indirectly via the acceleration of the tibia (14,22). Research in this area will likely increase considerably in the coming years and must therefore undergo adequate validation for the various measuring parameters and research queries (18). Overall, a great potential for application, even in the area of “citizen science” can be expected from this research area, since nowadays many watches and nearly all smart phones are equipped with an IMU.

Another research area with great potential lies in modern procedures of “artificial intelligence” and “Big data” (2, 19). Here mechanical learning can be emphasized, which has the goal of recognizing patterns and regularities in any given quantity of data. Mechanical learning offers both possibilities in the processing of large biomechanical datasets and in analyzing the multifactorial genesis of running-related injuries, with the aim of predicting such injuries (1, 2). The prediction of injuries is a very challenging and important component in the prevention of injuries.

In working out these future research areas, the interdisciplinarity of sports medicine is again required, and cooperation with the fields of sports sciences, physiotherapy, orthopedics/traumatology, biomechanics, engineering science, informatics and statics is absolutely essential.