Overuse injuries are generally defined as a repetitive micro-trauma to tissue. Many researchers have associated particular biomechanical parameters as an indicator of such injuries. However, while these parameters have been reported in single studies, in many instances, it has been difficult to verify these parameters as causative to the injury. We have investigated overuse injuries, such as patella-femoral pain syndrome, using a dynamical systems approach. Using such methods, the importance of the structure of coordinative variability (i.e. the variability of the interaction between segments or joints) becomes apparent. We view coordinative variability as functionally important to the movement and different from end-point or goal variability. Using concepts derived from the work of Bernstein, we conducted studies using a continuous relative phase and/or modified vector coding approaches to investigate the coordinative variability of overuse injuries. Consistently, we have found that the higher variability state of a coordinative structure is the healthy state while the lower variability state is the unhealthy or pathological state. It is clear that very high coordinative variability could also result in injury and that there must be a window of ‘higher variability’ in which non-injured athletes function. While this finding that coordinative variability is functional has been shown in several studies, it is still not clear if reduced variability contributes to or results from the injury. Studies are currently underway to determine the potential reasons for the reduced variability in injured athletes. Nevertheless, our laboratory believes that this understanding of how joints interact can be important in understanding overuse injuries.

Increased impact characteristics are often cited as a cause of running injuries. One method that has been used to reduce impact characteristics is to increase the thickness of the midsole of running footwear with the intention of attenuating greater shock from the foot-ground collision. A second method that has been suggested is to run barefoot. The purpose of this study was to compare the impact characteristics of running footwear of different midsole thickness to a barefoot condition. Three-dimensional kinematic and kinetic data were collected as participants ran at their preferred running speed and at a fixed speed. Impact characteristics (impact peak, time to impact peak and vertical loading rate) were derived from the vertical ground reaction force component. Ankle and knee joint stiffness during the loading phase of support were derived from the change in moment divided by the change in angle. The impact parameters were statistically analyzed using a two-way, repeated measures ANOVA. There were no significant speed by footwear condition interactions. For impact peak, ankle stiffness and knee stiffness, there was no difference among the shod conditions but there were significant differences between the shod and barefoot conditions. Based on their strike index, participants in this study appeared to alter their footfall pattern from a rearfoot to a midfoot pattern when changing from running shod to barefoot. It may be concluded that the change in the impact characteristics is a result of changing footfall pattern rather than midsole thickness.

The purpose of this retrospective study was to examine lower extremity joint stiffness between runners with and without low back pain. We compared data from three groups: current low back pain (LBP), resolved pain (RES), and a control (CTRL) group of runners. We hypothesized that the LBP group would exhibit increased ankle, knee, and hip joint stiffness when compared with the other groups. Subjects ran on a force treadmill at 3.8 m•s⁻¹ while data were collected. Joint stiffness was determined from the joint moment-angle profiles. Differences were observed in knee joint stiffness, with the LBP group exhibiting the greatest stiffness values. No differences in ankle or hip joint stiffness were observed. These data suggest that the LBP group of runners may not attenuate the foot–ground impact to the same level as the other groups. The decreased attenuation may increase the level of the shock to the low back region, thus potentially increasing the load on the low back.

It has been suggested that the development of a thick, soft midsole of running shoes over the past 30 years has been primarily responsible for the majority of runners adopting a rearfoot or heel-toe footfall pattern thus deviating from a more ‘natural’ forefoot pattern. The purpose of this study was to determine the freely chosen footfall pattern when running barefoot on a harder versus a softer surface. Forty habitual rearfoot runners performed two running conditions: barefoot over a harder surface and barefoot over a softer surface. Three-dimensional motion analysis and ground reaction force data were collected to measure the ankle angle, vertical impact peak and strike index. The kinematic and kinetic parameters were used to confirm the footfall pattern in each condition. Only 20% per cent of the participants ran with a midfoot or forefoot pattern on the soft surface whereas 65% of the participants ran with a midfoot or forefoot pattern when running on the hard surface. Out of the 80% of participants that maintained a rearfoot pattern on the soft surface, 43% of these participants ran with a midfoot or forefoot pattern on the hard surface. These results suggest that, while running barefoot, the hardness of the running surface may be a significant factor causing an alteration in a runner's footfall pattern.

Far too little attention has been paid to health effects of air pollution and physical (in)activity on musculoskeletal health. The purpose of the Healthy aging in industrial environment study (4HAIE) is to investigate the potential impact of physical activity in highly polluted air on musculoskeletal health. A total of 1500 active runners and inactive controls aged 18–65 will be recruited. The sample will be recruited using quota sampling based on location (the most air-polluted region in EU and a control region), age, sex, and activity status. Participants will complete online questionnaires and undergo a two-day baseline laboratory assessment, including biomechanical, physiological, psychological testing, and magnetic resonance imaging. Throughout one-year, physical activity data will be collected through Fitbit monitors, along with data regarding the incidence of injuries, air pollution, psychological factors, and behavior collected through a custom developed mobile application. Herein, we introduce a biomechanical and musculoskeletal protocol to investigate musculoskeletal and neuro-mechanical health in this 4HAIE cohort, including a design for controlling for physiological and psychological injury factors. In the current ongoing project, we hypothesize that there will be interactions of environmental, biomechanical, physiological, and psychosocial variables and that these interactions will cause musculoskeletal diseases/protection.