PURPOSE:​ The purpose of this investigation was to determine the association of gait kinematic and kinetic, anthropometric and muscular strength variables with injury frequency in distance runners. We hypothesize that frequency of injury will influence a discrete set of kinematic, kinetic, anthropometric, and strength variables. Specifically, increased injury frequency will be associated with greater joint motion and joint loads, a lower arch-index and Q-angle, as well as inferior lower extremity strength variables.

METHODS:​ Data from a subset of participants (159 out of 184) enrolled in The Runners and Injury Longitudinal Study (TRAILS) were used for this study. Runners between the ages of 18 and 60 years who had been running at least 5 mi/wk for a minimum of six months without developing an overuse injury were recruited and their training history, gait, anthropometrics, and lower extremity strength were assessed. Joint kinematics and kinetics were assessed using a 3-D gait analysis with a 37-reflective marker set arranged in a modified Cleveland Clinic full-body configuration, a 6-Camera Motion Analysis System set to sample data at 200 Hz, and a torque-driven musculoskeletal model (DeVita and Hortobagyi). Q-angle was measured using digital photographs, a technique developed by Herrington and Nester (2004). Arch-index was measured at half bodyweight stance using a method by Cavanagh et al (1987). Knee and ankle concentric strength were measured using a Kin-Com 125E isokinetic dynamometer set at an angular velocity of 60°/sec, while hip isometric and concentric strength were measured with the dynamometer set at an angular velocity of 30°/sec. Participants were then followed for 12-24 months and sorted into Never, Occasionally, and Frequently Injured groups. Regression equations were calculated for age, weekly mileage, training frequency, training pace, peak hip, knee and ankle joint angles and relative moments as well as knee compressive and A-P shear force at heel-strike and during stance, Q-angle, arch-index, and isokinetic concentric strength of the hip abductors, knee flexors and extensors, and ankle dorsiflexors and plantar flexors.

RESULTS:​ After controlling for gender and total years running, significant associations were found for age (p = 0.002), peak knee flexion angle at heel-strike (p = 0.042), peak knee flexion angle during stance (p = 0.015), peak relative ankle plantar flexion moment during stance (p = 0.032), and Q-angle (p = 0.03). Increased injury frequency was associated with lower age, increased peak knee flexion angle at heel-strike and during stance, greater peak ankle plantar flexion moment, and a greater Q-angle.

CONCLUSIONS:​ The significance of these results is tempered by the lack of corroborating evidence on the contralateral side, the relatively weakness of significant associations, and the many associations that did not reach statistical significance. While there is some evidence that less frequently injured runners have characteristics that may lead to reduce stress on lower extremity joints, taken together, the body of the evidence suggests that there are few, if any, significant associations between gait, strength, and anthropometrics and injury frequency. Our results also suggest that running may be a safer activity for older individuals as frequency of injury seems to be attenuated in this population.