Christopher L. Maclean and Jack Taunton
Christopher L. MacLean, Irene S. Davis and Joseph Hamill
The purpose of this study was to analyze the influence of varying running shoe midsole composition on lower extremity dynamics with and without a custom foot orthotic intervention. Three-dimensional dynamics were collected on 12 female runners who had completed 6 weeks of custom foot orthotic therapy. Participants completed running trials in 3 running shoe midsole conditions—with and without a custom foot orthotic intervention. Results from the current study revealed that only maximum rearfoot eversion velocity was influenced by the midsole durometer of the shoe. Maximum rearfoot eversion velocity was significantly decreased for the hard shoe compared with the soft shoe. However, the orthotic intervention in the footwear led to significant decreases in several dynamic variables. The results suggest that the major component influencing the rearfoot dynamics was the orthotic device and not the shoe composition. In addition, data suggest that the foot orthoses appear to compensate for the lesser shoe stability enabling it to function in a way similar to that of a shoe of greater stability.
Christopher L. MacLean, Richard van Emmerik and Joseph Hamill
The purpose of this study was to analyze the influence of a custom foot orthotic (CFO) intervention on lower extremity intralimb coupling during a 30-min run in a group of injured runners and to compare the results to a control group of healthy runners. Three-dimensional kinematic data were collected during a 30-min run on healthy female runners (Shoe-only) and a group of female runners who had a recent history of overuse injury (Shoe-only and Shoe with custom foot orthoses). Results from the study revealed that the coordination variability and pattern for the some couplings were influenced by history of injury, foot orthotic intervention and the duration of the run. These data suggest that custom foot orthoses worn by injured runners may play a role in the maintenance of coordination variability of the tibia (transverse plane) and calcaneus (frontal plane) coupling during the Early Stance phase. In addition, it appears that the coupling angle between the knee (transverse plane) and rearfoot (frontal plane) joints becomes more symmetrical in the late stance phase as a run progresses.
Christopher Napier, Christopher L. MacLean, Jessica Maurer, Jack E. Taunton and Michael A. Hunt
High magnitudes and rates of loading have been implicated in the etiology of running-related injuries. Knowledge of kinematic variables that are predictive of kinetic outcomes could inform clinic-based gait retraining programs. Healthy novice female runners ran on a treadmill while 3-dimensional biomechanical data were collected. Kinetic outcomes consisted of vertical impact transient, average vertical loading rate, instantaneous vertical loading rate, and peak braking force. Kinematic outcomes included step length), hip flexion angle at initial contact, horizontal distance from heel to center of mass at initial contact, shank angle at initial contact, and foot strike angle. Stepwise multiple linear regression was used to evaluate the amount of variance in kinetic outcomes explained by kinematic outcomes. A moderate amount of variance in kinetic outcomes (vertical impact transient = 46%, average vertical loading rate = 37%, instantaneous vertical loading rate = 49%, peak braking force = 54%) was explained by several discrete kinematic variables—predominantly speed, horizontal distance from heel to center of mass, foot strike angle, and step length. Hip flexion angle and shank angle did not contribute to any models. Decreasing step length and transitioning from a rearfoot strike may reduce kinetic risk factors for running-related injuries. In contrast, clinical strategies such as modifying shank angle and hip flexion angle would not appear to contribute significantly to the variance of kinetic outcomes after accounting for other variables.