Gerald K. Cole

Effects of arch height of the foot on angular motion of the lower extremities in running.

It has been suggested that a relationship exists between the height of the medial longitudinal arch of the foot and athletic injuries to the lower extremities. However, the functional significance of arch height in relation to injury is not well understood. The purpose of this study was to determine the influence of arch height on kinematic variables of the lower extremities that have been associated with the incidence of injury in running in an attempt to gain some insight into a functional relationship between arch height and injury. The three-dimensional kinematics of the lower extremities were measured during running for 30 subjects using high-speed video cameras. A joint coordinate system was used to calculate the three-dimensional orientation of the ankle joint complex for a single stance phase. Simple, linear regression analyses showed that arch height does not influence either maximal eversion movement or maximal internal leg rotation during running stance. However, assuming that knee pain in running can result from the transfer of foot eversion to internal rotation of the tibia, a functional relationship between arch height and injury may exist in that the transfer of foot eversion to internal leg rotation was found to increase significantly with increasing arch height. A substantial (27%), yet incomplete, amount of the variation in the transfer of movement between subjects was explained by arch height, indicating that there must be factors other than arch height that influence the kinematic coupling at the ankle joint complex. Additionally, the transfer of movement is only one factor of many associated with the etiology of knee pain in running.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of material characteristics of shoe soles on muscle activation and energy aspects during running

The purposes of this study were (a) to determine group and individual differences in oxygen consumption during heel-toe running and (b) to quantify the differences in EMG activity for selected muscle groups of the lower extremities when running in shoes with different mechanical heel characteristics. Twenty male runners performed heel-toe running using two shoe conditions, one with a mainly elastic and a visco-elastic heel. Oxygen consumption was quantified during steady state runs of 6 min duration, running slightly above the aerobic threshold providing four pairs of oxygen consumption results for comparison. Muscle activity was quantified using bipolar surface EMG measurements from the tibialis anterior, medial gastrocnemius, vastus medialis and the hamstrings muscle groups. EMG data were sampled for 5 s every minute for the 6 min providing 30 trials. EMG data were compared for the different conditions using an ANOVA (alpha=0.05). The findings of this study showed that changes in the heel material characteristics of running shoes were associated with (a) subject specific changes in oxygen consumption and (b) subject and muscle specific changes in the intensities of muscle activation before heel strike in the lower extremities. It is suggested that further study of these phenomena will help understand many aspects of human locomotion, including work, performance, fatigue and possible injuries.

Transfer of movement between calcaneus and tibia in vitro

Excessive foot eversion and/or abnormal tibial rotation have been associated with knee injuries. The mechanical coupling of leg and foot, which may be related to the aetiology of knee injuries, is still not well understood. The goal of this study was to determine in vitro, as a function of loading and flexion position of the foot, the movement transfer from calcaneal eversion-inversion to tibial rotation and vice versa occurring in the ankle-joint complex. A lower leg holding and loading device with 6 degrees of freedom was used in the investigation. Fourteen fresh-frozen, foot-leg specimens were tested. The movement transfer from calcaneus to tibia and vice versa differed significantly between the specimens. The transferred movement was not the same for all input modes. Specifically, calcaneal eversion resulted in significant internal tibial rotation; however, internal tibial rotation did not induce any calcaneal eversion. Vertical loading of the tibia and foot flexion position had a major influence on this movement transfer. The amount of calcaneal eversion transferred to internal tibial rotation depends on the individual mechanical coupling at the ankle-joint complex. Therefore excessive pronation, in running for instance, is only critical for high knee loading when coupled with a high movement transfer in the ankle-joint complex. The interindividual differences may also signal difficulties for prosthesis design in total ankle-joint replacement and for the design of shoe orthotics.

Lower extremity joint loading during impact in running

OBJECTIVE: The main purpose of this study was to estimate lower extremity joint impact loading in running and the influences of muscles on this loading. DESIGN: A 2D simulation model that included skeletal motion, muscles, and soft-tissue movement was developed in this study. BACKGROUND: Our understanding of joint impact loading has been mainly based on measurable external loading variables. Furthermore, changes in muscular forces have often been neglected, assuming that muscular activation cannot react during the period of impact, which ignores passive muscle properties. METHODS: Kinematics and ground reaction forces were collected for each of five subjects performing heel-toe running. Kinematic and inverse dynamics analyses provided the initial conditions for the simulation models. The motion of each subject was simulated for 50 ms following heelstrike. RESULTS: Motion of body segments following heelstrike reduced the rate of joint impact loading, sometimes substantially, in comparison to the ground reaction force. In addition, substantial changes in muscular forces were sometimes observed that further reduced the rates of joint loading. CONCLUSIONS: The rates of joint impact loading are reduced in comparison to the ground reaction force during normal heel-toe running. Changes in muscular forces may have a relevant effect on joint impact loading and should not be neglected in future studies. RELEVANCE: Repetitive external impact loading has resulted in degeneration of articular cartilage in animal models. However, runners, as a group, do not have a high incidence of osteoarthritis. The present study suggests that there are mechanisms available to the runner that can substantially reduce the rate of joint impact loading relative to the rate of external loading. These mechanisms may be sufficient to prevent overloading and degeneration of the joints.

Modelling of force production in skeletal muscle undergoing stretch

Many human movements involve eccentric contraction of muscles. Therefore, it is important that a theoretical model is able to represent the kinetic response of activated muscle during lengthening if it is to be applied to dynamic simulation of such movements. The so-called Hill and Distribution Moment models are two commonly used models of skeletal muscle. The Hill model is a phenomenological model based on experimental observations; the Distribution Moment model is based on the cross-bridge theory of muscle contraction. The ability of each of these models to predict the force-velocity relation has been considered previously; however, few attempts have been made to evaluate the force response of each model with respect to time during stretches at different velocities. The purpose of this study was to compare the predicted force-time responses of the Hill and Distribution Moment models to the actual force produced by the cat soleus during experimental iso-velocity stretches at maximal activation. Two stretch velocities were simulated: 7.2 and 400 mm s-1. Model parameters were derived from the literature where possible. In addition, model parameters were optimized to provide the best possible fit between model force predictions and experimental results at each velocity. The results of the study showed that using the Hill model, it was possible to describe qualitatively the force-time response of the muscle at both velocities of stretch using parameters derived from the literature. It was also possible to optimize a set of parameters for the Hill model to provide a quantitative description of the force-time response at each velocity. Using the Distribution Moment model, it was not possible to describe the force-time response of the muscle for both velocities using a single set of rate constants, suggesting that the cross-bridge theory, upon which the model is based, may have to be further evaluated for lengthening muscle. Further research is required to determine if the model results can be generalized to other muscles and other velocities of stretch.

Influence of selective arthrodesis on the movement transfer between calcaneus and tibia in vitro.

Arthrodeses of foot and ankle are well established, accepted, and practical methods for treatment of painful joint degeneration, foot deformity, and instability. Consecutive changes in gait and over-use injuries have been explained by the created lever arms and the overall compensatory motion in the neighbouring joints, rather than by changes in the mechanical coupling of foot and tibia. Thus the purpose of this study was to quantify the change of movement transferred from calcaneus to tibia, and vice versa, for selective joint fusions (ankle, subtalar, and talonavicular joints) under different flexion and loading conditions. In six fresh cadaveric foot-leg specimens, transfer of rotational movement between calcaneus and tibia occurred in all arthrodesis conditions. Fusion of the subtalar joint, which is commonly believed to be crucial in the transfer of rotational movement in the ankle joint complex, decreased the movement transfer from calcaneal inversion to external tibial rotation about 71.8% and, vice versa, from external tibial rotation to calcaneal inversion about 35.8%. However, the movement transfer did not change when calcaneal eversion and internal tibial rotation were the input movements. The ankle (talocrural) joint must have more than 1 degree of freedom, since significant movement transfer still occurred when the subtalar joint was fused. It could be that other structures such as ligaments also play an important role in transferring movement. Consequently it may be difficult to predict the effect of a planned arthrodesis since the resulting restriction of motion and movement transfer may be substantially determined by the integrity of the surrounding soft tissue, especially the ligaments.

Making soccer kicks better: a study in particle swarm optimization and evolution strategies

Biomechanics is a science of examining the internal and external forces on the human body. In biomechanics, forward dynamics simulation models can be used to study optimal control of the human musculoskeletal system. An example application is the soccer kick, where the optimal recruitment pattern of the muscles of the lower extremity can result in a high speed shot on net. We used evolutionary algorithms - particle swarm optimizers and evolution strategies - to adjust muscle control parameters for a soccer kick. In this paper we describe our implementation of the soccer kick project, optimization experiments performed with the soccer kick and comparing the results from particle swarm optimization and evolution strategies

Making soccer kicks better: a study in particle swarm optimization

Biomechanics is a science of examining the internal and external forces on the human body. In biomechanics, forward dynamics simulation models can be used to study optimal control of the human musculoskeletal system. An example application is the soccer kick, where the optimal recruitment pattern of the muscles of the lower extremity can result in a high speed shot on net. We used evolutionary algorithms - particle swarm optimizers and evolution strategies - to adjust muscle control parameters for a soccer kick. In this paper we describe our implementation of the soccer kick project, optimization experiments performed with the soccer kick and comparing the results from particle swarm optimization and evolution strategies