Analysis of Running in Wilson’s Disease

Aim of the study was to analyze the ability of long-term treated patients with Wilson’s disease (WD) to run a distance of 40 m. 30 WD-patients from a single center were consecutively recruited. All patients were able to walk a distance of 40 m without walking aids. Vertical ground reaction forces (GRF-curves) were analyzed by means of an Infotronic® gait analysis system (CDG®) and correlated with clinical and laboratory findings. Results of the WD-patients were compared to those of an age-and sex-matched control group. 25 of the 30 WD-patients were able to run. Patients being unable to run had a significantly (p < 0.03) higher non-motor score. In comparison to the controls speed of running was significantly (p < 0.02) reduced in WD-patients. Their duration of foot contact on the ground lasted significantly (p < 0.05) longer. Running was more irregular in WD and the variability of times to peak of the GRF-curves was significantly (p < 0.05) increased. All running parameters extracted from the GRF-curves of the CDG® did not correlate with severity of WD. Cadence of running was significantly (p < 0.03) negatively correlated with serum liver enzyme levels. Running appears to be rather unimpaired in long-term treated WD, only 16% of the 30 WD-patients were unable to run. This knowledge is highly relevant for the patient management, but because of the missing correlation with severity of WD, analysis of running is of minor importance for monitoring WD-therapy.

The Role of Water-Based Exercise on Vertical Ground Reaction Forces in Overweight Children: A Pilot Study

The aquatic environment represents an adequate and safe alternative for children with overweight to exercise. However, the magnitude of the vertical ground reaction force (Fz) during these exercises is unknown in this population. Therefore, our study aimed to compare the Fz during the stationary running exercise between the aquatic and land environments in children with overweight or obesity. The study is characterized as a cross-over study. Seven children, two with overweight and five with obesity (4 boys and 3 girls; 9.7 ± 0.8 years), performed two experimental sessions, one on land and another in the aquatic environment. In both conditions, each participant performed 15 repetitions of the stationary running exercise at three different cadences (60, 80, and 100 b min−1) in a randomized order. Their apparent weight was reduced by 72.1 ± 10.4% on average at the xiphoid process depth. The peak Fz, impulse, and loading rate were lower in the aquatic environment than on land (p < 0.001). Peak Fz was also lower at 80 b min−1 compared to 100 b min−1 (p = 0.005) and loading rate was higher at 100 b min−1 compared to 80 b min−1 (p = 0.003) and 60 b min−1 (p < 0.001) in the aquatic environment, whereas impulse was significantly reduced (p < 0.001) with the increasing cadence in both environments. It can be concluded that the aquatic environment reduces all the Fz outcomes investigated during stationary running and that exercise intensity seems to influence all these outcomes in the aquatic environment.

A simple computational method to estimate stance velocity in running

Running dynamical analyses typically approximate a runner's stance velocity as the average stride cycle velocity (the average running speed). That approximation necessarily overestimates stance velocity and biases subsequent results. Stance velocities are crucial in kinetic spring-mass analyses of running, where approximation of a runner's impact angle and calculation of leg stiffness require that input. Here, a new method is presented to approximate a runner's stance velocity via measurement of contact and flight times with the runner's average speed, leg length or height, and mass. This method accurately estimated stance velocities of simulated spring-mass systems across typical running speeds of 3.5-5.5 m/s (r&gt;0.99) and more accurately estimated impact angles of simulations and leg stiffnesses. The method also accurately estimated peak horizontal vertical ground reaction forces across speeds (r=0.82), but the bias magnitude increased with speed. Robustness of the new method was further tested for runners at 2.5, 3.5, and 4.5 m/s, and the new method provided steeper impact angles than those from traditional estimates and correspondingly higher leg stiffnesses, analogous to the observations in the simulation models. Horizontal ground reaction force estimates were weakly correlated in braking and propulsion. They were improved by a corrective algorithm, but the intra- and inter-individual variation persisted. The directionality and magnitude of angle and stiffness estimates in the human runners were similar to simulations, suggesting the new method more accurately modeled runners’ spring-mass characteristics by using an accurate approximation of stance velocity. The new method can improve traditional kinetic analyses of running where stance velocity recordings are not captured with kinematic recordings and extend opportunities for accurate field-based analyses with limited measurement sources.

Consistent inconsistencies in braking: a spatial analysis

The dynamic system that is the bipedal body in motion is of interest to engineers, clinicians and biological anthropologists alike. Spatial statistics is more familiar to public health researchers as a way of analysing disease clustering and spread; nonetheless, this is a practical approach to the two-dimensional topography of the foot. We quantified the clustering of the centre of pressure (CoP) on the foot for peak braking and propulsive vertical ground reaction forces (GRFs) over multiple, contiguous steps to assess the consistency of the location of peak forces on the foot during walking. The vertical GRFs of 11 participants were collected continuously via a wireless insole system (MoticonReGo AG) across various experimental conditions. We hypothesized that CoPs would cluster in the hindfoot for braking and forefoot for propulsion, and that braking would demonstrate more consistent clustering than propulsion. Contrary to our hypotheses, we found that CoPs during braking are inconsistent in their location, and CoPs during propulsion are more consistent and clustered across all participants and all trials. These results add to our understanding of the applied forces on the foot so that we can better predict fatigue failures and better understand the mechanisms that shaped the modern bipedal form.

Comparison of Countermovement and Preferred-Style Jump Biomechanics in Male Basketball Players

The purpose of this study was to investigate and compare the biomechanics of countermovement (CMJ) and preferred-style (PrefJ) jumps. Eight male basketball players (age: 19 ± 1 year; height: 1.84 ± 0.14 m; mass: 92.8 ± 11.4 kg) participated in a cross-sectional study for which they performed max effort CMJ and PrefJ while motion capture and force plate data were recorded. The CMJ were performed according to common procedures. For the PrefJ, the eight players chose to use a short approach run and a step-in jump, with a clear lead and trail leg foot contact pattern. Vertical ground reaction forces (GRF), center-of-mass (COM) parameters, as well as hip, knee, and ankle flexion angles, extension velocities, net joint moments, powers, and work were all calculated and used for analysis. Bi-lateral data from the CMJ were averaged, whereas lead and trail leg data from the PrefJ were kept separated. The PrefJ was characterized by greater jump height and GRF and shorter contact times. Joint-level differences indicated that the PrefJ was characterized by larger joint kinetics. Importantly, very few biomechanical variables of the CMJ and PrefJ were correlated, which suggests that each jump type is characterized by unique movement strategies. Since PrefJ may better represent athlete- and sport-specific movement pattern, these findings could have implications for assessing and monitoring neuromuscular performance of basketball players.

Evaluation of force feedback in walking using joint torques as 'naturalistic' stimuli

Control of adaptive walking requires the integration of sensory signals of muscle force and load. We have studied how mechanoreceptors (tibial campaniform sensilla) encode 'naturalistic' stimuli derived from joint torques of stick insects walking on a horizontal substrate. Previous studies showed that forces applied to the legs using the mean torque profiles of a proximal joint were highly effective in eliciting motor activities. However, substantial variations in torque direction and magnitude occurred at the more distal femoro-tibial joint, which can generate braking or propulsive forces and provide lateral stability. To determine how these forces are encoded, we utilized torque waveforms of individual steps that had maximum values in stance in the directions of flexion or extension. Analysis of kinematic data showed that the torques in different directions tended to occur in different ranges of joint angles. Variations within stance were not accompanied by comparable changes in joint angle but often reflected vertical ground reaction forces and leg support of body load. Application of torque waveforms elicited sensory discharges with variations in firing frequency similar to those seen in freely walking insects. All sensilla directionally encoded the dynamics of force increases and showed hysteresis to transient force decreases. Smaller receptors exhibited more tonic firing. Our findings suggest that dynamic sensitivity in force feedback can modulate ongoing muscle activities to stabilize distal joints when large forces are generated at proximal joints. Further, use of 'naturalistic' stimuli can reproduce characteristics seen in freely moving animals that are absent in conventional restrained preparations.

Joint angle estimation with wavelet neural networks

This paper presents a wavelet neural network (WNN) based method to reduce reliance on wearable kinematic sensors in gait analysis. Wearable kinematic sensors hinder real-time outdoor gait monitoring applications due to drawbacks caused by multiple sensor placements and sensor offset errors. The proposed WNN method uses vertical Ground Reaction Forces (vGRFs) measured from foot kinetic sensors as inputs to estimate ankle, knee, and hip joint angles. Salient vGRF inputs are extracted from primary gait event intervals. These selected gait inputs facilitate future integration with smart insoles for real-time outdoor gait studies. The proposed concept potentially reduces the number of body-mounted kinematics sensors used in gait analysis applications, hence leading to a simplified sensor placement and control circuitry without deteriorating the overall performance.