4,884 research outputs found
Lower-limb biomechanical asymmetry in maximal velocity sprint running
No full textAsymmetry analyses have provided valuable insight into submaximal running and walking gait. Knowledge of asymmetry in sprint running is limited due to traditional unilateral methods of data collection. The aims of the study were to develop asymmetry measures that included intra-limb variability and to investigate asymmetry of sprint running in an ecologically valid environment. Asymmetry was quantified for a group of sprint runners through the development of novel multifactorial asymmetry scores. The largest kinematic asymmetry values (7%) were smaller than the corresponding kinetic values (90%). The presence of significant athlete asymmetry suggested unilateral analyses may overlook important information. Information about individual athletes’ asymmetry may also help to inform the coaching process
Calculating centre of pressure from multiple force plates for kinetic analysis of sprint running
No full textForce plates are relatively small compared to athletes’ step lengths during sprint running. A large number of trials are subsequently rejected when collecting force plate data, which could be reduced by using multiple force plates. The aim of this study was to determine the suitability of foot contacts occurring across the boundaries of two force plates for use in inverse dynamics analyses. Centre of pressure data for a loaded wheel rolling across two force plates were compared to known positions of the wheel measured using an automated motion analysis system. A mean difference of 0.0027 [±0.0024] m was found between centre of pressure location and the measured wheel position as the wheel crossed the boundary between plates. The centre of pressure error resulted in joint power errors ranging from 0.27% to 1.47% for the ankle, knee and hip
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Goal Orientated stroke rehabilitation utilising electrical stimulation, iterative learning and Microsoft Kinect
No full textAn upper-limb stroke rehabilitation system is developed that assists patients in performing real world functionally relevant reaching tasks. The system provides de-weighting of the arm via a simple spring support whilst functional electrical stimulation is applied to the anterior deltoid and triceps via surface electrodes, and to the wrist and hand extensors via a 40 element surface electrode array. Iterative learning control (ILC) is used to mediate the electrical stimulation, and updates the stimulation signal applied to each muscle group based on the error between the ideal and actual movement in the previous attempt. The control system applies the minimum amount of stimulation required, maximising voluntary effort. Low-cost, markerless motion tracking is provided via a Microsoft Kinect, with hand and wrist data provided by an electrogoniometer or data glove. The system is described and initial experimental results are presented for a stroke patient starting treatment
Surface markers versus clusters for determining lower limb joint kinematics in sprint running
No full textThe purpose of this study was to compare lower limb joint angle time histories using surface markers and segmental clusters. An athlete completed three single leg standing trials whilst moving the joints of the free leg from maximum flexion to maximum extension followed by seven maximal sprint runs. Trials were tracked by a three-dimensional CODA system. For standing trials, mean timing differences were greatest in maximum extension at the ankle and hip (0.01 s). Angle differences ranged from 2° (knee flexion) to 11° (ankle extension). Timing differences in sprinting were greatest in extension (hip 0.03 s) with joint angle differences in maximum flexion and extension 7 & 9° (ankle), 3 & 6° (knee) and 23 & 4° (hip) respectively. When comparing results from surface markers and clusters, a good level of agreement was found in the continuous knee flexion-extension profile, and the discrete timings for all joints
Surface Electrode Array based Control of the Wrist and Hand
No full textSurface stimulation is a non-invasive method of muscle activation that uses adhesive electrodes placed on the surface of the patient skin above thelocation of the desired muscles. One application is in stroke rehabilitation where a controller is used to provide assistive stimulation to a patient completing a finite duration task with the impaired limb. Effectiveness of treatment is strongly related to the precision and accuracy of the stimulation applied, and the feasibility of advanced control approaches has been established in two recent clinical trials using iterative learning control algorithms.Commercially available large surface electrodes are not suitable for precise control of the hand and wrist due to their weak selectivity and simultaneous activation of several opposing muscles. An alternative is the use of electrode arrays where individual array element selection enables more precise control of muscle activation. Locating the optimal stimulation sites is critical to the effective application of surface electrode array stimulation and this paper develops a method for optimal selection of the stimulation sites. To overcome practical difficulties associated with efficient application of electrode array, the method utilises "Virtual Elements" and combinatorial optimization
Gait asymmetry: composite scores for mechanical analyses of sprint running
No full textGait asymmetry analyses are beneficial from clinical, coaching and technology perspectives. Quantifying overall athlete asymmetry would be useful in allowing comparisons between participants, or between asymmetry and other factors, such as sprint running performance. The aim of this study was to develop composite kinematic and kinetic asymmetry scores to quantify athlete asymmetry during maximal speed sprint running. Eight male sprint trained athletes (age 22±5 years, mass 74.0±8.7kg and stature 1.79±0.07m) participated in this study. Synchronised sagittal plane kinematic and kinetic data were collected via a CODA motion analysis system, synchronised to two Kistler force plates. Bilateral, lower limb data were collected during the maximal velocity phase of sprint running (velocity=9.05±0.37ms?1). Kinematic and kinetic composite asymmetry scores were developed using the previously established symmetry angle for discrete variables associated with successful sprint performance and comparisons of continuous joint power data. Unlike previous studies quantifying gait asymmetry, the scores incorporated intra-limb variability by excluding variables from the composite scores that did not display significantly larger (p<0.05) asymmetry than intra-limb variability. The variables that contributed to the composite scores and the magnitude of asymmetry observed for each measure varied on an individual participant basis. The new composite scores indicated the inter-participant differences that exist in asymmetry during sprint running and may serve to allow comparisons between overall athlete asymmetry with other important factors such as performance.<br/
Considerations of force plate transitions on centre of pressure calculation for maximal velocity sprint running
No full textThe aims of this study were to evaluate the accuracy of centre of pressure (COP) data obtained during transition of load across the boundary between two force plates, and secondly to examine the effect of such COP data on joint kinetics during sprint running performances. COP data were collected from two piezoelectric force plates as a trolley wheel was rolled across the boundary between the plates. Position data for the trolley were collected using an opto-electronic motion analysis system for comparison with COP data. Mean COP errors during transition across the plate boundary were 0.003 +/- 0.002 m relative to a control point. Kinematic and kinetic data were also collected from eight athletes during sprint running trials to demonstrate the sensitivity of the inverse dynamics analysis to COP error for the ground contact phase of the dynamic movement trials. Kinetic sensitivity to the COP error was assessed during the entire stance phase for the ankle, knee, and hip joints and was less than 5% and 3% for joint moment and power data, respectively. Based on the small COP error during transition across plate boundaries, it is recommended that foot contacts overlapping two force plates may be included in inverse dynamics analyses
Implications of intra-limb variability on asymmetry analyses.
No full textThe aim of this study was to investigate the effect of intra-limb variability on the calculation of asymmetry with the purpose of informing future analyses. Asymmetry has previously been quantified for discrete kinematic and kinetic variables; however, intra-limb variability has not been routinely included in these analyses. Synchronized lower-limb kinematic and kinetic data were collected from eight trained athletes (age 22 ± 5 years, mass 74.0 ± 8.7 kg, stature 1.79 ± 0.07 m) during maximal velocity sprint running. Asymmetry was quantified using a modified version of the symmetry angle for selected kinematic and kinetic variables. Significant differences (P < 0.05) between left and right values for each variable were calculated to indicate intra-limb variability relative to between-limb differences. Significant asymmetry was present in only 39% of kinematic variables and 23% of kinetic variables analysed. Large kinetic asymmetry values (>90%) were calculated for some athletes that were not significant, due to large intra-limb variability. Variables that displayed significant asymmetry were athlete-specific. Findings highlight the potential for misleading results if intra-limb variability is not included in asymmetry analyses. The exclusion of asymmetry scores for variables not displaying significant asymmetry will be useful when calculating overall asymmetry for different participants and could be applied to future running gait analyses
Upper limb and eye movement coordination during reaching tasks in people with stroke
No full textPurpose: to enhance understanding of the relationship between upper limb and eye movements during reaching tasks in people with stroke.Methods: eye movements were recorded from 10 control participants and 8 chronic stroke participants during a visual orienting task (Experiment 1) and a series of reaching tasks (Experiment 2). Stroke participants completed the reaching tasks using (i) their less impaired upper limb, (ii) their more impaired upper limb without support, and (iii) their more impaired upper limb, with support (SaeboMAS gravitational support and/or electrical stimulation). Participants were tested individually and completed both experiments in the same session.Results: oculomotor control and the coordination between the upper limb and the oculomotor system were found to be intact in stroke participants when no limb movements were required, or when the less impaired upper limb was used. However, when the more impaired upper limb was used, success and accuracy in reaching decreased and patterns of eye movements changed, with an observed increase in eye movements to the limb itself. With upper limb support, patterns of hand-eye coordination were found to more closely resemble those of the control group.Conclusion: deficits in upper limb motor systems result in changes in patterns of eye movement behavior during reaching tasks. These changes in eye movement behavior can be modulated by providing upper limb support
- …
