The biomechanics of human locomotion

Includes bibliographical references. The thesis on CD-ROM includes Animate, GaitBib, GaitBook and GaitLab, four quick time movies which focus on the functional understanding of human gait. The CD-ROM is available at the Health Sciences Library

Foot and Ankle Impairments Affecting Mobility in Stroke

Introduction: Altered foot characteristics are common in people with stroke, with a third presenting with abnormal foot posture which is associated with ambulatory difficulties. Understanding the relationship between measures of foot and ankle impairment and their association with mobility and balance outcomes is therefore important; however, poor clinimetric properties of foot and ankle measures after stroke precludes evaluation of these relationships. Therefore, this research, undertaken as part of a multicentred research project, had the following aims: Study 1: To evaluate the clinimetric properties (feasibility, test–retest reliability, and clinical relevance) of measures of foot and ankle impairments, for application in people with stroke. Study 2: To examine how these measures differ between people with stroke and normal controls; and whether they are associated with mobility and balance outcomes. Methods: In Study 1, community-dwelling people with stroke, able to walk 10 m (metres), attended two testing sessions to evaluate the clinimetric properties of different foot and ankle measures. These included: static foot posture and dynamic foot loading (peak plantar pressure, PPP, contact area, CA and centre of pressure, CP) using a plantar pressure mat; isometric muscle strength using a hand-held dynamometer (HHD); peak ankle and hallux dorsiflexion and stiffness using bespoke rigs; and ankle plantarflexion spasticity using the Tardieu scale. Statistical analysis used intraclass correlation coefficients (ICCs₍₃,₁₎), standard error of measurement (SEM) and Bland–Altman plots. In Study 2, measures identified as reliable from Study 1 were incorporated in a cross-sectional study design. Participants were recruited from acute and community neurological services in East London and North Devon. Statistical analysis tested the differences between groups and between affected limbs in people with stroke. Impairment measures were evaluated using multivariate regression analysis for their association with functional outcomes: walking speed (over 10 m); Timed Up and Go (TUAG), Forward Functional Reach Test (FFRT) and presence of falls (> 1 in the last 3 months). Results: In Study 1, 21 people with stroke tested the measures. These were found to be feasible and easy to administer, although loss of data (up to 33%) was observed. All measures had moderate to excellent test–retest reliability (coefficients 0.50‒0.98), except ankle plantarflexion stiffness (ICCs₍₃,₁₎ = 0.00‒0.11). In Study 2, there were significant differences in all measures between people with stroke (n = 180) and controls (n = 46), apart from static foot posture (p = 0.670), toe deformity (p = 0.782) and peak hallux dorsiflexion (p = 0.320). Between limb differences were identified for all measures except foot posture (p = 0.489) and foot CA (p > 0.05). Multicollinearity analysis found 10 measures appropriate for multivariate regression which identified the following R² and variance explained: 59% walking speed (R² = 0.543); 49% TUAG (R² = 0.435); 36% FFRT (R² = 0.285) and 26% for Falls Presence. Conclusion: The study demonstrated that seven foot and ankle measures of impairment after stroke were clinically feasible, reliable and associated with mobility and balance outcomes. The measures were ankle and foot isometric muscle strength, sway velocity, PPP (RFT and FFT), CA (MFT and FFT) and peak ankle dorsiflexion. These measures can now be incorporated into research to examine methods to improve the treatment of foot and ankle after stroke

Neuromuscular Control Strategy during Object Transport while Walking: Adaptive Integration of Upper and Lower Limb Movements

When carrying an object while walking, a significant challenge for the central nervous system (CNS) is to preserve the object’s stability against the inter-segmental interaction torques and ground reaction forces. Studies documented several strategies used by the CNS: modulation of grip force (GF), alterations in upper limb kinematics, and gait adaptations. However, the question of how the CNS organizes the multi-segmental joint and muscle coordination patterns to deal with gait-induced perturbations remains poorly understood. This dissertation aimed to explore the neuromuscular control strategy utilized by the CNS to transport an object during walking successfully. Study 1 examined the inter-limb coordination patterns of the upper limbs when carrying a cylinder-shaped object while walking on a treadmill. It was predicted that transporting an object in one hand would affect the movement pattern of the contralateral arm to maintain the overall angular momentum. The results showed that transporting an object caused a decreased anti-phase coordination, but it did not induce significant kinematic and muscle activation changes in the unconstrained arm. Study 2 examined muscle synergy patterns for upper limb damping behavior by using non-negative matrix factorization (NNMF) method. Four synergies were identified, showing a proximal-to-distal pattern of activation preceding heel contacts. Study 3 examined the effect of different precision demands (carrying a cup with or without a ball) and altered visual information (looking forward vs. looking at an object) on the upper limb damping behavior and muscle synergies. Increasing precision demand induced stronger damping behavior and increased the electromyography (EMG) activation of wrist/hand flexors and extensors. The NNMF results replicated Study 2 in that the stabilization of proximal joints occurred before the distal joints. The results indicated that the damping incorporates tonic and phasic muscle activation to ensure object stabilization. Overall, three experiments showed that the CNS adopts a similar synergy pattern regardless of task constraint or altered gaze direction while modulating the amount of muscle activation for object stabilization. Kinematic changes can differ depending on the different levels of constraint, as shown in the smaller movement amplitude of the shoulder joint in the transverse plane during the task with higher precision demand

The study of individual perception and neural control underlying movement in coordinating postural control when there is an increase in complexity of environmental and task constraints in CAI individuals compared to healthy controls

Individuals with Chronic Ankle Instability (CAI) commonly exhibit postural control (stability, adaptation) deficits and altered gait (walking, running) mechanics (Hertel, 2008; Hertel and Corbett, 2019). These impairments in motor behaviors have been hypothesized to be a result of inadequate, yet inherent interactions between individual perception (i.e., sensory systems) and movement (action) integrated at the central nervous system (CNS), resulting in less flexible and adaptable sensorimotor systems. Flexibility and adaptability of sensorimotor systems reflecting on underlying biological noise (movement variability) are critical to coordinate the sensory reweighting system. The sensory reweighting system assigns a relative weight to each sensory system based on the complexity of organismic, environmental, and task constraints to convey redundant and convergent sensory feedback at the CNS. An adequate sensory reweighting system results in sufficient multisensory integration by filtering all potential distractors, the irrelevant sensory information, to the context (e.g., task goals). Successful multisensory integration allows the CNS to integrate the context-relevant sensory information necessary to manage postural control that is the foundation of motor control to achieve suitable performance and adapt to a sudden environmental change. However, the gap exists in the literature to understand the integration phenomenon on how individual elements (i.e., sensory reweighting system, movement variability) contribute to the interaction between perception and movement, especially when environmental and task constraints increase in the same cohort of participants with and without CAI. Therefore, the primary purpose of this study was to understand the modulation of 1) the sensory reweighting system and postural control, 2) postural adaptation to a sudden change in the environment in the direction of lateral ankle sprain mechanisms, and 3) movement variability, an underlying biological noise pertaining to postural control, when the complexity of environmental and task constraints are manipulated in CAI individuals compared to healthy controls. A total of 44 physically active individuals, consisting of 22 individuals with CAI (13 females, 9 males; age: 26.09 ± 5.76 years; height: 172.25 ± 9.76 cm; weight: 76.18 ± 14.91 kg) and 22 individuals without CAI (13 females, 9 males; age: 25.41 ± 5.92 years; height: 169.70 ± 9.32 cm; weight: 71.98 ± 14.79 kg) volunteered to participate in this mixed-model repeated-measures study. The NeuroCom Sensory Organization Test (SOT) and Adaptation Test (SMART EquiTest, NeuroCom International Inc., Clackamas, OR) were utilized to examine postural control (equilibrium scores), postural adaptation (sway energy scores), the sensory reweighting system (sensory reweighting ratios), and movement variability (sample entropy) while controlling posture in double- and single-limb (injured, uninjured) stances in individuals with and without CAI. Interestingly, CAI individuals controlled posture very similar to healthy controls. The unique finding of this study was that group differences in the sensory reweighting system depended on both task constraints and sensory systems; CAI individuals upweighted on vestibular feedback when the SOT manipulated somatosensory and visual feedback while controlling posture in the injured-limb. Both groups weighted on somatosensory and visual feedback similarly with continuous emphasis on vision during individual tasks (stance limbs: double, injured, uninjured). Therefore, we contend CAI individuals upweighted on vestibular feedback, which is an independent sole veridical reference to self-motion, when sensory conflicts and task constraints became greater standing in the injured-limb. These findings also imply an effective multisensory integration among CAI. CAI individuals exhibited respective superior postural adaptation to a sudden environmental change in a support surface with plantarflexion rotation and in the uninjured-limb than healthy controls. Superior postural adaptation is indicative of pre-programmed feedforward motor control. In addition, lower movement variability in postural control was noted in the uninjured- and injured-limbs in CAI. Group differences in movement variability depended on task constraints: those individuals with CAI lowered variability in the uninjured-limb when no sensory feedback was manipulated, and in both the uninjured- and injured-limbs when they were forced to reweight on vestibular feedback with manipulation of somatosensory and visual feedback. Lowered movement variability exhibited with an increase in task constraints in the injured- and uninjured-limbs may be indicative of a mechanism that CAI implemented to provide a boundary to freeze the degree-of-freedom (redundancy in sensory feedback) to achieve effective multisensory integration. Collectively, our findings of superior postural adaptation and lower movement variability in postural control for CAI may imply an existent change in central organization and implementation of supraspinal mechanisms of postural control. Furthermore, postural control, postural adaptation, and movement variability in individuals with and without CAI depended on the environmental or task constraints. Environment- and task-dependent postural control, postural adaptation, and movement variability contribute to motor behaviors throughout the lifespan. Therefore, taking a multisensory-feedback approach by recognizing when to increase environmental and task constraints may optimize rehabilitation intervention to prevent subsequent ankle sprains in individuals with CAI

Computational Intelligence in Electromyography Analysis

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG may be used clinically for the diagnosis of neuromuscular problems and for assessing biomechanical and motor control deficits and other functional disorders. Furthermore, it can be used as a control signal for interfacing with orthotic and/or prosthetic devices or other rehabilitation assists. This book presents an updated overview of signal processing applications and recent developments in EMG from a number of diverse aspects and various applications in clinical and experimental research. It will provide readers with a detailed introduction to EMG signal processing techniques and applications, while presenting several new results and explanation of existing algorithms. This book is organized into 18 chapters, covering the current theoretical and practical approaches of EMG research

Proceedings SIAMOC 2019

Il congresso annuale della Società Italiana di Analisi del Movimento in Clinica, giunto quest'anno alla sua ventesima edizione, ritorna a Bologna, che già ospitò il terzo congresso nazionale nel 2002. Il legame tra Bologna e l'analisi del movimento è forte e radicato, e trova ampia linfa sia nel contesto accademico che nel ricco panorama di centri clinici d'eccellenza. Il congresso SIAMOC, come ogni anno, è l’occasione per tutti i professionisti dell’ambito clinico, metodologico ed industriale di incontrarsi, presentare le proprie ricerche e rimanere aggiornati sulle più recenti innovazioni nell’ambito dell’applicazione clinica dei metodi di analisi del movimento. Questo ha contribuito, in questi venti anni, a fare avanzare sensibilmente la ricerca italiana nel settore, conferendole un respiro ed un impatto internazionale, e a diffonderne l'applicazione clinica per migliorare la valutazione dei disordini motori, aumentare l'efficacia dei trattamenti attraverso l'analisi quantitativa dei dati e una più focalizzata pianificazione dei trattamenti, ed inoltre per quantificare i risultati delle terapie correnti

Proceedings SIAMOC 2019

Il congresso annuale della Società Italiana di Analisi del Movimento in Clinica, giunto quest'anno alla sua ventesima edizione, ritorna a Bologna, che già ospitò il terzo congresso nazionale nel 2002. Il legame tra Bologna e l'analisi del movimento è forte e radicato, e trova ampia linfa sia nel contesto accademico che nel ricco panorama di centri clinici d'eccellenza. Il congresso SIAMOC, come ogni anno, è l’occasione per tutti i professionisti dell’ambito clinico, metodologico ed industriale di incontrarsi, presentare le proprie ricerche e rimanere aggiornati sulle più recenti innovazioni nell’ambito dell’applicazione clinica dei metodi di analisi del movimento. Questo ha contribuito, in questi venti anni, a fare avanzare sensibilmente la ricerca italiana nel settore, conferendole un respiro ed un impatto internazionale, e a diffonderne l'applicazione clinica per migliorare la valutazione dei disordini motori, aumentare l'efficacia dei trattamenti attraverso l'analisi quantitativa dei dati e una più focalizzata pianificazione dei trattamenti, ed inoltre per quantificare i risultati delle terapie correnti

Detecting kinematic gait abnormalities in people with multiple sclerosis using clinically practical measures

The effects of multiple sclerosis (MS) on the central nervous system often manifest as abnormalities in gait kinematics. Clinically practical, valid, and reliable measures of gait kinematics are necessary to address research and clinical questions about MS. Wireless flexible electrogoniometry (EG) is a clinically practical measure of joint angles. The GAITRite walkway system is a clinically practical, valid and reliable measure of temporal and spatial gait characteristics. The overall objective of this two-study research project was to explore whether these clinically practical measures of gait kinematics can be used to accurately detect gait abnormalities in people with multiple sclerosis. Study 1 examined the reliability and validity of EG and Study 2 examined the gait kinematics of people with MS (PWMS) using EG and GAITRite. For Study 1, angle at initial contact and total joint excursion were measured by EG at both the knee and ankle while ten healthy adults walked at a self-selected comfortable speed. Measurements were repeated for two testers and two visits to assess reliability. The same variables were measured concurrently with three-dimensional motion analysis (3D) to assess validity. For all variables, reliability was good as indicated by low measurement error and validity was good as indicated by association and agreement of EG with 3D. For Study 2, the same joint angles, along with speed, cadence, step length, stride length, stance duration and double support duration were assessed for six PWMS and six controls without MS. PWMS showed significantly reduced speed, cadence, and ankle excursion and increased stance and double support duration as previously shown with 3D. Spasticity and/or instability may lead to these kinematic gait abnormalities in PWMS; however, reduced velocity may confound this interpretation by affecting the other observed gait abnormalities. Further research about the determinants of gait dysfunction in PWMS is required. EG and GAITRite are clinically practical, valid and reliable measures of gait kinematics and should be included in further clinic-based research to determine which kinematic gait abnormalities are causes and which are effects of the observed decrease in gait speed in PWMS