Wearable inertial sensors for human movement analysis

Introduction: The present review aims to provide an overview of the most common uses of wearable inertial sensors in the field of clinical human movement analysis.Areas covered: Six main areas of application are analysed: gait analysis, stabilometry, instrumented clinical tests, upper body mobility assessment, daily-life activity monitoring and tremor assessment. Each area is analyzed both from a methodological and applicative point of view. The focus on the methodological approaches is meant to provide an idea of the computational complexity behind a variable/parameter/index of interest so that the reader is aware of the reliability of the approach. The focus on the application is meant to provide a practical guide for advising clinicians on how inertial sensors can help them in their clinical practice.Expert commentary: Less expensive and more easy to use than other systems used in human movement analysis, wearable sensors have evolved to the point that they can be considered ready for being part of routine clinical routine

Balance and Motor Control in Dynamic Tasks

openNella prima parte dello studio si è descritto il mantenimento dell’equilibrio in seguito a perturbazioni indotte da stimoli esterni. La risposta posturale è stata analizzata dal punto di vista dinamico, cinematico ed elettromiografico, ottenendo una descrizione completa dei meccanismi adottati per contrastare la perdita di equilibrio. Vari parametri sono stati estratti dallo spostamento del centro di pressione e del centro di massa e sulla base dell’attività muscolare acquisita mediante elettromiografia di superficie, con lo scopo di ottenere indici che correlino con le diverse caratteristiche della perturbazione. Sulla base dei dati cinematici sono state descritte le strategie posturali adottate per contrastare la perturbazione indotta, allo scopo di quantificare se differenti condizioni perturbative facciano sorgere differenti risposte, che prevedono l’uso di differenti strategie articolari. Infine il controllo dell’equilibrio è stato descritto attraverso un modello a doppio pendolo inverso, attraverso tecniche che, sebbene ben note ed impiegate in altri ambiti, risultano poco usate per la descrizione della postura in condizioni dinamiche. Nella seconda parte si è indagato il controllo della dinamica del cammino in termini di attività muscolare, acquisita su centinaia di passi consecutivi, permettendo un nuovo tipo di descrizione non basata solamente su parametri temporali ma anche sulla frequenza con cui ogni modalità di attivazione muscolare di presenta durante il cammino. I principali risultati includono la quantificazione dei pattern di co-contrazione dei flessori di caviglia e la loro ricorrenza durante il cammino. Si sono inoltre descritte le differenze legate al genere riguardanti l’attività dei principali muscoli dell’intero arto inferiore. Basandosi sui precedenti risultati si sono poi quantificate le differenze legate al genere nei pattern di co-contrazione degli antagonisti che regolano la meccanica dell’articolazione di caviglia durante il cammino.In the first part of this work a characterization of the upright stance recovery after balance perturbation administered through external stimuli was performed. Balance response has been analyzed in dynamics, kinematics and electromyographic terms, in order to obtain a complete description of which mechanisms are employed to withstand sudden stance perturbations. A series of parameters have been extracted from center of pressure and center of mass displacement and from electromyographic signals, acquired from lower limb and trunk muscles, in order to obtain a series of indexes which can correlate with the different characteristic of perturbations. From kinematic data, a description of the postural strategies adopted to withstand perturbations has been performed, in order to observe whether different perturbation conditions evoke different responses, employing different articular joints. Eventually, a first attempt to model perturbed upright stance through a double-link inverted pendulum is proposed, applying control systems seldom employed in describing this kind of dynamic motor task. In the second part, the motor control during the walking task was described in terms of muscular activity. Myoelectric signals were acquired in hundreds of consecutive strides, obtaining a new type of description, not only in terms of temporal parameters of muscles activity but also in terms of the occurrence frequency of each muscular activation modality during gait. The main outcomes include the description of co-contraction activity between ankle flexor muscles and the assessment of the recurrence of each co-activation pattern during walking. Furthermore, a description of the whole lower limb muscles behavior was performed, aimed to the quantification of gender-based differences in muscular recruitment during gait. Then, these two aspects were joined in assessing gender-related differences in co-contraction activity of muscles which control the ankle joint mechanics during walking.INGEGNERIA DELL'INFORMAZIONEMengarelli, AlessandroMengarelli, Alessandr

Changes in the Dynamics of Postural and Locomotor Control as a Result of Varying Task Demands

The aim of this study was to examine changes in postural and locomotor control under varying task demands. Three experiments were designed to address the impact that fast walking had on standing posture over time, slow walking had on gait dynamics over time, and the extent to which gait speed interacts with the ability to walk randomly. For experiment I, the aim was to identify the time course in which postural adaptation occurred while walking at faster than preferred speeds. Postural motion was assessed at specific intervals over a 35-min walking trial. Findings revealed that walking at a faster speed increased the amount, variability, and structure (Approximate Entropy-ApEn) of postural motion compared to baseline assessments. Subsequent trials following baseline assessments revealed a leveling-off for specific center of pressure (COP) variables and decline in path length, although heart rate (HR) and rate of perceived exertion (RPE) increased over the entire walking trial. In experiment II, the aim was to examine changes in stride-to-stride variability over time while walking at slower than preferred speeds. The results revealed an increased stride-to-stride variability and signal regularity (lower ApEn) during walking at 80% preferred walking speed (PWS) compared to PWS. After 10-15 mins a decrease stride-to-stride variability and increase in signal irregularity was seen. Changes leveled-off for the remainder of the session. Experiment III was designed to examine the effect that intentionally increasing variability (random) had on gait dynamics. Participants were asked to vary their gait while walking on a treadmill at three different speeds. The results revealed gait speed was a significant factor in the amount of variability (CV, range), with higher levels produced during the slower speed than at PWS and the faster speed. Higher levels of complexity (higher SampEn) were seen in stride time and knee joint motion during the random condition irrespective of gait speed. Overall, young adults are able to walk at speeds faster or slower than preferred as well as increase gait variability when instructed. These changes in postural and locomotor dynamics reveal that a healthy motor control system can quickly adapt to the task demands imposed upon it