RESUMEN
The five-times-sit-to-stand test (FTSS) is an established assessment of lower limb strength, balance dysfunction and falls risk. Clinically, the time taken to complete the task is recorded with longer times indicating increased falls risk. Quantifying the movement using tri-axial accelerometers may provide a more objective and potentially more accurate falls risk estimate. 39 older adults, 19 with a history of falls, performed four repetitions of the FTSS in their homes. A tri-axial accelerometer was attached to the lateral thigh and used to identify each sit-stand-sit phase and sit-stand and stand-sit transitions. A second tri-axial accelerometer, attached to the sternum, captured torso acceleration. The mean and variation of the root-mean-squared amplitude, jerk and spectral edge frequency of the acceleration during each section of the assessment were examined. The test-retest reliability of each feature was examined using intra-class correlation analysis, ICC(2,k). A model was developed to classify participants according to falls status. Only features with ICC>0.7 were considered during feature selection. Sequential forward feature selection within leave-one-out cross-validation resulted in a model including four reliable accelerometer-derived features, providing 74.4% classification accuracy, 80.0% specificity and 68.7% sensitivity. An alternative model using FTSS time alone resulted in significantly reduced classification performance. Results suggest that the described methodology could provide a robust and accurate falls risk assessment.
Asunto(s)
Acelerometría/instrumentación , Accidentes por Caídas , Equilibrio Postural/fisiología , Medición de Riesgo/métodos , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Reproducibilidad de los ResultadosRESUMEN
The current study examined the role of vision in spatial updating and its potential contribution to an increased risk of falls in older adults. Spatial updating was assessed using a path integration task in fall-prone and healthy older adults. Specifically, participants conducted a triangle completion task in which they were guided along two sides of a triangular route and were then required to return, unguided, to the starting point. During the task, participants could either clearly view their surroundings (full vision) or visuo-spatial information was reduced by means of translucent goggles (reduced vision). Path integration performance was measured by calculating the distance and angular deviation from the participant's return point relative to the starting point. Gait parameters for the unguided walk were also recorded. We found equivalent performance across groups on all measures in the full vision condition. In contrast, in the reduced vision condition, where participants had to rely on interoceptive cues to spatially update their position, fall-prone older adults made significantly larger distance errors relative to healthy older adults. However, there were no other performance differences between fall-prone and healthy older adults. These findings suggest that fall-prone older adults, compared to healthy older adults, have greater difficulty in reweighting other sensory cues for spatial updating when visual information is unreliable.
Asunto(s)
Marcha/fisiología , Desempeño Psicomotor/fisiología , Percepción Espacial/fisiología , Baja Visión/fisiopatología , Percepción Visual/fisiología , Accidentes por Caídas/prevención & control , Accidentes por Caídas/estadística & datos numéricos , Anciano , Femenino , Humanos , Masculino , Modelos Biológicos , Distorsión de la Percepción/fisiología , Factores de RiesgoRESUMEN
One in three adults aged over 65 falls every year, resulting in enormous costs to society. Incidents of falling vary with time of day, peaking in the early morning. The aim of this study was to determine if the ability of instrumented gait and balance assessments to discriminate between participants based on their falls history varies diurnally. Body-worn sensors were used during a 3 m gait assessment and a series of quiet standing balance tests. Each assessment was performed four times during a single day under supervised conditions in the participant's homes. 40 adults aged over 60 years (19 fallers) participated in this study. A range of parameters were derived for each assessment, and the ability of each parameter to discriminate between fallers and non-fallers at each recording time was examined. The effect of falls history on single support time varied significantly with recording time, with a significantly reduced single support time observed at the first and last recording session of the day. Differences were observed between fallers and non-fallers for a range of other gait parameters; however, these effects did not vary with assessment time. The quiet standing assessments examined in this study revealed significant variations with falls history; however, the sensitivity of the examined quiet standing assessments to falls risk does not appear to be time dependent. These results indicate that, with the exception of single support time, the association of gait and quiet standing balance parameters with falls risk does not vary diurnally.
Asunto(s)
Accidentes por Caídas/estadística & datos numéricos , Ritmo Circadiano/fisiología , Marcha/fisiología , Equilibrio Postural/fisiología , Anciano , Anciano de 80 o más Años , Femenino , Evaluación Geriátrica , Humanos , Masculino , Persona de Mediana Edad , Monitoreo Ambulatorio , Factores de RiesgoRESUMEN
This study compares the performance of algorithms for body-worn sensors used with a spatiotemporal gait analysis platform to the GAITRite electronic walkway. The mean error in detection time (true error) for heel strike and toe-off was 33.9 ± 10.4 ms and 3.8 ± 28.7 ms, respectively. The ICC for temporal parameters step, stride, swing and stance time was found to be greater than 0.84, indicating good agreement. Similarly, for spatial gait parameters--stride length and velocity--the ICC was found to be greater than 0.88. Results show good to excellent concurrent validity in spatiotemporal gait parameters, at three different walking speeds (best agreement observed at normal walking speed). The reported algorithms for body-worn sensors are comparable to the GAITRite electronic walkway for measurement of spatiotemporal gait parameters in healthy subjects.
Asunto(s)
Algoritmos , Prueba de Esfuerzo/instrumentación , Marcha/fisiología , Monitoreo Ambulatorio/instrumentación , Monitoreo Ambulatorio/métodos , Reconocimiento de Normas Patrones Automatizadas/métodos , Transductores de Presión , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Adulto JovenRESUMEN
Falls in the elderly are a major problem worldwide with enormous associated economic and societal costs. Minimum ground clearance (MGC) is an important gait variable when considering trip-related falls risk. This study aimed to investigate the clinical relevance of inertial sensor derived parameters, previously shown to be related to MGC. Previous research by the authors reported a surrogate method for assessing minimum ground clearance (MGC) using shank-mounted inertial sensors in young controls. The present study tests this method on a cohort of 114 community dwelling elderly adults, with and without a history of falls, completing a 30 m continuous walk. Parameters based on the shank angular velocity signals that were shown to be associated with MGC showed significant differences (p<0.05) between fallers and non-fallers yet did not correlate strongly (r<0.7) with two standard measures of falls risk (TUG & BBS). Weak correlations were observed between the angular velocity derived parameters and gait velocity. We conclude that these parameters are clinically meaningful and therefore may constitute a new measure of falls risk.
Asunto(s)
Accidentes por Caídas/prevención & control , Marcha , Monitoreo Ambulatorio/métodos , Anciano , Estudios de Cohortes , Diseño de Equipo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Movimiento , Equilibrio Postural , Características de la Residencia , Medición de Riesgo , CaminataRESUMEN
An instrumented version of the five-times-sit-to-stand test was performed in the homes of a group of older adults, categorised as fallers or non-fallers. Tri-axial accelerometers were secured to the sternum and anterior thigh of each participant during the assessment. Accelerometer data were then used to examine the timing of the movement, as well as the root mean squared amplitude, jerk and spectral edge frequency of the mediolateral (ML) acceleration during the total assessment, each sit-stand-sit component and each postural transition (sit-stand and stand-sit). Differences between fallers and non-fallers were examined for each parameter. Six parameters significantly discriminated between fallers and non-fallers: sit-stand time, ML acceleration for the total assessment, and the ML spectral edge frequency for the complete assessment, individual sit-stand-sit components, as well as sit-stand and stand-sit transitions. These results suggest that each of these derived parameters would provide improved discrimination of fallers from non-fallers, for the cohort examined, than the standard clinical measure - the total time to complete the assessment. These results indicate that accelerometry may enhance the utility of the five-times-sit-to-stand test when assessing falls risk.
Asunto(s)
Accidentes por Caídas , Postura , Anciano , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
Wireless sensor networks have become increasingly common in everyday applications due to decreasing technology costs and improved product performance, robustness and extensibility. Wearable physiological monitoring systems have been utilized in a variety of studies, particularly those investigating ECG or EMG during human movement or sleep monitoring. These systems require extensive validation to ensure accurate and repeatable functionality. Here we validate the physiological signals (EMG, ECG and GSR) of the SHIMMER (Sensing Health with Intelligence, Modularity, Mobility and Experimental Reusability) against known commercial systems. Signals recorded by the SHIMMER EMG, ECG and GSR daughter-boards were found to compare well to those obtained by commercial systems.
Asunto(s)
Monitoreo Fisiológico/instrumentación , Algoritmos , Fenómenos Biomecánicos , Electrocardiografía/instrumentación , Electromiografía/instrumentación , Humanos , Movimiento , SueñoRESUMEN
Inertial sensors have become increasingly popular in gait analysis, due to their highly portable, low cost, and potentially wireless nature. However, accurate spatial gait analysis using few sensors remains a challenge. A gyroscope-based algorithm for spatial gait analysis is presented. This novel algorithm (SGA) uses data from a single gyroscope attached to each shank. The performance of the SGA was compared to that of an electronic walkway, GAITRite®. The two systems compared favorably, with a mean error in stride length of 0.09 ± 0.07 m, and a mean error in stride velocity of 0.11 ± 0.10 m/s. The error between the SGA and GAITRite was also similar to that reported by previous inertial sensor based algorithms. The relationship between stride length and stride velocity, as well as that of subject height and stride length was also examined. This new method provides an inexpensive, portable system for spatial or spatio-temporal gait analysis, which has potential for use in any location.
Asunto(s)
Aceleración , Algoritmos , Marcha/fisiología , Locomoción/fisiología , Modelos Biológicos , Monitoreo Ambulatorio/métodos , Simulación por Computador , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Hypertension is a condition of persistently elevated blood pressure, associated with increased cardiovascular risk. Non-invasive BP measurement using Korotkoff sounds is the most common method of screening for the condition. The possibility of inaccurate readings leading to a false diagnosis of hypertension (pseudo-hypertension) is of concern. Stiffened arteries in the elderly have been proposed as being the primary cause of pseudo-hypertension. Non-invasive detection of pseudo-hypertension remains problematic. This paper reviews clinical literature on pseudo hypertension and approaches to measuring the compressive stiffness of arteries, as well as biomechanical literature regarding models of arterial stiffness and the origin of Korotkoff sounds. Models of the latter show the importance of the relationship between transmural pressure and cross-sectional area (P1/Csa curve) of the brachial artery as it closes under the influence of the pressure cuff. The review concludes that future research on pseudo-hypertension should include development of new instrumentation to measure the P1/Csa curve of the brachial artery in vivo using non-invasive techniques suitable for application to an elderly population.
Asunto(s)
Arteriosclerosis/fisiopatología , Hipertensión/fisiopatología , Resistencia Vascular/fisiología , Animales , Arteriosclerosis/complicaciones , Humanos , Hipertensión/complicacionesRESUMEN
Stiffening of the brachial artery is implicated in pseudo-hypertension. To date, a reliable clinical predictor of the condition has not been developed. This paper describes the development of prototype instrumentation and methodology for measurement of the brachial artery transmural pressure/cross-sectional area relationship in vivo. The methodology has been validated using a model of an arm and a thin-walled rubber tube. Application of the technique to a healthy subject shows that the technique is viable and gives good reproducibility. Closure of the brachial artery with reducing transmural pressure is observed and recorded. The new technique has some important advantages over existing methodologies.