Estimating fall risk with inertial sensors using gait stability measures that do not require step detection

Falls have major consequences both at societal (health-care and economy) and individual (physical and psychological) levels. Questionnaires to assess fall risk are commonly used in the clinic, but their predictive value is limited. Objective methods, suitable for clinical application, are hence needed to obtain a quantitative assessment of individual fall risk. Falls in older adults often occur during walking and trunk position is known to play a critical role in balance control. Therefore, analysis of trunk kinematics during gait could present a viable approach to the development of such methods. In this study, nonlinear measures such as harmonic ratio (HR), index of harmonicity (IH), multiscale entropy (MSE) and recurrence quantification analysis (RQA) of trunk accelerations were calculated. These measures are not dependent on step detection, a potentially critical source of error. The aim of the present study was to investigate the association between the aforementioned measures and fall history in a large sample of subjects (42 fallers and 89 non-fallers) aged 50 or older. Univariate associations with fall history were found for MSE and RQA parameters in the AP direction; the best classification results were obtained for MSE with scale factor τ = 2 and for maximum length of diagonals in RQA (72.5% and 71% correct classifications, respectively). MSE and RQA were found to be positively associated with fall history and could hence represent useful tools in the identification of subjects for fall prevention programs. © 2013 Elsevier B.V

THE EFFECT OF WORD LENGTH, ORAL-MOTOR MOVEMENT, ARTICULATION, AND LEXICALITY ON GAIT AND BALANCE

Performing two tasks in dual-task situations is a requirement in activities of daily living. An inability to dual-task is demonstrated generally by diminished performance on one or both of the tasks. Performing a verbal task can produce a reduced ability to perform a gait task and to maintain balance. Impairment on either of these postural tasks can increase the likelihood of falling, particularly among older adults. Dual-task interference has been demonstrated to be significantly impacted by a number of characteristics of secondary verbal tasks (including dimensions of both motoric and cognitive complexity]. Previous studies have not, however, exerted sufficient control over articulation or cognitive-linguistic processing, within the secondary task. The studies presented in this thesis used a dual-task paradigm that manipulated word length, oral-motor movement, articulation, and lexicality, within a verbal task, while assessing the affects of dual-task interference on both gait and balance. A sample of healthy young adults (pilotstudy: 15 women; gait and balance studies: 20womenand20 men) were asked to repeat a series of verbal stimuli while walking approximately 6m, and while maintaining an independent upright posture for 10 seconds at a time. Participants also were asked to complete a test of perceptual speed, as an indicator of information processing speed, separate from the dual-task protocol. Results suggest that oral-motor movement, articulation, and lexicality had unique effects on dual-task performance, with women demonstrating significantly more dual-task interference than men. Furthermore, results suggested that the ability to dual-task is directly related to an individual’s information processing capacity. Results supported the capacity-sharing model of dual-task interferenc

Mediolateral Damping of an Overhead Body Weight Support System Assists Stability During Treadmill Walking

Background Body weight support systems with three or more degrees of freedom (3-DoF) are permissive and safe environments that provide unloading and allow unrestricted movement in any direction. This enables training of walking and balance control at an early stage in rehabilitation. Transparent systems generate a support force vector that is near vertical at all positions in the workspace to only minimally interfere with natural movement patterns. Patients with impaired balance, however, may benefit from additional mediolateral support that can be adjusted according to their capacity. An elegant solution for providing balance support might be by rendering viscous damping along the mediolateral axis via the software controller. Before use with patients, we evaluated if control-rendered mediolateral damping evokes the desired stability enhancement in able-bodied individuals. Methods A transparent, cable-driven robotic body weight support system (FLOAT) was used to provide transparent body weight support with and without mediolateral damping to 21 able-bodied volunteers while walking at preferred gait velocity on a treadmill. Stability metrics reflecting resistance to small and large perturbations were derived from walking kinematics and compared between conditions and to free walking. Results Compared to free walking, the application of body weight support per-se resulted in gait alterations typically associated with body weight support, namely increased step length and swing phase. Frontal plane dynamic stability, measured by kinematic variability and nonlinear dynamics of the center of mass, was increased under body weight support, indicating reduced balance requirements in both damped and undamped support conditions. Adding damping to the body weight support resulted in a greater increase of frontal plane stability. Conclusion Adding mediolateral damping to 3-DoF body weight support systems is an effective method of increasing frontal plane stability during walking in able-bodied participants. Building on these results, adjustable mediolateral damping could enable therapists to select combinations of unloading and stability specifically for each patient and to adapt this in a task specific manner. This could extend the impact of transparent 3-DoF body weight support systems, enabling training of gait and active balance from an early time point onwards in the rehabilitation process for a wide range of mobility activities of daily life

The role of conscious control in maintaining stable posture

© 2017 Elsevier B.V. This study aimed to examine the relationship between conscious control of movements, as defined by the Theory of Reinvestment (Masters & Maxwell, 2008; Masters, Polman, & Hammond, 1993), and both traditional and complexity-based COP measures. Fifty-three young adults (mean age = 20.93 ± 2.53 years), 39 older adults with a history of falling (mean age = 69.23 ± 3.84 years) and 39 older adults without a history of falling (mean age = 69.00 ± 3.72 years) were asked to perform quiet standing balance in single- and dual-task conditions. The results showed that higher scores on the Movement Specific Reinvestment Scale (MSRS; Masters, Eves, & Maxwell, 2005; Masters & Maxwell, 2008), a psychometric measure of the propensity for conscious involvement in movement, were associated with larger sway amplitude and a more constrained (less complex) mode of balancing in the medial–lateral direction for young adults only. Scores on MSRS explained approximately 10% of total variation in the medial–lateral sway measures. This association was not apparent under dual-task conditions, during which a secondary task was used to limit the amount of cognitive resources available for conscious processing. No relationship between postural control and score on the MSRS was found for either older adult fallers or non-fallers. Possible explanations for these results are discussed

Aquatic Therapy after Incomplete Spinal Cord Injury: Gait Initiation Analysis Using Inertial Sensors

: Populations with potential damage to somatosensory, vestibular, and visual systems or poor motor control are often studied during gait initiation. Aquatic activity has shown to benefit the functional capacity of incomplete spinal cord injury (iSCI) patients. The present study aimed to evaluate gait initiation in iSCI patients using an easy-to-use protocol employing four wearable inertial sensors. Temporal and acceleration-based anticipatory postural adjustment measures were computed and compared between dry-land and water immersion conditions in 10 iSCI patients. In the aquatic condition, an increased first step duration (median value of 1.44 s vs. 0.70 s in dry-land conditions) and decreased root mean squared accelerations for the upper trunk (0.39 m/s2 vs. 0.72 m/s2 in dry-land conditions) and lower trunk (0.41 m/s2 vs. 0.85 m/s2 in dry-land conditions) were found in the medio-lateral and antero-posterior direction, respectively. The estimation of these parameters, routinely during a therapy session, can provide important information regarding different control strategies adopted in different environments

Falls in older people: Examining risk factors in specific subgroups and the effectiveness of a specialist-led falls prevention intervention

Accidental falls remain an important healthcare issue for older people. We report on three studies examining risk predictors for further falls, falls-related hospital attendances and mortality, and then test the effectiveness of a hospital-based falls prevention intervention. A prospective study of 498 older people who attended an Emergency Department (E.D.) with a fall showed that age 80 years and older was the greatest predictor of further falls, with a 2-fold increased adjusted risk by 5 years (HR 2.00; 95% C.I. 1.42 – 2.82). Mortality following an E.D. presentation with a fall was 19% at 1 year, increasing to 52% by 5 years. Increasing age and assistance with ADLs predicted both ED re-presentation and mortality. Being female and falls due to syncope were protective. The Concord Health and Ageing in Men (CHAMP), is a longitudinal study of 1705 men. Previous history of falls was the most significant predictor of future falls (IRR 3.12; 95% C.I. 2.49 – 3.91) and falls injury hospitalisations at 10 years (HR 1.48; 95% C.I. 1.09 – 1.99) in this cohort. Risk factors for falls included increasing age, disability in ADLs, being single, dementia, having 3 or more comorbidities, polypharmacy and reduced visual acuity. Dementia was associated with 2-fold increased risk of falls injury hospitalisation at 10 years (HR 2.67; 95% C.I. 1.69 – 4.22). Men born in a non-English-speaking country and men who were still working were less likely to be hospitalised die to a fall injury. A randomised controlled trial (n = 81) of a specialist-led CONFABs clinic versus enhanced G.P. coordinated care, showed an increased rate of falls (IRR 2.39; 95% C.I. 1.09 – 5.27) and risk of falls (RR 1.79; 95% C.I. 1.10 – 2.96) at 1 year with the CONFABS clinic intervention. There was no significant difference in the rate of injurious falls or in the number of fractures between the interventions. Compliance with recommendations was similar in both groups, although more falls prevention strategies were recommended to the falls clinic participants. There are shared risk factors for falls, fall hospitalisations and mortality, with increasing age, functional disability and dementia the most important to consider. Falls prevention strategies may be successfully provided in General Practice, supported by specialist risk assessment and recommendations