Exoskeleton plantarflexion assistance for elderly

Elderly are confronted with reduced physical capabilities and increased metabolic energy cost of walking. Exoskeletons that assist walking have the potential to restore walking capacity by reducing the metabolic cost of walking. However, it is unclear if current exoskeletons can reduce energy cost in elderly. Our goal was to study the effect of an exoskeleton that assists plantarflexion during push-off on the metabolic energy cost of walking in physically active and healthy elderly. Seven elderly (age 69.3 ± 3.5 y) walked on treadmill (1.11 m s²) with normal shoes and with the exoskeleton both powered (with assistance) and powered-off (without assistance). After 20 min of habituation on a prior day and 5 min on the test day, subjects were able to walk with the exoskeleton and assistance of the exoskeleton resulted in a reduction in metabolic cost of 12% versus walking with the exoskeleton powered-off. Walking with the exoskeleton was perceived less fatiguing for the muscles compared to normal walking. Assistance resulted in a statistically nonsignificant reduction in metabolic cost of 4% versus walking with normal shoes, likely due to the penalty of wearing the exoskeleton powered-off. Also, exoskeleton mechanical power was relatively low compared to previously identified optimal assistance magnitude in young adults. Future exoskeleton research should focus on further optimizing exoskeleton assistance for specific populations and on considerate integration of exoskeletons in rehabilitation or in daily life. As such, exoskeletons should allow people to walk longer or faster than without assistance and could result in an increase in physical activity and resulting health benefits.     

Effects of buffer size and shape on associations between the built environment and energy balance

Uncertainty in the relevant spatial context may drive heterogeneity in findings on the built environment and energy balance. To estimate the effect of this uncertainty, we conducted a sensitivity analysis defining intersection and business densities and counts within different buffer sizes and shapes on associations with self-reported walking and body mass index. Linear regression results indicated that the scale and shape of buffers influenced study results and may partly explain the inconsistent findings in the built environment and energy balance literature.     

Walk Score and Australian adults' home-based walking for transport

The relationships of Walk Score, a publicly-accessible walkability assessment tool, with walking for transport to and from home were examined among a large representative sample of Australian adults aged 18–64 years (N=16,944). Residents in highly and somewhat walkable areas were twice and 1.4 times more likely to accumulate 30 min of walking per day compared to those in very car-dependent neighborhoods, respectively. Mean duration of walking was also longer for participants living in highly and somewhat walkable areas compared to those in very car-dependent areas. Walk Score has potential as a widely-applicable tool for identifying the walkability of local neighborhoods.     

Orthostatic hypotension and physical functioning in older adults: A systematic review and meta-analysis

BackgroundOrthostatic hypotension (OH) may negatively affect physical functioning and aggravate morbidities, but existing evidence is contradictory.MethodsMEDLINE (from 1946), PubMed (from 1966) and EMBASE databases (from 1947) were systematically searched for studies on the association of OH and physical functioning in older adults, categorized as: balance, gait characteristics, walking speed, Timed Up and Go time, handgrip strength (HGS), physical frailty, exercise tolerance, physical activity, activities of daily living (ADL), and performance on the Hoehn and Yahr scale (HY) and Unified Parkinson’s Disease Rating Scale (UPDRS). Study quality was assessed using the Newcastle Ottawa Scale.ResultsForty-two studies were included in the systematic review (29,421 individuals) and 29 studies in the meta-analyses (23,879 individuals). Sixteen out of 42 studies reported a significant association of OH with worse physical functioning. Meta-analysis showed a significant association of OH with impaired balance, ADL performance and HY/UPDRS III performance, but not with gait characteristics, mobility, walking speed, TUG, HGS, physical frailty, exercise tolerance, physical activity and UPDRS II performance.ConclusionsOH was associated with impaired balance, ADL performance and HY/UPDRS III performance, but not with other physical functioning categories. The results suggest that OH interventions could potentially improve some aspects of physical functioning.     

Time-integrated propulsive and braking impulses do not depend on walking speed

BackgroundEnhancing propulsion during walking is often a focus in physical therapy for those with impaired gait. However, there is no consensus in the literature for assessing braking and propulsion. Both are typically measured from the anterior-posterior ground reaction force (AP-GRF). While normalization of AP-GRF force by bodyweight is commonly done in the analysis, different methods for AP-GRF time axis normalization are used.Research questionDoes walking speed affect propulsion and/or braking, and how do different methods for calculating propulsion and braking impact the conclusion, in both healthy adults and those with lower limb impairment?MethodsWe investigated three different analysis methods for assessing propulsion. 1. BW-TimeIntegration: Bodyweight (BW) normalized time integration of AP-GRF (units of BWs). 2. BW-%StanceIntegration: BW normalized AP-GRF is resampled to percent stance phase prior to integration (units of BW%Stance). 3. BW-Peak: BW normalized peak force (units of BW). We applied these methods to two data sets. One data set included AP-GRFs from trials of slow, self-selected, and fast walking speeds for 203 healthy controls (HCs); a second data set included subjects with lower limb orthopedic injuries.ResultsUsing the BW-TimeIntegration method, we found no effect of walking speed on propulsion for HCs. Time integration over the longer stance phase of slower walking balanced the lower magnitude AP-GRFs of slower walking, resulting in a time-integrated impulse that was the same regardless of walking speed. In contrast, the other two methods that are not time integration methods found that propulsion increased with walking speed. Similarly, in the gait pathology data set, differences in results were found depending on the analysis method used.SignificanceFor many gait studies concerning propulsion and/or braking, the impulse measure used should be related to the body’s change of momentum, necessitating an analysis method with a time integration of the AP-GRF.     

Residual limb strength and functional performance measures in individuals with unilateral transtibial amputation

BackgroundIndividuals with lower limb amputation exhibit lower residual limb strength compared to their sound limb. Deficits in residual limb knee flexion and extension strength may impact functional performance during tasks relevant to daily living.Research questionDoes knee flexor and extensor strength in the residual limb impact functional outcome measures, such as walking energetics and performance metrics, in individuals with unilateral transtibial amputation?MethodsFourteen individuals with traumatic unilateral transtibial amputation were recruited for this observational study. Participants completed metabolic testing at three standardized speeds based on leg length, as well maximum isokinetic knee flexion and extension strength for both residual and sound limbs. Participants also completed a series of functional outcome tests, including a two-minute walk test, timed stair ascent test, and four-square step test. Walking energetics (metabolic cost, heart rate, and rating of perceived exertion) and performance metrics were compared to percent deficit of residual limb to sound limb knee flexion and extension muscle strength. A linear regression assessed significant relationships (p < 0.05).ResultsA significant relationship was observed between percent deficit of knee extension strength and heart rate (p = 0.024) at a fast walking speed. Additionally, percent deficit knee flexion strength related to rating of perceived exertion at slow and moderate walking speeds (p = 0.038, p = 0.024). Percent deficit knee extension strength related to two-minute walk time performance (p = 0.035) and percent deficit knee flexion strength related to timed stair ascent time (p = 0.025).SignificanceThese findings suggest the importance of strength retention of the residual limb knee flexion and extension musculature to improve certain functional outcomes in individuals with unilateral transtibial amputation.     

Treading on the unknown increases prefrontal activity: A pilot fNIRS study

BackgroundComplex walking conditions (e.g. dual tasking) have been associated with increased prefrontal (PFC) activity. However, most paradigms include a predictable environment, specifically, a predictable walking terrain. In the present study we investigate PFC activity under an unusual walking condition where each foot placement was on unexpected terrain, thus causing a mismatch between visuospatial perception and lower-extremity proprioception.Research objectiveTo assess whether PFC activity increases under unstable unpredictable conditions compared to unstable but predictable conditions.MethodsThis was a prospective study involving twenty healthy adults. Participants walked in two conditions: unstable but predictable, and unstable and unpredictable. To assess walking stability, both stride-time (ST) and stride-time variability (CV) were measured. To assess PFC activity, two wireless near-infrared spectroscopy devices were used. The group hemodynamic response (GHR) was calculated for each condition. For statistical analysis, a linear-mixed-effects model was used.ResultsWalking with unpredictable perturbations did not change the ST (t = 0.51, p = 0.61) but significantly increased the parameter CV (t = 11.74, p < 0.001). The GHR of both conditions indicated brief per-initiation PFC activity that was similar across conditions. However, when GHRs were calculated relative to normal walking (i.e., the participants’ own shoes), continuous activity was evident. Compared to the predictable condition, the unpredictable condition significantly increased this activity during steady-state walking (t = 2.13, p = 0.033).SignificanceObservations from the present study suggest that at least two neural components are present in the measured signal—a brief one, occurring per-initiation, and a continuous one, sensitive to the predictability of the terrain. The second component was accompanied by a decrease in walking stability. These results may contribute to our understanding of the control mechanism underlying gait and future planning of rehabilitation protocols.     

焦氏头针平衡区电针加康复治疗对中风患者步行能力的影响

目的探讨焦氏头针平衡区予电针治疗对中风患者步行能力的影响。方法将符合入选标准的中风患者随机分为对照组(普通针灸组)和治疗组(焦氏头针组)。两组在治疗前、治疗1个疗程后和治疗2个疗程后使用Fugl-Meyer下肢评分、Berg平衡评分和Holden步行分级进行评分。结果治疗1疗程后两组Fugl-Meyer、Berg、Holden步行分级均较前提升(P0.01),治疗组的Fugl-Meyer、Berg、Holden步行分级优于对照组,差异有统计学意义(P0.01),治疗2个疗程后两组Fugl-Meyer、Berg、Holden步行分级均较治疗前、治疗1个疗程后显著提升(P0.01),但两组间比较,差异无统计学意义(P0.05)。结论焦氏头针平衡区电针治疗能有效改善卒中患者的平衡,增加下肢能力,从而提高步行功能,降低跌倒风险。     

Changes to foot pressure pattern in post-stroke individuals who have started to walk independently during the convalescent phase

BackgroundAbnormal foot contact patterns following stroke affect functional gait; however, objective analysis targeting independent walking is lacking.Research questionHow do walking abilities and foot pressure patterns differ between post-stroke individuals who achieved independent walking and healthy controls? Secondarily, how do the abilities and patterns in post-stroke individuals change before and after achieving independent walking? Can these changes become criteria for permitting independent walking?MethodsTwenty-eight individuals with hemiplegia and 32 controls were enrolled. Motor dysfunction score (MDScore), walking speed (WSpeed), and foot pressure patterns were measured when they were first able to walk without orthosis or physical assistance (1st assessment) and when they achieved independent walking around discharge (2nd assessment). Foot pressure patterns were measured using insole-type foot pressure-measuring system. Ratios of partial foot pressure to body weight (%PFP), ratios of anteroposterior length of center of pressure (COP; %Long), and backward moving distance of COP to the foot length (%Backward) were calculated. Parameters during the 2nd assessment were compared with those of controls and those during the 1st assessment. During the 2nd assessment, relationships among the parameters, MDScore, and WSpeed were analyzed.ResultsDuring the 2nd assessment, no difference was observed in both %Long and %Backward between the non-paretic limbs and the controls. While the %Backward was higher, the %PFP of toes and %Long were lower in the paretic limb than in the controls. Although the %Backward was lower, both %PFP of toes and %Long of the paretic limb were higher in the 2nd assessment than in the 1st assessment. During the 2nd assessment, both %Long and % Backward values of the paretic limb moderately correlated with MDScore and WSpeed.SignificanceAfter improvement of foot pressure in toes, both an increase in anteroposterior length and a decrease in backward moving of COP path were objective signs permitting independent walking.