Real-time feedback control of split-belt ratio to induce targeted step length asymmetry.

INTRODUCTION: Split-belt treadmill training has been used to assist with gait rehabilitation following stroke. This method modifies a patient's step length asymmetry by adjusting left and right tread speeds individually during training. However, current split-belt training approaches pay little attention to the individuality of patients by applying set tread speed ratios (e.g., 2:1 or 3:1). This generalization results in unpredictable step length adjustments between the legs. To customize the training, this study explores the capabilities of a live feedback system that modulates split-belt tread speeds based on real-time step length asymmetry. MATERIALS AND METHODS: Fourteen healthy individuals participated in two 1.5-h gait training sessions scheduled 1 week apart. They were asked to walk on the Computer Assisted Rehabilitation Environment (CAREN) split-belt treadmill system with a boot on one foot to impose asymmetrical gait patterns. Each training session consisted of a 3-min baseline, 10-min baseline with boot, 10-min feedback with boot (6% asymmetry exaggeration in the first session and personalized in the second), 5-min post feedback with boot, and 3-min post feedback without boot. A proportional-integral (PI) controller was used to maintain a specified step-length asymmetry by changing the tread speed ratios during the 10-min feedback period. After the first session, a linear model between baseline asymmetry exaggeration and post-intervention asymmetry improvement was utilized to develop a relationship between target exaggeration and target post-intervention asymmetry. In the second session, this model predicted a necessary target asymmetry exaggeration to replace the original 6%. This prediction was intended to result in a highly symmetric post-intervention step length. RESULTS AND DISCUSSION: Eleven out of 14 participants (78.6%) developed a successful relationship between asymmetry exaggeration and decreased asymmetry in the post-intervention period of the first session. Seven out of the 11 participants (63.6%) in this successful correlation group had second session post-intervention asymmetries of < 3.5%. CONCLUSIONS: The use of a PI controller to modulate split-belt tread speeds demonstrated itself to be a viable method for individualizing split-belt treadmill training.

The Responsiveness of Gait and Balance Outcomes to Disease Progression in Friedreich Ataxia.

To identify gait and balance measures that are responsive to change during the timeline of a clinical trial in Friedreich ataxia (FRDA), we administered a battery of potential measures three times over a 12-month period. Sixty-one ambulant individuals with FRDA underwent assessment of gait and balance at baseline, 6 months and 12 months. Outcomes included GAITRite® spatiotemporal gait parameters; Biodex Balance System Postural Stability Test (PST) and Limits of Stability; Berg Balance Scale (BBS); Timed 25-Foot Walk Test; Dynamic Gait Index (DGI); SenseWear MF Armband step and energy activity; and the Friedreich Ataxia Rating Scale Upright Stability Subscale (FARS USS). The standardised response mean (SRM) or correlation coefficients were reported as effect size indices for comparison of internal responsiveness. Internal responsiveness was also analysed in subgroups. SenseWear Armband daily step count had the largest effect size of all the variables over 6 months (SRM = -0.615), while the PST medial-lateral index had the largest effect size (SRM = 0.829) over 12 months. The FARS USS (SRM = 0.824) and BBS (SRM = -0.720) were the only outcomes able to detect change over 12 months in all subgroups. The DGI was the most responsive outcome in children, detecting a mean change of -2.59 (95% CI -3.52 to -1.66, p < 0.001, SRM = -1.429). In conclusion, the FARS USS and BBS are highly responsive and can detect change in a wide range of ambulant individuals with FRDA. However, therapeutic effects in children may be best measured by the DGI.

Superposition principle applies to human walking with two simultaneous interventions.

Gait rehabilitation therapies provide adjusted sensory inputs to modify and retrain walking patterns in an impaired gait. Asymmetric walking is a common gait abnormality, especially among stroke survivors. Physical therapy interventions using adaptation techniques (such as treadmill training, auditory stimulation, visual biofeedback, etc.) train gait toward symmetry. However, a single rehabilitation therapy comes up short of affecting all aspects of gait performance. Multiple-rehabilitation therapy applies simultaneous stimuli to affect a wider range of gait parameters and create flexible training regiments. Understanding gait responses to individual and jointly applied stimuli is important for developing improved and efficient therapies. In this study, 16 healthy subjects participated in a four-session experiment to study gait kinetics and spatiotemporal outcomes under training. Each session consisted of two stimuli, treadmill training and auditory stimulation, with symmetric or asymmetric ratios between legs. The study hypothesizes a linear model for gait response patterns. We found that the superposition principle largely applies to the gait response under two simultaneous stimuli. The linear models developed in this study fit the actual data from experiments with the r-squared values of 0.95 or more.

Unique Noncontact Monitoring of Human Respiration and Sweat Evaporation Using a CsPb2Br5-Based Sensor.

Respiration monitoring and human sweat sensing have promising application prospects in personal healthcare data collection, disease diagnostics, and the effective prevention of human-to-human transmission of fatal viruses. Here, we have introduced a unique respiration monitoring and touchless sensing system based on a CsPb2Br5/BaTiO3 humidity-sensing layer operated by water-induced interfacial polarization and prepared using a facile aerosol deposition process. Based on the relationship between sensing ability and layer thickness, the sensing device with a 1.0 µm thick layer was found to exhibit optimal sensing performance, a result of its ideal microstructure. This sensor also exhibits the highest electrical signal variation at 0.5 kHz due to a substantial polarizability difference between high and low humidity. As a result, the CsPb2Br5/BaTiO3 sensing device shows the best signal variation of all types of breath-monitoring devices reported to date when used to monitor sudden changes in respiratory rates in diverse situations. Furthermore, the sensor can effectively detect sweat evaporation when placed 1 cm from the skin, including subtle changes in capacitance caused by finger area and motion, skin moisture, and contact time. This ultrasensitive sensor, with its fast response, provides a potential new sensing platform for the long-term daily monitoring of respiration and sweat evaporation.

Human Gait Analysis Metric for Gait Retraining.

The combined gait asymmetry metric (CGAM) provides a method to synthesize human gait motion. The metric is weighted to balance each parameter's effect by normalizing the data so all parameters are more equally weighted. It is designed to combine spatial, temporal, kinematic, and kinetic gait parameter asymmetries. It can also combine subsets of the different gait parameters to provide a more thorough analysis. The single number quantifying gait could assist robotic rehabilitation methods to optimize the resulting gait patterns. CGAM will help define quantitative thresholds for achievable balanced overall gait asymmetry. The study presented here compares the combined gait parameters with clinical measures such as timed up and go (TUG), six-minute walk test (6MWT), and gait velocity. The comparisons are made on gait data collected on individuals with stroke before and after twelve sessions of rehabilitation. Step length, step time, and swing time showed a strong correlation to CGAM, but the double limb support asymmetry has nearly no correlation with CGAM and ground reaction force asymmetry has a weak correlation. The CGAM scores were moderately correlated with TUG and strongly correlated to 6MWT and gait velocity.

Relearning functional and symmetric walking after stroke using a wearable device: a feasibility study.

BACKGROUND: Gait impairment is a common consequence of stroke and typically involves a hemiparetic or asymmetric walking pattern. Asymmetric gait patterns are correlated with decreased gait velocity and efficiency as well as increased susceptibility to serious falls and injuries. RESEARCH QUESTION: This paper presents an innovative device worn on a foot for gait rehabilitation post stroke. The device generates a backward motion to the foot, which is designed to exaggerate the existing step length asymmetry while walking over ground. We hypothesize this motion will decrease gait asymmetry and improve functional walking in individuals with chronic stroke. METHODS: Six participants with chronic stroke, more than one year post stroke, received four weeks of gait training with three sessions per week. Each session included 30 min of walking over ground using the wearable device. Gait symmetry and functional walking were assessed before and after training. RESULTS: All participants improved step length symmetry, and four participants improved double limb support symmetry. All participants improved on all three functional outcomes (gait velocity, Timed Up and Go Test, and 6-Minute Walk Test), and five participants improved beyond the minimal detectable change or meaningful change in at least one functional outcome. CONCLUSION: The results indicate that the presented device may help improve stroke patients' walking ability and warrant further study. A gait training approach using this new device may enable and expand long-term continuous gait rehabilitation outside the clinic following stroke. TRIAL REGISTRATION: NCT02185404. Registered July 9, 2014, https://clinicaltrials.gov/ct2/show/NCT02185404.

Effect of Synthesis Time and Composition on Magnetic Properties of FeCo Nanoparticles by Polyol Method.

This study investigated the effect of synthesis time and composition on magnetic properties of FeCo nanoparticles. Fe75Co25, Fe66Co34, Fe52Co48 nanoparticles were synthesized by the polyol method. The saturation magnetization of Fe75 Co25, Fe66Co34, Fe52Co48 nanoparticles was 178 emu/g, 191 emu/g and 197 emu/g, respectively. The coercivity of Fe75 Co25, Fe66Co34, Fe52Co48 was 113 Oe, 131 Oe and 89.2 Oe respectively. The synthesis time of Fe52Co48 nanoparticles was also varied (2 h and 3 h) to determine the optimal synthesis time. The saturation magnetization of Fe52Co48 synthesized for 2 h, 3 h was 243 emu/g, 202 emu/g, respectively. The coercivity of Fe52Co48 synthesized for 2 h and 3 h was 46 Oe and 111 Oe, respectively. The highest saturation magnetization and lowest coercivity was obtained using a synthesis time of 2 h. Based on these results, it was confirmed that Fe52Co48 had the highest saturation magnetization and lowest coercivity among all of the compositions tested, and optimal synthesis time was 2 h.

Longitudinal gait and balance decline in Friedreich's Ataxia: A pilot study.

INTRODUCTION: Friedreich's Ataxia (FA) is a devastating, progressive, neurodegenerative disease. Objective measures that detect changes in neurological function in FA patients are needed to facilitate therapeutic clinical trials. The purpose of this pilot study was to analyze longitudinal changes in gait and balance in subjects with FA using the GAITRite Walkway System® and Biodex Balance System™, respectively, and to test the ability of these measures to detect change over time compared to the Friedreich's Ataxia Rating Scale (FARS). METHODS: This was a 24-month longitudinal study comparing ambulatory FA subjects with age- and gender-matched, healthy controls. Eight FA subjects and 8 controls were tested at regular intervals using the GAITRite and Biodex Balance systems and the FARS. RESULTS: In the FA group, comfortable and fast gait velocity declined 8.0% and 13.9% after 12 months and 24.1% and 30.3% after 24 months, respectively. Postural stability indices increased in FA subjects an average of 41% from baseline to 24 months, representing a decline in balance. Subjects with FA also demonstrated a 17.7% increase in FARS neurological exam scores over 24 months. There were no changes in gait or balance variables in controls. In the FA group, multiple gait and balance measures correlated significantly with FARS neurological exam scores. CONCLUSIONS: The GAITRite and Biodex Balance systems provided objective and clinically relevant measures of functional decline in subjects with FA that correlated significantly with performance measures in the FARS. Gait velocity may be an important objective measure to identify disease progression in adults with FA.

Differences in Military Obstacle Course Performance Between Three Energy-Storing and Shock-Adapting Prosthetic Feet in High-Functioning Transtibial Amputees: A Double-Blind, Randomized Control Trial.

BACKGROUND: Approximately 683 persons engaged in military service experienced transtibial amputation (TTA) related to recent war in Iraq and Afghanistan. Military TTAs function at a level beyond basic ambulation. No empirical data demonstrate which higher functioning prosthetic feet maximize injured service personnel's ability to continue performing at a level commensurate with return to duty. This study's purpose was to determine which of three high-functioning, energy-storing prosthetic feet maximize performance and preference in a field obstacle course (OC) and to quantify physical performance differences between TTAs and high-functioning nonamputees. PROCEDURES: A randomized, double-blind, repeated measures experimental design compared three prosthetic feet (Ossur Variflex, Endolite Elite Blade, and Ossur Re-Flex Rotate) during performance on a field OC. TTAs accommodated with study feet and the OC before assessment. 14 TTAs and 14 nonamputee controls completed the course. Subjective and objective performance differences were compared across feet conditions and between groups. RESULTS: Total OC completion times were similar between prosthetic feet: Elite-Blade (419 seconds ± 130), Variflex (425 seconds ± 144), and Re-Flex Rotate (444 seconds ± 220). Controls' OC completion time (287.2 seconds ± 58) was less (p ≤ 0.05) than TTA times. In total, controls had faster completion times (p ≤ 0.05) compared to all prosthetic feet conditions in 13/17 obstacles. Re-Flex Rotate had 2 additional obstacles different (p ≤ 0.05) than controls and required more time to complete. Median RPE values were lower (p ≤ 0.05) for controls than TTA regardless of foot. Regarding foot preference for OC completion, 7/14 (50%) preferred Elite Blade, 5/14 (36%) preferred Re-Flex Rotate, and the remaining 2/14 (14%) preferred Variflex. CONCLUSION: Controls completed the OC faster and with less effort than TTAs regardless of prosthetic foot. No clear differences in prosthetic feet emerged during OC completion; however, individual task performance, perceived effort, and preference resulted in trends of slight performance improvement with and preference for Elite Blade, a dual function energy-storing and return foot combined with vertical shock absorption. Understanding how to maximally improve performance in such functional tasks may allow service members to best sustain physical fitness, return to their military occupational specialty and possibly in-theater duty.

Correlations between residual limb length and joint moments during sitting and standing movements in transfemoral amputees.

BACKGROUND AND AIM: Longer residual limb lengths provide an increased lever arm. Longer residual limbs may produce increased joint moments; the two may be correlated. These correlations have not been evaluated in transfemoral amputees during transitional movements. Correlations between residual limb length and involved side joint moment could contribute to justification supporting maximal residual limb length preservation. This study investigated possible correlations between hip or knee moment and residual limb length. TECHNIQUE: Hip and knee joint moments were determined while 21 transfemoral amputees performed sitting and standing movements and then evaluated for correlation with residual limb length. DISCUSSION: Residual limb length was not correlated with either knee or involved side hip moments during sit to stand or stand to sit. Conversely, weak inverse correlations (p < 0.05) existed between sound hip moment magnitude and residual limb length. These correlations suggest that in community ambulating transfemoral amputees, longer residual limb length could decrease sound hip kinetic burden during transitional movement. Beyond correlations between residual limb length and sound hip transitional movement kinetics, there are other considerations in determining residual limb length during amputation. CLINICAL RELEVANCE: This study examines relationships between lower limb joint moments and residual limb length related to sit-to-stand and stand-to-sit activities. The results have implications for amputation surgery and rehabilitation.

Multicomponent exercise for physical fitness of community-dwelling elderly women.

[Purpose] The purpose of this study was to identify whether a 4-week multicomponent exercise program could improve the level of physical fitness of community-dwelling elderly women. [Subjects and Methods] Twenty-two healthy community-dwelling elderly women were randomly allocated to either an experimental or a control group. Experimental subjects performed a multicomponent exercise program that consisted of balance, strengthening, and stretching exercises for 4 weeks, whereas the control subjects did not perform any specific exercise. The subjects' level of physical fitness was assessed prior to and after training using the Senior Fitness Test which assesses muscle strength, flexibility, dynamic balance/agility, aerobic endurance, and body composition. [Results] Subjects in the experimental group showed significant improvements in lower and upper body strength, lower and upper body flexibility, dynamic balance/agility following training, but not in aerobic endurance or body composition. Significant group differences were shown in lower and upper body strength, lower body flexibility, and dynamic balance/agility. [Conclusion] The results suggest that a multicomponent training program that consists of balance, strengthening, and stretching exercises is a relevant intervention for the improvement of the level of physical fitness of community-dwelling elderly women.

Effects of seat surface inclination on respiration and speech production in children with spastic cerebral palsy.

BACKGROUND: Respiratory and speech problems are commonly observed in children with cerebral palsy (CP). The purpose of this study was to identify if inclination of seat surface could influence respiratory ability and speech production in children with spastic diplegic CP. METHODS: Sixteen children with spastic diplegic CP, ages 6 to 12 years old, participated in this study. The subjects' respiratory ability (forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), peak expiratory flow (PEF), and maximum phonation time (MPT)) were measured in three sitting conditions: a seat surface inclined 0°, anterior 15°, and posterior 15°. RESULTS: FVC was significantly different across three inclinations of seat surface, F(2, 45) = 3.81, P = 0.03. In particular, the subjects' FVC at a seat surface inclined anterior 15° was significantly greater than at a seat surface inclined posterior 15° (P < 0.05). However, FEV1, PEF, and MPT were not significantly affected by seat surface inclination (P > 0.05). CONCLUSIONS: The results suggest that anterior inclination of seat surface may provide a positive effect on respiratory function in children with spastic diplegic CP.

Gait and balance in adults with Friedreich's ataxia.

Friedreich's ataxia (FA) is an autosomal recessive, neurodegenerative disease characterized by progressive muscle weakness and sensory loss, balance deficits, and gait ataxia. Gait and balance impairments become worse as the disease progresses, but limited research has quantitatively assessed these deficits in adults with FA. The purpose of this study was to analyze gait and balance in this population and investigate the relationship between these variables. Eight subjects with genetically confirmed FA (29.4±9.0 years) and eight healthy, matched control subjects (29.6±9.1 years) participated in this study. Spatiotemporal gait parameters were examined using the GAITRite Walkway System while balance was examined utilizing the Biodex Balance System SD and the Berg Balance Scale (BBS). The FA group exhibited approximately 50% slower gait velocity and 32% shorter step and stride lengths compared to the control group for both comfortable and fast walking (p<0.001). Further, stride length variability in the FA group was 3.4 and 2.7 times that of controls for comfortable and fast walking, respectively (p<0.01). Subjects with FA took 72% longer to complete the limits of stability (LOS) test and attained an overall directional control score that was 50% that of controls (p<0.05). Lastly, age at FA symptom onset correlated with stride length variability during fast walking (p<0.05), and BBS and LOS test scores correlated with stride length variability during both comfortable and fast walking (p<0.05). Results demonstrate that adults with FA have significantly impaired gait and balance and several measures of these impairments are correlated.

Assist-as-Needed Robot-Aided Gait Training Improves Walking Function in Individuals Following Stroke.

A novel robot-aided assist-as-needed gait training paradigm has been developed recently. This paradigm encourages subjects' active participation during training. Previous pilot studies demonstrated that assist-as-needed robot-aided gait training (RAGT) improves treadmill walking performance post-stroke. However, it is not known if there is an over-ground transfer of the training effects from RAGT on treadmill or long-term retention of the effects. The purpose of the current study was to examine the effects of assist-as-needed RAGT on over-ground walking pattern post-stroke. Nine stroke subjects received RAGT with visual feedback of each subject's instantaneous ankle malleolus position relative to a target template for 15 40-minute sessions. Clinical evaluations and gait analyses were performed before, immediately after, and 6 months post-training. Stroke subjects demonstrated significant improvements and some long-term retention of the improvements in their self-selected over-ground walking speed, Dynamic Gait Index, Timed Up and Go, peak knee flexion angle during swing phase and total hip joint excursion over the whole gait cycle for their affected leg . These preliminary results demonstrate that subjects improved their over-ground walking pattern and some clinical gait measures post-training suggesting that assist-as-needed RAGT including visual feedback may be an effective approach to improve over-ground walking pattern post-stroke.

Robot-assisted balance training for gait modification.

Diminished balance control while walking is a main concern for people with stroke. An appropriate training method would help improve their balance during walking. In this study, we examined if a novel robot-assisted balance training (RABT) program could change human gait patterns. Five healthy individuals underwent a RABT program with either stepping or standing movements. An external perturbation using a force field was applied to the lower trunk to alter weight distribution patterns during training. The results showed that people who had a RABT with stepping movements demonstrated a greater change in gait patterns compared to those who had the RABT with standing movements. This suggests that the RABT program with stepping movements can be used as a rehabilitation approach to facilitate an adaptation of a new balance control pattern in human beings.

Robot-assisted modifications of gait in healthy individuals.

This study investigated whether short-term modifications of gait could be induced in healthy adults and whether a combination of kinetic (a compliant force resisting deviation of the foot from the prescribed footpath) and visual guidance was superior to either kinetic guidance or visual guidance alone in producing this modification. Thirty-nine healthy adults, 20-33 years old, were randomly assigned to the three groups receiving six 10-min blocks of treadmill training requiring them to modify their footpath to match a scaled-down path. Changes of the footpath, specific joint events and joint moments were analyzed. Persons receiving combined kinetic and visual guidance showed larger modifications of their gait patterns that were maintained longer, persisting up to 2 h after intervening over-ground activities, than did persons receiving training with primarily kinetic guidance or with visual guidance alone. The results emphasize the short-term plasticity of locomotor circuits and provide a possible basis for persons learning to achieve more functional gait patterns following a stroke or other neurological disorders.

Robot assisted gait training with active leg exoskeleton (ALEX).

Gait training of stroke survivors is crucial to facilitate neuromuscular plasticity needed for improvements in functional walking ability. Robot assisted gait training (RAGT) was developed for stroke survivors using active leg exoskeleton (ALEX) and a force-field controller, which uses assist-as-needed paradigm for rehabilitation. In this paradigm undesirable gait motion is resisted and assistance is provided towards desired motion. The force-field controller achieves this paradigm by effectively applying forces at the ankle of the subject through actuators on the hip and knee joints. Two stroke survivors participated in a 15-session gait training study each with ALEX. The results show that by the end of the training the gait pattern of the patients improved and became closer to a healthy subject's gait pattern. Improvement is seen as an increase in the size of the patients' gait pattern, increased knee and ankle joint excursions and increase in their walking speeds on the treadmill.

Effects of practice and unpredictable distractors on planning and executing aiming after stroke.

The primary purpose of this study was to examine practice effects on the planning and execution of an aiming movement after right versus left stroke. A secondary purpose was to investigate the effects of a distractor that appeared randomly on motor performance after stroke. Right-hand dominant individuals, 15 with right stroke (right-sided brain damage), 16 with left stroke, and 30 without stroke, performed aiming movements to targets. Those with stroke used the ipsilesional upper extremity (UE). Right and left comparison groups used the right and left UE, respectively. Reaction time (RT) and movement time (MT) were collected to represent movement planning and execution, respectively. Individuals with right stroke improved RT with practice. Individuals with left stroke did not improve RT with practice and made more errors than their comparison group. Those with left stroke achieved faster MT with practice, but MT remained slower than their comparison group. There were no effects of the distractor on RT or MT. Adults with left stroke have persistent deficits in movement planning and execution. Further studies are needed to determine how the performance of older adults, with or without stroke, is affected by an unpredictable visual distractor.

Ipsilateral deficits of targeted movements after stroke.

OBJECTIVE: To test the hypotheses that targeted movements of both the ipsilateral and the contralateral extremities of stroke survivors would be prolonged compared with those from a control group without stroke, and that the ipsilateral deficit would occur in movements toward small, but not large, targets. DESIGN: Descriptive study. SETTING: Motor performance laboratory. PARTICIPANTS: Convenience sample of right-handed individuals including 10 who were more than 6 months poststroke with Fugl-Meyer Motor Assessment scores greater than 75% for the upper (UEs) and lower (LEs) extremities, and a comparison group of 20 age-matched adults without stroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The average time required for the stylus, held with the hand or strapped to the foot, to travel from leaving 1 target to contacting the second target (ie, movement time) and the average time the stylus rested on the target (ie, dwell time). RESULTS: Regardless of target size, movement and dwell times for both UEs of the stroke group were prolonged compared with those of the comparison group. Regardless of target size, dwell time for both LEs of the stroke group was prolonged compared with that of the comparison group. CONCLUSIONS: After stroke, the ipsilateral extremities may show subtle deficits in targeted movements.

Anticipatory postural adjustments and the latency of compensatory stepping reactions in humans.

A compensatory stepping response is a commonly used strategy in recovering balance control after a postural perturbation. Unlike gait initiation, the compensatory stepping often occurs without an anticipatory postural adjustment (APA), in which body weight is shifted to the swing leg first and then back to the stance leg prior to foot lifting. In postural perturbation studies using a moving platforms stepping responses without an APA were found to have shorter latency to foot lifting than trials with an APA. We studied stepping responses of healthy young adults under postural perturbation of a pulling force impulse on the subject's waist. In contrast to previous studies, the latency of foot lifting was found in the current study to be shorter in the trials with an APA than trials without an APA. Furthermore, greater amplitude of an APA was associated with a shorter latency of foot lifting. Response with an APA of large amplitude may indicate high level of determinant for foot lifting. A pause as to whether or not to initiate/complete a stepping response is suggested to be partially the cause of delayed foot lifting in trials without an APA or with small amplitude of the APA.