Optimizing shoulder elevation assist rate in exoskeletal rehabilitation based on muscular activity indices: a clinical feasibility study.

BACKGROUND: Restoring shoulder function is critical for upper-extremity rehabilitation following a stroke. The complex musculoskeletal anatomy of the shoulder presents a challenge for safely assisting elevation movements through robotic interventions. The level of shoulder elevation assistance in rehabilitation is often based on clinical judgment. There is no standardized method for deriving an optimal level of assistance, underscoring the importance of addressing abnormal movements during shoulder elevation, such as abnormal synergies and compensatory actions. This study aimed to investigate the effectiveness and safety of a newly developed shoulder elevation exoskeleton robot by applying a novel optimization technique derived from the muscle synergy index. METHODS: Twelve chronic stroke participants underwent an intervention consisting of 100 robot-assisted shoulder elevation exercises (10 × 10 times, approximately 40 min) for 10 days (4-5 times/week). The optimal robot assist rate was derived by detecting the change points using the co-contraction index, calculated from electromyogram (EMG) data obtained from the anterior deltoid and biceps brachii muscles during shoulder elevation at the initial evaluation. The primary outcomes were the Fugl-Meyer assessment-upper extremity (FMA-UE) shoulder/elbow/forearm score, kinematic outcomes (maximum angle of voluntary shoulder flexion and elbow flexion ratio during shoulder elevation), and shoulder pain outcomes (pain-free passive shoulder flexion range of motion [ROM] and visual analogue scale for pain severity during shoulder flexion). The effectiveness and safety of robotic therapy were examined using the Wilcoxon signed-rank sum test. RESULTS: All 12 patients completed the procedure without any adverse events. Two participants were excluded from the analysis because the EMG of the biceps brachii was not obtained. Ten participants (five men and five women; mean age: 57.0 [5.5] years; mean FMA-UE total score: 18.7 [10.5] points) showed significant improvement in the FMA-UE shoulder/elbow/forearm score, kinematic outcomes, and pain-free passive shoulder flexion ROM (P < 0.05). The shoulder pain outcomes remained unchanged or improved in all patients. CONCLUSIONS: The study presents a method for deriving the optimal robotic assist rate. Rehabilitation using a shoulder robot based on this derived optimal assist rate showed the possibility of safely improving the upper-extremity function in patients with severe stroke in the chronic phase.

Working memory load modulates anticipatory postural adjustments during step initiation.

Working memory (WM) can influence selective attention. However, the effect of WM load on postural standing tasks has been poorly understood, even though these tasks require attentional resources. The purpose of this study was to examine whether WM load would impact anticipatory postural adjustments (APAs) during step initiation. Sixteen healthy young adults performed stepping tasks alone or concurrently with a WM task in a dual-task design. The stepping tasks involved volitional stepping movements in response to visual stimuli and comprised of simple and choice reaction time tasks and the Flanker task which consisted of congruent and incongruent (INC) conditions. In the dual-task condition, subjects were required to memorize either one or six digits before each stepping trial. Incorrect weight transfer prior to foot-lift, termed APA errors, reaction time (RT), and foot-lift time were measured from the vertical force data. The results showed that APA error rate was significantly higher when memorizing six-digit than one-digit numerals in the INC condition. In addition, RT and foot-lift time were significantly longer in the INC condition compared to the other stepping conditions, while there was no significant effect of WM load on RT or foot-lift time. These findings suggest that high WM load reduces the cognitive resources needed for selective attention and decision making during step initiation.

Categorizing knee hyperextension patterns in hemiparetic gait and examining associated impairments in patients with chronic stroke.

BACKGROUND: Post-stroke hemiparetic gait exhibits considerable variations in motion patterns and abnormal muscle activities, notably knee hyperextension during the stance phase. Existing studies have primarily concentrated on its joint angle or moment. However, the underlying causes remain unclear. Thus, the causes of knee hyperextension were explored from a new perspective based on temporal-durational factors. RESEARCH QUESTION: Does the temporal-durational difference of knee hyperextension presence result from specific decreased motor functions? METHODS: Barefoot gait at a comfortable speed was captured using a three-dimensional camera system. Scores of knee hyperextension used a metric with the temporal-durational factor of knee hyperextension presence in each of four stance phases (1st double support, DS1; early single-leg stance, ESS; late single-leg stance, LSS; 2nd double support, DS2). These scores were used in cluster analysis. The classification and regression tree analysis characterizing each knee hyperextension cluster used the clinical measures of the lower limb and trunk motor function, muscle strength, and spasticity as explanatory variables. RESULTS: Thirty patients with hemiparetic chronic stroke who exhibited knee hyperextension during gait were included. Four knee hyperextension clusters were shown: Momentary (almost no hyperextension), Continuous (DS1-DS2), ESS-LSS, and ESS-DS2. Knee flexor strength was lower in the groups with long hyperextension durations (Continuous and ESS-DS2) compared with short durations (ESS-LSS and Momentary). ESS-DS2 exhibited higher trunk motor function than Continuous, whereas more severe spasticity was observed in ESS-LSS than in Momentary. SIGNIFICANCE: This study successfully classified four hemiparetic gait patterns with knee hyperextension based on the temporal-durational factor, providing valuable perspectives for understanding and addressing specific functional physical impairments. These findings offer guidance for focusing on related physical functions when striving for gait improvement with knee hyperextension and are expected to serve as a reference for treatment decision-making.

Blind Spots in Hospital Fall Prevention: Falls in Stroke Patients Occurred Not Only in Those at a High Risk of Falling.

OBJECTIVES: Although the standard falls prevention strategy is to identify and respond to patients with high-risk conditions, it remains unclear whether falls in patients with high fall risk account for most observed falls. In this study, fall risk and number of falls were calculated based on patients' motor and cognitive abilities, and the relationship between the two was examined. DESIGN: We conducted a retrospective cohort study. SETTING AND PARTICIPANTS: We included 2518 consecutive patients with stroke who were admitted to a rehabilitation hospital. METHODS: Data on falls during hospitalization and biweekly assessed Functional Independence Measure scores were retrieved from the medical records. The average Functional Independence Measure scores for the motor and cognitive items were obtained and categorized as complete dependence, modified dependence, and independence. The fall rate (falls/1000 person-days) and number of observed falls in each combined condition were investigated. RESULTS: Modified dependence on motor ability and complete dependence on cognitive ability had the highest risk of falls, with a fall rate of 10.8/1000 person-days and 51 fall observations, which accounted for 4.3% of all falls. Independent motor and cognitive ability had the lowest risk of falls, a fall rate of 2.6/1000 person-days and 146 observed falls, accounting for 12.4% of all falls, which was 2.8 times higher than the number of falls observed in the highest risk of falls condition. CONCLUSIONS AND IMPLICATIONS: The combined motor-cognitive ability with the highest risk of falls in stroke inpatients did not have the highest number of observed falls. Rather, the combined motor-cognitive ability with the lowest risk of falls tended to have a high number of observed falls. A different strategy is needed to reduce the total number of falls.

Feasibility of a neurorehabilitation pipeline and an automated algorithm to select appropriate treatments for upper extremity motor paralysis in individuals with chronic stroke.

OBJECTIVE: This study aimed to investigate the feasibility of a neurorehabilitation pipeline and develop an algorithm to automatically select the appropriate treatment for individuals with upper extremity motor paralysis after stroke in the chronic phase. DESIGN: In Experiment 1, eight post-stroke participants in the chronic phase who underwent treatment sustaining two to three phases were assessed before and after treatment. In Experiment 2, a decision tree analysis was performed in which the dependent variable was set as the treatment option determined by a board-certified physiatrist for 95 post-stroke participants; the independent variables were only motor function scores or both motor function scores and electromyogram variables. RESULTS: In Experiment 1, the clinical assessment scores were improved significantly after treatment. Experiment 2 showed that the agreements of the model with only motor function scores as the dependent variable and with motor function scores and electromyogram variables as the dependent variables were 75.8% and 82.1%, respectively. CONCLUSIONS: This novel treatment package is feasible for improvement of motor function in post-stroke individuals with severe motor paralysis. The study also established an automated algorithm for selecting appropriate treatments for upper extremity motor paralysis after stroke, identifying standard values of key variables, including electromyography variables.

Intermuscular Coherence during Quiet Standing in Sub-Acute Patients after Stroke: An Exploratory Study.

Asymmetrically impaired standing control is a prevalent disability among stroke patients; however, most of the neuromuscular characteristics are unclear. Therefore, the main purpose of this study was to investigate between-limb differences in intermuscular coherence during quiet standing. Consequently, 15 patients who had sub-acute stroke performed a quiet standing task without assistive devices, and electromyography was measured on the bilateral tibialis anterior (TA), soleus (SL), and medial gastrocnemius (MG). The intermuscular coherence of the unilateral synergistic (SL-MG) pair and unilateral antagonist (TA-SL and TA-MG) pairs in the delta (0-5 Hz) and beta (15-35 Hz) bands were calculated and compared between the paretic and non-paretic limbs. The unilateral synergistic SL-MG coherence in the beta band was significantly greater in the non-paretic limb than in the paretic limb (p = 0.017), while unilateral antagonist TA-MG coherence in the delta band was significantly greater in the paretic limb than in the non-paretic limb (p < 0.01). During quiet standing, stroke patients showed asymmetry in the cortical control of the plantar flexor muscles, and synchronous control between the antagonistic muscles was characteristic of the paretic limb. This study identified abnormal muscle activity patterns and asymmetrical cortical control underlying impaired standing balance in patients with sub-acute stroke using an intermuscular coherence analysis.