Intrinsic properties of the knee extensor muscles after subacute stroke

Structural and pathophysiological muscle changes up to one year after post-stroke hemiplegia: a systematic review

INTRODUCTION

Muscle changes after stroke cannot be explained solely on the basis of corticospinal bundle damage. Muscle-specific changes contribute to limited functional recovery but have been poorly characterized.

EVIDENCE ACQUISITION

We conducted a systematic review of muscular changes occurring at the histological, neuromuscular and functional levels during the first year after the onset of post-stroke hemiplegia. A literature search was performed on PubMed, Embase and CINHAL databases up to November 2022 using a keyword combination comprising cerebral stroke, hemiplegic, atrophy, muscle structure, paresis, skeletal muscle fiber type, motor unit, oxidative stress, strength, motor control.

EVIDENCE SYNTHESIS

Twenty-seven trial reports were included in the review, out of 12,798 articles screened. Structural modifications described on the paretic side include atrophy, transformation of type II fibers into type I fibers, decrease in fiber diameter and apparent myofilament disorganization from the first week post-stroke up to the fourth month. Reported biochemical changes comprise the abnormal presence of lipid droplets and glycogen granules in the subsarcolemmal region during the first month post-stroke. At the neurophysiological level, studies indicate an early decrease in the number and activity of motor units, correlated with the degree of motor impairment. All these modifications were present to a lesser degree on the non-paretic side. Although only sparse data concerning the subacute stage are available, these changes seem to appear during the first two weeks post-stroke and continue up to the third or fourth month.

CONCLUSIONS

Considering these early pathophysiological changes on both the paretic and non-paretic sides, it seems crucial to promptly stimulate central and also peripheral muscular activation after stroke through specific rehabilitation programs focused on the maintenance of muscle capacities associated with neurological recovery or plasticity.

Effect of power training on rate of torque development and spatiotemporal gait parameters post stroke

BACKGROUND

Maximizing independence and function post-stroke are two common therapy goals. Rate of torque development in lower-extremity muscles was recently reported to be associated with walking speed; however, trainability and subsequent effect on gait is unknown. This study aimed to determine effect of power training on paretic and non-paretic limb torque parameters, spatiotemporal gait parameters, and walking speed in chronic stroke survivors.

METHODS

Individuals with chronic stroke (n = 22; 7 females; 62.7 ± 8.8 yrs) completed 24 progressive power-training sessions over 8 weeks with pre and post assessments. Knee extensor strength was assessed via dynamometry with torque parameters measured from maximal voluntary isometric contractions. Gait speed and spatiotemporal gait parameters were assessed via an instrumented gait mat, and a 6-min walk test was performed.

FINDINGS

Rate of torque development at 200 ms and peak torque improved 58.6% and 14.1%, respectively, in the quadricep of the paretic limb (p < 0.05); conversely the non-paretic limb was unchanged. On average, self-selected walking speed, fastest-comfortable walking speed, and 6-min walk test improved 21.7%, 21.1%, and 19.5%, respectively (all p < 0.05). Change in torque development at 100 ms in the quadricep of the non-paretic limb was positively associated with improvements in self-selected and fastest-comfortable walking speeds (both r = 0.70, p < 0.05) and 6-min walk (r = 0.78, p < 0.001).

INTERPRETATIONS

These findings suggest power training may be an effective intervention for improving torque development in the quadricep of the paretic limb in individuals with chronic stroke. Further research to explore utility and mechanistic aspects of force development for gait function in chronic stroke survivors is warranted.

Evidence-based improvement of gait in post-stroke patients following robot-assisted training: A systematic review

BACKGROUND

The recovery of walking after stroke is a priority goal for recovering autonomy. In the last years robotic systems employed for Robotic Assisted Gait Training (RAGT) were developed. However, literature and clinical practice did not offer standardized RAGT protocol or pattern of evaluation scales.

OBJECTIVE

This systematic review aimed to summarize the available evidence on the use of RAGT in post-stroke, following the CICERONE Consensus indications.

METHODS

The literature search was conducted on PubMed, Cochrane Library and PEDro, including studies with the following criteria: 1) adult post-stroke survivors with gait disability in acute/subacute/chronic phase; 2) RAGT as intervention; 3) any comparators; 4) outcome regarding impairment, activity, and participation; 5) both primary studies and reviews.

RESULTS

Sixty-one articles were selected. Data about characteristics of patients, level of disability, robotic devices used, RAGT protocols, outcome measures, and level of evidence were extracted.

CONCLUSION

It is possible to identify robotic devices that are more suitable for specific phase disease and level of disability, but we identified significant variability in dose and protocols. RAGT as an add-on treatment seemed to be prevalent. Further studies are needed to investigate the outcomes achieved as a function of RAGT doses delivered.

Muscle contractile properties of cancer patients receiving chemotherapy: Assessment of feasibility and exercise effects

Background

This pilot trial explores the feasibility of measuring muscle contractile properties in patients with cancer, effects of exercise during chemotherapy on muscle contractile properties and the association between changes in contractile muscle properties and perceived fatigue.

Method

Patients who received (neo)adjuvant chemotherapy for breast or colon cancer were randomized to a 9‐12 week exercise intervention or a waitlist‐control group. At baseline and follow‐up, we measured knee extensor strength using maximal voluntary contraction (MVC), contractile muscle properties of the quadriceps muscle using electrical stimulation, and perceived fatigue using the Multidimensional Fatigue Inventory. Feasibility was assessed by the proportion of patients who successfully completed measurements of contractile muscle properties. Exercise effects on muscle contractile properties were explored using linear regression analyses. Between‐group differences >10% were considered potentially relevant. Pearson correlation (r_p) of changes in contractile muscle properties and changes in perceived fatigue was calculated.

Results

Twenty two of 30 patients completed baseline and follow‐up assessments. Measurements of contractile properties were feasible except for muscle fatigability. We found a potentially relevant between‐group difference in the rate of force development favoring the intervention group (1192 N/s, 95% CI = −335; 2739). Change in rate of force development was negatively correlated with change in perceived general (r_p = −0.54, P = .04) and physical (r_p = −0.59, P = .02) fatigue.

Conclusion

Chemotherapy induces a decrease in the rate of force development, which may reflect a larger loss in type II muscle fibers. This may be attenuated with (resistance) exercise. The increase in the rate of force development was related to a decrease in perceived fatigue.

Distinct Patterns of Fiber Type Adaptation in Rat Hindlimb Muscles 4 Weeks After Hemorrhagic Stroke

OBJECTIVE

The aim of this study was to evaluate adaptations in soleus and tibialis anterior muscles in a rat model 4 wks after hemorrhagic stroke.

DESIGN

Young adult Sprague Dawley rats were randomly assigned to two groups: stroke and control, with eight soleus and eight tibialis anterior muscles per group. Hemorrhagic stroke was induced in the right caudoputamen of the stroke rats. Control rats had no intervention. Neurologic status was evaluated in both groups before stroke and 4 wks after stroke. Muscles were harvested after poststroke neurologic testing. Muscle fiber types and cross-sectional areas were determined in soleus and tibialis anterior using immunohistochemical labeling for myosin heavy chain.

RESULTS

No generalized fiber atrophy was found in any of the muscles. Fiber types shifted from faster to slower in the tibialis anterior of the stroke group, but no fiber type shifts occurred in the soleus muscles of stroke animals.

CONCLUSIONS

Because slower myosin heavy chain fiber types are associated with weaker contractile force and slower contractile speed, this faster to slower fiber type shift in tibialis anterior muscles may contribute to weaker and slower muscle contraction in this muscle after stroke. This finding may indicate potential therapeutic benefit from treatments known to influence fiber type plasticity.

Systematic Review of Appropriate Robotic Intervention for Gait Function in Subacute Stroke Patients

The purpose of this study was to critically evaluate the effects of robot-assisted gait training (RAGT) on gait-related function in patients with acute/subacute stroke. We conducted a systematic review of randomized controlled trials published between May 2012 and April 2016. This search included 334 articles (Cochrane, 51 articles; Embase, 175 articles; PubMed, 108 articles). Based on the inclusion and exclusion criteria, 7 studies were selected for this review. We performed a quality evaluation using the PEDro scale. In this review, 3 studies used an exoskeletal robot, and 4 studies used an end-effector robot as interventions. As a result, RAGT was found to be effective in improving walking ability in subacute stroke patients. Significant improvements in gait speed, functional ambulatory category, and Rivermead mobility index were found with RAGT compared with conventional physical therapy (p < 0.05). Therefore, aggressive weight support and gait training at an early stage using a robotic device are helpful, and robotic intervention should be applied according to the patient's functional level and onset time of stroke.

Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors

Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU) mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC). A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s) than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045). The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04). Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03). MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively), and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04). This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the affected and less-affected side post-stroke, and may suggest that central mechanisms observed here as changes in firing rate are the dominant processes leading to task failure on the affected side.

Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture.

Dynamometry for the measurement of grip, pinch, and trunk muscles strength in subjects with subacute stroke: reliability and different number of trials

Background

Muscle strength is usually measured in individuals with stroke with Portable dynamometers (gold standard). However, no studies have investigated the reliability, the standard error of measurement (SEM) and the minimal detectable difference (MDD_95%) of the dynamometry for the measurement of hand grip, pinch grip and trunk strength in subjects with subacute stroke.

Objective

1) To investigate the intra and inter-rater reliability, the SEM and the MDD_95% of the portable dynamometers for the measurement of grip, pinch and trunk strength in subjects with subacute stroke, and 2) to verify whether the use of different number of trials (first trial and the average of the first two and three trials) affected the results.

Method

32 subjects with subacute stroke (time since stroke onset: 3.6 months, SD=0.66 months) were evaluated. Hand grip, 3 pinch grips (i.e. pulp-to-pulp/palmar/lateral) and 4 trunk muscles (i.e. flexors, extensors, lateral flexors and rotators) strength were bilaterally assessed (except trunk flexors/extensors) with portable dynamometry by two independent examiners over two sessions (1-2 weeks apart). One-way ANOVAs and intraclass correlation coefficients (ICC_2,k) were used for analysis (α=0.05). SEM and MDD_95% were also calculated.

Results

For all muscular groups and sources of outcome values, including one trial, after familiarization, similar results were found (0.01≤F≤0.08; 0.92≤p≤0.99) with significant and adequate values of intra-rater (0.64≤ICC≤0.99; 0.23≤95%CI≤0.99) and inter-rater (0.66≤ICC≤0.99; 0.25≤95%CI≤0.99) reliability. SEM and MDD_95% were considered low (0.39≤EPM≤2.21 Kg; 0.96≤MMD_95%≤6.12 Kg) for all outcome scores.

Conclusion

Only one trial, following familiarization, demonstrated adequate intra-rater and inter-rater reliability of the portable dynamometers for the measurement of hand grip, pinch grip and trunk strength in subjects with subacute stroke.

Gait training in subacute non-ambulatory stroke patients using a full weight-bearing gait-assistance robot: A prospective, randomized, open, blinded-endpoint trial

BACKGROUND

This study was a prospective, randomized, open, blinded-endpoint trial with the aim of examining whether gait training with a gait-assistance robot (GAR) improves gait disturbances in subacute non-ambulatory hemiplegic stroke patients more than overground conventional gait training. The GAR adopts a robot arm control system with full weight bearing and foot pressure visual biofeedback.

METHODS

Twenty-six hemiplegic patients were randomly assigned to either the GAR-assisted gait training (GAGT) group or the overground conventional gait training (OCGT) group. Both groups underwent 60 min of standard physical therapy and 20 min of GAGT or OCGT 5 days a week for 4 weeks. The primary outcome measure was the Functional Ambulation Classification (FAC). The secondary outcome measures were the peak torque of the extensor muscles in the lower extremities and a 10-m walking test. The lower extremity function was evaluated using the Fugl-Meyer Assessment, and activities of daily living were assessed using the Functional Independence Measure.

RESULTS

The GAGT group demonstrated significantly greater improvements in FAC and peak torque on the unaffected side (p=0.02) than the OCGT group. Additionally, gait speed tended to be faster (p=0.07) in the GAGT group.

CONCLUSIONS

GAGT combined with standard physical therapy in subacute non-ambulatory hemiplegic patients led to significant improvements in gait and peak torque on the unaffected side compared to OCGT.

Skeletal muscle fatigue

Skeletal muscle fatigue is defined as the fall of force or power in response to contractile activity. Both the mechanisms of fatigue and the modes used to elicit it vary tremendously. Conceptual and technological advances allow the examination of fatigue from the level of the single molecule to the intact organism. Evaluation of muscle fatigue in a wide range of disease states builds on our understanding of basic function by revealing the sources of dysfunction in response to disease.

Development of a fuzzy logic based intelligent system for autonomous guidance of post-stroke rehabilitation exercise

This paper presents preliminary studies in developing a fuzzy logic based intelligent system for autonomous post-stroke upper-limb rehabilitation exercise. The intelligent system autonomously varies control parameters to generate different haptic effects on the robotic device. The robotic device is able to apply both resistive and assistive forces for guiding the patient during the exercise. The fuzzy logic based decision-making system estimates muscle fatigue of the patient using exercise performance and generates a combination of resistive and assistive forces so that the stroke survivor can exercise for longer durations with increasing control. The fuzzy logic based system is initially developed using a study with healthy subjects and preliminary results are also presented to validate the developed system with healthy subjects. The next stage of this work will collect data from stroke survivors for further development of the system.

Towards more effective robotic gait training for stroke rehabilitation: a review

Background

Stroke is the most common cause of disability in the developed world and can severely degrade walking function. Robot-driven gait therapy can provide assistance to patients during training and offers a number of advantages over other forms of therapy. These potential benefits do not, however, seem to have been fully realised as of yet in clinical practice.

Objectives

This review determines ways in which robot-driven gait technology could be improved in order to achieve better outcomes in gait rehabilitation.

Methods

The literature on gait impairments caused by stroke is reviewed, followed by research detailing the different pathways to recovery. The outcomes of clinical trials investigating robot-driven gait therapy are then examined. Finally, an analysis of the literature focused on the technical features of the robot-based devices is presented. This review thus combines both clinical and technical aspects in order to determine the routes by which robot-driven gait therapy could be further developed.

Conclusions

Active subject participation in robot-driven gait therapy is vital to many of the potential recovery pathways and is therefore an important feature of gait training. Higher levels of subject participation and challenge could be promoted through designs with a high emphasis on robotic transparency and sufficient degrees of freedom to allow other aspects of gait such as balance to be incorporated.

Neuromuscular performance of paretic versus non-paretic plantar flexors after stroke

The objective of this study was to compare the neuromuscular function of the paretic and non-paretic plantar flexors (i.e. soleus, gastrocnemius medialis, lateralis) in chronic stroke patients. It was hypothesized that the contractile rate of force development (RFD) and neural activation, assessed by electromyogram (EMG) and V-waves normalized to the M-wave, and voluntary activation (twitch interpolation) would be reduced during plantar flexor maximum voluntary isometric contraction and that the evoked muscle twitch properties would be reduced in the paretic limb. Ten chronic stroke survivors completed the study. The main findings were that the paretic side showed deteriorated function compared to the non-paretic leg in terms of (1) RFD in all analyzed time windows from force onset to 250 ms, although relative RFD (i.e. normalized to maximum voluntary force) was similar; (2) fast neural activation (for most analyzed time windows), assessed by EMG activity in time windows from EMG onset to 250 ms; (3) V-wave responses (except for gastrocnemius medialis); (4) voluntary activation; (5) the evoked peak twitch force, although there was no evidence of intrinsic muscle slowing; (6) EMG activity obtained at maximal voluntary force. In conclusion, this study demonstrates considerable neuromuscular asymmetry of the plantar flexors in chronic stroke survivors. Effective rehabilitation regimes should be investigated.

Neurorehabilitation using the virtual reality based Rehabilitation Gaming System: methodology, design, psychometrics, usability and validation

BACKGROUND

Stroke is a frequent cause of adult disability that can lead to enduring impairments. However, given the life-long plasticity of the brain one could assume that recovery could be facilitated by the harnessing of mechanisms underlying neuronal reorganization. Currently it is not clear how this reorganization can be mobilized. Novel technology based neurorehabilitation techniques hold promise to address this issue. Here we describe a Virtual Reality (VR) based system, the Rehabilitation Gaming System (RGS) that is based on a number of hypotheses on the neuronal mechanisms underlying recovery, the structure of training and the role of individualization. We investigate the psychometrics of the RGS in stroke patients and healthy controls.

METHODS

We describe the key components of the RGS and the psychometrics of one rehabilitation scenario called Spheroids. We performed trials with 21 acute/subacute stroke patients and 20 healthy controls to study the effect of the training parameters on task performance. This allowed us to develop a Personalized Training Module (PTM) for online adjustment of task difficulty. In addition, we studied task transfer between physical and virtual environments. Finally, we assessed the usability and acceptance of the RGS as a rehabilitation tool.

RESULTS

We show that the PTM implemented in RGS allows us to effectively adjust the difficulty and the parameters of the task to the user by capturing specific features of the movements of the arms. The results reported here also show a consistent transfer of movement kinematics between physical and virtual tasks. Moreover, our usability assessment shows that the RGS is highly accepted by stroke patients as a rehabilitation tool.

CONCLUSIONS

We introduce a novel VR based paradigm for neurorehabilitation, RGS, which combines specific rehabilitative principles with a psychometric evaluation to provide a personalized and automated training. Our results show that the RGS effectively adjusts to the individual features of the user, allowing for an unsupervised deployment of individualized rehabilitation protocols.