Ankle stiffness and tissue compliance in stroke survivors: A validation of Myotonometer measurements11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

Effect of age on postural performance and control strategies during changes in visual input and dual-tasking stances

Background

With age, people begin to experience deterioration in standing balance, especially when sensory input is suddenly removed or added. Here, we sought to explore the effects of age on postural performance and postural control strategies.

Methods

The convenience sample consisted of 15 young, 10 middle-aged, and 14 elderly healthy adults. They were instructed to stand with their feet together in four randomly administered conditions involving visual input removal/addition and single-/dual-tasking. Dual-tasking involved continuous subtraction by 3s.

Results

Postural sway displacement in the two older groups seemed larger than that in the younger group; however, neither the main effect of group (F_{2, 36} = 1.152, p = .327) nor the group × time interaction effect (F_{4, 27} = 0.229, p = .922) was significant. Greater stiffness of the lower leg muscles was observed in the vision-addition condition than in the vision-removal condition in only the elderly group (t₁₃ = -2.755, p = .016). The dual-tasking condition resulted in smaller sway displacement (F_{1, 36} = 7.690, p = .009) and greater muscle stiffness (F_{1, 36} = 5.495, p = .025). In the vision-removal condition, the increase in muscle stiffness due to dual-tasking was significantly larger in the middle-aged (t₉ = -3.736, p = .005) and elderly groups (t₁₃ = -2.512, p = .026).

Conclusions

In healthy older individuals, age-related changes were observed in control strategies used to maintain standing balance upon changes in visual input. The dual-task paradigm induced the use of an ankle-stiffening strategy in middle-aged and elderly adults.

Quantitative assessment of spasticity: a narrative review of novel approaches and technologies

Spasticity is a complex neurological disorder, causing significant physical disabilities and affecting patients' independence and quality of daily lives. Current spasticity assessment methods are questioned for their non-standardized measurement protocols, limited reliabilities, and capabilities in distinguishing neuron or non-neuron factors in upper motor neuron lesion. A series of new approaches are developed for improving the effectiveness of current clinical used spasticity assessment methods with the developing technology in biosensors, robotics, medical imaging, biomechanics, telemedicine, and artificial intelligence. We investigated the reliabilities and effectiveness of current spasticity measures employed in clinical environments and the newly developed approaches, published from 2016 to date, which have the potential to be used in clinical environments. The new spasticity scales, taking advantage of quantified information such as torque, or echo intensity, the velocity-dependent feature and patients' self-reported information, grade spasticity semi-quantitatively, have competitive or better reliability than previous spasticity scales. Medical imaging technologies, including near-infrared spectroscopy, magnetic resonance imaging, ultrasound and thermography, can measure muscle hemodynamics and metabolism, muscle tissue properties, or temperature of tissue. Medical imaging-based methods are feasible to provide quantitative information in assessing and monitoring muscle spasticity. Portable devices, robotic based equipment or myotonometry, using information from angular, inertial, torque or surface EMG sensors, can quantify spasticity with the help of machine learning algorithms. However, spasticity measures using those devices are normally not physiological sound. Repetitive peripheral magnetic stimulation can assess patients with severe spasticity, which lost voluntary contractions. Neuromusculoskeletal modeling evaluates the neural and non-neural properties and may gain insights into the underlying pathology of spasticity muscles. Telemedicine technology enables outpatient spasticity assessment. The newly developed spasticity methods aim to standardize experimental protocols and outcome measures and enable quantified, accurate, and intelligent assessment. However, more work is needed to investigate and improve the effectiveness and accuracy of spasticity assessment.

Measuring Mechanical Properties of Spastic Muscles After Stroke. Does Muscle Position During Assessment Really Matter?

OBJECTIVE

To investigate the influence of muscle position (relaxed vs stretched) on muscle mechanical properties and the ability of myotonometry to detect differences between sides, groups, and sites of testing in patients with stroke. We also analyzed the association between myotonometry and clinical measures of spasticity.

DESIGN

Cross-sectional study.

SETTING

Outpatient rehabilitation units including private and public centers.

PARTICIPANTS

Seventy-one participants (20 subacute stroke, 20 chronic stroke, 31 controls) were recruited (N=71).

INTERVENTION

Muscle mechanical properties were measured bilaterally with a MyotonPRO at muscle belly and musculotendinous sites during 2 protocols (muscle relaxed or in maximal bearable stretched position).

MAIN OUTCOME MEASURES

Muscle tone and stiffness of the biceps brachii and gastrocnemius. Poststroke spasticity was evaluated with the Modified Tardieu Scale (MTS). A mixed-model analysis of variance was used to detect differences in the outcome measures.

RESULTS

The analysis of variance showed a significant effect of muscle position on muscle mechanical properties (higher tone and stiffness with the muscle assessed in stretched position). Measurements with the stretched muscle could help discriminate between spastic and nonspastic sides, but only at the biceps brachii. Overall, there was a significant increase in tone and stiffness in the chronic stroke group and in myotendinous sites compared with muscle belly sites (all, P<.05). No correlations were found between myotonometry and the MTS.

CONCLUSIONS

Myotonometry assessment of mechanical properties with the muscle stretched improves the ability of myotonometry to discriminate between sides in patients after stroke and between people with and without stroke.

Young's moduli of subcutaneous tissues and muscles under different loads at the gluteal region calculated using ultrasonography

[Purpose] Young's modulus distributions for subcutaneous and muscle tissues in a large sample of healthy individuals, based on ultrasonography and compression testing, remains uninvestigated till date. This study aimed to separately estimate the hardness of subcutaneous tissues and muscles in the human gluteal region under a range of loads in terms of mean Young's moduli and associated distributions. [Participants and Methods] Data of 21 males aged 20-22 years were acquired using synchronous compression testing and ultrasonography. Stress-strain curves comprised the loads applied (stress) were plotted against ultrasonographic changes in subcutaneous/muscle tissue thickness (strain). Young's moduli were calculated as slopes of approximation curves fitted to highly linear regions of the stress-strain curves. [Results] Young's moduli (mean ± standard deviation) for gluteal subcutaneous and muscle tissues were estimated as: 26.1 ± 19.0 kPa, 1-N load; 2,199.1 ± 1,354.8 kPa, 30-N load; and 62.2 ± 10.3 kPa, 5-N load; 440.4 ± 80.0 kPa, 30-N load, respectively. No correlation between any pair of these measures reached statistical significance. [Conclusion] Young's moduli were successfully measured for subcutaneous and muscle tissues in a large participant sample using ultrasonography and compression testing. Our results may serve as reference data when assessing tissue hardness by palpation.

Effect of Stretching of Spastic Elbow Under Intelligent Control in Chronic Stroke Survivors-A Pilot Study

Objective: To assess the short-term effects of strenuous dynamic stretching of the elbow joint using an intelligent stretching device in chronic spastic stroke survivors.

Methods: The intelligent stretching device was utilized to provide a single session of intensive stretching to the spastic elbow joint in the sagittal plane (i.e., elbow flexion and extension). The stretching was provided to the extreme range, safely, with control of the stretching velocity and torque to increase the joint range of motion (ROM) and reduce spasticity and joint stiffness. Eight chronic stroke survivors (age: 52.6 ± 8.2 years, post-stroke duration: 9.5 ± 3.6 years) completed a single 40-min stretching intervention session. Elbow passive and active ROM, strength, passive stiffness (quantifying the non-reflex component of spasticity), and instrumented tendon reflex test of the biceps tendon (quantifying the reflex component of the spasticity) were measured before and after stretching.

Results: After stretching, there was a significant increase in passive ROM of elbow flexion (p = 0.021, r = 0.59) and extension (p = 0.026, r = 0.59). Also, elbow active ROM and the spastic elbow flexors showed a trend of increase in their strength.

Conclusion: The intelligent stretching had a short-term positive influence on the passive movement ROM. Hence, intelligent stretching can potentially be used to repeatedly and regularly stretch spastic elbow joints, which subsequently helps to reduce upper limb impairments post-stroke.

Convergent Validity and Test-Retest Reliability of Multimodal Ultrasonography and Related Clinical Measures in People With Chronic Stroke

OBJECTIVE

To assess the test-retest reliability of diagnostic ultrasonography measurements of the bilateral biceps brachii (BB), brachial artery, medial gastrocnemius (MG), and popliteal artery in survivors of stroke and their convergent validity with related clinical comparators.

DESIGN

Cross-sectional study.

SETTING

All procedures were conducted in a university laboratory.

PARTICIPANTS

Sixty-five community dwelling adults (N=65; 26 women, 39 men) with an average age of 60.9±7.7 years and stroke duration of 5.7±3.9 years participated in this study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Measures of muscle structure (ie, thickness, cross-sectional area, fascicle length, pennation angle), stiffness, and intramuscular blood perfusion were conducted using B-mode, elastography and color flow Doppler ultrasonography modes, respectively. Convergent validity was assessed by examining correlations between ultrasonography measures and assessments of related constructs (ie, dynamic stiffness, isometric peak torque, spasticity, and systemic vascular function using myotonometry, dynamometry, the Composite Spasticity Scale, and the Ankle-Brachial Index, respectively). A 2-way random-effects intraclass correlation coefficient (ICC) model (ICC_2,3) was used to determine agreement between intersession measures among a smaller cohort of participants with stroke (n=20).

RESULTS

ICC estimates ranged from moderate to excellent for muscle stiffness (paretic: ICC=0.74-0.89; nonparetic: ICC=0.66-0.88), structure (paretic: ICC=0.87-0.99; nonparetic: ICC=0.81-0.98), and blood perfusion measures (paretic: ICC=0.74-0.84; nonparetic: ICC=0.73-0.88). Weak to moderate associations were found between myotonometry and elastography measures of the bilateral BB (r=0.29-0.52, P≤.05) and MG muscles (r=0.31-0.69, P≤.05). The correlations between elastography measures and spasticity scores for the paretic upper (r=0.35-0.63, P≤.05) and lower limbs (r=0.25-0.37, P≤.05) were also weak to moderate.

CONCLUSIONS

Elastography demonstrated mostly weak to moderate correlation with measures of stiffness using myotonometry as well as scores of paretic upper and lower limb spasticity. The results also indicate acceptable intersession reliability for muscle and vascular measures using several ultrasonography modalities among individuals with chronic stroke.

Characterization and clinical implications of ankle impedance during walking in chronic stroke

Individuals post-stroke experience persisting gait deficits due to altered joint mechanics, known clinically as spasticity, hypertonia, and paresis. In engineering, these concepts are described as stiffness and damping, or collectively as joint mechanical impedance, when considered with limb inertia. Typical clinical assessments of these properties are obtained while the patient is at rest using qualitative measures, and the link between the assessments and functional outcomes and mobility is unclear. In this study we quantify ankle mechanical impedance dynamically during walking in individuals post-stroke and in age-speed matched control subjects, and examine the relationships between mechanical impedance and clinical measures of mobility and impairment. Perturbations were applied to the ankle joint during the stance phase of walking, and least-squares system identification techniques were used to estimate mechanical impedance. Stiffness of the paretic ankle was decreased during mid-stance when compared to the non-paretic side; a change independent of muscle activity. Inter-limb differences in ankle joint damping, but not joint stiffness or passive clinical assessments, strongly predicted walking speed and distance. This work provides the first insights into how stroke alters joint mechanical impedance during walking, as well as how these changes relate to existing outcome measures. Our results inform clinical care, suggesting a focus on correcting stance phase mechanics could potentially improve mobility of chronic stroke survivors.

Validity and reliability of myotonometry for assessing muscle viscoelastic properties in patients with stroke: a systematic review and meta-analysis

There is a lack of consensus about the measurement of the muscle viscoelastic features in stroke patients. Additionally, the psychometric properties of the most-commonly used clinical tools remain controversial. Our objective is to investigate the validity and reliability of myotonometry to assess viscoelastic muscle features in stroke survivors. Pubmed, PEDro, Scopus and Cinahl were systematically searched to include studies reporting the psychometric properties of myotonometric devices used in people after stroke. The QUADAS-2 and the COSMIN checklists were used to assess the methodological quality of the studies and the psychometric properties of myotonometry. Nine studies were included in the qualitative synthesis and data from five of these were pooled in a meta-analysis. Overall, low to moderate risk of bias and applicability concerns were observed. Pooled data from intra-rater reliability for muscle tone showed a mean coefficient of correlation of 0.915 (95% CI: 0.880-0.940, I 2 = 69.2%) for upper limbs, and a mean coefficient of 0.785 (95%CI: 0.708-0.844, I 2 = 4.02%) for lower limbs. Myotonometry seems to be a valid and reliable complementary tool to assess muscle viscoelastic properties in stroke survivors, although definite conclusions about concurrent validity need further research.

How Well Do Commonly Used Co-contraction Indices Approximate Lower Limb Joint Stiffness Trends During Gait for Individuals Post-stroke?

Muscle co-contraction generates joint stiffness to improve stability and accuracy during limb movement but at the expense of higher energetic cost. However, quantification of joint stiffness is difficult using either experimental or computational means. In contrast, quantification of muscle co-contraction using an EMG-based Co-Contraction Index (CCI) is easier and may offer an alternative for estimating joint stiffness. This study investigated the feasibility of using two common CCIs to approximate lower limb joint stiffness trends during gait. Calibrated EMG-driven lower extremity musculoskeletal models constructed for two individuals post-stroke were used to generate the quantities required for CCI calculations and model-based estimation of joint stiffness. CCIs were calculated for various combinations of antagonist muscle pairs based on two common CCI formulations: Rudolph et al. (2000) (CCI₁) and Falconer and Winter (1985) (CCI₂). CCI₁ measures antagonist muscle activation relative to not only total activation of agonist plus antagonist muscles but also agonist muscle activation, while CCI₂ measures antagonist muscle activation relative to only total muscle activation. We computed the correlation between these two CCIs and model-based estimates of sagittal plane joint stiffness for the hip, knee, and ankle of both legs. Although we observed moderate to strong correlations between some CCI formulations and corresponding joint stiffness, these associations were highly dependent on the methodological choices made for CCI computation. Specifically, we found that: (1) CCI₁ was generally more correlated with joint stiffness than was CCI₂, (2) CCI calculation using EMG signals with calibrated electromechanical delay generally yielded the best correlations with joint stiffness, and (3) choice of antagonist muscle pairs significantly influenced CCI correlation with joint stiffness. By providing guidance on how methodological choices influence CCI correlation with joint stiffness trends, this study may facilitate a simpler alternate approach for studying joint stiffness during human movement.

The Effects of Extracorporeal Shock Wave Therapy on Spastic Muscle of the Wrist Joint in Stroke Survivors: Evidence From Neuromechanical Analysis

Background: This study combined neuromechanical modeling analysis, muscle tone measurement from mechanical indentation and electrical impedance myography to assess the neural and peripheral contribution to spasticity post stroke at wrist joint. It also investigated the training effects and explored the underlying mechanism of radial extracorporeal shock wave (rESW) on spasticity.

Methods: People with first occurrence of stroke were randomly allocated to rESW intervention or control group. The intervention group received one session of rESW therapy, followed by routine therapy which was the same frequency and intensity as the control group. Outcome measures were: (1) NeuroFlexor method measured neural component (NC), elastic component (EC) and viscosity component (VC), and (2) myotonometer measured muscle tone (F) and stiffness (S), (3) electrical impedance myography measured resistance (R), reactance (X) and phase angle (θ); (4) modified Asworth scale; (5) Fugl Meyer Upper limb scale. All outcome measures were recorded at baseline, immediately post rESW and at 1-week follow-up. The differences between the paretic and non-paretic side were assessed by t-test. The effectiveness of rESW treatment were analyzed by repeated-measures one-way analysis of variance (ANOVA) at different time points.

Results: Twenty-seven participants completed the study. NC, EC, and VC of the Neuroflexor method, F and S from myotonometer were all significantly higher on the paretic side than those from the non-paretic side. R, X, and θ from electrical impedance were significantly lower on the paretic side than the non-paretic side. Immediately after rESW intervention, VC, F, and S were significantly reduced, and X was significantly increased. The clinical scores showed improvements immediate post rESW and at 1-week follow-up.

Conclusions: The observed changes in upper limb muscle properties adds further support to the theory that both the neural and peripheral components play a role in muscle spasticity. ESW intervention may be more effective in addressing the peripheral component of spasticity in terms of muscle mechanical properties changes. The clinical management of post stroke spasticity should take into consideration of both the neural and non-neural factors in order to identify optimal intervention regime.

Development and Preliminary Validation of a Pneumatic Focal Vibration System to the Mitigation of Post-Stroke Spasticity

Some evidence has demonstrated that focal vibration (FV) plays an important role in the mitigation of spasticity. However, the research on developing the FV system to mitigate the spasticity effectively has been seldom reported. To relieve post-stroke spasticity, a new pneumatic FV system has been proposed in this paper. An image processing approach, in which the edge of vibration actuator was identified by the Canny edge detector, was utilized to quantify this system's parameters: the frequency ranging from 44 Hz to 128 Hz and the corresponding amplitude. Taking one FV protocol with the frequency of 87 Hz and the amplitude 0.28 mm of this system as an example, a clinical experiment was carried out. In the clinical experiment, FV was applied over the muscle belly of the antagonist of spastic muscle for twelve chronic spastic stroke patients. Spasticity was quantified by the muscle compliance and area under the curve for muscle (AUC_muscle). The result has demonstrated that, in the state of flexion of spastic muscle, the AUC_muscle and muscle compliance of the spastic muscle significantly increased immediately after FV compared with before-FV, illustrating the mitigation of the spasticity. This study will not only provide a potential tool to relieve post-stroke spasticity, but also contribute to improving the sensory and motor function of patients with other neurological diseases, e.g. spinal cord injury, multiple sclerosis, Parkinson and dystonia, etc.

Biomechanical control of paretic lower limb during imposed weight transfer in individuals post-stroke

Background

Stroke is a leading cause of disability with associated hemiparesis resulting in difficulty bearing and transferring weight on to the paretic limb. Difficulties in weight bearing and weight transfer may result in impaired mobility and balance, increased fall risk, and decreased community engagement. Despite considerable efforts aimed at improving weight transfer after stroke, impairments in its neuromotor and biomechanical control remain poorly understood. In the present study, a novel experimental paradigm was used to characterize differences in weight transfer biomechanics in individuals with chronic stroke versus able-bodied controls

Methods

Fifteen participants with stroke and fifteen age-matched able-bodied controls participated in the study. Participants stood with one foot on each of two custom built platforms. One of the platforms dropped 4.3 cm vertically to induce lateral weight transfer and weight bearing. Trials involving a drop of the platform beneath the paretic lower extremity (non-dominant limb for control) were included in the analyses. Paretic lower extremity joint kinematics, vertical ground reaction forces, and center of pressure velocity were measured. All participants completed the clinical Step Test and Four-Square Step Test.

Results

Reduced paretic ankle, knee, and hip joint angular displacement and velocity, delayed ankle and knee inter-joint timing, increased downward displacement of center of mass, and increased center of pressure (COP) velocity stabilization time were exhibited in the stroke group compared to the control group. In addition, paretic COP velocity stabilization time during induced weight transfer predicted Four-Square Step Test scores in individuals post-stroke.

Conclusions

The induced weight transfer approach identified stroke-related abnormalities in the control of weight transfer towards the paretic limb side compared to controls. Decreased joint flexion of the paretic ankle and knee, altered inter-joint timing, and increased COP stabilization times may reflect difficulties in neuromuscular control during weight transfer following stroke. Future work will investigate the potential of improving functional weight transfer through induced weight transfer training exercise.

Effect of an EMG-FES Interface on Ankle Joint Training Combined with Real-Time Feedback on Balance and Gait in Patients with Stroke Hemiparesis

This study evaluated the effects of an electromyography-functional electrical stimulation interface (EMG-FES interface) combined with real-time balance and gait feedback on ankle joint training in patients with stroke hemiplegia. Twenty-six stroke patients participated in this study. All subjects were randomly assigned to either the EMG-FES interface combined with real-time feedback on ankle joint training (RFEF) group (n = 13) or the EMG-FES interface on ankle joint training (EF) group (n = 13). Subjects in both groups were trained for 20 min a day, 5 times a week, for 4 weeks. Similarly, all participants underwent a standard rehabilitation physical therapy for 60 min a day, 5 times a week, for 4 weeks. The RFEF group showed significant increases in weight-bearing lunge test (WBLT), Tardieu Scale (TS), Timed Up and Go Test (TUG), Berg Balance Scale (BBS), velocity, cadence, step length, stride length, stance per, and swing per (p < 0.05). Likewise, the EF group showed significant increases in WBLT, TUG, BBS, velocity, and cadence (p < 0.05). Moreover, the RFEF group showed significantly greater improvements than the EF group in terms of WBLT, Tardieu Scale, TUG, BBS, velocity, step length, stride length, stance per, and swing per (p < 0.05). Ankle joint training using an EMG-FES interface combined with real-time feedback improved ankle range of motion (ROM), muscle tone, balance, and gait in stroke patients. These results suggest that an EMG-FES interface combined with real-time feedback is feasible and suitable for ankle joint training in individuals with stroke.

In-Vivo Study of Passive Musculotendon Mechanics in Chronic Hemispheric Stroke Survivors

We characterized the passive mechanical properties of the affected and contralateral musculotendon units in 9 chronic stroke survivors as well as in 6 neurologically-intact controls. Using a position-controlled motor, we precisely indented the distal tendon of the biceps brachii to a 20 mm depth from skin, recording both its sagittal motion using ultrasound movies and the compression force at the tip of the indenter. Length changes of 8 equally-spaced features along the aponeurosis axis were quantified using a pixel-tracking protocol. We report that, on the aggregate and with respect to contralateral and control, respectively, the affected side initiates feature motion at a shorter indentation distance by 61% and 50%, travels further by 15% and 9%, at a lower rate of 28% and 15%, and is stiffer by 40% and 57%. In an extended analysis including the spatial location of the 8 designated features, we report that in contrast to the contralateral and control muscles, the affected musculotendon unit does not strain measurably within the imaging window. These results confirm that chronic stroke-induced spasticity changes musculotendon unit passive mechanics, causing it to not strain under stretch. The mechanisms responsible for altered passive mechanics may lie within extracellular matrix fibrosis.

Advanced quantitative estimation methods for spasticity: a literature review

Post-stroke spasticity seriously affects patients’ quality of life. Spasticity is considered to involve both neural and non-neural factors. Current clinical scales, such as the Modified Ashworth Scale and the Modified Tardieu Scale, lack reliability and reproducibility. These scales are also unable to identify the neural and non-neural contributions to spasticity. Surface electromyography and biomechanical and myotonometry measurement methods for post-stroke spasticity are discussed in this report. Surface electromyography can provide neural information, while myotonometry can estimate muscular properties. Both the neural and non-neural contributions can be estimated by biomechanical measurement. These laboratory methods can quantitatively assess spasticity. They can provide more valuable information for further study on treatment and rehabilitation than clinical scales.

The evidence for prolonged muscle stretching in ankle joint management in upper motor neuron lesions: considerations for rehabilitation - a systematic review

BACKGROUND

As clinicians, muscles stretching approaches are one of the most commonly used interventions in rehabilitation. However, there is a need for an in-depth evaluation of research on prolonged stretching in terms of the features of the stretching approaches, such as duration and frequency, as well as the compatible measures of a successful stretching approach.

OBJECTIVE

This review is an effort to synthesize findings from studies on "prolonged" stretching approaches in patients with UMNs including stroke, spinal cord injuries, and traumatic brain injuries. We investigated the compatible features of successful stretching regimens in terms of reducing spasticity, improving the Active Range of Motion (AROM), Passive Range of Motion (PROM), and gait training of spastic patient with upper motor neuron lesions.

METHODS

Studies evaluating the effectiveness of "prolonged" stretching on spastic ankle planterflexor muscles and its complications were critically reviewed, and the level of evidence was analyzed.

RESULTS

There is a sufficient level of evidence to support the use of stretching as and effective techniques in rehabilitation. However, more research is yet to be done to objectively examine the ideal parameters of a successful stretching approach using functional assessments, such as walking, speed, walking capacity, and balance.

CONCLUSION

The review adds stronger understanding with regard to stretching considerations in rehabilitation following UMNs. The ideal approach, as well as the functional implications on motor performance are yet to be further studied.

Assessing muscle compliance in stroke with the Myotonometer

BACKGROUND

This study explores changes of the intrinsic biomechanical property in the biceps brachii muscle after a hemispheric stroke using the Myotonometry technique.

METHODS

Nineteen subjects with chronic hemiplegia participated in the study. Myotonometer was used to measure tissue displacement when compression force was applied at 8 levels from 2.45N to 19.6N. Muscle displacement and compliance were determined and averaged over multiple trials.

FINDINGS

Statistical analysis indicated a significant decrease in muscle displacement and compliance in the spastic muscles compared with the contralateral side (muscle displacements: spastic: 4.51 (0.31) mm, contralateral: 5.74 (0.37) mm, p<0.005; compliance: spastic: 0.17 (0.011) mm/N, contralateral: 0.22 (0.014) mm/N, p<0.005). Correlation analysis, however, did not show any association between clinical assessments and myotonometric measurement (p>0.1).

INTERPRETATION

Alterations of muscle compliance in the spastic side reflect changes in the contractile or intrinsic mechanical properties after a stroke. Findings of the study have demonstrated high sensitivity and effectiveness of the Myotonometer in assessing muscle compliance changes.

Relative and Absolute Interrater Reliabilities of a Hand-Held Myotonometer to Quantify Mechanical Muscle Properties in Patients with Acute Stroke in an Inpatient Ward

Introduction

The reliability of using MyotonPRO to quantify muscles mechanical properties in a ward setting for the acute stroke population remains unknown.

Aims

To investigate the within-session relative and absolute interrater reliability of MyotonPRO.

Methods

Mechanical properties of biceps brachii, brachioradialis, rectus femoris, and tibialis anterior were recorded at bedside. Participants were within 1 month of the first occurrence of stroke. Relative reliability was assessed by intraclass correlation coefficient (ICC). Absolute reliability was assessed by standard error of measurement (SEM), SEM%, smallest real difference (SRD), SRD%, and the Bland-Altman 95% limits of agreement.

Results

ICCs of all studied muscles ranged between 0.63 and 0.97. The SEM of all muscles ranged within 0.30-0.88 Hz for tone, 0.07-0.19 for decrement, 6.42-20.20 N/m for stiffness, and 0.04-0.07 for creep. The SRD of all muscles ranged within 0.70-2.05 Hz for tone, 0.16-0.45 for decrement, 14.98-47.15 N/m for stiffness, and 0.09-0.17 for creep.

Conclusions

MyotonPRO demonstrated acceptable relative and absolute reliability in a ward setting for patients with acute stroke. However, results must be interpreted with caution, due to the varying level of consistency between different muscles, as well as between different parameters within a muscle.

Quantitative Evaluation of Passive Muscle Stiffness in Chronic Stroke

OBJECTIVE

The aim of this study was to evaluate the potential for shear wave elastography (SWE) to measure passive biceps brachii individual muscle stiffness as a musculoskeletal manifestation of chronic stroke.

DESIGN

This was a cross-sectional study. Nine subjects with stroke were evaluated using the Fugl-Meyer and Modified Ashworth scales. Electromyography, joint torque, and SWE of the biceps brachii were obtained during passive elbow extension in subjects with stroke and four controls. Torque values at the time points corresponding to each SWE measurement during all trials were selected for direct comparison with the respective SWE stiffness using regression analysis. Intraclass correlation coefficients (ICC(1,1)) were used to evaluate the reliability of expressing alterations in material properties.

RESULTS

Torque and passive stiffness increased with elbow extension-minimally for the controls and most pronounced in the contralateral limb of those with stroke. In the stroke group, several patterns of shear moduli and torque responses to passive elbow extension were identified, with a subset of several subjects displaying a very strong torque response coupled with minimal stiffness responses (y = 2.712x + 6.676; R = 0.181; P = 0.0310). Values of ICC(1,1) indicate consistent muscle stiffness throughout testing for the dominant side of controls, but largely inconsistent stiffness for other study conditions.

CONCLUSIONS

SWE shows promise for enhancing evaluation of skeletal muscle after stroke. The wide variability between subjects with stroke highlights the need for precise, individualized measures.

Electrical Impedance Myography for Evaluating Paretic Muscle Changes After Stroke

Electrical impedance myography (EIM) was used to assess the paretic muscle intrinsic electrical properties post stroke. Twenty-seven subjects with chronic hemiparesis participated in this study. Muscle impedance was measured by applying high-frequency, low-intensity alternating current to biceps brachii muscles. Major EIM parameters, resistance ( ), reactance ( ), phase angle ( ), and electrical anisotropy ratios (AR) of the three parameters, were examined at 50 kHz. Statistical analysis demonstrated significant reduction of reactance, phase angle, AR of resistance, and AR of reactance in the paretic muscle compared with the contralateral side (Paretic X: , contralateral X: , and p < 0.001; Paretic : , contralateral : 14.5 ± 0.82°, and p < 0.001; Paretic AR of R: 0.969 ± 0.013, contralateral AR of R: 1.008 ± 0.011, and p < 0.02; and Paretic AR of X: 0.981 ± 0.066, contralateral AR of X: 1.114 ± 0.041, and p < 0.02). Correlation analysis, however, did not show any significant relationship between EIM parameters and clinical assessments. Findings of this paper indicated significant changes in the muscular intrinsic electrical properties after stroke, possibly related to structural modifications induced by loss of muscle fibers or fat infiltration as well as changes in the quality of cell membranes post stroke.

Assessing muscle spasticity with Myotonometric and passive stretch measurements: validity of the Myotonometer

Spasticity of the biceps brachii muscle was assessed using the modified Ashworth Scale (MAS), Myotonometry and repeated passive stretch techniques, respectively. Fourteen subjects with chronic hemiplegia participated in the study. Spasticity was quantified by muscle displacements and compliance from the Myotonometer measurements and resistive torques from the repeated passive stretch at velocities of 5 °/s and 100 °/s, respectively. Paired t-tests indicated a significant decrease of muscle displacement and compliance in the spastic muscles as compared to the contralateral side (muscle displacement: spastic: 4.84 ± 0.33 mm, contralateral: 6.02 ± 0.49 mm, p = 0.038; compliance: spastic: 1.79 ± 0.12 mm/N, contralateral: 2.21 ± 0.18 mm/kg, p = 0.048). In addition, passive stretch tests indicated a significant increase of total torque at the velocity of 100 °/s compared with that of 5 °/s (T_t5 = 2.82 ± 0.41 Nm, T_t100 = 6.28 ± 1.01 Nm, p < 0.001). Correlation analysis revealed significant negative relationships between the stretch test and the Myotonometer measurements (r < −0.5, p < 0.05). Findings of this study provided validation of the Myotonometry technique and its high sensitivity in examination of spasticity in stroke.

Ultrasound shear wave elastography in assessment of muscle stiffness in patients with Parkinson's disease: a primary observation

OBJECTIVE

The aim of this study was to assess the capability of ultrasound shear wave elastography (SWE) in evaluating the muscle stiffness in patients with Parkinson's diseases (PD).

METHODS

Ultrasound SWE of the longitudinal biceps brachii was performed on 46 patients with PD and 31 healthy controls from May 2013 to October 2013. The stiffness of the biceps brachii muscles measured with quantitative Young's modulus (kPa) was compared between the remarkably symptomatic arms and mildly symptomatic arms in the PD and between PD and controls with unpaired t test. The correlation between the Young's modulus of the biceps brachii measured by SWE and motion scores assessed by unified Parkinson's disease rating scale (UPDRS) part III was analyzed by Pearson's correlation coefficient. The reliability of SWE in assessment of biceps brachii stiffness was tested using intraclass correlation coefficient (ICC).

RESULTS

The mean Young's modulus of biceps brachii in remarkably symptomatic arms, mildly symptomatic arms, and healthy controls was 59.94±20.91 kPa, 47.77±24.00 kPa, and 24.28±5.09 kPa, respectively. A significant difference in Young's modulus of biceps brachii was found between healthy controls and all PD patients (all P<.05); however, it was not between remarkably symptomatic and mildly symptomatic arms. A positive linear correlation was found between the Young's modulus of the biceps brachii and the motion score by UPDRS in patients with PD (r=0.646, P=.000). The ICC for interobserver and intraobserver variation in measuring Young's modulus of the biceps brachii with SWE was 0.74 (95% confidence interval 0.68-0.78) and 0.78 (95% confidence interval 0.75-0.82), respectively.

CONCLUSIONS

SWE of the biceps brachii can be used as a quantitative assessment of muscle stiffness in the patients with PD.

Energetic Passivity of the Human Ankle Joint

Understanding the passive or nonpassive behavior of the neuromuscular system is important to design and control robots that physically interact with humans, since it provides quantitative information to secure coupled stability while maximizing performance. This has become more important than ever apace with the increasing demand for robotic technologies in neurorehabilitation. This paper presents a quantitative characterization of passive and nonpassive behavior of the ankle of young healthy subjects, which provides a baseline for future studies in persons with neurological impairments and information for future developments of rehabilitation robots, such as exoskeletal devices and powered prostheses. Measurements using a wearable ankle robot actuating 2 degrees-of-freedom of the ankle combined with curl analysis and passivity analysis enabled characterization of both quasi-static and steady-state dynamic behavior of the ankle, unavailable from single DOF studies. Despite active neuromuscular control over a wide range of muscle activation, in young healthy subjects passive or dissipative ankle behavior predominated.

Measurement of Resistive Plantar Flexion Torque of the Ankle during Passive Stretch in Healthy Subjects and Patients with Poststroke Hemiplegia

BACKGROUND

Quantification of increased muscle tone for patients with spasticity has been performed to date using various devices to replace the manual scales, such as the modified Ashworth scale or the Tardieu scale. We developed a device that could measure resistive plantar flexion (PF) torque of the ankle during passive dorsiflexion (DF) as an indicator of muscle tone of ankle plantar flexors.

METHODS

The primary objective was to explore the test-retest intrarater reliability of a custom-built device. Participants were 11 healthy subjects (7 men, 4 women; mean age 47.0 years) and 22 patients with poststroke hemiplegia (11 hemorrhagic, 11 ischemic; 14 men, 8 women; mean age 57.2 years). The device was affixed to the ankle. Subjects were seated with knees either flexed or extended. The ankle was passively dorsiflexed from 20° of PF to more than 10° of DF at 5°/second (slow stretch) or 90°/second (fast stretch). Angle and torque were measured twice during the stretches. The intraclass correlation coefficients (ICCs) of torque at 10° of DF (T10) in the 4 conditions-slow and fast stretches with knee flexed or extended-were calculated.

RESULTS

The T10 ICCs of the 4 conditions were .95-.99 in both groups. The healthy subjects showed significantly higher T10 of knee extension than of knee flexion during slow and fast stretches. The patients showed increased velocity-dependent torque during fast stretches.

CONCLUSIONS

Excellent reliability was observed. The device is suitable for measuring resistive PF torque during passive stretch in a flexed knee condition.

Multivariable dynamic ankle mechanical impedance with active muscles

Multivariable dynamic ankle mechanical impedance in two coupled degrees-of-freedom (DOFs) was quantified when muscles were active. Measurements were performed at five different target activation levels of tibialis anterior and soleus, from 10% to 30% of maximum voluntary contraction (MVC) with increments of 5% MVC. Interestingly, several ankle behaviors characterized in our previous study of the relaxed ankle were observed with muscles active: ankle mechanical impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness; stiffness was greater in the sagittal plane than in the frontal plane at all activation conditions for all subjects; and the coupling between dorsiflexion-plantarflexion and inversion-eversion was small-the two DOF measurements were well explained by a strictly diagonal impedance matrix. In general, ankle stiffness increased linearly with muscle activation in all directions in the 2-D space formed by the sagittal and frontal planes, but more in the sagittal than in the frontal plane, resulting in an accentuated "peanut shape." This characterization of young healthy subjects' ankle mechanical impedance with active muscles will serve as a baseline to investigate pathophysiological ankle behaviors of biomechanically and/or neurologically impaired patients.

Effects of virtual reality-based ankle exercise on the dynamic balance, muscle tone, and gait of stroke patients

[Purpose] The purpose of this study was to investigate the therapeutic effects of virtual reality-based ankle exercise on the dynamic balance, muscle tone, and gait ability of stroke subjects. [Subjects and Methods] Twenty persons who were in the chronic stroke subjects of this study and they were included and assigned to two groups: experimental (VRAE; Virtual Reality-based Ankle Exercise group) (n=10) and control groups (n=10). The VRAE group performed virtual environment system ankle exercise, and the control group watched a video. Both groups performed their respective interventions for 30 minutes per day, 5 times per week over a 6-week period. To confirm the effects of the intervention, dynamic balance, muscle tone, and spatiotemporal gait were evaluated. [Results] The results showed that the dynamic balance and muscle tone was significantly more improved after the intervention compared to before in the VRAE group (dynamic balance: 5.50±2.57; muscle tone: 0.90±0.39), and the improvements were more significant than those in the control (dynamic balance: 1.22±2.05; muscle tone: 0.10±0.21). Spatiotemporal gait measures were significantly more increased in the paretic limb after the intervention compared to before in the VRAE group and the improvements were more significant than those in the control group. [Conclusion] This study demonstrated that virtual reality-based ankle exercise effectively improves the dynamic balance, muscle tone, and gait ability of stroke patients.

A study of structural foot deformity in stroke patients

[Purpose] The aim of this study was to evaluate the structural deformity of the foot joint on the affected side in hemiplegic patients to examine factors that affect this kind of structural deformity. [Subjects and Methods] Thirty-one hemiplegic patients and 32 normal adults participated. The foot posture index (FPI) was used to examine the shape of the foot, the modified Ashworth scale test was used to examine the degree of ankle joint rigidity, the navicular drop test was used to investigate the degree of navicular change, and the resting calcaneal stance position test was used to identify location change of the heel bone. [Results] The FPIs of the paretic side of the hemiplegic patients, the non-paretic side of the hemiplegic patients, and normal participants were −0.25 ± 2.1, 1.74 ± 2.3, and 2.12 ± 3.4 respectively. [Conclusion] Our findings indicated that in stroke-related hemiplegic patients, the more severe the spasticity, the more supinated the foot. Further, the smaller the degree of change in the navicular height of hemiplegic patients is, the more supinated the paretic side foot is. Additionally, a greater change in the location of the calcaneus was associated with greater supination of the overall foot.

Measurement of passive skeletal muscle mechanical properties in vivo: recent progress, clinical applications, and remaining challenges

The ability to measure and quantify the properties of skeletal muscle in vivo as a method for understanding its complex physiological and pathophysiological behavior is important in numerous clinical settings, including rehabilitation. However, this remains a challenge to date due to the lack of a "gold standard" technique. Instead, there are a myriad of measuring techniques each with its own set of pros and cons. This review discusses the current state-of-the-art in elastography imaging techniques, i.e., ultrasound and magnetic resonance elastography, as applied to skeletal muscle, and briefly reviews other methods of measuring muscle mechanical behavior in vivo. While in vivo muscle viscoelastic properties can be measured, these techniques are largely limited to static or quasistatic measurements. Emerging elastography techniques are able to quantify muscle anisotropy and large deformation effects on stiffness, but, validation and optimization of these newer techniques is required. The development of reliable values for the mechanical properties of muscle across the population using these techniques are required to enable them to become more useful in rehabilitation and other clinical settings.

Acute effects of static stretching on muscle hardness of the medial gastrocnemius muscle belly in humans: an ultrasonic shear-wave elastography study

This study investigated the acute effects of static stretching (SS) on shear elastic modulus as an index of muscle hardness and muscle stiffness and the relationship between change in shear elastic modulus and change in muscle stiffness after SS. The patients were 17 healthy young males. Muscle stiffness was measured during passive ankle dorsiflexion using a dynamometer and ultrasonography before (pre) and immediately after (post) 2 min of SS. In addition, shear elastic modulus was measured by a new ultrasound technique called ultrasonic shear wave elastography. The post-SS values for muscle stiffness and shear elastic modulus were significantly lower than the pre-SS values. In addition, Spearman's rank correlation coefficient indicated a significant correlation between rate of change in shear elastic modulus and rate of change in muscle stiffness. These results suggest that SS is an effective method for decreasing shear elastic modulus as well as muscle stiffness and that shear elastic modulus measurement using the shear wave elastography technique is useful in determining the effects of SS.

Effects of electroacupuncture on muscle state and electrophysiological changes in rabbits with lumbar nerve root compression

OBJECTIVE

To observe the effects of electroacupuncture on force-displacement value (FDV) of muscle state and electrophysiology of the muscle in rabbits with lumbar nerve root compression.

METHODS

Thirty New Zealand white rabbits were randomly divided into a control, a model, an electro-acupuncture acupoints (EAA), a medication, and an electro-acupuncture un-acupoints (EAU) group. All rabbits except those in the control group were subject to modeling (surgical lumbar nerve root compression). The control group was sham-operated without nerve root compression. The EAA group received electro-acupuncture at bilateral Shenshu (BL23) and Dachangshu (BL25) that were located 1.5 cun lateral to the posterior midline on the lower border of the spinous process of the 2nd and 4th lumbar vertebra, respectively. The EA was 15 mm deep and the frequency was 2 Hz. Each session lasted for 20 min per day for a total of 14 times. The medication group was treated with Loxoprofen sodium by gastrogavage at 4 mg/kg per day for 14 days. The EAU group received electro-acupuncture identical to the EAA group with regard to the treatment frequency and duration except a different acupoint at the tip of rabbit tail. Muscle states were determined by measuring FDVs of the bilateral biceps femoris using the Myotonometer® fast muscle state detector. Meanwhile, the prolonged and non-prolonged insertion potentials were measured by electromyography before and after modeling and after treatment. Latency, amplitude (Amp) of evoked potential, motor nerve conduction velocity (MNCV) were also determined after treatment.

RESULTS

(1) After modeling, FDVs of right side activation (RSA, P=0.003) and right side relaxation (RSR) in the model group (P=0.000) were significantly decreased in comparison to the control group. The number of rabbits with non-prolonged insertion potentials in the model group was also significantly decreased (P=0.015) in comparison to the control group. (2) After treatment, FDVs of RSR were significantly increased in the EAA (P=0.000) and medication groups (P=0.018) in comparison to the model group. The increase in FDVs of RSR in the EAA group was significantly higher than that in EAU (P=0.000) and medication groups (P=0.002). MNCV in the model group was reduced compared with the control group (P=0.000). The reduction in MNCV after modeling was reversed in the EAA group (P=0.000) and medication group (P=0.008) after treatment and the increases were significant in both treatment groups in comparison to the model group. The EAA group had a greater MNCV recovery than the medication group (P=0.022).

CONCLUSION

Electro-acupuncture could improve the rehabilitation and regeneration of FDVs and the electrophysiology index of the muscle with nerve control impairment.

Relative and absolute reliabilities of the myotonometric measurements of hemiparetic arms in patients with stroke

OBJECTIVE

To investigate the relative and absolute reliabilities of the myotonometer.

DESIGN

Psychometric study.

SETTING

Three medical centers.

PARTICIPANTS

Patients with stroke (N=61).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Muscle tone, elasticity, and stiffness of relaxed affected deltoid, triceps brachii, biceps brachii, extensor digitorum, flexor carpi radialis, and flexor carpi ulnaris were measured twice, 30 minutes apart, using the myotonometer. Intraclass correlation coefficient, a relative reliability index, was calculated for 3 muscular properties and for each muscle to examine the degree of consistency and agreement between the 2 test sessions. Absolute reliability indices, including the SEM, smallest real difference, and Bland-Altman limits of agreement, were used to quantify measurement errors and check systematic biases of the 2 test sessions.

RESULTS

The intraclass correlation coefficients were .83 to .95 for muscle tone, elasticity, and stiffness of all muscle groups. The SEM and the smallest real difference of muscle tone, elasticity, and stiffness of the biceps were the smallest among the 6 muscles tested. The Bland-Altman analyses showed no systematic bias between most of the repeated measurements. Compared with other muscles, biceps had narrower limits-of-agreement ranges, indicating that the myotonometric measurements of the biceps had higher stability and less variation over time.

CONCLUSIONS

The myotonometer reliably measures muscular properties, with good relative and absolute reliabilities. These findings are useful for clinicians and researchers to assess muscle properties reliably and determine whether a real change has occurred in groups and on individual levels of patients with stroke.

Quantitative mechanical properties of the relaxed biceps and triceps brachii muscles in patients with subacute stroke: a reliability study of the myoton-3 myometer

Objective. Test-retest reliability of the myotonometer was investigated in patients with subacute stroke. Methods. Twelve patients with substroke (3 to 9 months poststroke) were examined in standardized testing position twice, 60 minutes apart, with the Myoton-3 myometer to measure tone, elasticity, and stiffness of relaxed bilateral biceps and triceps brachii muscles. Intrarater reliability of muscle properties was determined using intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and the minimal detectable change (MDC). Results. Intrarater reliability of muscle properties of bilateral biceps and triceps brachii muscles were good (ICCs = 0.79–0.96) except for unaffected biceps tone (ICC = 0.72). The SEM and MDC of bilateral biceps and triceps brachii muscles indicated small measurement error (SEM% <10%, MDC% <25%). Conclusion. The Myoton-3 myometer is a reliable tool for quantifying muscle tone, elasticity, and stiffness of the biceps and triceps brachii in patients with subacute stroke.

Quadriceps muscle tone, elasticity and stiffness in older males: reliability and symmetry using the MyotonPRO

BACKGROUND

The MyotonPRO (Myoton Ltd; London) is a new portable device for measuring muscle mechanical properties (e.g. tone) and its reliability has yet to be established. Little is known about between-limb symmetry of mechanical properties in healthy older people, despite symmetry often being used as a measure of unilateral abnormalities in clinical assessment. Since quadriceps is important for mobility, it was selected for the present study.

AIMS

To investigate: (i) between-day intra-rater reliability of a novice user of MyotonPRO; (ii) between-side symmetry of mechanical properties of quadriceps in older males.

METHODS

Twenty healthy, community dwelling, right-lower-limb-dominant males (mean age 71.7, range 65-82 years) were studied. With the participant in relaxed supine lying, the MyotonPRO applied two consecutive sets of 10 taps to induce muscle oscillations of rectus femoris, from which measurements of decrement (elasticity), frequency (tone), and stiffness were obtained. Tests were performed on two occasions at the same time and day of the week, one week apart.

RESULTS

Repeated measurements had very high within-day (intraclass correlation coefficient, ICC 3,1>0.90) and high between-day (ICC 3,2>0.70; mean of two measurement sets) reliability. There was no statistically significant difference between muscle mechanical properties of the dominant and non-dominant muscles (<2.5% difference; p>0.05), thereby indicating symmetry.

CONCLUSIONS

High intra-rater reliability was established for MyotonPRO measurements of quadriceps in healthy older males, which were symmetrical between sides. These findings indicate that larger studies are warranted to establish normal reference ranges of data with which to compare patients with muscle abnormalities.

Strength and aerobic requirements during stair ambulation in persons with chronic stroke and healthy adults

OBJECTIVE

To estimate the cost of stair ascent and descent in relation to a measured standard of strength and metabolic (aerobic) capacities in persons with chronic stroke compared with healthy adults.

DESIGN

Descriptive cross-sectional study.

SETTING

Motion analysis laboratory.

PARTICIPANTS

Persons with stroke (n=10) and sex- and age-matched older adults (n=10).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

Lower limb peak joint moments generated during stair walking, expressed as a percentage of the respective isokinetic peak torque, provided an estimate of the relative strength cost. The oxygen consumed during stair walking as a percentage of the maximum oxygen consumption estimated from a submaximal cycle ergometer test reflected the relative aerobic cost of stair ambulation.

RESULTS

During ascent, plantarflexor strength cost was highest on the affected side (stroke) compared with the less affected side and control subjects. The costs associated with the knee extensors were highest in stroke (both sides) for both ascent and descent, and similarly the costs were highest for the less affected and affected plantarflexors during descent. No differences were detected between the affected and less affected sides. The oxygen consumed when ambulating 1 flight of stairs was comparable between groups, but the relative aerobic cost of stair ascent and descent was higher in stroke survivors because of their lower aerobic capacity.

CONCLUSIONS

To our knowledge, this is the first study to compare the relative costs of stair ambulation in people with stroke and healthy controls. The higher strength and aerobic costs associated with stair negotiation in stroke resulting primarily from reduced strength and aerobic capacities, respectively, may limit mobility.

Reliability, validity, and responsiveness of myotonometric measurement of muscle tone, elasticity, and stiffness in patients with stroke

OBJECTIVE

To assess the metric properties of a myotonometer.

DESIGN

Metric study.

SETTING

Three medical centers.

PARTICIPANTS

Stroke patients (N=67).

INTERVENTION

Upper-extremity rehabilitation programs.

MAIN OUTCOME MEASURES

The tone, elasticity, and stiffness of relaxed extensor digitorum, flexor carpi radialis, and flexor carpi ulnaris were measured using the myotonometer. Fifty-eight patients completed the myotonometer measures twice at pretreatment. The myotonometric measurement and the criteria measures, including hand strength (grip, lateral pinch, and palmar pinch strength) and Action Research Arm Test (ARAT) were administered at pretreatment and posttreatment.

RESULTS

The myotonometer showed high test-retest reliability for muscle properties in 3 muscles. Significant correlations existed between the tone and stiffness of the 3 muscles and palmar pinch strength, between those of the flexor carpi muscles and lateral pinch strength, and between those of the flexor carpi radialis and the ARAT at posttreatment. The posttreatment elasticity of the 2 flexor carpi muscles was significantly correlated with grip strength. The pretreatment elasticity of the flexor carpi ulnaris was significantly correlated with posttreatment grip strength, and the pretreatment muscle tone and stiffness of the flexor carpi radialis were significantly correlated with palmar pinch strength and the ARAT. The responsiveness of the extensor digitorum was higher than that of the flexor carpi radialis and ulnaris. Muscle stiffness was more responsive than tone and elasticity in 3 muscles.

CONCLUSIONS

Myotonometry can be a reliable, valid, and responsive outcome measure for assessing muscle properties after stroke rehabilitation.

Mood and Balance are Associated with Free-Living Physical Activity of People after Stroke Residing in the community

Purpose. To determine which characteristics are most associated with free-living physical activity in community-dwelling ambulatory people after stroke. Method. Factors (age, gender, side of stroke, time since stroke, BMI, and spouse), sensory-motor impairments (weakness, contracture, spasticity, coordination, proprioception, and balance), and non-sensory-motor impairments (cognition, language, perception, mood, and confidence) were collected on 42 people with chronic stroke. Free-living physical activity was measured using an activity monitor and reported as time on feet and activity counts. Results. Univariate analysis showed that balance and mood were correlated with time on feet (r = 0.42, 0.43, P < 0.01) and also with activity counts (r = 0.52, 0.54, P < 0.01). Stepwise multiple regression showed that mood and balance accounted for 25% of the variance in time on feet and 40% of the variance in activity counts. Conclusions. Mood and balance are associated with free-living physical activity in ambulatory people after stroke residing in the community.

Multivariable static ankle mechanical impedance with relaxed muscles

Quantitative characterization of ankle mechanical impedance is important to understand how the ankle supports lower-extremity functions during interaction with the environment. This paper reports a novel procedure to characterize static multivariable ankle mechanical impedance. An experimental protocol using a wearable therapeutic robot, Anklebot, enabled reliable measurement of torque and angle data in multiple degrees of freedom simultaneously, a combination of inversion-eversion and dorsiflexion-plantarflexion. The measured multivariable torque-angle relation was represented as a vector field, and approximated using a method based on thin-plate spline smoothing with generalized cross validation. The vector field enabled assessment of several important characteristics of static ankle mechanical impedance, which are not available from prior single degree of freedom studies: the directional variation of ankle mechanical impedance, the extent to which the ankle behaves as a spring, and evidence of uniquely neural contributions. The method was validated by testing a simple physical "mock-up" consisting of passive elements. Experiments with young unimpaired subjects quantified the behavior of the maximally relaxed human ankle, showing that ankle mechanical impedance is spring-like but strongly direction-dependent, being weakest in inversion. Remarkably, the analysis was sufficiently sensitive to detect a subtle but statistically significant deviation from spring-like behavior if subjects were not fully relaxed. This method may provide new insight about the function of the ankle, both unimpaired and after biomechanical or neurological injury.

Measurement of passive ankle stiffness in subjects with chronic hemiparesis using a novel ankle robot

Our objective in this study was to assess passive mechanical stiffness in the ankle of chronic hemiparetic stroke survivors and to compare it with those of healthy young and older (age-matched) individuals. Given the importance of the ankle during locomotion, an accurate estimate of passive ankle stiffness would be valuable for locomotor rehabilitation, potentially providing a measure of recovery and a quantitative basis to design treatment protocols. Using a novel ankle robot, we characterized passive ankle stiffness both in sagittal and in frontal planes by applying perturbations to the ankle joint over the entire range of motion with subjects in a relaxed state. We found that passive stiffness of the affected ankle joint was significantly higher in chronic stroke survivors than in healthy adults of a similar cohort, both in the sagittal as well as frontal plane of movement, in three out of four directions tested with indistinguishable stiffness values in plantarflexion direction. Our findings are comparable to the literature, thus indicating its plausibility, and, to our knowledge, report for the first time passive stiffness in the frontal plane for persons with chronic stroke and older healthy adults.

Intrarater and interrater reliability of Myotonometer measurements of muscle tone in children

The aim of this study was to investigate reliability of Myotonometer measurements, by assessing muscle tone in muscle rectus femoris in children with cerebral palsy and children without disabilities. Differences in muscle tone between groups and conditions, contracted or relaxed, were also investigated. A total of 15 children with cerebral palsy and 15 children without disabilities participated. Intrarater reliability of Myotonometer measurements showed high to very high intraclass correlation, under both conditions and in both groups. Interrater reliability showed high to very high intraclass correlation under both conditions in the control group and in the cerebral palsy group under contracted condition and moderate under relaxed condition. There were slight differences in tissue displacement between groups, although not statistically significant. Myotonometer measurements are reliable when assessing muscle tone in children. However, there is still a need to investigate this method for objectively quantifying increased muscle tone in children with cerebral palsy.