Validity and reliability of the chronic composite XA, an upper limb motor assessment using Active Range of Motion in patients with chronic stroke.

BACKGROUND: Upper limb (UL) spastic paresis has been classically evaluated with assessments of passive movements with limited functional validity. The aim of this study was to assess whether a composite measure of active range of motion (AROM, or XA) is valid and reliable in chronic post-stroke spastic paresis. AIM: The primary objective was to investigate the validity and reliability of a composite score, comprising multiple XA measurements, to assess UL spastic paresis in patients in chronic stages post-stroke. In addition to this, an exploratory analysis was conducted to identify which muscles should be optimally included in this composite score. DESIGN: A psychometric proprieties study. SETTING: Physical and Rehabilitation Medicine Department. POPULATION: twenty-eight chronic post-stroke participants with spastic paresis. METHODS: Composite UL XA measurement in twenty-eight chronic post-stroke participants (age=59±11 years; delay post-stroke=29±37 months) with spastic paresis was repeated twice about 40 days apart in a standardized body position. Concurrent and construct validity was evaluated exploring correlation with the Fugl-Meyer Assessment Upper Extremity (FMA-UE), Action Research Arm Test (ARAT), and grip strength (JAMAR™). Reliability was assessed by calculating intraclass correlation coefficients (ICC). Regarding the exploratory analysis, a linear regression analysis was performed to examine the value of including various muscles. RESULTS: Composite XA against the resistance of elbow, wrist and finger flexors showed strong correlation with FMA-UE and ARAT (r=0.88; P<0.001 and r=0.82; P<0.001 respectively) and a weak association with grip strength (r=0.43; P=0.03). Test-retest reliability was excellent (ICC=0.92). However, the most effective regression model also included XA against the resistance of shoulder adductors as well as forearm pronator (adjusted R2=0.85; AIC=170). CONCLUSIONS: The present study provided satisfactory psychometric data for the upper limb composite active movement (CXA), derived from the Five Step Assessment. For overall measurement of UL mobility after stroke, we strongly recommend including shoulder and forearm muscles to the score. CLINICAL REHABILITATION IMPACT: Composite XA is a valid and reliable measure of upper limb motor function in chronic post-stroke patients and could be used in clinical practice and research.

Deterministic placement of ultra-bright near-infrared color centers in arrays of silicon carbide micropillars.

We report the enhancement of the optical emission between 850 and 1400 nm of an ensemble of silicon mono-vacancies (VSi), silicon and carbon divacancies (VCVSi), and nitrogen vacancies (NCVSi) in an n-type 4H-SiC array of micropillars. The micropillars have a length of ca. 4.5 µm and a diameter of ca. 740 nm, and were implanted with H+ ions to produce an ensemble of color centers at a depth of approximately 2 µm. The samples were in part annealed at different temperatures (750 and 900 °C) to selectively produce distinct color centers. For all these color centers we saw an enhancement of the photostable fluorescence emission of at least a factor of 6 using micro-photoluminescence systems. Using custom confocal microscopy setups, we characterized the emission of VSi measuring an enhancement by up to a factor of 20, and of NCVSi with an enhancement up to a factor of 7. The experimental results are supported by finite element method simulations. Our study provides the pathway for device design and fabrication with an integrated ultra-bright ensemble of VSi and NCVSi for in vivo imaging and sensing in the infrared.

Adaptations of fatigue and fatigability after a short intensive, combined rehabilitation program in patients with multiple sclerosis.

OBJECTIVE: Fatigue and fatigability are common problems in patients with multiple sclerosis, which might be improved by rehabilitation. The aim of this pilot study was to assess changes in the fatigue and fatigability of knee extensors in patients with multiple sclerosis after a short intensive, combined rehabilitation programme (including physiotherapy primarily focused on gait and balance, endurance and resistance training). METHODS: Twenty-three patients with multiple sclerosis (10 men, 13 women) underwent isokinetic evaluations of fatigability of the knee extensor muscles during concentric contractions and rated a self-reported fatigue scale (Modified Fatigue Impact Scale; MFIS) before and after a rehabilitation programme. Patients performed rehabilitation for 150 min, 4 days per week for 4 weeks, with physiotherapy focused primarily on gait and balance, endurance training and resistance training. RESULTS: After rehabilitation, perception of fatigue decreased significantly (median MFIS scores [1st; 3rd quartiles], pre: 44 [33; 53] vs post: 33.5 [16; 43]; <0.00025). Moment fatigue index increased (pre: 37.70±13.40 vs post: 48.10±9.39; p<0.0125), but end-test moment did not change. After rehabilitation, strength increased during both isometric and concentric contraction (mean first 5 and mean 50 contractions of the fatigue protocol) (p<0.0125). After rehabilitation, neuromuscular efficiency improved (p<0.0125). CONCLUSION: After a short, intensive, combined rehabilitation programme, fatigue decreased but fatigability increased (moment fatigue index). Indeed, fatigability increased because strength in the initial state increased and strength in the fatigued state did not change. Although the rehabilitation programme was designed so that resistance training was carried out after endurance training to specifically train muscles in a fatigued state, no improvements in strength in the fatigued state were measured.

Fatigability in Patients With Multiple Sclerosis During Maximal Concentric Contractions.

OBJECTIVE: To compare quadriceps fatigability during maximal concentric contractions in persons with multiple sclerosis (MS) and healthy subjects. DESIGN: Observational study. SETTING: Hospital rehabilitation department. PARTICIPANTS: Persons with MS (n=38) and healthy subjects (n=14) were included (N=52). Torque of the knee flexor and extensor muscles and fatigability of the knee extensor muscles were evaluated using an isokinetic device. Surface electromyographic activity of the rectus femoris, vastus lateralis, biceps femoris, and semitendinosus muscles was recorded. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Muscle fatigability (torque fatigue index). RESULTS: The torque fatigue index was lower in persons with MS than in healthy subjects, but when torque was normalized to maximal isometric peak torque, persons with MS and healthy subjects finished the fatigue protocol at exactly the same level of relative strength (50% of the maximal isometric peak torque). Moreover, the reduction in torque was primarily because of a reduction in neuromuscular efficiency, with no changes of coactivation of antagonist muscles. CONCLUSIONS: Although fatigue is a disabling symptom of MS, persons with MS develop less muscle fatigability than healthy subjects during repeated maximal concentric contractions, but they end up at the same level of relative strength.

Relationship between neuromuscular and perceived fatigue and locomotor performance in patients with multiple sclerosis.

BACKGROUND: Fatigue is a common problem in patients with multiple sclerosis; however, the impact of neuromuscular and perceived fatigue on locomotor performance is currently unknown in these patients. AIM: The aim of this study was: 1) to determine the relationship between perceived and neuromuscular fatigue and locomotor performance in patients with multiple sclerosis; 2) to determine if neuromuscular and perceived fatigue depend on the severity of the pathology defined by the Expanded disability status scale score (EDSS). DESIGN: Observational study. SETTING: Outpatients from a hospital rehabilitation department. POPULATION: Thirty patients with multiple sclerosis underwent clinical (spasticity, strength, perceived fatigue and locomotor performance) and isokinetic evaluations (peak torque of knee flexor and extensor muscles and neuromuscular fatigue of knee extensor muscles). METHODS: The main outcome measures were perceived and neuromuscular fatigue and locomotor performance. Secondary outcomes were strength of the weakest limb and peak isometric torque of knee flexor and extensor muscles, spasticity, EDSS. RESULTS: There were no significant correlations between perceived or neuromuscular fatigue and locomotor performance. Locomotor performance was correlated with EDSS, spasticity, strength of the weakest limb and peak isometric torque of knee flexor and extensor muscles. Eighty­three percent of the variance of the 6MWT could be explained by EDSS score, strength of the weakest limb (MRCsum), torque produced during the last five contractions of the fatigue protocol and peak isometric torque of knee flexor muscles. Patients with moderate disability (EDSS Score 4-6) had greater levels of neuromuscular fatigue than patients with mild disability (<4). CONCLUSIONS: Although fatigue is a disabling symptom of multiple sclerosis, and neuromuscular fatigue was found to be higher in more disabled patients, locomotor performance was correlated with strength and spasticity but not with fatigue. CLINICAL REHABILITATION IMPACT: Nevertheless, fatigue was related to 6MWT performance since torque produced during the last five contractions of the fatigue protocol was one of the factors which explained performance.

Coactivation of Lower Limb Muscles during Gait in Patients with Multiple Sclerosis.

BACKGROUND: Coactivation of agonist and antagonist lower limb muscles during gait stiffens joints and ensures stability. In patients with multiple sclerosis, coactivation of lower limb muscles might be a compensatory mechanism to cope with impairments of balance and gait. OBJECTIVE: The aim of this study was to assess coactivation of agonist and antagonist muscles at the knee and ankle joints during gait in patients with multiple sclerosis, and to evaluate the relationship between muscle coactivation and disability, gait performance, dynamic ankle strength measured during gait, and postural stability. METHODS: The magnitude and duration of coactivation of agonist-antagonist muscle pairs at the knee and ankle were determined for both lower limbs (more and less-affected) in 14 patients with multiple sclerosis and 11 healthy subjects walking at a spontaneous speed, using 3D-gait analysis. RESULTS: In the patient group, coactivation was increased in the knee muscles during single support (proximal strategy) and in the ankle muscles during double support (distal strategy). The magnitude of coactivation was highest in the patients with the slowest gait, the greatest motor impairment and the most instability. CONCLUSION: Increased muscle coactivation is likely a compensatory mechanism to limit the number of degrees of freedom during gait in patients with multiple sclerosis, particularly when postural stability is impaired.

Excitonic linewidth of organic quantum wires generated in reduced dimensionality matrices.

Luminescent organic quantum wires are generated in diacetylene crystalline ultra-thin films grown on orientation-inducing surfaces obtained by poly-tetrafluoroethylene (teflon) deposition. The films are characterized by atomic force microscopy showing that quasi-two-dimensional surroundings are achieved. In this particular environment, pure dephasing processes still determine the wires' homogeneous emission widths, measured using micro-photoluminescence. Coherence times that are slightly shorter in the films also exhibit a distinctive temperature dependence. A model inspired by semiconductor physics for exciton-phonon coupling accounts for the observed behaviour and evidences the role of matrix dimensionality on the coherence properties.

Relationship between neuromuscular fatigue and spasticity in chronic stroke patients: a pilot study.

INTRODUCTION: The aim of this study was to assess the effects of neuromuscular fatigue on stretch reflex-related torque and electromyographic activity of spastic knee extensor muscles in hemiplegic patients. The second aim was to characterize the time course of quadriceps muscle fatigue during repetitive concentric contractions. METHODS: Eighteen patients performed passive, isometric and concentric isokinetic evaluations before and after a fatigue protocol using an isokinetic dynamometer. Voluntary strength and spasticity were evaluated following the simultaneous recording of torque and electromyographic activity of rectus femoris (RF), vastus lateralis (VL) and biceps femoris (BF). RESULTS: Isometric knee extension torque and the root mean square (RMS) value of VL decreased in the fatigued state. During the fatigue protocol, the normalized peak torque decreased whereas the RMS of RF and BF increased between the first five and last five contractions. There was a linear decrease in the neuromuscular efficiency-repetitions relationships for RF and VL. The peak resistive torque and the normalized RMS of RF and VL during passive stretching movements were not modified by the fatigue protocol for any stretch velocity. DISCUSSION: This study showed that localized quadriceps muscle fatigue caused a decrease in voluntary strength which did not modify spasticity intensity. Changes in the distribution of muscle fiber type, with a greater number of slow fibers on the paretic side, may explain why the stretch reflex was not affected by fatigue.

Reversible quenching of a chromophore luminescence by color transition of a polydiacetylene.

A new reactive diacetylene molecule has been synthesized, incorporating a strongly luminescent chromophore, tetrazine (Tz). It readily polymerizes into the blue polydiacetylene (PDA) form, quenching the Tz luminescence already at concentrations ≤1 %. The blue to red PDA transition is thermally induced in the solid state and the original strong Tz emission is restored. This might lead to a new type of detection for sensors using the PDA color transition.

Coherent control of the optical emission in a single organic quantum wire.

We report on the first coherent control experiments on a purely electronic exciton state in an extended quasi-perfect organic quantum wire, a polydiacetylene chain isolated in the crystalline matrix of its own monomer. The time-integrated luminescence of a single wire is measured as the relative phase between two exciting sub-picosecond laser pulses is varied. From visibility functions the exciton dephasing time is extracted and its temperature dependence studied. Our work points the predominant role of thermalization upon the phase relaxation dynamics. By means of microscopic imaging spectroscopy we also show that despite local excitation coherent control is achieved on states delocalized over the chain at the micrometric scale.