Changes In Muscle Properties Research Articles

Ultrasound assessment of muscle and fascia properties and the effects of spasticity and botulinum toxin injections on spastic muscles in chronic stroke survivors.

To objectively quantify changes in muscle properties in chronic stroke survivors and the effects of spasticity and botulinum toxin injections (BoNTi) on muscle properties using ultrasonography. In this cross-sectional observational study, 24 stroke subjects with history of BoNTi to biceps brachii muscles (BB) but without BoNTi to the triceps (TRI) were included. 12 subjects had spastic TRI, the other half did not. 20 subjects had spasticity in wrist flexors, and 11 subjects received BoNTi to the flexor carpii ulnaris (FCU). On average, a significant decrease in muscle thickness (16.5% loss in TRI), a thicker fascia with higher echo intensity were noted on muscles in the paretic limb. Percent muscle loss (PML) was significantly less (11.0%) in spastic TRI than in non-spastic TRI (22.1%). There was no statistically significant difference in muscle and fascia properties in spastic FCU with and without BoNTi. Spasticity did not correlate significantly with muscle loss, fascia thickness or echo intensity. Our results provided evidence that muscles on the spastic-paretic side had less muscle mass, thicker fascia and greater echo intensity. Our results showed that spasticity helped maintain muscle mass, but failed to reveal additional muscle loss after botulinum toxin injection.

Verification of the superiority of radiofrequency irradiation with static stretching over static stretching alone for hamstring tightness

IntroductionHealthy hamstring muscles are necessary for active living. Hamstring tightness is a widely reported problem among individuals from all levels of society. The effects of combining radiofrequency (RF) therapy with static stretching (SS) on hamstring tightness have not been investigated. Therefore, we aimed to verify the superiority of combining RF and SS over SS alone by comparing their immediate effects on hamstring flexibility. MethodsThis randomized controlled study included 33 participants with hamstring tightness. The participants were allocated to the RF (intervention; n = 17) or sham (n = 16) group. The RF group underwent SS simultaneously with RF therapy. The sham group underwent SS with sham RF (powered off). The range of motion (ROM) for knee extension and five muscle properties (tone, stiffness, elasticity, relaxation, and creep) of the lateral and medial hamstrings were measured before and after the intervention. ResultsThere was no significant difference in the ROM for knee extension (p = 0.295) between the RF and sham groups. The interaction between group and period (p > 0.05) was not significant for any of the muscle properties of the lateral and medial hamstrings besides lateral hamstring elasticity (p = 0.001). ConclusionRF therapy in conjunction with SS for hamstring tightness produced different changes in muscle properties compared with SS alone. However, these changes did not produce differences in the ROM for knee extension.

Immediate Effects of TECAR Therapy on Gastrocnemius and Quadriceps Muscles with Spastic Hypertonia in Chronic Stroke Survivors: A Randomized Controlled Trial.

The aim of this study was to assess changes in muscle properties after a single session of capacitive and resistive energetic transfer (TECAR) therapy on spastic gastrocnemius and quadriceps muscles in chronic post-stroke. A total of 36 chronic stroke survivors with lower limb hypertonia were enrolled in a double-blind randomized controlled trial. The experimental group (n = 18) received a single 30 min session of TECAR therapy in combination with functional massage (FM) on the gastrocnemius and quadriceps muscles. The control group (n = 18) received a sham treatment of TECAR therapy (without electrical stimulation) in combination with real FM. The primary outcome was muscle tone of the lower limb muscles assessed with the Modified Ashworth Scale (MAS). The secondary outcomes were goniometric degrees of the MAS (goniometer), neuromuscular properties of the gastrocnemius/quadriceps (myotonometer), and passive range of motion (inclinometer). All measurements were performed at baseline (T0), immediately after treatment (T1), and at 30 min post-treatment (T2) by a blinded assessor. The MAS score ankle dorsiflexion significantly decreased at T0-T1 (p = 0.046), and the change was maintained at T0-T2 (p = 0.019) in the experimental group. Significant improvements were noted in the passive range of motion for knee flexion (p = 0.012) and ankle dorsiflexion (p = 0.034) at T2. In addition, knee flexion improved at T1 (p = 0.019). A single session of Tecar therapy at the same time with FM on the gastrocnemius and rectus femoris immediately reduces muscle tone and increases the passive range of motion of both ankle and knee in chronic stroke survivors. There were no significant changes in the neuromuscular properties measured with myotonometer.

Development of a muscle electrical stimulation parameter selection method with an intelligent system

In this study, we propose a methodology for the selection of electrical stimulation parameters for muscle rehabilitation. This methodology uses a particle swarm optimizer to find a set of parameters that maximizes the muscle contraction force during the stimulation session. The optimization makes use of a previously validated mathematical muscle contraction model. To adjust the model to this application, we propose a series of adaptations to the model, such as the inclusion of a muscle fatigue function and different levels of muscle atrophy representations thru parametric variation. We based our model adaptations on the results of parametric sensitivity analysis and the qualitative changes in muscle properties during atrophy and fatigue described in the current literature. With the fatigue function, we successfully recreated the qualitative behavior reported in the literature for muscle fatigue caused by electrical stimulation. The parametric variations proposed following the sensitivity analysis are consistent with the physiological changes occurring during muscle atrophy, and the simulations with the model supported our hypothesis. Finally, we showed that with the model and the particle swarm optimizer, it is possible to find a set of electrical stimulation parameters that maximize the muscle contraction force during the stimulation session.

Evaluation of Changes in Quadriceps Femoris Muscle in Critically III Children Using Ultrasonography.

To measure changes in muscle thickness and echogenicity, reflecting muscle bulk and quality, respectively, of quadriceps femoris (QF), in critically ill children. This study was done on 58 children aged 1-18 y requiring mechanical ventilation, admitted in a pediatric intensive care unit (PICU) of a tertiary care hospital from January 2018 to June 2019. QF thickness was measured twice in longitudinal plane and twice in transverse plane, and an average of these four measurements was used. Muscle quality was assessed using ImageJ software to determine the mean echogenicity, and was calculated separately for vastus intermedius and rectus femoris. These observations were repeated on day 3 and day 7 of the ICU stay. The median muscle thickness of QF was 1.58cm, and vastus intermedius and rectus femoris echogenicity was 35.5 and 25.88 units, respectively in the present cohort, with median age of 6 y. Only 36 of the 58 patients underwent day 7 ultrasonography, as the remainder were either extubated or died. There was no significant change in the muscle thickness over 7 d. Rectus femoris echogenicity increased significantly over 7 d by 16.1% (p = 0.03). Baseline vastus intermedius echogenicity was significantly higher in patients who subsequently died during the course of their illness (p = 0.026). There was a significant change in rectus femoris echogenicity, but not in QF thickness. Echogenicity rather than muscle thickness may be a more sensitive marker for changes in muscle properties.

Association of Physical Activity and Nutritional Intake with Muscle Quantity and Quality Changes in Acute Stroke Patients

ObjectivesTo evaluate longitudinally the muscle properties of acute stroke patients and examine the association between physical activity and nutritional intake. Materials and methodsThis study enrolled 21 stroke patients (72.7±10.4 years). Muscle quantity (fat-free mass, appendicular skeletal muscle mass) and quality (extracellular water/intracellular water ratio, phase angle) were assessed using a bioelectrical impedance device at baseline (within three days) and two weeks after stroke onset. Physical activity and sedentary were calculated from the accelerometer data. Total energy and protein intake were calculated from the dietary surveys as nutritional intake. The association of physical activity, sedentary, and nutritional intake with the rate of changes in muscle properties was examined. ResultsThe fat-free mass significantly decreased (from 43.4±8.0 to 42.2±7.6 kg), and the skeletal muscle was unchanged (from 17.8±4.2 to 17.7±4.0 kg) after two weeks. The extracellular water/intracellular water ratio significantly increased (from 0.63±0.02 to 0.65±0.03) and the phase angle significantly decreased (from 5.1±0.6 to 4.9±0.8°), suggesting that the muscle quality have declined. Correlation analysis showed that the extracellular water/intracellular water ratio was significantly associated with physical activity [metabolic equivalents (ρ=-0.61)] and sedentary (ρ=0.67) and that the phase angle was significantly associated with physical activity [metabolic equivalents (ρ=0.69)], sedentary (ρ=-0.68), and nutritional intake [total energy (r=0.45), protein (r=0.45)]. ConclusionsThe fat-free mass and muscle quality (extracellular water/intracellular water ratio and phase angle) declined two weeks after stroke. Physical activity and nutritional intake were lower in patients with decreased muscle quality, suggesting the importance of exercise and nutrition in the acute phase.

Age- and muscle-specific reliability of muscle architecture measurements assessed by two-dimensional panoramic ultrasound

BackgroundAge-related changes in muscle properties affect daily functioning, therefore a reliable assessment of such properties is required. We examined the effects of age on reliability, muscle quality and interrelation among muscle architecture (MA) parameters of the gastrocnemius medialis (GM), tibialis anterior (TA), and vastus lateralis (VL) muscles.MethodsThree raters scored ultrasound (US) scans of 12 healthy younger and older adults, on fascicle length (FL), pennation angle (PA) and muscle thickness (MT). Intra- and inter-rater reliability of MA measures in rest and contraction was assessed by intraclass correlation coefficients (ICC) and standard error of measurements (SEM, SEM%). The relationship between MA parameters was examined using Pearson correlation coefficients. Muscle quality (MQ) was examined using mean pixel intensity.ResultsReliability was moderate to excellent for TA in both groups (ICCs: 0.64–0.99, SEM% = 1.6–14.8%), and for VL in the younger group (ICCs: 0.67–0.98, SEM% = 2.0–18.3%). VL reliability was poor to excellent in older adults (ICCs: 0.22–0.99, SEM% = 2.7–36.0%). For GM, ICCs were good to excellent (ICCs: 0.76–0.99) in both groups, but GM SEM% were higher in older adults (SEM%Younger = 1.5–10.7%, SEM%Older = 1.6–28.1%). Muscle quality was on average 19.0% lower in older vs. younger adults. In both groups, moderate to strong correlations were found for VL FL and MT (r ≥ 0.54), and TA PA and MT (r ≥ 0.72), while TA FL correlated with MT (r ≥ 0.67) in younger adults only.ConclusionsIn conclusion, age- and muscle-specificities were present in the relationships between MT and PA, and MT and FL at rest. Furthermore, the reliability of MA parameters assessed with 2D panoramic US is acceptable. However, the level of reliability varies with age, muscle and MA measure. In older adults notably, the lowest reliability was observed in the VL muscle. Among the MA parameters, MT appears to be the simplest and most easily reproducible parameter in all muscles and age groups.

The Physicochemical, Microbiological, and Structural Changes in Beef Are Dependent on the Ultrasound System, Time, and One-Side Exposition.

The effect of high-intensity ultrasound (HIU) system (bath, 37 kHz and 90 W/cm2; or probe, 24 kHz and 400 W) and application time (25 or 50 min, one-side exposition) on the properties of bovine Longissimus lumborum after 7 d of storage at 4 °C was studied. The bath system significantly increased the lightness of the muscle, while other color parameters (a*, b*, hue, and chroma) were not different from the control. The water holding capacity and shear force decreased significantly (3.1–5% and 0.59–0.72 kgf, respectively) in sonicated meat independently of the system, favoring the tenderization of the muscle after storage. Microstructural changes observed in the HIU-exposed surface provided evidence of a higher area of interfibrillar spaces (1813 vs. 705 µm2 in the control), producing tenderization of the muscle, compared with the control. HIU significantly increased counts of total aerobic and coliform bacteria, especially after 50 min of ultrasonication. HIU also increased lactic acid bacterial counts in the bath system. Single-sided muscle exposition to ultrasound may produce sufficient significant changes in muscle properties, which could decrease long treatment times that would be needed for the exposition of both sides. HIU in bath systems increases tenderness by modifying meat ultrastructure, with no significant changes in physicochemical parameters. Nevertheless, microbiological quality may need to be considered during the process due to a slight increase in bacterial counts.

Właściwości fizjologiczne i mechaniczne mięśni szkieletowych - czy są takie same w różnych mięśniach i u wszystkich osób?

Nasze zdolności do wykonywania ruchów i wysiłków fizycznych uwarunkowane jest prawidłowym funkcjonowaniem mięśni szkieletowych zależnym od właściwości mięśni. Dlatego celem niniejszego artykułu była charakterystyka właściwości mięśni szkieletowych, począwszy od pobudzenia mięśnia, jego zdolności kurczenia się i rozwijania siły, po właściwości mechaniczne tkanki mięśniowej. W artykule omawiamy kolejno właściwości fizjologiczne, w tym pobudzenie mięśnia i zdolności do rozwijania siły, i czynniki je warunkujące, oraz właściwości mechaniczne tkanki mięśnia. Głównie opisujemy i podajemy wyniki badań własnych w tym zakresie. Następnie, na podstawie wyników badań własnych opisujemy właściwości badanych przez nas mięśni, odnosząc różnice między nimi do pełnionej funkcji. W dwóch ostatnich rozdziałach opisujemy właściwości mięśni u osób w różnym wieku oraz osób chorujących na chorobę Parkinsona, wykazując i odpowiadając na postawione pytania, że właściwości mięśni zmieniają się z wiekiem i w chorobach neurodegeneracyjnych, jaką jest choroba Parkinsona, co zmniejsza zdolność tych osób do rozwijania siły i wykonywania wysiłku fizycznego.

Effect of diacutaneous fibrolysis on the muscular properties of gastrocnemius muscle

Diacutaneous fibrolysis is a noninvasive technique that has been shown to be effective in the treatment of musculoskeletal disorders such as shoulder pain, lateral epicondylalgia, patellofemoral pain syndrome and carpal tunnel syndrome. However, while diacutaneous fibrolysis is applied to soft tissue, its effects on muscular properties are unknown. The purpose of the present study was to evaluate the effects of diacutaneous fibrolysis on muscle properties as measured by tensiomyography and myotonometry in asymptomatic subjects. An analytical descriptive study was performed. A single session of diacutaneous fibrolysis on the gastrocnemius muscle was applied to one limb (treated limb group) and the other limb was the control (control limb group). Subjects were assessed with tensiomyography and myotonometry before treatment (T0), after treatment (T1) and 30 minutes later (T2). The primary outcomes were tensiomyography and myotonometry variables. The treated limb group showed a statistically significant increase (p<0.05) in tensiomyography parameters. A decrease in rigidity and increase in relaxation was also observed on myotonometry at T1, with some of the effects being maintained at T2. Rigidity and relaxation at T1 were statistically significant between groups (p<0.05). A single session of diacutaneous fibrolysis to the gastrocnemius muscle of asymptomatic subjects produced immediate changes in muscle properties. These changes were maintained 30 minutes after the application of the technique.

Prolonged sitting and physical inactivity are associated with limited hip extension: A cross-sectional study

BackgroundIt is possible that physical inactivity and prolonged sitting could lead to changes in muscle properties or bony limitations which may reduce passive hip extension. ObjectivesThis study explored the association between passive hip extension and sitting/physical activity patterns. DesignCross sectional study. MethodThe modified Thomas Test is a clinical test used to characterise hip flexion contracture. This test was used to measure passive hip extension across 144 individuals. In addition, sitting behaviours and physical activity patterns were quantified using the Global Physical Activity Questionnaire. Cut off points were defined for low/high physical activity (150 min per week), prolonged sitting (>7 h per day) and minimal sitting (<4 h per day). ANOVA testing was then used to compare passive hip extension between three groups, defined using the specified thresholds: low activity & prolonged sitting, high activity & minimal sitting and high activity & prolonged sitting. ResultsA total of 98 participants were allocated to one of the three groups which were shown to differ significantly in passive hip extension (P < 0.001). Importantly, there was 6.1° more passive hip extension in the high activity & minimal sitting group when compared to the low activity & prolonged sitting group. ConclusionThis study is the first to demonstrate an association between passive hip extension and prolonged sitting/physical inactivity. It is possible that these findings indicate a physiological adaptation in passive muscle stiffness. Further research is required to understand whether such adaptation may play a role in the aetiology of musculoskeletal pain linked to prolonged sitting.

Right ventricular function inpulmonary (arterial) hypertension.

The right ventricle (RV) is the main determinant of prognosis in pulmonary hypertension. Adaptation and maladaptation of the RV are of crucial importance. In the course of disease, RV contractility increases through changes in muscle properties and muscle hypertrophy. At acertain point, the point of "uncoupling," the afterload exceeds contractility, and maladaptation as well as dilation occurs to maintain stroke volume (SV). To understand the adaptational processes and to further develop targeted medication directly affecting load-independent contractility, an accurate and precise assessment of contractility and RV-pulmonary artery (PA) coupling should be performed. In this review, we shed light on existing methods to assess RV function, including the gold standard measurement of contractility and RV-PA coupling, and we evaluate existing surrogates of RV-PA coupling.

Toward Electrical Impedance Tomography Coupled Ultrasound Imaging for Assessing Muscle Health.

This paper establishes for the first time that a coupled ultrasound (US) and electrical impedance tomography (EIT) system can serve as a non-invasive, spatially localized approach to extract clinically relevant muscle properties. The US/EIT system represents a potential enhancement to electrical impedance myography (EIM), which has shown promise as a non-invasive technology that may have important clinical use in indicating neuromuscular disease status and as a diagnostic tool. A 2.5D EIT algorithm evaluated on simulation, measured phantoms, and measured patient data was studied to evaluate US/EIT's ability to distinguish different aspects of muscle tissue. Simulated and phantom experiments revealed the depths of distinguishability of 3.2 and 4.2 mm in simulation for 10% and 20% changes in muscle properties, respectively, and 3.6 mm in measured phantom experiments assuming a 12% muscle conductivity change. Reconstructions from the patient data established that there were consistent differences 1) between longitudinal (along) and transverse (across) muscle conductivity reconstructions at frequencies of 40 and 80 kHz and 2) side-by-side comparison between healthy and diseased tissue in terms of conductivity, permittivity, and phase at 40 and 80 kHz. Comparisons were made between the EIT reconstructed values and electrical impedance spectroscopy (EIS) measurements (an available surrogate in place of standard EIM measurements) made with the US/EIT system, wherein 1) EIS and EIT show similar sensitivity to longitudinal and transverse differences and 2) EIT showed a more consistent ability to differentiate healthy and diseased tissue. These results suggest that US/EIT appears very promising for non-invasive and spatially localized diagnosis of muscle health.

Extensibility of the supraspinatus muscle can be predicted by combining shear wave elastography and magnetic resonance imaging-measured quantitative metrics of stiffness and volumetric fat infiltration: A cadaveric study

BackgroundA torn rotator cuff tendon will retract over time causing changes in muscle properties and decreasing its extensibility, or deformation. During surgery, large tensile loads are applied to bring the torn tendon to the footprint. Poor muscle extensibility and large tensile stresses at the repair might lead to gap formation or re-tear of the repair. A quantitative evaluation of muscle properties could be used to predict the extensibility of the supraspinatus (SSP) muscle. MethodMagnetic resonance imaging (MRI)-measured volumetric fat fraction and shear wave elastography (SWE)-measured elastic modulus of the SSP muscle were obtained on seventeen cadaveric shoulders. Experimental extensibility and stiffness were then measured by axially pulling the tendon up-to 60 N. Univariate and multivariate analyses were used to determine the correlation and contribution of fat fraction and elastic modulus to experimental outcomes. FindingsSWE moduli negatively correlated with SSP muscle extensibility (r = 0.54–0.58, P ≤ 0.0259); fat fraction resulted in a positive correlation (r = 0.69, P = 0.0021). SWE measurements, solely, explained up to 34% and 33% of the variability in measured extensibility and stiffness, respectively. Fat Fraction, solely, explained 48% of the variability in extensibility and 36% of the variability in stiffness. These methods combined predicted up to 62% of the musculotendinous extensibility. InterpretationThis study showed a comprehensive quantitative assessment of SSP muscle properties using SWE to estimate stiffness and MRI to measure fatty infiltration. The extensibility of the detached muscle/tendon unit was highly correlated to material properties of the muscle when these methods were used in combination.

Effects of Duchenne muscular dystrophy on muscle stiffness and response to electrically-induced muscle contraction: A 12-month follow-up

The present study aimed to assess the ability of muscle stiffness (shear modulus) and response to electrically-induced muscle contraction to detect changes in muscle properties over a 12-month period in children with Duchenne muscular dystrophy (DMD). Ten children with DMD and nine age-matched healthy male controls participated in two experimental sessions (T0 and T+12months) separated by 12.4 ± 0.9 months. Two contractions of the biceps brachii were electrically-induced during which an ultrasound probe was placed over the muscle. The resting shear modulus was measured using elastography from six muscles. Evoked maximal torque was increased at T+12months in controls (+11.2 ± 7.6%, P < 0.001) but was not modified in children with DMD (P = 0.222). Electromechanical delay (+12.9 ± 11.3%, P < 0.001) and its force transmission component (+10.1 ± 21.6%, P = 0.003) were significantly longer at T+12months than T0 for children with DMD. The results revealed an increase in muscle stiffness at T+12months in children with DMD for tibialis anterior (+75.1 ± 93.5%, P = 0.043), gastrocnemius medialis (+144.8 ± 180.6%, P = 0.050) and triceps brachii (+35.5 ± 32.2%, P = 0.005). This 12-month follow-up study demonstrates that electromechanical delay and elastography may help detect subtle muscle impairments in patients with DMD. These sensitive outcomes may improve the follow-up of innovative therapeutic interventions within the field of DMD.

Measurement of ageing effects on muscle tone and mechanical properties of rectus femoris and biceps brachii in healthy males and females using a novel hand-held myometric device

BackgroundAge and gender effects on muscle tone and mechanical properties have not been studied using hand-held myometric technology. Monitoring changes in muscle properties with ageing in community settings may provide a valuable assessment tool for detecting those at risk of premature decline and sarcopenia. ObjectiveThis study aimed to provide objective data on the effects of ageing and gender on muscle tone and mechanical properties of quadriceps (rectus femoris) and biceps brachii muscles. MethodsIn a comparative study of 123 healthy males and females (aged 18–90 years; n=61 aged 18–35; n=62 aged 65–90) muscle tone, elasticity and stiffness were measured using the MyotonPRO device. ResultsStiffness was greater and elasticity lower in older adults for BB and RF (p<0.001). Tone was significantly greater in older adults for BB but not for RF when data for males and females were combined (p=0.28). There were no gender differences for BB in either age group. In RF, males had greater stiffness (young males 292 vs females 233N/m; older males 328 vs females 311N/m) and tone (young 16.4 vs 13.6Hz; older 16.7 vs 14.9Hz). Elasticity in RF was lower in young males than females but did not differ between the older groups (both males and females log decrement 1.6). ConclusionsStiffness and tone increased with ageing and elasticity decreased. These findings have implications for detecting frailty using a novel biomarker. Age and gender differences are important to consider when assessing effects of pathological conditions on muscle properties in older people.

My research life: from synaptic transmission to behavior

I have studied signal transmission at synapses and the effects of drugs on it at the molecular and cellular levels. Specific areas of research interest are outlined here. 1) Electrophysiological experiments in cats and rabbits suggested that a new type of analgesic, the phenothiazine derivative levomepromazine, exerts analgesic effects by depressing emotional responses accompanying the sensation of pain. 2) It was hypothesized that motoneurons had long-term effects on muscle cell membrane properties, in addition to controlling moment-to-moment activities. The substance to recover the post-denervation changes in muscle properties in culture was partially purified from mouse nerve extract, which suggested that trophic influences were exerted by substances released from motoneurons. 3) Muscles innervated by adrenergic fibers had sites responsive to acetylcholine as well as to adrenaline in early life in chicks, but only the adrenaline-responsive sites remained during development. Acetylcholine receptor clusters on Xenopus muscles were concentrated at the cholinergic neuromuscular junctions by the movement of receptors from outside the junctions during development. The passive diffusion-trap mechanism explained the accumulation of synaptic receptors at synapses. 4) We found two endocytic pathways and pools of synaptic vesicles contributing to low- and high-frequency synaptic transmission at Drosophila nerve terminals. We then identified two Ca2+ channels designated for the low- and high-frequency endocytosis of synaptic vesicles, straightjacket Ca2+ channels in the active zone and La3+-sensitive Ca2+ channels in the inactive zone at the terminals, respectively. Recently, Drosophila melanogaster has been used as a model for studying the social brain, and the heat avoidance response of the flies was found to be socially enhanced. Future studies are expected to reveal mechanisms underlying social brain functions at the gene level.

Passive muscle properties are altered in children with cerebral palsy before the age of 3 years and are difficult to distinguish clinically from spasticity

Clinical determination of spasticity is confounded by the difficulty in distinguishing reflex from passive contributions to muscle stiffness. There is, therefore, a risk that children with cerebral palsy (CP) receive antispasticity treatment unnecessarily. To investigate this, we aimed to determine the contribution of reflex mechanisms to changes in the passive elastic properties of muscles and tendons in children with CP. Biomechanical and electrophysiological measures were used to determine the relative contribution of reflex and passive mechanisms to ankle muscle stiffness in 35 children with spastic CP (21 males, 14 females; mean age 9 y, SD 3 y 4 mo; range 3-15 y) and 28 control children without CP (19 males, nine females; mean age 8 y 11 mo, SD 2 y 10 mo; range 3-15 y). Twenty-seven children were diagnosed as having spastic hemiplegia, six with spastic diplegia, and two with spastic tetraplegia. According to the Gross Motor Function Classification System, 31 children were classified in level I, two in level II, and two in level III. Only seven children with spastic CP showed reflex stiffness outside the range of the control children. In contrast, 20 children with spastic CP showed abnormal passive muscle stiffness (p<0.001). No correlation between increased reflex or increased passive muscle stiffness and age was observed within the age range studied. These data suggest that increased reflex-mediated muscle stiffness is difficult to distinguish clinically from changes in passive muscle stiffness and that signs of changes in muscle properties are already present from the age of 3 years in children with CP. This emphasizes the importance of accurately distinguishing different contributions to muscle stiffness to avoid unnecessary antispasticity treatment.

FK506 Induces Changes in Muscle Properties and Promotes Metabosensitive Nerve Fiber Regeneration

Accumulating evidence indicates that in addition to its immunosuppressant properties, FK506 (tacrolimus), an FDA-approved molecule, promotes nerve regeneration. However, the neuroprotective and neurotrophic effects of this molecule on sensitive fiber regeneration have never been studied. In order to fill this gap in our knowledge, we assessed the therapeutic potential of FK506 in a rat model of peripheral nerve repair. A 1-cm segment of left peroneal nerve was cut out and immediately autografted in an inverted position. After surgery, the animals were treated with FK506 (1.2 mg/kg/d) via an osmotic pump and compared to untreated animals. Recovery of use of the injured leg was assessed weekly for 12 weeks using a walking track apparatus and a camcorder. At the end of this period, motor and metabosensitive responses of the regenerated axons were recorded and histological analysis was performed. We observed that FK506 significantly: (1) increased the diameter of regenerated axons in the distal portion of the graft; (2) improved the responses of sensory neurons to metabolites such as potassium chloride and lactic acid; and (3) induced a fast-to-slow-fiber-type transition of the tibialis anterior muscle. Taken together, these data indicate that FK506 potentiates metabosensitive nerve fiber regeneration. Pharmacological studies of various dosages and concentrations of FK506 are required before recommending this drug for therapeutic treatment of nerve injuries.

Shift in the quadriceps angle of peak torque following a downhill marathon

Background: A shift in the angle of peak torque (APT) during maximal voluntary isokinetic concentric knee flexions and extensions has been demonstrated following eccentric and stepping exercise. Objective: To test the hypothesis that downhill marathon running is associated with a shift in the APT towards longer muscle length. Methods: Twelve male runners performed an isokinetic muscle test three to four days before and 18 hours after a downhill marathon. Both legs were tested and the testing protocol consisted of concentric and eccentric quadriceps and hamstring contractions at 60°/s. Results: There were no significant differences between quadriceps peak torque (PT) before and after the race. There was a bilateral shift in the APT of the quadriceps to a more extended position in the concentric but not in the eccentric testing mode. Conclusion: Running a downhill marathon is not associated with concentric and eccentric quadriceps fatigue. Prolonged downhill running could result in changes in muscle properties expressed in a shift in the APT towards shorter muscle lengths without significant force deficits in the concentric testing mode. By contrast, there was no shift in the APT in the eccentric testing mode challenging the functional significance of moving the angle of peak maximal voluntary concentric torque of the quadriceps muscles in connection with a downhill marathon.