Force Levels Research Articles

The Biomechanics of Spinal Orthoses for Adolescent Idiopathic Scoliosis: A Systematic Review of the Controlling Forces

Background: Orthotic treatment is a well-acknowledged conservative treatment for moderate adolescent idiopathic scoliosis (AIS). The efficacy of this treatment is significantly determined by the forces applied to the bodies of patients. However, there is uncertainty regarding the optimal force levels that should be applied to the patient’s torso by spinal orthosis. This study aims to identify reference values for the controlling forces in AIS management. Methods: A comprehensive literature search was performed in five databases (PubMed, Scopus, Cochrane Library, CINAHL, and Web of Science). Only studies written in English and covering the force/pressure measurements of spinal orthosis for the treatment of AIS were included, without publication date restrictions. The methodological index for non-randomized studies (MINORS) was employed for the methodological quality assessment, and force measurements were standardized to pressure in kilopascals (kPa) for comparison. Results: From the initial 10,452 records, 10 studies were admitted for the final analysis. All the included studies reported the interface pressure between the thoracic (T) pad and patient’s trunk, and seven studies evaluated the pressure from the thoracolumbar/lumbar (TL/L) pad. These studies used different pressure sensors or transducers with the range from 5.6 to 82.5 kPa for the T pads, and 4.8 to 85.1 kPa for the TL/L pads. Four studies reported strap tensions of 26.8 to 60.4 N. Higher strap tension was correlated with increased interface pressure (r = 0.84). Conclusion: The mean strap tension was 42.5 N, the median interface pressure of the T pads was 8.75 kPa, and the median pressure of TL/L regions was 7.11 kPa without the outliers. The findings provide a baseline value for designing adjustable straps and strategically distributing pressure in orthoses.

Simplified Procedure for Estimating Seismic Displacement Capacity of Concrete Piles in Wharves

The procedure of estimating the seismic displacement capacity of piles under each performance level in current wharf practices involves monitoring the material strains specified in the design criteria during nonlinear static pushover analysis with a complex numerical model. Thus, a simplified procedure for concrete piles is proposed by developing closed-form formulas for displacement ductility capacity and yield displacement of piles, while the displacement capacity is the product of ductility capacity and yield displacement. The ductility capacity assures that the pile material strain limits specified in the criteria are not exceeded. The basic form of the formula for ductility capacity is established by using the equivalent cantilever concept to model the pile–soil interaction. Then, large quantities of moment–curvature analyses of sections and pushover analyses of concrete piles were conducted to determine the related parameters in the formula by considering numerous influencing factors. The results show that the ductility capacity can be expressed as a function of the curvature ductility capacity of pile sections at the selected performance level and parameter ψ. Based on the outcomes of curvature and pushover analyses, a set of practical formulas are proposed to determine the curvature ductility capacity, which depends on the longitudinal or transverse reinforcement ratios and axial force level, along with ψ, which depends on the aforementioned factors as well as the unsupported length of the pile.

Bone conduction stimulation efficiency at coupling locations closer to the cochlea

Bone conduction implants enable patients to hear via vibrations transmitted to the skull. The main constraint of current bone conduction implants is their maximum output force level. Stimulating closer to the cochlea is hypothesized to increase efficiency and improve force transfer, addressing this limitation. This study evaluated stimulation at four positions in human cadaveric specimens: the cochlear promontory, the posterior wall of the outer ear canal, the lateral semi-circular canal, and the standard Bone-Anchored Hearing Aid (Baha) location. To assess potential hearing sensation, three objective measures were simultaneously recorded. For intracochlear pressure and promontory velocity, stimulating at the lateral semi-circular canal and promontory results in the highest response, with a gain of up to 20 dB. Ear canal pressure shows less conclusive results, with significant differences at only a few frequencies. These findings suggest that stimulation closer to the cochlea offers higher efficiency, which could benefit patients needing higher output force levels than currently available or those eligible for electro-vibrational stimulation, e.g. a cochlear implant combined with a bone conduction device.

Effect of carbon black properties on cut and chip wear of natural rubber

The effect of carbon black colloidal properties on cut and chip wear of natural rubber compounds is investigated across a wide range of applied impact normal forces using an Instrumented Cut and Chip Analyzer (ICCA). The objective of the study is to determine the basic fatigue and fracture mechanisms that drive cut and chip wear. Natural rubber compounds reinforced with eight different carbon blacks varying in structure and surface area are studied. The loading of the carbon blacks in the rubber compounds is fixed at 50 parts per hundred rubber (phr). The cut and chip performance strongly correlates to both the carbon black morphological properties and the resulting compound mechanical and fracture properties. The cut and chip performance also depends on the applied impact normal force level. At low forces, high structure carbon blacks result in compounds which are stiffer and deflect less under the applied impact normal forces and minimize cut and chip wear. At high forces, low structure carbon black compounds, which are softer and more readily able to crystallize under force-controlled deflection, minimize cut and chip wear. It is argued that at low applied impact normal forces, the cut and chip behavior is dominated by a force-controlled fatigue crack growth mechanism which transitions to a critical tearing energy dominated mechanism at high applied impact normal forces. It is therefore important to understand the severity of application to select optimum compound properties such as the carbon black type to minimize cut and chip wear in application.

Study on Error Influence Analysis of an Annular Cable Bearing-Grid Structure

Manufacturing errors of cable length, external node coordinates and tension force by the passive tension method are inevitable, which will inevitably affect the prestressing of cable bearing-grid structures, while existing studies lack the error analysis of error influences in this area. This paper proposes a method for analyzing random errors in constructing annular cable bearing-grid structures. An error control index and a normal distribution-based random error model, considering the impact of cable and ring beam length errors on cable force, were established afterwards. Taking the roof of the Qatar Education City Stadium as an example, the influence of the length errors of the radial cable, ring cable, and outer pressure ring beam on the structural cable force and stress level was analyzed, and the coupling error effect analysis was carried out. The results show that ring cable force and radial cable force are less affected by the length error of each other’s cables, while they are more affected by the length error of the outer ring beam. Stress levels exhibit greater sensitivity to outer ring beam errors compared to cable length errors. As the error limits of outer ring beam increase, radial and ring cable error ratios and outer ring beam stress errors also rise.

Influence of different drilling forces on drill bit wear in automated drilling of concrete with industrial robots

AbstractThis article investigates the effect of different drilling forces on drill bit wear and their effects on drilling time within the context of the development of a drilling robot for on‐site construction applications. The study explores variations in three force levels (80, 120, 160 N), three directional orientations (upwards, downwards, horizontal), four drill bit diameters (8, 10, 12, 16 mm), and two concrete strength types (C25/30, C70/85). The findings indicate that while there is little divergence in drill bit wear across force levels, the influence of concrete strength is undeniable. Furthermore, drilling time increases, by 7 % to 11 % after 37.5 m drilling depth and up to 68% after 150 m depending on the drilling configuration. In conclusion, the study reveals a notable discrepancy between the progressive increase in drilling time and the relatively stable progression of drill bit wear, particularly in achieving code‐compliant boreholes.

Tetrandrine induces muscle atrophy involving ROS-mediated inhibition of Akt and FoxO3

Tetrandrine (Tet), a well-known drug of calcium channel blocker, has been broadly applied for anti-inflammatory and anti-fibrogenetic therapy. However, due to the functional diversity of ubiquitous calcium channels, potential side-effects may be expected. Our previous report revealed an inhibitory effect of Tet on myogenesis of skeletal muscle. Here, we found that Tet induced protein degradation resulting in the myofibril atrophy. Upon administration with a relative high dose (40 mg/kg) of Tet for 28 days, the mice displayed significantly reduced muscle mass, strength force, and myosin heavy chain (MyHC) protein levels. The MyHC reduction was further detected in C2C12 myotubes after treating with Tet. Interestingly, the expression of Atrogin-1 and Murf-1, the skeletal muscle specific E3 ligases of protein ubiquitin–proteasome system (UPS), was accordingly up-regulated, and the reduced MyHC was significantly mitigated by MG132, a 26S proteasome inhibitor, indicating a key role of UPS in the protein degradation of muscle cells. Further study showed that Tet induced autophagy also participated in the protein degradation. Mechanistically, Tet treatment caused ROS production in myotubes that in turn targeted on FoxO3/AKT signaling, resulting in the activation of UPS and autophagy processes that were involved in the protein degradation. Our study reveals a potential side-effect of Tet on skeletal muscle atrophy, particularly when the drug dose is relatively high.

The Relationship Between Length and Active Force for Submaximal Skeletal Muscle Contractions: a Review.

The force-length relationship is usually obtained for isometric contractions with maximal activation, but less is known about how sarcomere length affects force during submaximal activation. During submaximal activation, length-dependent alterations in calcium sensitivity, owing to changes in cross-bridge kinetics (rate of attachment and/or detachment), result in an activation-dependent shift in optimal length to longer sarcomere lengths. It is known that sarcomere length, as well as temperature and phosphorylation of the regulatory light chains of myosin, can modify Ca2⁺ sensitivity by altering the probability of cross-bridge interaction. This altered calcium sensitivity is particularly important for submaximal force levels, as it can change the shape of the length dependence of force, with peak force occurring at sarcomere lengths longer than those associated with maximal filament overlap. In athletic contexts, contractions typically do not reach maximal intensity. Therefore, understanding that the ability to produce force under both maximal and submaximal conditions can differ, and that peak force can be generated at different lengths, could influence the development of targeted training regimens optimal for each sport.

Modulating Fibrotic Mechanical Microenvironment for Idiopathic Pulmonary Fibrosis Therapy.

Idiopathic pulmonary fibrosis (IPF) is exacerbated by injurious mechanical forces that destabilize the pulmonary mechanical microenvironment homeostasis, leading to alveolar dysfunction and exacerbating disease severity. However, given the inherent mechanosensitivity of fibrotic lungs, where type II alveolar epithelial cells (AEC IIs) are subjected to persistent stretching and overactivated myofibroblasts experience malignant interactions during mechanotransduction, it becomes imperative to develop effective strategies to modulate the pulmonary mechanical microenvironment. Herein, cyclo (RGDfC) peptide-decorated zeolitic imidazolate framework-8 nanoparticles (named ZDFPR NPs) are constructed to target and repair the aberrant mechanical force levels in pathological lungs. Specifically, reduces mechanical tension in AEC IIs by pH-responsive ZDFPR NPs that release zinc ions and 7, 8-dihydroxyflavone to promote alveolar repair and differentiation. Meanwhile, malignant interactions between myofibroblast contractility and extracellular matrix stiffness during mechanotransduction are disrupted by the fasudil inhibition ROCK signaling pathway. The results show that ZDFPR NPs successfully restored pulmonary mechanical homeostasis and terminated the fibrosis process in bleomycin-induced fibrotic mice. This study not only presents a promising strategy for modulating pulmonary mechanical microenvironment but also pioneers a novel avenue for IPF treatment.

A portable and sensitive DNA-based electrochemical sensor for detecting piconewton-scale cellular forces

BackgroundCell-generated forces are a key player in cell biology, especially during cellular shape formation, migration, cancer development, and immune response. The measurement of forces exerted and experienced by cells is fundamental in understanding these mechanosensitive cellular behaviors. While cell-generated forces can now be detected based on techniques like fluorescence microscopy, atomic force microscopy, optical/magnetic tweezers, however, most of these approaches rely on complicated instruments or materials, as well as skilled operators, which could limit their potential broad applications in regular biological laboratories. ResultsA new type of smartphone-based electrochemical sensor is developed here for cellular force measurement. In this system, a double-stranded DNA-based force probe, known as tension gauge tether, is attached to the surface of a gold screen-printed electrode, which is then incorporated into a portable smartphone-based electrochemical device. Cellular force-induced DNA detachment on the sensor surface results in multiple redox reporters to reach the surface of the electrode and generate enhanced electrochemical signals. To further improve the sensitivity, a CRISPR-Cas12a system has also been incorporated to cleave the remaining surface-attached anchor DNA strand. Using integrin-mediated tension as an example, piconewton-scale adhesion forces generated by ≤ 10 HeLa cells could now be reliably detected. Meanwhile, the threshold forces of these electrochemical sensors can also be modularly tuned to detect different levels of cellular forces. SignificanceThese novel DNA-based highly sensitive, portable, cost-efficient, and easy-to-use electrochemical sensors can be potentially powerful tools for detecting different cell-generated molecular forces. Functioning as complementary tools with traction force microscopy and fluorescent probes, these electrochemical sensors can be straightforwardly applied in regular biological laboratories for understanding the basic mechanical principles of cell signaling and for developing novel strategies and materials in tissue engineering, regenerative medicine, and cell therapy.

An Assist-as-Needed Control Strategy Based on a Subjective Intention Decline Model.

In the rehabilitation training process for stroke patients, the level of excitement in the patient's physiological state has a positive impact on the efficacy of the training. In order to improve patients' initiative during training and prevent dependence on assistive systems, this study proposes an assist-as-needed control strategy based on a subjective intention decline model. The strategy primarily consists of two modules: a subjective intention decline control module and a limb movement assessment module. The subjective intention decline module collects surface electromyography (sEMG) data during patient training and optimizes support vector machine (SVM) using quantum particle swarm optimization (QPSO) algorithms to establish a subjective intention decline model. The limb movement assessment module collects information such as interaction force and position error during training and proposes a method for evaluating the motion state of the affected limb. This model combines traditional impedance control with a method for assessing limb movement and subjective status, automatically adjusting the level of assistive force on the affected limb in real time to enhance its active participation in tasks. Finally, we performed two verification experiments to assess the patient's initiative in participating in the training. The experimental results show that the proposed method effectively reduced the average assist force by 65.66% for the traditional impedance control training system and effectively the average assist force by 35.2% for the control training system using only the assist force module based on force position information. At the same time, the accuracy of the subjective intention attenuation module established in the experiment to identify the fatigue level of the subjects reached 93.41%. Therefore, the proposed method effectively improves the initiative of trainers and also prevents patients from relying on the assist-as-needed control training system.

Motor unit adaptation to disuse: crossing the threshold from firing rate suppression to neuromuscular junction transmission.

Neural conditioning to scenarios of muscle disuse is undoubtedly a cause of functional decrements that typically exceed losses of muscle size. Yet establishing the relative contribution of neural adaptation and the specific location in the motor pathway remains technically challenging. Several studies of healthy humans have targeted this system and have established that motor unit firing rate is suppressed following disuse, with a number of critical caveats. It is suppressed in the immobilized limb only, at relative and absolute force levels, and preferentially targets lower-threshold motor units. Concomitantly, electrophysiological investigation of neuromuscular junction transmission (NMJ) stability of lower-threshold motor units reveals minimal change following disuse. These findings contrast with numerous other methods, which show clear involvement of the NMJ but are unable to characterize the motor unit to which they belong. It is physiologically plausible that decrements observed following disuse are a result of suppressed firing rate of lower-threshold motor units and impairment of transmission of the NMJ of higher-threshold motor units. As such, motor units within the pool should be viewed in light of their varying susceptibility to disuse.

Effects of Moderate and Heavy Slow Resistance Training on Achilles and Patellar Tendons and Muscles Aponeuroses in Elderly Men.

To investigate the effect of moderate or heavy slow resistance training on structural and mechanical properties of patellar and Achilles tendons in older men, invivo. Healthy older men (n = 27) undertook a 12-week resistance training program (3 times/week) of triceps surae and quadriceps muscle-tendon complexes. Participants were randomly assigned to either a moderate load of 55% 1RM (O55, n = 13, age: 70.0 ± 4.6 years) or a progressively heavier load from 55% up to 80% 1RM (O80, n = 14, age: 69.8 ± 4.4 years). Tendon morphology was investigated using a 1.5 T MRI scanner. Mechanical properties of the free Achilles tendon (AT) and medial gastrocnemius (MG) aponeurosis, patellar tendon (PT), and deep aponeurosis of the vastus lateralis (VL) muscle were assessed using ultrasound imaging. Both training programs led to an increase in mean CSA of the PT (O55; +2.7%, O80; +1.7%, p = 0.002) and AT (O55; +2.8%, O80; +2.5%, p < 0.001). Force and stress were increased for all the four regions investigated, while stiffness and Young's modulus assessed at a common force level were only increased for the AT and VL aponeurosis. No interaction between group and time was demonstrated for any of the outcomes. No interaction between time and the four tendon sites was observed for any of the outcomes at common force. A supervised short-term heavy or moderate slow resistance training of equal volume yielded an increase in tendon size and altered mechanical properties of tendinous tissue.

Gesture recognition framework for upper-limb prosthetics using entropy features from electromyographic signals and a Gaussian kernel SVM classifier

This paper puts forward a novel entropy features based multi-class SVM classifier framework to predict the limb movement of the transradial amputees from the surface electromyography (sEMG) signals. The major challenges with the sEMG signal are nonlinear and non-stationary characteristics and susceptibility to noise. Consequently, a robust and an effective feature extraction framework which is invariant to force level variations is central in sEMG based prosthesis control. To address the aforementioned challenges, this study leverages the potential of variational mode decomposition (VMD) technique to identify the prominent frequency modes of the sEMG signals, and performs the spectral evaluation of the decomposed sEMG modes to identify the dominant ones to extract the entropy features. Subsequently, we evaluate the efficacy of four nonlinear optimal feature selection techniques and identify the prominent entropy features to train the multi-class SVM model that can predict the gestures. Specifically, to handle the nonlinearly separable input data, this study implements a kernelization named a radial basis function (RBF), which has good generalization and noise tolerance features. The efficacy of the proposed framework is tested using the publicly available datasets that contain gestures from transradial and congenital amputees for functional gestures. Experimental results obtained for various gestures with dynamic force levels underscore that the proposed framework is highly robust against the force level variations and can achieve a classification accuracy of 99.07%.

The Role of Agricultural Inputs on Crop Productivity: The Case of Zigam Woreda

In spite of the importance of agriculture in Ethiopia, it is characterized by low productivity and has been unable to produce sufficient quantities of output to feed the country’s population. In light of this various development strategies has been undertaken to improve the performance of agriculture. Intensification of agriculture through the use of new agricultural technologies has been emphasized over the last three decades. This study attempted to examine the contribution of agricultural input for crop productivity. The data for the study was collected from 91 sample farmers. This study was the study used both primary and secondary data. In this study researcher was used simple random sampling techniques. This research was use cross sectional approach and econometric method of data analysis to investigate the role of age, sex, land size, labor force, fertilizer, improved seed, extension service, and access to credit, education level and pesticides for crop production by collecting data from the household. In econometric method of data analysis researcher was used ordinary least square (OLS) Model. The econometric result show that land size, labor force, improved seed, fertilizer, credit service, extension service and education level have positive and significant effect on crop production. However, pesticide has a negative and significant impact on crop production. From the explanatory variables, education level has a higher coefficient. This indicates education level is more significant for crop production. According regression result &amp;lt;i&amp;gt;R&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;&amp;lt;i&amp;gt;2&amp;lt;/i&amp;gt;&amp;lt;/sup&amp;gt; is 0.97, which implies 97% of output function is explained by the selected ten (10) explanatory variables. The policy implication is that to reduce farmers resistant to use farm inputs and to create knowledge about the optimal input use educate and training of farmers is necessary.

Facial and dental arch shape in individuals with different bite force levels : A pilot study using geometric morphometrics.

This pilot study aimed to assess the relationship between bite force variation and dental arch and facial shape using geometric morphometrics, an advanced method of statistical analysis that provides adetailed shape analysis of astructure considering the spatial relationship of its parts. The sample consisted of 16German adult men and women. For each individual, maximum bite force was recorded in four positions: maximum intercuspation, protrusion, laterotrusion to the right and to the left. Facial and three-dimensional (3D) dental reconstructions were obtained from 3D facial photographs and 3D scans of dental stone models. Atotal of 51landmarks were placed. General shape variation was assessed by principal component analysis. Partial least squares analyses were performed to evaluate the covariation between bite force, facial shape, and dental shape. There was no clear pattern or statistically significant covariation between our variables. Our results suggest aweak relationship between bite force, dental arch, and facial shape. Considering previous work in this field, we propose that low masticatory loads, characteristic in Western urban populations, may explain this. Further studies should, therefore, address this issue, taking into account effect size, the mechanical properties of the diet, and other relevant variables.

Depletion forces beyond the diluted limit

The determination of the effective interactions in many-body systems still possesses a tremendous challenge in Condensed Matter Physics. The problem mainly resides in the fact that, on the one hand, there is not a unique route to obtain the effective forces between the ”observable” constituents and, on the other hand, one typically considers that the diluted limit of those components always corresponds to the effective forces at all particle concentrations. In the particular case of colloidal dispersions, it is very important to have experimental, theoretical, and computational tools that allow us to determine, accurately and without using significant approximations, the effective interactions between colloids. In this contribution, we report on a detailed study of depletion potentials in colloidal mixtures at finite concentration, namely, binary and ternary mixtures of disks (in two dimensions or 2D) and spheres (in three dimensions or 3D). To this end, the depletion forces between the large colloidal species are determined through a recently developed scheme based on the so-called contraction of the description, which has been extended and built at the level of the bare forces, i.e., we basically consider that all particles interact through the bare potentials and the net force acting on a given particle is determined by the second’s Newton law. This scheme can be easily adapted to Molecular Dynamics simulations. To verify the physical consistency of the formalism, we explicitly show that in the diluted limit of large particles, the resulting depletion potential reproduces correctly the AO-Vrij limit. As further proof of the accuracy of the results, a comparison of the structure of the large colloids in the whole mixture with the one that results using exclusively the depletion potential is carried out. In 3D, the results are explicitly compared with the potential of mean force and those obtained with the integral equations formalism. We also report a new colloidal stability mechanism based on the use of two different species of depletant agents at low and equal concentrations. Although we highlight the fact that the depletion potential depends on the concentration of the large species, we show that this dependence can be eliminated when the colloidal dispersion is open to a reservoir of small particles, i.e., when the chemical potential of small particles is fixed. Finally, we report the effects of polydispersity on the depletion interaction between large colloids.

The Effect of Intraoral Thermal Changes on the Mechanical Behavior of Nickel-Titanium Wires: An In-Vitro Study.

Background The continuous light force with a wide range of activation describes the excellent properties of nickel-titanium (NiTi) archwires. Shape memory is mainly affected by intraoral thermal changes. This study evaluated the effect of three different constant temperatures (i.e., 12°C, 37°C, and 50°C) on the unloading value of three different 0.016 × 0.022 NiTi archwires. Methodology Three types of 0.016 × 0.022-inch diameter NiTi archwires (American Orthodontics®, Sheboygan, Wisconsin, USA) were used. These were the superelastic type (NT3-SE®), the heat-activated type at 25°C (Thermal Ti-D®), and the thermally activated type at 35°C (Thermal Ti-Lite®). The unloading forces of the wires were evaluated using a classic three-point bending test (a universal testing machine: Testometric 350M®, Instron, Lincoln Close, Rochdale, England) under three different constant temperatures (12°C, 37°C, and 50°C). Results All types of wires showed thermal sensitivity; at higher temperatures, the unloading forces increased differentially between small and large deflections, while at lower temperatures, the residual strain increased for all wire types. The most affected type by the thermal changes was thermal Ti-Lite®, followed by thermal Ti-D®, and the superelastic type NT3-SE® showed a behavior similar to thermal wires. At the low temperature (12°C), all wire types showed an incomplete load/deflection curve, whereas no value was measured at unloading points 2, 1, and 0.5 mm. At the normal temperature (37°C), NT3-SE® type and thermal Ti-D® were similar in force level, while significant differences were noted between both previous types and Thermal Ti-Lite®. At the high temperature (50°C), all wire types showed a higher force level, while significant differences between the wire types were inconsistent. In contrast, increasing the temperature from 37°C to 50°C increased the force levels between 40% and 84% for NT3-SE®, between 44% and 64% for the thermal Ti-D®, and between 61% and 268% for the Thermal Ti-Lite®. When comparing the force levels between 12°C and 50°C at 3 mm, the force levels increased by 66% for NT3-SE®, 25% for Thermal Ti-D®, and 109% for thermal Ti-Lite®, while on comparing the forces between 12°C to 37°C, the forces increased between 15% and 95% for NT3-SE®, 20% and 88% for thermal Ti-D®, and 26% and 78% for thermal Ti-Lite®. The value of residual strain was greater at low temperatures and smaller at higher temperatures, while no significant differences were detected between 37°C and 50°C. Conclusions The temperature degree deeply affected the mechanical behavior of all test NiTi wires; the superelastic type behaved similarly to thermal wires. Increasing the temperature degree leads to more unloading forces and less residual strain.

Trapeziometacarpal joint movement during pinching measured by ultrasonography

ObjectiveFunctional hand activity induces complex motion of the trapeziometacarpal (TMC) joint. Analyzing the TMC joint motion in vivo can aid in understanding joint behavior and lead to advancements in joint health evaluation. The purpose of this study was to quantify TMC joint motion during pinching using ultrasonography. DesignHealthy participants (n = 10) held a pinch meter in key pinch configuration and pinched to three prescribed force levels. Ultrasonography was used to record the motion of the TMC joint. The position and rotation of the first metacarpal were calculated. Repeated measures one-way ANOVAs were used for comparisons (α = 0.05). ResultsWhen the pinch force was increased from 0 to 10, 20 and 30 N, the first metacarpal translated in the dorsal(+)/volar(-) direction -0.3 mm [95 % CI: (-0.5 mm, -0.1 mm); p = 0.0151], -0.5 mm [95 % CI: (-0.8 mm, -0.1 mm); p = 0.0113] and -0.8 mm [95 % CI: (-1.4 mm, -0.2 mm); p = 0.0146]. Significance was not observed for proximal(+)/distal(-) translation (p = 0.224). The metacarpal rotated in the abduction(+)/adduction(-) direction 0.7° [95 % CI: (-0.8°, 2.1°); p = 0.3239], 2.6° [95 % CI: (0.1°, 5.1°); p = 0.0416] and 3.3° [95 % CI: (0.2°, 6.3°); p = 0.0393], at pinch forces of 10, 20 and 30 N, respectively. ConclusionsThe TMC joint undergoes volar translation and abduction rotation during pinch tasks. Ultrasonography can be used to quantify this motion and aid in the advancement of joint behavioral study.

Unaltered Responses of Distal Motor Neurons to Non-Targeted Thoracic Spinal Cord Stimulation in Chronic Pain Patients.

Spinal cord stimulation (SCS) represents an established interventional pain therapeutic; however, the SCS effects of SCS waveforms on motor neuron recruitment of the lower limbs of chronic pain patients remain largely unknown. We investigated these effects by performing isometric ankle-dorsal flexions at varying force levels under four SCS conditions: SCS Off (1week), burst SCS (40Hz), SCS Off (acute), and tonic SCS (130Hz). Muscle activity was recorded via high-density surface electromyography (64-electrode grid) on the tibialis anterior muscle. Motor unit action (MUs) potentials were analyzed for recruitment and de-recruitment thresholds, discharge rate, inter-spike interval, and common synaptic input. In this prospective study, we included nine patients (five females; four males; mean age 59years) with chronic pain treated with thoracic (Th7-Th8) epidural spinal stimulation. A total of 97 MUs were found for 15% maximal voluntary torque (MVT) and 83 for 30%MVT, an average of 10.8±3.7 for 15%MVT and 10.4±3.5 for 30%MVT. While a few subject-specific variations were observed, our study suggests that the different SCS frequencies applied do not significantly influence motor unit discharge characteristics in the TA muscle among the participants (p values at 15%MVT were 0.586 (Chi2=1.933), 0.737 (Chi2=1.267), 0.706 (Chi2=1.4) and 0.586 (Chi2=1.933), respectively. The p values of the Friedman test at 30%MVT were 0.896 (Chi2=0.6), 0.583 (Chi2=1.95), 0.896 (Chi2=0.6) and 0.256 (Chi2=4.05). No significant difference was found for the different stimulation types for the delta (0-5Hz), alpha (5-12Hz), and beta (15-30Hz) bands at both force levels. In summary, we did not observe any changes in motor unit oscillatory activity at any low and high bandwidths, indicating that SCS using different waveforms (tonic/burst) does not significantly influence motor neuron recruitment for non-motor individuals with chronic pain.