Extension Force Research Articles

Motion Tape Strain During Trunk Muscle Engagement in Young, Healthy Participants.

Motion Tape (MT) is a low-profile, disposable, self-adhesive wearable sensor that measures skin strain. Preliminary studies have validated MT for measuring lower back movement. However, further analysis is needed to determine if MT can be used to measure lower back muscle engagement. The purpose of this study was to measure differences in MT strain between conditions in which the lower back muscles were relaxed versus maximally activated. Ten participants without low back pain were tested. A matrix of six MTs was placed on the lower back, and strain data were captured under a series of conditions. The first condition was a baseline trial, in which participants lay prone and the muscles of the lower back were relaxed. The subsequent trials were maximum voluntary isometric contractions (MVICs), in which participants did not move, but resisted the examiner force in extension or rotational directions to maximally engage their lower back muscles. The mean MT strain was calculated for each condition. A repeated measures ANOVA was conducted to analyze the effects of conditions (baseline, extension, right rotation, and left rotation) and MT position (1-6) on the MT strain. Post hoc analyses were conducted for significant effects from the overall analysis. The results of the ANOVA revealed a significant main effect of condition (p < 0.001) and a significant interaction effect of sensor and condition (p = 0.01). There were significant differences in MT strain between the baseline condition and the extension and rotation MVIC conditions, respectively, for sensors 4, 5, and 6 (p = 0.01-0.04). The largest differences in MT strain were observed between baseline and rotation conditions for sensors 4, 5, and 6. MT can capture maximal lower back muscle engagement while the trunk remains in a stationary position. Lower sensors are better able to capture muscle engagement than upper sensors. Furthermore, MT captured muscle engagement during rotation conditions better than during extension.

Surgical Management for Boutonniere Disease

Boutonniere disease is a hand injury causing extension lag or restriction in the proximal interphalangeal joint and hyperextension in the distal interphalangeal joint. This condition often arises from direct laceration or closure damage to the central tendon, rheumatoid arthritis, osteoarthritis, Dupuytren contracture, pulley injury, burns, and other conditions. Surgical management for Boutonniere deformity relies on the expertise of the attending physician and involves both non-surgical and surgical options. In acute cases, conservative therapy should be pursued, while in chronic cases, conservative management may be advised. Surgical intervention is used to transform excessive extension force of the distal interphalangeal joint into extension force of the proximal interphalangeal joint. This is necessary to heal an open rupture of the central tendon. Surgical techniques for chronic deformity are complex due to variables and hand surgeons' expertise. There is no definitive surgical therapy for persistent buttonhole deformity, but several approaches have been documented in case studies. These include terminal tenotomy, collateral band surgery, central tendon surgery, tendon transfer and grafting, stepwise extension mechanism readjustment surgery, and arthrodesis. Central tendon surgery addresses the central tendon, where injured tissue transforms into scar tissue, resulting in delayed extension of the proximal interphalangeal joint. Tendon transfer or grafting have been documented for rotator cuff mechanism rehabilitation, but no definitive guidance exists for these techniques. Curtis treatment introduced a sequential therapy approach for traumatic buttonhole deformity, which involves splinting, excising the transverse reticular ligament, resecting and lengthening the collateral ligament, and repositioning the core tendon. Arthrodesis may be applicable in cases of advanced arthritis, coronal plane deformity, functional impairment, or elderly patients. There are no definitive indications for surgical interventions for persistent buttonhole deformity, and outcomes may be variable or inferior. Understanding the deformity, its progression, and patient's functional constraints is crucial for effective treatment

The Role of Pretarsal Fascia in Upper Eyelid Crease Formation and its Implications in East Asians.

This study aims to investigate the role of pretarsal fascia in the formation of upper eyelid crease in East Asians. Through intraoperative fascia retraction observation, fascia-stretching test, histological examination, and anatomical analysis of pretarsal fascia and surrounding tissues, we explored the mechanical consequences and their impact on upper eyelid crease formation. The levator aponeurosis extension comprises three parts to impact sub-orbicularis fat pad mechanically. The pretarsal fascia is anatomically distinct from the aponeurosis extension but is influenced by its mechanic forces. Differential distribution of collagen fiber bundles within the pretarsal fascia can buffer and transmit the forces of aponeurosis extension, leading to diverse upper eyelid crease patterns. The factors determining upper eyelid crease are multifaceted, and the buffering-conduction theory of pretarsal fascia can explain both physiological and postoperative crease in East Asians. It determines the presence, depth, and stability of crease, laying the foundation for the formation of upper eyelid crease in East Asians. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

While the subcortical and supraspinal excitability differs between athletes with and without patellar tendinopathy – only subcortical excitability and maximal knee extension force are related

While the subcortical and supraspinal excitability differs between athletes with and without patellar tendinopathy – only subcortical excitability and maximal knee extension force are related

Neuroplastic alterations in common synaptic inputs and synergistic motor unit clusters controlling the vastii muscles of individuals with ACL reconstruction.

This cross-sectional study aims to elucidate the neural mechanisms underlying the control of knee extension forces in individuals with anterior cruciate ligament reconstruction (ACLR). Eleven soccer players with ACLR and nine control players performed unilateral isometric knee extensions at 10% and 30% of their maximum voluntary force (MVF). Simultaneous recordings of high-density surface electromyography (HDEMG) and force output were conducted for each lower limb, and HDEMG data from the vastus lateralis (VL) and vastus medialis (VM) muscles were decomposed into individual motor unit spike trains. Force steadiness was estimated using the coefficient of variation of force. An intramuscular coherence analysis was adopted to estimate the common synaptic input (CSI) converging to each muscle. A factor analysis was applied to investigate the neural strategies underlying the control of synergistic motor neuron clusters, referred to as motor unit modes. Force steadiness was similar between lower limbs. However, motor neurons innervating the VL on the reconstructed side received a lower proportion of CSI at low-frequency bandwidths (<5 Hz) compared with the unaffected lower limbs (P < 0.01). Furthermore, the reconstructed side demonstrated a higher proportion of motor units associated with the neural input common to the synergistic muscle, as compared with the unaffected lower limbs (P < 0.01). These findings indicate that the VL muscle of reconstructed lower limbs contribute marginally to force steadiness and that a plastic rearrangement in synergistic clusters of motor units involved in the control of knee extension forces is evident following ACLR.NEW & NOTEWORTHY Chronic quadriceps dysfunction is common after anterior cruciate ligament reconstruction (ACLR). We investigated voluntary force control strategies by estimating common inputs to motor neurons innervating the vastii muscles. Our results showed attenuated common inputs to the vastus lateralis and plastic rearrangements in functional clusters of motor neurons modulating knee extension forces in the reconstructed limb. These findings suggest neuroplastic adjustments following ACLR that may occur to fine-tune the control of quadriceps forces.

Comparison of Measurements for Recording Postural Control in Standing and Seated Position in Healthy Individuals.

Background: A standard method of assessing postural control is to measure while standing. However, its implementation is usually limited. Recording postural control directly on the trunk in a seated position could provide an alternative diagnostic method for quantifying neuromuscular control. Methods: A comparison of center of pressure (CoP) measurements in the standing and sitting positions was performed on 66 healthy adult subjects. The reliability of the measurements in the sitting position was tested in 23 subjects. In addition, the extension force of all test subjects was recorded. Results: The assessments of CoP fluctuations in standing and seated positions showed adequate agreement (deviation 9.1%). Furthermore, good internal consistencies with a sufficient test-retest reliability could be demonstrated for the measurements in seated position. Both CoP measurement methods showed a comparable Spearman correlation to obtained extension force measurements (standing: 0.24, seated: 0.23). Conclusions: Our results show that recording CoP fluctuations in the sitting position is a reliable and valid adjunct to single-leg stance measurements. It could serve as an additional alternative to quantify neuromuscular control in impaired patients who cannot adequately perform the single-leg stance. In addition, measurement in the seated position allows direct recording of neuromuscular control at the trunk.

Is There a Strength Deficit of the Quadriceps Femoris Muscle in Patients Treated Conservatively or Surgically after Primary or Recurrent Patellar Dislocations? A Systematic Review and Meta-Analysis.

Background: Patellar dislocation is a knee injury affecting generally young, active individuals, damaging joint ligaments and structures, and impacting sports activity and quality of life. Objective: This review aimed to evaluate the role of the quadriceps femoris muscle in knee extension and to consider whether extensor strength deficits are present in patients who have suffered from a primary or recurrent patellar dislocation and have been treated surgically or conservatively. Methods: This systematic literature review with meta-analysis was performed following the PRISMA Statement criteria. The search engines consulted to select studies were MEDLINE/PubMed, Scopus, and Web of Science/ISI. The JBI Critical Appraisal Checklist tools were applied for the quality assessment based on the specific study design. The outcomes were measurements of the knee extension force of the quadriceps femoris muscle, which were objectively quantifiable with an isokinetic or mobile dynamometer. Results: Of the 891 articles initially identified through the databases, 10 studies with a total of 370 patients were included in the analysis. The results indicated a strength deficit of the quadriceps in patients who had undergone a patellar dislocation, in comparison with the control group, when examining the uninvolved limb or in comparison with the pre-operative values. The overall effect size was large, with a value of -0.99. Conclusions: Our review concluded that after a primary or recurrent patellar dislocation, strength deficits of the quadriceps femoris muscle in the knee extension of the affected limb are frequently observed in surgically or conservatively treated patients. This deficit may persist even after a protracted follow-up of up to three years after injury.

β-barrel proteins dictate the effect of core oligosaccharide composition on outer membrane mechanics.

The outer membrane is the defining cellular structure of Gram-negative bacteria, a group that contains many important pathogens like Escherichia coli , Vibrio cholerae , and Pseudomonas aeruginosa . One role of the outer membrane is to block the uptake of small molecules like antibiotics. However, it is becoming increasingly clear that it also functions as a structural exoskeleton that is critical for the cell's ability to cope with internal and external mechanical forces. Here, we carefully dissect the molecular basis for the load-bearing capacity of the outer membrane by screening a set of mutants with a new cell biophysics assay.

The Functional Organization of Corticomotor Neurons Within the Motor Cortex Differs Among Basketball and Volleyball Athletes With Patellar Tendinopathy Compared to Asymptomatic Controls.

Patellar tendinopathy (PT) typically affects jumping-sport athletes with functional impairments frequently observed. Alterations to the functional organization of corticomotor neurons within the motor cortex that project to working muscles are evident in some musculoskeletal conditions and linked to functional impairments. We aimed to determine if functional organization of corticomotor neuron projections differs between athletes with PT and asymptomatic controls, and if organization is associated with neuromuscular control. We used a cross-sectional design, and the setting was Monash Biomedical Imaging. Basketball and volleyball athletes with (n = 8) and without PT (n = 8) completed knee extension and ankle dorsiflexion force matching tasks while undergoing fMRI. We determined functional organization via identification of the location of peak corticomotor neuron activation during respective tasks (expressed in X, Y, and Z coordinates) and calculated force matching accuracy for both tasks to quantify neuromuscular control. We observed significant interactions between group and coordinate plane for functional organization of corticomotor projections to knee extensors (p < 0.001) and ankle dorsiflexors (p = 0.016). Compared to controls, PT group peak corticomotor activation during the knee extension task was 9.6 mm medial (p < 0.001) and 5.2 mm posterior (p = 0.036), and during the ankle dorsiflexion task 8.2 mm inferior (p = 0.024). In the PT group, more posterior Y coordinate peak activation location during the knee extension task was associated with greater task accuracy (r = 0.749, p = 0.034). Functional organization of corticomotor neurons differed in jumping athletes with PT compared to controls. Links between functional organization and neuromuscular control in the PT group suggest organizational differences may be relevant to knee extension neuromuscular control preservation.

The Effects of Static Stretching 2-Hours Prior to a Traditional Warm-Up on Performance.

Whereas prolonged static stretching (SS: >60-seconds per muscle) can increase range of motion (ROM) for up to 2-hours, it can also decrease maximal voluntary isometric contraction (MVIC) forces, countermovement (CMJ) and drop jump (DJ) heights, and muscle activation immediately after the stretching exercise. When an appropriate SS duration (<60-seconds per muscle) is incorporated into a dynamic warm-up, performance decrements are often trivial. However, there is a lack of studies that observed the effects of extensive SS (180-seconds) 2-hours prior to a dynamic warm-up. The objective was to investigate ROM and performance effects of prolonged SS, 2-hours prior to a traditional warm-up. This study investigated 9 female and 8 male healthy recreationally active, young adult participants on the effects of prolonged SS (180-seconds per muscle) of the quadriceps and hamstrings, 2-hours before a traditional warm-up compared to an active control condition on hip flexion ROM, knee extension and flexion MVIC forces, CMJ, DJ, and quadriceps and hamstrings electromyography (EMG). There were no significant changes in knee flexion/extension MVIC forces, EMG, CMJ, or DJ height. However, there was significant, small magnitude (p = 0.002) greater post-warm-up left hip flexion ROM (115.4° ± 17.2) than pre-SS (108.9° ± 17.13, Effect size [ES]: 0.28) and control post-warm-up (p = 0.05, ES: 0.31, 109.5° ± 20.55). Similarly, right hip flexion ROM (117.2° ± 16.5) also demonstrated significant small magnitude (p = 0.003) greater than the pre-SS (112.4° ± 18.4, ES: 0.22) and control post-warm-up (p = 0.046, ES: 0.33, 110.8° ± 20.5). Additionally, significant, large magnitude greater hip flexion ROM was observed with the women vs. men (ES: 1.29 - 1.34). Significant hip flexion ROM increases were not accompanied by significant changes in knee flexion/extension MVIC forces, EMG, or jump heights, suggesting that extensive SS can positively impact ROM without performance deficits when followed by a traditional warm-up, 2-hours after SS.

Soft pneumatic actuators for pushing fingers into extension

BackgroundCompliant pneumatic actuators possess many characteristics that are desirable for wearable robotic systems. These actuators can be lightweight, integrated with clothing, and accommodate uncontrolled degrees of freedom. These attributes are especially desirable for hand exoskeletons, where the soft actuator can conform to the highly variable digit shape. In particular, locating the pneumatic actuator on the palmar side of the digit may have benefits for assisting finger extension and resisting unwanted finger flexion, but this configuration requires suppleness to allow digit flexion while retaining sufficient stiffness to assist extension.MethodsTo meet these needs, we designed an actuator consisting of a hollow chamber long enough to span the joints of each digit while sufficiently narrow not to inhibit finger adduction. We explored the geometrical design parameter space for this chamber in terms of shape, dimensions, and wall thickness. After fabricating an elastomer-based prototype for each actuator design, we measured active extension force and passive resistance to bending for each chamber using a mechanical jig. We also created a finite element model for each chamber to enable estimation of the impact of chamber deformation, caused by joint rotation, on airflow through the chamber. Finally, we created a prototype hand exoskeleton with the chamber parameters yielding the best outcomes.ResultsA rectangular cross-sectional area was preferable to a semi-obround shape for the chamber; wall thickness also impacted performance. Extension joint torque reached 0.33 N-m at a low chamber pressure of 48.3 kPa. The finite element model confirmed that airflow for the rectangular chamber remained high despite deformation resulting from joint rotation. The hand exoskeleton created with the rectangular chambers enabled rapid movement, with a cycle time of 1.1 s for voluntary flexion followed by actuated extension.ConclusionsThe developed soft actuators are feasible for use in promoting finger extension from the palmar side of the hand. This placement utilizes pushing rather than pulling for digit extension, which is more comfortable and safer. The small chamber volumes allow rapid filling and evacuation to facilitate relatively high frequency finger movements.

Exploring anisotropic mechanical properties of lobster claw exoskeleton through fractal models

The outstanding mechanical properties of lobster claw exoskeletons are intricately tied to their internal microstructure. Investigating this relationship can offer vital insights for designing high-performance additive manufacturing structures. Fractal theory, with its fractional dimensional perspective, suits the complexity of real-world phenomena. Our study examines fully hydrated lobster claw exoskeletons using a multifaceted approach: four-point bending tests, scanning electron microscopy observations, and fractal models. Test results reveal superior mechanical properties in longitudinal specimens. Scanning electron microscopy shows non-uniform fiber helical structures and porous elements in the exoskeleton. Fracture mechanisms involve both breaking fiber fragments perpendicular to the cross-section and tearing between these fragments. The observed crack propagation paths exhibit statistical self-similarity. Consequently, we develop fractal models for the crack propagation paths in longitudinal and transverse specimens, calculating crack extension forces. Using the box-counting method and its improved variant, we determine the fractal dimensions of specimen sections. The fractal dimension of longitudinal models exceeds that of transverse models, and calculated crack extension forces are higher in longitudinal models. These findings align well with experimental data, demonstrating fractal theory's efficacy in analyzing the lobster claw exoskeleton's anisotropic mechanical properties.

Concussion Reduction in Division I and II Athletes: Effects of Simple Cervical Spine Exercise Regimen.

Primary preventative medicine lacks a consensus on effective concussion prevention strategies for collegiate athletes. Cervical strength has been identified as a potential factor in concussion risk reduction. This study evaluates the impact of a commercially available, portable cervical muscle stretching and strengthening device, NeckX®, on cervical strength, range of motion (ROM), and concussion incidence in collegiate athletes participating in high-concussion-risk sports. A single-arm prospective cohort study was conducted with 162 collegiate athletes from various sports. Participants underwent a 12-week neck exercise protocol using the NeckX® device. Clinical data, including neck strength and ROM, were collected at weeks 0, 6, and 12. Concussion incidence was self-reported by participants and cross-referenced with records from the athletic department. Data were analyzed for significant neck strength and ROM changes throughout the 12-week study. A two-way analysis of variance multiple comparisons with the Tukey-Kramer significant difference test was utilized, using the Holm-Sidak method, with an alpha of 0.05. All athletic teams experienced a significant increase in cervical strength during the 12-week intervention (α = 0.05, p < 0.05). Increases in cervical flexion and extension force were most consistent between teams. Cervical ROM increased significantly in male and female soccer players (α = 0.05, p < 0.05). The overall incidence of head and neck injuries, including concussions, was reduced to 6.60% during the study period, the lowest recorded value in the university's athletic department history. The use of the NeckX® device for 12 weeks was effective in enhancing pericervical muscle strength and ROM while reducing concussion incidence in collegiate athletes participating in high-concussion-risk sports. Interestingly, the positive outcomes were consistent for both males and females, indicating the universal advantages of neck training among collegiate athletes. These findings support existing research on the benefits of cervical strengthening exercises for reducing concussions in collegiate athletes and highlight the convenience and affordability of using this device.

Reliability of cervicocephalic sense of force

Cervicocephalic proprioception (CCP) is an important assessment item for people with a range of clinical conditions, where reduced CCP is associated with neck pain and imbalance. Reliability has been established for a range of positional and movements tests, but there is limited data regarding sense of force, particularly across three planes of movement. The current test–retest study assessed reliability when evaluating sense of force in healthy adults (8 males, 6 females, mean age 31.50 years [SD 10.14]) over two sessions, 4–7 days apart. A force matching protocol was used to evaluate reliability of absolute error (AE), constant error (CE), and variable error (VE) for 10 % and 25 % maximal voluntary contraction (MVC) target forces for flexion, extension, lateral flexion, and rotation. Participants were strapped to a chair to limit trunk movement and data was captured using a compressive force transducer fixed to an adjustable wall mount. Six trials were performed for each contraction-type, totaling 72 submaximal MVCs per session. ICC estimates for AE (0.15–0.77), CE (0.01–0.85), and VE (0.00–0.83) were varied and confidence intervals were mostly wide. Considering lower limits of confidence intervals, CE had best reliability values generally, but more specifically the most reliable contraction type and movement was 25 % MVC flexion (ICC 0.85, confidence interval 0.54–0.95). This study found that reliability for sense of force testing was dependent upon contraction, type of error, and target force utilized. Further reliability analysis should be performed when applying this test to measure validity outcomes in clinical populations.

Unveiling the influence of hip isokinetic strength on lower extremity running kinematics in male national middle-distance runners: a correlational analysis

BackgroundThe relationship between hip strength deficiency in various planes and musculoskeletal injuries within the movement system has been well-established in numerous studies. The present study sought to explore the relationships between hip strength and specific aspects of lower extremity running kinematics.MethodologyTo achieve this objective, the three-dimensional running kinematics of 21 male elite middle-distance runners (mean age: 19.7 ± 1.2 years; mean experience 6.5 ± 1.0 years) were assessed using nine high-speed cameras on a treadmill at a speed of 16 km·h⁻¹. Concurrently, isokinetic hip strength was measured at a speed of 60 deg·s⁻¹ in both the dominant and non-dominant legs. The Pearson correlation coefficient and Paired Samples t-test were utilized.ResultsWhile no significant differences were found in several isokinetic strength measurements, notable differences in running kinematics were observed. Specifically, pelvic drop at midstance (MS) was significantly lower in the DL (5.79 ± 3.00°) compared to the NDL (8.71 ± 1.39°) with a large effect size (t=-4.04, p < 0.001, Cohen’s d = 1.25). Additionally, knee adduction at maximum showed a moderate effect size difference, with the DL at 2.99 ± 1.13° and the NDL at 3.81 ± 1.76° (t=-2.74, p = 0.03, Cohen’s d = 0.55). Results indicated a moderate to highly positive association between running knee adduction in the dominant leg and hip external rotation (r = 0.67, p < 0.05), concentric extension (r = 0.77, p < 0.05), and concentric abduction (r = 0.78, p < 0.05). Additionally, the running tibial external rotation angle in the dominant leg exhibited an inverse relationship with all strength measurements, with statistical significance observed only for concentric extension force (r=-0.68, p < 0.05). Furthermore, hip internal rotation force demonstrated a highly inverse correlation with foot pronation in the dominant leg (r=-0.70, p < 0.05) and anterior pelvic tilt in the non-dominant leg (r=-0.76, p < 0.05).ConclusionsThese findings underscore the interrelation between hip strength and running kinematics, particularly on the dominant side. In light of these observations, it is imperative to consider hip strength exercises as integral components for correcting running kinematics. Coaches should also be mindful that kinematic deviations contributing to running injuries may manifest unilaterally or specifically in the dominant leg.

Design for disassembly: Using a multi-material approach in 3D printing for easier recycling strategies

Due to the rapid expansion of the electronics sector, e-waste is becoming a growing issue that requires immediate attention. In particular, the complex assemblies and miniaturisation of these devices makes it difficult to recycle them properly. Additive manufacturing (AM), also known as 3D printing, offers a potential solution to this problem. The ability to print structures in μm- range makes it possible to print and manufacture electronic components in such a way that predetermined breaking points can be incorporated. Parts printed in this way are subject to the concept of Design for Disassembly, which describes the production of multi-material compounds or composites that can be easily separated or recycled. Using a multi-material approach in combination with Thermally Expandable Microspheres (TEMs) and processed by 3D printing, we produced easily separable compounds on demand. The compounds were characterized regarding their (thermo)mechanical behaviour. The study investigated the influence of the printed separation layer on the mechanical properties of the overall compound for various layer orientations. The printed parts were separated using heat as an external impulse, without requiring extensive force. This was achieved by subjecting the parts to a temperature of 200 °C for 10 minutes in a conventional oven.

Climate smart agriculture practices by crop farmers: Evidence from south east Nigeria

Climate change has severely impacted African countries, particularly Nigeria, affecting farmers' productivity due to adverse weather conditions. Climate Smart Agriculture (CSA) has emerged as a crucial approach to ensure sustainable agricultural growth and food security. This study aims to identify the sources of awareness, prevalent innovative agricultural practices, determinants of CSA adoption, and the intensity of CSA practices among crop farmers in Southeast Nigeria. A two-stage multi-random sampling technique was employed to collect data from 270 farmers across various locations in Southeast Nigeria through questionnaires. The analysis used descriptive statistics and Heckman's two-stage selection model to evaluate the sources of awareness, the extent of CSA practice, and factors influencing CSA adoption and its intensity. Results indicate that cooperative societies and extension workers are the primary sources of CSA awareness in the region. Key determinants of CSA adoption identified in the study include gender, household size, farming experience, education level, labor force size, income, extension exposure, credit access, risk orientation, and cooperative membership. The Heckman model revealed that cooperative membership significantly increases the probability of CSA adoption, while risk-averse farmers are less likely to adopt CSA practices. The study concludes that while CSA practices are recognized and adopted to some extent, their implementation is insufficient to comprehensively combat the effects of climate change. Enhanced efforts to promote and integrate CSA practices more widely are critically needed. To improve CSA adoption and effectiveness, it is recommended to provide increased support for cooperative societies and extension services, better access to credit, and targeted education and training programs for farmers. Additionally, policies should focus on reducing risk aversion among farmers by providing insurance schemes and other risk management tools.

Dynamic biaxial loading of vascular smooth muscle cell seeded tissue equivalents

An intricate reciprocal relationship exists between adherent synthetic cells and their extracellular matrix (ECM). These cells deposit, organize, and degrade the ECM, which in turn influences cell phenotype via responses that include sensitivity to changes in the mechanical state that arises from changes in external loading. Collagen-based tissue equivalents are commonly used as simple but revealing model systems to study cell–matrix interactions. Nevertheless, few quantitative studies report changes in the forces that the cells establish and maintain in such gels under dynamic loading. Moreover, most prior studies have been limited to uniaxial experiments despite many soft tissues, including arteries, experiencing multiaxial loading in vivo. To begin to close this gap, we use a custom biaxial bioreactor to subject collagen gels seeded with primary aortic smooth muscle cells to different biaxial loading conditions. These conditions include cyclic loading with different amplitudes as well as different mechanical constraints at the boundaries of a cruciform sample. Irrespective of loading amplitude and boundary condition, similar mean steady-state biaxial forces emerged across all tests. Additionally, stiffness-force relationships assessed via intermittent equibiaxial force–extension tests showed remarkable similarity for ranges of forces to which the cells adapted during periods of cyclic loading. Taken together, these findings are consistent with a load-mediated homeostatic response by vascular smooth muscle cells.

Towards Efficient Neural Decoder for Dexterous Finger Force Predictions.

Dexterous control of robot hands requires a robust neural-machine interface capable of accurately decoding multiple finger movements. Existing studies primarily focus on single-finger movement or rely heavily on multi-finger data for decoder training, which requires large datasets and high computation demand. In this study, we investigated the feasibility of using limited single-finger surface electromyogram (sEMG) data to train a neural decoder capable of predicting the forces of unseen multi-finger combinations. We developed a deep forest-based neural decoder to concurrently predict the extension and flexion forces of three fingers (index, middle, and ring-pinky). We trained the model using varying amounts of high-density EMG data in a limited condition (i.e., single-finger data). We showed that the deep forest decoder could achieve consistently commendable performance with 7.0% of force prediction errors and R2 value of 0.874, significantly surpassing the conventional EMG amplitude method and convolutional neural network approach. However, the deep forest decoder accuracy degraded when a smaller amount of data was used for training and when the testing data became noisy. The deep forest decoder shows accurate performance in multi-finger force prediction tasks. The efficiency aspect of the deep forest lies in the short training time and small volume of training data, which are two critical factors in current neural decoding applications. This study offers insights into efficient and accurate neural decoder training for advanced robotic hand control, which has the potential for real-life applications during human-machine interactions.

Accuracy of a portable lower-limb muscle strength measuring device with a training function.

[Purpose] Quadriceps muscle strength is essential for daily living activities. Therefore, we developed a compact and simple lower limb muscle strength measuring device (LocomoScan [LCS]). This study aimed to compare LCS with other instruments to analyze its simplicity, reproducibility, and accuracy. [Participants and Methods] One hundred and four healthy university students (56 males and 48 females) were included in the study. The knee extension force was measured using LCS, and the knee extension torque was measured using other devices (Cybex). In addition, lower leg muscle mass was measured using a body composition meter. The reproducibility of LCS and the correlation between the knee extension torque and lower leg muscle mass were evaluated. [Results] The measurement reproducibility of LCS was significantly higher. The knee extension force confirmed the proportional relative reliability of Cybex with knee extension torque. A relationship between knee extension force and lower limb muscle mass was also observed, indicating that muscle mass cannot be estimated as muscle strength. [Conclusion] The high reproducibility of the knee extension force measurement using LCS demonstrates its potential as a portable alternative instrument for muscle strength measurement in clinical practice. Therefore, LCS device is a simple and effective tool for assessing muscle strength.