Contraction Strength Research Articles

Modernization of a Traditional Siddha Medicine Paccai eruvai into a Novel Nanogel Formulation for the Potent Wound Healing Activity-A Phyto- Pharmaceutical Approach.

Paccai eruvai formulation has been widely used in traditional Siddha practice to treat ulcerous wounds due to the content of potentially active compounds. The present study aimed to determine the enhancement potency of wound healing of nanogels containing Paccai eruvai in an incision and excision wound models. Paccai eruvai nanogel was synthesized using the high-energy milling method, and characterization and enhancement of the wound healing potential of Paccai eruvai nanogel were assessed. Reportedly, Paccai eruvai nanogel has been produced successfully and its chemical properties confirmed, and physical properties characterized. Paccai eruvai nanogel showed homogeneity, green color, transparency, and an average size of 19.73 nm. We observed a significant reduction of wound area (p<0.001) in the Paccai eruvai nanogel-treated rats. The percentage of wound contraction on the 16th day was higher than the traditional formulation and nitrofurazone treatment. Notably, a lesser epithelialization period (14.33 days) and higher hydroxyproline content were observed in the 10% Paccai eruvai nanogel rats. We found that 10 % Paccai eruvai nanogel treatment increased tensile strength suggesting a better therapeutic indication. The present findings indicate that Paccai eruvai nanogel significantly contributes wound healing activities with the enhancement of collagen synthesis, wound contraction, and wound tensile strength.

Effects of remote facilitation on ankle joint movement: Focusing on occlusal strength and balance.

Remote facilitation refers to teeth occlusion-activated spinal cord activity resulting in increased trunk and limb muscle strength. Facilitation depends on dentition-related pressure during occlusion and masticatory muscle contraction strength. This study aimed to clarify the neurophysiological phenomenon and mechanisms by which occlusal strength and balance affect leg muscle activity and smooth joint movement execution. To examine occlusal strength, three conditions were set: no contact between teeth and Moderate- and Maximum-strength occlusion (No-bite, Moderate, and Max conditions, respectively). To assess occlusal balance, we measured occlusal forces and calculated the left-right force ratio. We designated the sides with higher and lower occlusal pressure as hypertonic and hypotonic, respectively. We assessed ankle dorsiflexion movements with joint movement and isometric tasks. The rate of joint development and peak ankle dorsiflexion torque were significantly higher under occlusion (moderate and max compared to No-bite conditions), and the joint movement performance time was significantly shorter under Moderate compared to No-bite conditions. The joint movement execution time change rate from No-bite to Moderate condition was significantly lower on the Hypertonic side. Joint movement function was most improved under Moderate conditions. While remote facilitation improves with higher occlusal strength, leading to increased muscle strength, there is optimal occlusion intensity in joint movement. Moreover, an occlusal balance-dependent imbalance exists in remote facilitation between the Hyper- and Hypotonic sides. Thus, low-intensity occlusion is optimal for smooth joint movement, and unbalanced occlusion results in asymmetrical motor function facilitation.

Digoxin: Review of Current Laboratory Practice and Considerations

Digoxin is a drug used for its effects on the heart, particularly its effect on rate and strength of contraction. Levels are particularly useful in clinical practice owing to its narrow therapeutic index, with toxicity and therapeutic levels being relatively close. Clinically, digoxin toxicity can be acute or chronic, and can manifest with signs and symptoms related to the gastrointestinal system, nervous system, and cardiovascular system. Given digoxin toxicity can lead to fatal dysrhythmias, accurate and reproducible analysis by the laboratory is essential in the treatment of patients with suspected digoxin toxicity. However, the laboratory workup for digoxin toxicity is not as simple as performing a digoxin level. Other factors such as cross-reacting molecules, the effect of other biochemical findings, and the effect of the digoxin antidote (anti-digoxin antibody fragments) on immunoassay results need to be considered in clinical settings where the results aren’t consistent with clinical findings. The laboratory is ideally placed to help with issues relating from these factors to digoxin level interpretation.

Effects of adductor canal block combined with infiltration between the popliteal artery and capsule of the knee on pain management and early rehabilitation compared with epidural analgesia for patients undergoing total knee arthroplasty: a prospective randomised controlled trial

Total knee arthroplasty (TKA) is often regarded as one of the most painful orthopedic operations. Variety of regional anesthetic procedures are used to reduce this pain. Infiltration between the popliteal artery and capsule of the posterior knee (IPACK) is increasingly being utilized in conjunction with adductor canal block (ACB) to provide adequate analgesia for TKA. The aim of study is to assess the analgesic effectiveness of ACB + IPACK block and epidural analgesia (EA) after TKA during the early stages of physical therapy. This prospective study included 58 patients who underwent unilateral TKA surgery. Patients were randomized into two groups as EA group (n = 30) and ACB + IPACK group (n = 28). The visual analogue scale (VAS) scores of the patients at the postoperative 8th (PO8th) hour, 1st postoperative day (POD1), and postoperative 2nd day (POD2) during the active and passive physical therapy movements, VAS scores during the ambulation, and active and passive range of movement values in POD1 were recorded. In addition, ambulation rates of the patients at the PO8th hour, 25 meters ambulation times in POD1, and completion times of 10 assisted squats in POD1 were recorded. The ACB + IPACK group had a substantially higher PO8th hour VAS score (p = 0.038). However, there was no significant difference in POD1, POD2 VAS scores. The analgesics consumption and VAS scores during ambulation were comparable among groups. Ambulation rate (22 (78.5%) vs. 16 (53.3%), p = 0.043) and speed (139.65 ± 57.12 sec. vs. 188.66 ± 77.95 sec., p = 0.023) were significantly better in the ACB + IPACK group. The strength of quadriceps contractions was similar in both groups. The use of a combination of ACB + IPACK block for postoperative analgesia in TKA patients is not only successful in reducing postoperative pain, but also a promising treatment with favourable effects on early ambulation and rehabilitation.

MÉTODOS DE TREINAMENTO DE FORÇA PARA ESQUIADORES

ABSTRACT Introduction: The ski jumping sequence can be divided into four steps: support, take-off, flight, and landing. Each stage has specific tasks and functions and is closely related, with the completion of each stage depending on the previous one. Objective: Explore the effectiveness of special strength training methods for ski sportsmen. Methods: Using the method of scientific literature review, expert interview, experience, and mathematical statistics to perform the special strength training for Chinese ski athletes, comparing the changes in the jump speed and take-off of the big jumps before and after 16 weeks of strength training with a specially developed protocol. Results: There were significant differences in take-off speed and air height before and after the experiment (P&lt;0.05). The athletes in the experimental group significantly differed in takeoff speed before and after participation in the experiment (P=0.01). Conclusion: The experimental results fully evidence that by improving the rapid contraction strength of flexor and extensor muscles of the trunk and hip joints, modern abdominal center strength training methods are more effective than traditional methods. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Effects of Ethanol on Contraction Strength of Chick Neck Striatum Muscle Following Electrical Stimulation of the Nerve

Introduction: Ethanol is a suitable solvent for many in vivo and ex vivo studies. However, it can interfere with normal muscle contraction and make variations in the results. Contrary to the present study, previous investigations revealed the suppressant effect of ethanol on muscle contraction. Methods: This study was based on an isolated chick biventer cervicis nerve-muscle using the twitch tension recording technique. Nerve and muscle complexes were exposed to several concentrations of ethanol (100, 200, 300, 400, and 500 mM), and impulses were recorded. Results: Twitch height increased in time and dose-dependent manner, and the concentration of 500 mM of ethanol after 30 minutes revealed the most elevation of muscle impulses. Conclusion: The potential effects of ethanol on striated muscle contraction are important and should be considered in studies using ethanol as a solvent.

ELDERLY MOUSE DETRUSOR MAINTAINS ITS PEAK FORCE OF CONTRACTION OVER TIME

Abstract Aging is a risk factor for urinary dysfunction. Detrusor weakening has been thought to contribute to the old bladder phenotype. Animal detrusor strips have been used to study bladder function. Strength of contraction in detrusor strips depends on length. This is referred to as the “length-tension relationship.” The aim of our study was to investigate this relationship in a mouse model by comparing the length-tension relationship in old and mature mice. We hypothesize that aging is associated with no change in active detrusor tension capability, however maximal tension will occur at longer lengths.We used two groups of male C57/Bl6 mice for this study, mature 11-12 month old mice and old 22-23 month old mice. Longitudinal intact bladder strips were harvested and placed in a vertical tissue bath between tension recording transducer hooks. Passive tensions and KCl induced contraction tensions for step-wise increments of stretch were observed.In the old group, normalized strip length at the point of maximum active tension was increased by ~13% on average as compared to the mature group with a statistically significant difference (P value 0.0171). Interestingly, the maximum active tension between groups did not differ by age. In conclusion, detrusor from old mice achieve similar maximum active tensions as that from mature mice, however at an increased length. This finding argues against a common belief that the bladder weakens with age. Instead, the aging bladder may adapt to increased filling volumes with an ability to operate at a similar strength of a younger bladder.

Formulation, Characterization, and Evaluation of Wound Healing Potency of a Novel Mattan tailam Nanogel Based on a Famous Traditional Siddha Formula.

The Mattan tailam mixture has been extensively used to heal ulcerous wounds in traditional Siddha practice. The present study aimed to synthesize a Mattan tailam nanogel and evaluate the enhancement of wound healing potential in an experimental wound model. Mattan tailam nanogel was synthesized using the high-energy milling approach, and characterization of nanogel and potency of wound healing was investigated. The novelty of this study was the nanogel preparation of Mattan tailam. As expected, a synthesized novel nanogel of Mattan tailam has a distinct, prominent peak with a spherical form, is negatively charged and has an average particle size of 20-30 nm. Mattan tailam nanogel treated rats showed a remarkable reduction (p<0.001) in the wound area. On the 16th day, 10% Mattan tailam nanogel treatment resulted in a higher percentage of wound contraction. The 10% Mattan tailam nanogel group exhibited a faster epithelialization time (14.33 days) and a greater hydroxyproline concentration than the others. The topical application of 10% Mattan tailam nanogel increased tensile strength, signifying a better therapeutic indication. The present findings prove that polyherbal Mattan tailam nanogel formulation significantly improves collagen production, wound contraction, and tensile strength.

Activation of small conductance Ca2+ -activated K+ channels suppresses Ca2+ transient and action potential alternans in ventricular myocytes.

At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and Ca2+ transient (CaT) amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We tested the hypothesis that in single rabbit ventricular myocytes pharmacological modulation of SK channels plays a causative role for the development of pacing-induced CaT and AP duration (APD) alternans. SK channel blockers (apamin, UCL1684) had only a minor effect on AP repolarization. However, SK channel activation by NS309 resulted in significant APD shortening, demonstrating that functional SK channels are well expressed in ventricular myocytes. The effects of NS309 were prevented or reversed by apamin and UCL1684, indicating that NS309 acted on SK channels. SK channel activation abolished or reduced the degree of pacing-induced CaT and APD alternans. Inhibition of KV 7.1 (with HMR1556) and KV 11.1 (with E4031) channels was used to mimic conditions of long QT syndromes type-1 and type-2, respectively. Both HMR1556 and E4031 enhanced CaT alternans that was prevented by SK channel activation. In AP voltage-clamped cells the SK channel activator had no effect on CaT alternans, confirming that suppression of CaT alternans was caused by APD shortening. APD shortening contributed to protection from alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest that SK activation could be a potential intervention to avert development of alternans with important ramifications for arrhythmia prevention and therapy for patients with long QT syndrome. KEY POINTS: At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and intracellular Ca2+ release amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We investigated whether pharmacological modulation of SK channels affects the development of cardiac alternans in normal ventricular cells and in cells with drug-induced long QT syndrome (LQTS). While SK channel blockers have only a minor effect on AP morphology, their activation leads to AP shortening and abolishes or reduces the degree of pacing-induced Ca2+ and AP alternans. AP shortening contributed to protection against alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest SK activation as a potential intervention to avert the development of alternans with important ramifications for arrhythmia prevention for patients with LQTS.

The day-to-day reliability of residual force enhancement during voluntary and electrically stimulated contractions.

Residual force enhancement (rFE) is characterized by increased steady-state isometric force following active muscle lengthening compared to a fixed-end isometric contraction at the same muscle length and level of neuromuscular activation. Many studies have characterized rFE in humans; however, the day-to-day reliability of rFE is unclear. We aimed to examine day-to-day reliability of rFE across various contraction types in the dorsiflexors in males and females. Twenty-five recreationally active young adults completed 2 visits, 1 week apart. Following determination of maximum voluntary contraction (MVC) strength, rFE was assessed during maximal voluntary effort, 20% MVC electrically stimulated, and 20% MVC torque-matching conditions. Each rFE condition was completed at 2 joint excursions: 0-20º plantar flexion (PF) and 0-40ºPF. Intraclass correlation coefficients (ICC) assessed relative reliability, and typical error of measurement (TEM), and the correlation variability of TEM (CVTEM) assessed absolute reliability. Electrically stimulated contractions demonstrated the highest reliability at 40ºPF (ICC:0.9; CVTEM:22.8 %) and 20ºPF (ICC:0.8; CVTEM:34.3 %), followed by maximal voluntary contractions at 40ºPF (ICC:0.7; CVTEM:55.1%) and 20ºPF (ICC:0.1; CVTEM:81.1%). The torque-matching trials showed poor reliability for 20º and 40ºPF (ICC: -0.1-0.3; CVTEM: 118.1 %-155.2 %). Our results demonstrate higher reliability of rFE when stretching to the descending limb of the torque-angle relationship compared to the plateau region, and in electrically stimulated compared to voluntary contractions in the dorsiflexors for both males and females.

Muscle damage induced by maximal eccentric exercise of the elbow flexors after 3-week immobilization.

The present study investigated the effects of a 3-week immobilization (IM) on muscle damage induced by maximal eccentric exercise (MaxEC) to test the hypothesis that the IM would make muscles prone to muscle damage. Young healthy sedentary men were pseudo-randomly assigned to IM or control group (n=12/group). Non-dominant arms of the IM group participants were immobilized at 90° elbow flexion by a cast for 21 days. All participants performed MaxEC consisting of five sets of six elbow flexor contractions by lowering a dumbbell set at 100% of pre-exercise maximal voluntary isometric contraction (MVC) strength of the non-dominant arm. This was performed at 2 days after the cast removal for the IM group. MVC torque, range of motion (ROM), muscle thickness (MT), muscle hardness, position sense (PS), and joint reaction angle (JRA) of the elbow flexors were measured at baseline, post-immobilization, and before, immediately after, and one to 5 days after MaxEC. The IM decreased MVC torque (-17 ± 2%), ROM (-2 ± 1%), MT (-7 ± 3%), and JRA (-12 ± 6%), and increased in muscle hardness (20 ± 6%) and PS (11 ± 2%) (p < 0.05). Changes in MVC (e.g., 2 days: -40± 5 vs. -30 ± 9%), ROM (2 days: -11 ± 2 vs. -9 ± 3%), muscle soreness (peak: 63 ± 22 vs. 48 ± 14 mm), plasma CK activity (peak: 7820 ± 4011 vs. 4980 ± 1363 IU/L), PS (maximal change: -23 ± 2 vs. -18 ± 3%), and JRA (maximal change: -37 ± 4 vs. -26 ± 3%) after MaxEC were greater (p < 0.05) for the IM than control group. These results supported the hypothesis and showed that the IM made the muscles more vulnerable to muscle damage induced by eccentric exercise.

Effects of motor imagery training on skeletal muscle contractile properties in sports science students.

Studies on motor imagery (MI) practice based on different designs and training protocols have reported changes in maximal voluntary contraction (MVC) strength. However, to date, there is a lack of information on the effects of MI training on contractile properties of the trained muscle. Forty-five physically active sport science students (21 female) were investigated who trained three times per week over a 4-week period in one of three groups: An MI group conducted MI practice of maximal isometric contraction of the biceps brachii; a physical exercise (PE) group physically practiced maximal isometric contractions of the biceps brachii in a biceps curling machine; and a visual imagery (VI) group performed VI training of a landscape. A MVC test of the arm flexors was performed in a biceps curling machine before and after 4 weeks of training. The muscular properties of the biceps brachii were also tested with tensiomyography measurements (TMG). Results showed an interaction effect between time and group for MVC (p=0.027, η 2 = 0.17), with a higher MVC value in the PE group (Δ5.9%) compared to the VI group (Δ-1.3%) (p=0.013). MVC did not change significantly in the MI group (Δ2.1%). Analysis of muscle contractility via TMG did not show any interaction effects neither for maximal radial displacement (p=0.394, η 2 = 0.05), delay time (p=0.79, η 2 = 0.01) nor contraction velocity (p=0.71, η 2 = 0.02). In spite of MVC-related changes in the PE group due to the interventions, TMG measurements were not sensitive enough to detect concomitant neuronal changes related to contractile properties.

Thick filament activation is different in fast- and slow-twitch skeletal muscle.

The contractile properties of fast-twitch and slow-twitch skeletal muscles are primarily determined by the myosin isoform content and modulated by a variety of sarcomere proteins. X-ray diffraction studies of regulatory mechanisms in muscle contraction have focused predominately on fast- or mixed-fibre muscle with slow muscle being much less studied. Here, we used time-resolved X-ray diffraction to investigate the dynamic behaviour of the myofilament proteins in relatively pure slow-twitch-fibre rat soleus (SOL) and pure fast-twitch-fibre rat extensor digitorum longus (EDL) muscle during twitch and tetanic contractions at optimal length. During twitch contractions the diffraction signatures indicating a transition in the myosin heads from ordered OFF states, where heads are held close to the thick filament backbone, to disordered ON states, where heads are free to bind to thin filaments, were found in EDL and not in SOL muscle. During tetanic contraction, changes in the disposition of myosin heads as active tension develops is a quasi-stepwise process in EDL muscle whereas in SOL muscle this relationship appears to be linear. The observed reduced extensibility of the thick filaments in SOL muscle as compared to EDL muscles indicates a molecular basis for this behaviour. These data indicate that for the EDL, thick filament activation is a cooperative strain-induced mechano-sensing mechanism, whereas for the SOL, thick filament activation has a more graded response. These different approaches to thick filament regulation in fast- and slow-twitch muscles may be adaptations for short-duration, strong contractions versus sustained, finely controlled contractions, respectively. KEY POINTS: Fast-twitch muscle and slow-twitch muscle are optimized for strong, short-duration contractions and for tonic postural activity, respectively. Structural events (OFF to ON transitions) in the myosin-containing thick filaments in fast muscle help determine the timing and strength of contractions, but these have not been studied in slow-twitch muscle. The X-ray diffraction signatures of structural OFF to ON transitions are different in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle, being completely absent during twitches in soleus muscle and blunted during tetanic contractions SOL as compared to EDL Quasi-stepwise thick filament structural OFF to ON transitions in fast twitch muscle may be an adaptation for rapid, ballistic movements, whereas more graded OFF to ON structural transitions in slow-twitch muscle may be an adaptation for slower, finer motions.

Evaluation of Longitudinal Lymphatic Function Changes upon Injury in the Mouse Tail with Photodynamic Therapy.

The lymphatic system is an essential but often understudied component of the circulatory system in comparison with its cardiovascular counterpart. Such disparity could often be explained by the difficulty in imaging lymphatics and the specialized microsurgical skills that are often required for lymphatic injury models. Recently, it has been shown that verteporfin, a photosensitive drug used for photodynamic therapy (PDT) to ablate the blood vessels, provides a similar effect on lymphatic vessels. Here, we seek to administer verteporfin and perform a modified form of PDT on collecting lymphatics in the mouse tail, a commonly used location for the study of lymphatic disorders, and examine lymphatic remodeling, contractility, and transport in response to the procedure. Mice collecting lymphatics in the tail were injured by PDT through an intradermal injection of verteporfin in the distal tip of the tail followed by light activation on the proximal portion of the tail downstream of the injection site. Lymphatic function was evaluated using a near-infrared (NIR) imaging system weekly for up to 28days after injury. PDT resulted in a loss in lymphatic function contractile frequency that persisted for up to 7days after injury. Packet transport and packet amplitude, measurements reflective of the strength of contraction, were significantly reduced 14days after injury. The lymphatics showed a delayed increase in lymphatic leakage at 7days that persisted until the study endpoint on day 28. This technique provides an easy-to-use method for injuring lymphatics to understand their remodeling response to injury by PDT as well as potentially for screening therapeutics that seek to normalize lymphatic permeability or contractile function after injury.

Month-of-Birth Effect on Muscle Mass and Strength in Community-Dwelling Older Women: The French EPIDOS Cohort.

Background. Vitamin D is involved in muscle health and function. This relationship may start from the earliest stages of life during pregnancy when fetal vitamin D relies on maternal vitamin D stores and sun exposure. Our objective was to determine whether there was an effect of the month of birth (MoB) on muscle mass and strength in older adults. Methods. Data from 7598 community-dwelling women aged ≥ 70 years from the French multicentric EPIDOS cohort were used in this analysis. The quadricipital strength was defined as the mean value of 3 consecutive tests of the maximal isometric voluntary contraction strength of the dominant lower limb. The muscle mass was defined as the total appendicular skeletal muscle mass measured using dual energy X-ray absorptiometry scanner. The MoB was used as a periodic function in regressions models adjusted for potential confounders including age, year of birth, latitude of recruitment center, season of testing, body mass index, number of comorbidities, IADL score, regular physical activity, sun exposure at midday, dietary protein intake, dietary vitamin D intake, use vitamin D supplements, history and current use of corticosteroids. Results. A total of 7133 older women had a measure of muscle strength (mean age, 80.5 ± 3.8 years; mean strength, 162.3 ± 52.1 N). Data on total ASM were available from 1321 women recruited in Toulouse, France (mean, 14.86 ± 2.04 kg). Both the sine and cosine functions of MoB were associated with the mean quadricipital strength (respectively β = -2.1, p = 0.045 and β = -0.5, p = 0.025). The sine function of MoB was associated with total ASM (β = -0.2, p = 0.013), but not the cosine function (β = 0.1, p = 0.092). Both the highest value of average quadricipital strength (mean, 163.4 ± 20.2 N) and the highest value of total ASM (15.24 ± 1.27 kg) were found among participants born in August. Conclusions. Summer-early fall months of birth were associated with higher muscle mass and strength in community-dwelling older women.

Peristaltic regimes in esophageal transport.

A FLIP device gives cross-sectional area along the length of the esophagus and one pressure measurement, both as a function of time. Deducing mechanical properties of the esophagus including wall material properties, contraction strength, and wall relaxation from these data are a challenging inverse problem. Knowing mechanical properties can change how clinical decisions are made because of its potential for in-vivo mechanistic insights. To obtain such information, we conducted a parametric study to identify peristaltic regimes by using a 1D model of peristaltic flow through an elastic tube closed on both ends and also applied it to interpret clinical data. The results gave insightful information about the effect of tube stiffness, fluid/bolus density and contraction strength on the resulting esophagus shape through quantitive representations of the peristaltic regimes. Our analysis also revealed the mechanics of the opening of the contraction area as a function of bolus flow resistance. Lastly, we concluded that peristaltic driven flow displays three modes of peristaltic geometries, but all physiologically relevant flows fall into two peristaltic regimes characterized by a tight contraction.

Quantitative analysis for grading uterine electromyography activities during labor

The strength of uterine contraction is one of the decisive factors for labor progression and parturition. Clinicians usually encounter difficulties in early identification of inadequate contractions and in oxytocin treatment. Electromyography-an emerging technology for uterine contraction monitoring-can quantify the intensity of myoelectric activity of uterine contraction. Therefore, grading patients with different uterine contraction intensities by electromyography is of great significance to the clinical intensive management of uterine contraction and labor process. This study aimed to quantify and grade electromyography activity during the latent phase of the first stage of labor and explore its relationship with oxytocin treatment and length of labor. We performed a retrospective cohort study to identify electromyography parameters as a predictor for oxytocin treatment and length of labor among a cohort of term singleton primipara (n=508) during the latent phase who delivered in Guangzhou between August 2018 and December 2021. The electromyography parameters were graded according to the quartile method, and the significance of grading and delivery outcome was explored. Univariateandmultivariate logistic regression were used to determine the predictors of oxytocin treatment. Maternal gestational age (adjusted risk ratio, 1.2; 95% confidence interval, 1.0-1.5), root mean square (adjusted risk ratio, 0.01; 95% confidence interval, 0.004-0.03), and power (adjusted risk ratio, 0.02; 95% confidence interval, 0.01-0.05) were significant predictors of oxytocin argumentation. The low electromyography activity group had a longer first stage labor and total labor time and were more likely to use oxytocin. Electromyography parameters root mean square and power had high predictive values for later oxytocin treatment among patients with spontaneous labor. Patients with low-grade electromyography were more likely need oxytocin treatment. Electromyography grading is very important for its clinical promotion and use, and it could lead to more reliable analyses of oxytocin treatments and eventually to more effective interventions to prevent prolonged labor.

Multiple shapes from a single nematic elastomer sheet activated via patterned illumination

Liquid crystal elastomers (LCEs) undergo a large uniaxial contraction upon thermal or optical stimulation. LCE sheets are often fabricated with a spatially patterned direction of contraction, which can sculpt the sheet into a Gauss-curved surface. Here, we instead consider LCE sheets subject to patterned stimulation intensity, leading to a control of contraction strength. We show such patterns may also sculpt a complex surface, but with the advantage that arbitrarily many surfaces may be achieved sequentially in the same sample, thus breaking the link between microstructure and shape. We first consider a monodomain LCE in which some regions are actuated and others are not. We discuss how to join actuated and unactuated regions compatibly, and use this design rule to generate patterns for cones, anti-cones, arrays of cones and a rolling bi-strip. We validate the patterns numerically via elastic shell simulations and demonstrate them experimentally via patterned photo-chemical actuation. Secondly, we consider an LCE disk with an azimuthal director profile actuated by a radially varying stimulus. We show, theoretically and numerically, how to design a stimulation profile to sculpt any surface of revolution. Such re-configurable actuation offers enticing possibilities for haptics, robotics and locomotion.

An iterated map model with CaMKII feedback in modeling the force frequency relationship of a cardiac cell

Experiment data on isolated rat hearts shows that the transient behaviors after switching pacing intervals are very complicated with increasing, decreasing, and rebound of the contraction force. The strength of contraction in the heart muscle is strongly related to intracellular free Ca2+ mediated by an action potential. This behavior can be explained by calcium cycling inside the excitable cardiac myocytes coupled with their action potential. The previous and recently proposed models can only explain a short period of time after changing the pacing frequency. Our aim is to develop a simple feedback model based on the role of the enzyme CaMKII to describe the whole dynamic picture captured from experiments.

Modeling of the maximum endurance time of coal miners muscle fatigue for one-handed carrying tasks

To prevent safety production accidents caused by muscle fatigue among coal miners, a modified model of maximum tolerance time (TME) was established to predict the TME for one-handed handling tasks. Thirty-one participants including different types of coal miners volunteered to participate in one-handed handling of oil drums for loading, unloading and horizontal walking operations. The maximum voluntary contraction strength (fMVC), subjective fatigue rating (Erp) and TME of coal miners' backs and legs were measured before and after handling operations, as well as during the three task phases. An Erp one-dimensional linear regression prediction model was established under the effect of individual factors. A simplified TME prediction model was developed using power and exponential functions in the relative role of fMVC. A TME-modified model was further constructed considering the effects of weight and heart rate of coal miners. It was found that when fMVC ≤ 0.12, the simplified power model (median function model) provided higher estimates than the exponential model, and the predictions were closer to the true values. With fMVC < 0.2 or lower, incorporating indicators of instantaneous heart rate and body weight of coal miners, the TME modified model was used to accurately assess the TME of coal miners. It is suggested that workers engaged in manual handling operations on a daily basis should not carry a maximum weight of more than 22 kg on the back or legs to avoid musculoskeletal disorders that could lead to safety accidents.