Flexed State Research Articles

APLICAÇÃO DO TREINAMENTO FÍSICO NA REABILITAÇÃO DE LESõES EM ATLETAS DE TÊNIS DE MESA

ABSTRACT Introduction: Table tennis is a combative sport, and although there is no physical confrontation between athletes, its fast and intense movements require high physical conditioning. The knee joint is held in the flexed state for an extended period, and a deficiency in its stability can lead to disabling injuries. The International Table Tennis Federation reforms have led scientists to research further the stability and strengthening of the CORE muscles for injury prevention. Functional Motion Scanning is a screening technique devised to assess and guide musculoskeletal therapeutic protocol. However, there is still a misunderstanding about using this technique in table tennis players. Objective: Study the application of Functional Motion Scanning in the rehabilitation of sports injuries in male table tennis players. Methods: 20 college table tennis players from Hebei Normal University, aged 18 to 24 years, with sport level grade 2 and test score <8 and knee assessment scale score less than 90 points had the following data evaluated: Functional Motion Scan results, body composition, vertical jump, circumference, and lower limb strength. The exercise intensity and load were adjusted according to the individual physical condition of the participants who did not perform any other parallel activities during the 12 weeks of training. There was intervention three times a week for 20 to 25 minutes during the first six weeks. From the seventh to the twelfth week, intervention two times a week for 25 to 30 minutes. SPSS20.0 software was used for statistical analysis and graphing. Results: The number of knee injuries in table tennis gradually decreased from 3 to 1. An overall reduction in BMI and an increase in thigh and calf circumference were also observed. Conclusions: Physical training with screening positively impacted the prevention and treatment of knee injuries. Evidence Level II; Therapeutic Studies - Investigating the result.

Elastin-Dependent Aortic Heart Valve Leaflet Curvature Changes During Cyclic Flexure.

The progression of calcific aortic valve disease (CAVD) is characterized by extracellular matrix (ECM) remodeling, leading to structural abnormalities and improper valve function. The focus of the present study was to relate aortic valve leaflet axial curvature changes as a function of elastin degradation, which has been associated with CAVD. Circumferential rectangular strips (L × W = 10 × 2.5 mm) of normal and elastin-degraded (via enzymatic digestion) porcine AV leaflets were subjected to cyclic flexure (1 Hz). A significant increase in mean curvature (p < 0.05) was found in elastin-degraded leaflet specimens in comparison to un-degraded controls at both the semi-constrained (50% of maximum flexed state during specimen bending and straightening events) and fully-constrained (maximally-flexed) states. This significance did not occur in all three flexed configurations when measurements were performed using either minimum or maximum curvature. Moreover, the mean curvature increase in the elastin-degraded leaflets was most pronounced at the instance of maximum flexure, compared to un-degraded controls. We conclude that the mean axial curvature metric can detect distinct spatial changes in aortic valve ECM arising from the loss in bulk content and/or structure of elastin, particularly when there is a high degree of tissue bending. Therefore, the instance of maximum leaflet flexure during the cardiac cycle could be targeted for mean curvature measurements and serve as a potential biomarker for elastin degradation in early CAVD remodeling.

Biodegradable photolithography compatible substrate for transparent transient electronics and flexible energy storage devices

Transient electronic devices (TED) can disappear with non-traceable or minimal remains once their intended lifetime is over, and hence form a growing area of research in defence and healthcare industry. However, due to the incompatibility of the TED substrates with high throughput micro-fabrication processes like UV lithography, they are obligated to rely on slow and low resolution processes like transfer printing and stencil printing. Therefore, the development of a substrate that is compatible with UV lithography would not only enable micro-fabrication but would also allow for a smooth transition of TED from lab to shelf.In this study, we demonstrate the suitability of agarose, a carbohydrate, as a substrate for transient electronics. Agarose is chemically modified with HMDS that imparts a hydrophobic character to otherwise hydrophilic agarose. Consequently, unlike other available biodegradable substrates that are incompatible with water based processing during UV lithography, these silylated agarose substrates provide a compatible window for aqueous processing steps. After establishing suitable thermal and optical properties of such a substrate, its compatibility with UV lithography is demonstrated by micropatterning antibody and aluminium patterns. Additionally, in order to demonstrate its wider applicability in the area of energy storage, a flexible-biodegradable battery is stencil printed on it that can sustain a small electronic device in both relaxed and flexed state.

Inter- and intra-rater reliability of patellofemoral kinematic and contact area quantification by fast spin echo MRI and correlation with cartilage health by quantitative T1ρ MRI

BackgroundPatellar maltracking is a leading cause of patellofemoral pain syndrome (PFPS). The aim of this study was to determine the inter- and intra-rater reliability of a semi-automated program for magnetic resonance imaging (MRI) based patellofemoral kinematics. MethodsSixteen subjects (10 with PFPS [mean age 32.3; SD 5.2; eight females] and six controls without PFPS 19 [mean age 28.6; SD 2.8; three females]) participated in the study. One set of T2-weighted, fat-saturated fast spin-echo (FSE) MRIs were acquired from each subject in full extension and 30° of knee flexion. MRI including axial T1ρ relaxation time mapping sequences was also performed on each knee. Following image acquisitions, regions of interest for kinematic MRI, and patellar and trochlear cartilage were segmented and quantified with in-house designed spline- based MATLAB semi-automated software. ResultsIntraclass Correlations Coefficients (ICC) of calculated kinematic parameters were good to excellent, ICC > 0.8 in patellar flexion, rotation, tilt, and translation (anterior -posterior, medial -lateral, and superior -inferior), and contact area translation. Only patellar tilt in the flexed position and motion from extended to flexed state was significantly different between PFPS and control patients (p=0.002 and p=0.006, respectively). No significant correlations were identified between patellofemoral kinematics and contact area with T1ρ relaxation times. ConclusionsA semi-automated, spline-based kinematic MRI technique for patellofemoral kinematic and contact area quantification is highly reproducible with the potential to help better understand the role of patellofemoral maltracking in PFPS and other knee disorders. Level of EvidenceLevel IV

MRI-based analysis of patellofemoral cartilage contact, thickness, and alignment in extension, and during moderate and deep flexion

BackgroundSeveral factors are believed to contribute to patellofemoral joint function throughout knee flexion including patellofemoral (PF) kinematics, contact, and bone morphology. However, data evaluating the PF joint in this highly flexed state have been limited. Therefore, the purpose of this study was to evaluate patellofemoral contact and alignment in low (0°), moderate (60°), and deep (140°) knee flexion, and then correlate these parameters to each other, as well as to femoral morphology. MethodsSagittal magnetic resonance images were acquired on 14 healthy female adult knees (RSRB approved) using a 1.5T scanner with the knee in full extension, mid-flexion, and deep flexion. The patellofemoral cartilage contact area, lateral contact displacement (LCD), cartilage thickness, and lateral patellar displacement (LPD) throughout flexion were defined. Intra- and inter-rater repeatability measures were determined. Correlations between patellofemoral contact parameters, alignment, and sulcus morphology were calculated. ResultsMeasurement repeatability ICCs ranged from 0.94 to 0.99. Patellofemoral cartilage contact area and thickness, LCD, and LPD were statistically different throughout all levels of flexion (p<0.001). The cartilage contact area was correlated to LPD, cartilage thickness, sulcus angle, and epicondylar width (r=0.47–0.72, p<0.05). DiscussionThis study provides a comprehensive analysis of the patellofemoral joint throughout its range of motion. ConclusionsThis study agrees with past studies that investigated patellofemoral measures at a single flexion angle, and provides new insights into the relationship between patellofemoral contact and alignment at multiple flexion angles. Clinical RelevanceThe study provides a detailed analysis of the patellofemoral joint in vivo, and demonstrates the feasibility of using standard clinical magnetic resonance imaging scanners to image the knee joint in deep flexion.

14%-efficient flexible CdTe solar cells on ultra-thin glass substrates

Flexible glass enables high-temperature, roll-to-roll processing of superstrate devices with higher photocurrents than flexible polymer foils because of its higher optical transmission. Using flexible glass in our high-temperature CdTe process, we achieved a certified record conversion efficiency of 14.05% for a flexible CdTe solar cell. Little has been reported on the flexibility of CdTe devices, so we investigated the effects of three different static bending conditions on device performance. We observed a consistent trend of increased short-circuit current and fill factor, whereas the open-circuit voltage consistently dropped. The quantum efficiency under the same static bend condition showed no change in the response. After storage in a flexed state for 24 h, there was very little change in device efficiency relative to its unflexed state. This indicates that flexible glass is a suitable replacement for rigid glass substrates, and that CdTe solar cells can tolerate bending without a decrease in device performance.

Structural Analysis of Mold Temperature Dependence of Polycarbonate by Mid-Infrared Spectroscopy

The mold temperature dependence of bisphenol A polycarbonate (BPAPC) in the view of changing the "flexed state" was investigated by mid-infrared spectroscopy combined with a previously developed thin sample preparation system. The differences in the samples of different mold temperatures were clearly detected. The structural changes in the flexed state of each mold temperature were analyzed by comparing the results using dielectric function analysis of different cutting procedures. Some structure parameters were associated with the contact angle of liquids on polymer plate. The evidence suggests that mold temperature and surface wettability affects the cohesive or entanglement state of polymers at the chemical structure level.

A New Approach to Investigate Thin Surface Layers of Polymers: Fatigue Analysis of Polycarbonate

A new technique to investigate chemical structures of very thin surface (mesoscopic scale) layers of polar polymers is proposed. The chemical structures and conformations of ∼100 nm-thick slabs that were obtained from a polymer surface were studied by infrared spectroscopy combined with a previously developed thin sample preparation system. The dielectric functions were calculated using oscillator models from reflection spectra of the slabs, which were cut with a diamond blade. The molecular movements caused by shear force perturbations after the cutting process ("flexed state") were observed. The technique was applied to analyze the changes in the chemical structure of bisphenol A polycarbonate (BPAPC) throughout a bending cyclic fatigue test. Three characteristic stages of structural changes in the flexed state under the cyclic fatigue test were observed. Our technique has the potential to clarify the intrinsic structures of solid polymers such as the degree of entanglement and the tendency for order or disorder caused by the surrounding chain interaction.

Highly flexible pseudocapacitor based on freestanding heterogeneous MnO2/conductive polymer nanowire arrays

Flexible electronics such as wearable electronic clothing, paper-like electronic devices, and flexible biomedical diagnostic devices are expected to be commercialized in the near future. Flexible energy storage will be needed to power these devices. Supercapacitor devices based on freestanding nanowire arrays are promising high power sources for these flexible electronics. Electrodes for these supercapacitor devices consisting of heterogeneous coaxial nanowires of poly (3,4-ethylenedioxythiophene) (PEDOT)-shell and MnO(2)-core materials have been shown in a half cell system to have improved capacitance and rate capabilities when compared to their pure nanomaterials; however, their performance in a full cell system has not been fully investigated. Herein, these coaxial nanowires are tested in both a symmetric and an asymmetric (utilizing a PEDOT nanowire anode) full cell configuration in the aspect of charge storage, charge rate, and flexibility without using any carbon additives and polymer binders. It is found that the asymmetric cell outperforms the symmetric cell in terms of energy density, rate capability, and cycle ability. The asymmetric device's electrode materials display an energy density of 9.8 Wh/kg even at a high power density of 850 W kg(-1). This device is highly flexible and shows fast charging and discharging while still maintaining 86% of its energy density even under a highly flexed state. The total device is shown to have a total capacitance of 0.26 F at a maximum voltage of 1.7 V, which is capable of providing enough energy to power small portable devices.

A Novel Flex-Stretch-Flow Bioreactor for the Study of Engineered Heart Valve Tissue Mechanobiology

Tissue engineered heart valves (TEHV) have been observed to respond to mechanical conditioning in vitro by expression of activated myofibroblast phenotypes followed by improvements in tissue maturation. In separate studies, cyclic flexure, stretch, and flow (FSF) have been demonstrated to exhibit both independent and coupled stimulatory effects. Synthesis of these observations into a rational framework for TEHV mechanical conditioning has been limited, however, due to the functional complexity of tri-leaflet valves and the inherent differences of separate bioreactor systems. Toward quantifying the effects of individual mechanical stimuli similar to those that occur during normal valve function, a novel bioreactor was developed in which FSF mechanical stimuli can be applied to engineered heart valve tissues independently or in combination. The FSF bioreactor consists of two identically equipped chambers, each having the capacity to hold up to 12 rectangular tissue specimens (25 x 7.5 x 1 mm) via a novel "spiral-bound" technique. Specimens can be subjected to changes-in-curvature up to 50 mm(-1) and uniaxial tensile strains up to 75%. Steady laminar flow can be applied by a magnetically coupled paddlewheel system. Computational fluid dynamic (CFD) simulations were conducted and experimentally validated by particle image velocimetry (PIV). Tissue specimen wall shear stress profiles were predicted as a function of paddlewheel speed, culture medium viscosity, and the quasi-static state of specimen deformation (i.e., either undeformed or completely flexed). Velocity profiles predicted by 2D CFD simulations of the paddlewheel mechanism compared well with PIV measurements, and were used to determine boundary conditions in localized 3D simulations. For undeformed specimens, predicted inter-specimen variations in wall shear stress were on average +/-7%, with an average wall shear stress of 1.145 dyne/cm(2) predicted at a paddlewheel speed of 2000 rpm and standard culture conditions. In contrast, while the average wall shear stress predicted for specimens in the quasi-static flexed state was approximately 59% higher (1.821 dyne/cm(2)), flexed specimens exhibited a broad intra-specimen wall shear stress distribution between the convex and concave sides that correlated with specimen curvature, with peak wall shear stresses of approximately 10 dyne/cm(2). This result suggests that by utilizing simple flexed geometric configurations, the present system can also be used to study the effects of spatially varying shear stresses. We conclude that the present design provides a robust tool for the study of mechanical stimuli on in vitro engineered heart valve tissue formation.

Cyclic fatigue testing of nickel-titanium endodontic instruments

Cyclic fatigue of nickel-titanium, engine-driven instruments was studied by determining the effect of canal curvature and operating speed on the breakage of Lightspeed instruments. A new method of canal curvature evaluation that addressed both angle and abruptness of curvature was introduced. Canal curvature was simulated by constructing six curved stainless-steel guide tubes with angles of curvature of 30, 45, or 60 degrees, and radii of curvature of 2 or 5 mm. Size #30 and #40 Light-speed instruments were placed through the guide tubes and the heads secured in the collet of a Mangtrol Dynamometer. A simulated operating load of 10 g-cm was applied. Instruments were able to rotate freely in the test apparatus at speeds of 750, 1300, or 2000 rpm until separation occurred. Cycles to failure were determined. Cycles to failure were not affected by rpm. Instruments did not separate at the head, but rather at the point of maximum flexure of the shaft, corresponding to the midpoint of curvature within the guide tube. The instruments with larger diameter shafts, #40, failed after significantly fewer cycles than did #30 instruments under identical test conditions. Multivariable analysis of variance indicated that cycles to failure significantly decreased as the radius of curvature decreased from 5 mm to 2 mm and as the angle of curvature increased greater than 30 degrees (p < 0.05, power = 0.9). Scanning electron microscopic evaluation revealed ductile fracture as the fatigue failure mode. These results indicate that, for nickel-titanium, engine-driven rotary instruments, the radius of curvature, angle of curvature, and instrument size are more important than operating speed for predicting separation. This study supports engineering concepts of cyclic fatigue failure and suggests that standardized fatigue tests of nickel-titanium rotary instruments should include dynamic operation in a flexed state. The results also suggest that the effect of the radius of curvature as an independent variable should be considered when evaluating studies of root canal instrumentation.

Effects of carbohydrate loading and weight-lifting on muscle girth.

Bodybuilders have used different carbohydrate loading regimens in conjunction with resistance exercise prior to competition in the belief that this would result in increased muscle size. To investigate this possibility, muscle girth measurements were obtained from nine weight-trained males before and after a control (standard isocaloric diet) and an experimental trial (carbohydrate loading). The latter regimen consisted of 3 days of intense weight-lifting while the subjects ingested a diet of 10% carbohydrate (CHO), 57% fat (F), and 33% protein (P), followed by 3 days of light weight-lifting and a day of rest while ingesting a diet of 80% CHO, 5% F, and 15% P. The control trial consisted of an identical weight-lifting regimen while subjects ingested an isocaloric (45 kcal/kg BW/day) diet. Body weight and girths (forearm, upper arm, chest, thigh, waist, and calf) were obtained before and after each trial in a relaxed and flexed state. The results indicate that an exercise/carbohydrate loading regimen had no significant effect on muscle girth as compared to the control trial. It is concluded that CHO loading has no additional advantage to enhancing muscle girth in bodybuilders over weight-lifting alone.