Reproducibility of knee extensor and flexor contraction velocity in healthy men and women assessed using tensiomyography: A study protocol

Tensiomyography measures the radial displacement of a muscle during an electrically evoked twitch contraction. The rate of muscle displacement is increasingly reported to assess contractile properties. Several formulas currently exist to calculate the rate of displacement during the contraction phase of the maximal twitch response. However, information on the reproducibility of these formulas is scarce. Further, different rest intervals ranging from 10 s to 30 s are applied between consecutive stimuli during progressive electrical stimulation until the maximum twitch response. The effect of different rest intervals on the rate of displacement has not been investigated so far. The first aim of this study is to investigate the within and between-day reliability of the most frequently used formulas to calculate the rate of displacement. The second aim is to investigate the effect of changing the inter-stimulus interval on the rate of displacement. We will determine the rectus femoris and biceps femoris rate of displacement of twenty-four healthy subjects’ dominant leg on two consecutive days. The maximum displacement curve will be determined two times within three minutes on the first day and a third time 24 h later. On day two, we will also apply three blocks of ten consecutive stimuli at a constant intensity of 50 mA. Inter-stimuli intervals will be 10 s, 20 s or 30 s in each block, respectively, and three minutes between blocks. The order of inter-stimulus intervals will be randomized. This study will allow a direct comparison between the five most frequently used formulas to calculate the rate of displacement in terms of their reproducibility. Our data will also inform on the effect of different inter-stimulus intervals on the rate of displacement. These results will provide helpful information on methodical considerations to determine the rate of displacement and may thus contribute to a standardized approach.

Scalar and tensor perturbations in DHOST bounce cosmology

We investigate the bounce realization in the framework of DHOST cosmology, focusing on the relation with observables. We perform a detailed analysis of the scalar and tensor perturbations during the Ekpyrotic contraction phase, the bounce phase, and the fast-roll expansion phase, calculating the power spectra, the spectral indices and the tensor-to-scalar ratio. Furthermore, we study the initial conditions, incorporating perturbations generated by Ekpyrotic vacuum fluctuations, by matter vacuum fluctuations, and by thermal fluctuations. The scale invariance of the scalar power spectrum can be acquired introducing a matter contraction phase before the Ekpyrotic phase, or invoking a thermal gas as the source. The DHOST bounce scenario with cosmological perturbations generated by thermal fluctuations proves to be the most efficient one, and the corresponding predictions are in perfect agreement with observational bounds. Especially the tensor-to-scalar ratio is many orders of magnitude within the allowed region, since it is suppressed by the Hubble parameter at the beginning of the bounce phase.

Algorithmic extraction of smartphone accelerometer-derived mechano-biological descriptors of resistance exercise is robust to changes in intensity and velocity

Background It was shown that single repetition, contraction-phase specific and total time-under-tension (TUT) can be extracted reliably and validly from smartphone accelerometer-derived data of resistance exercise machines using user-determined resistance exercise velocities at 60% one repetition maximum (1-RM). However, it remained unclear how robust the extraction of these mechano-biological descriptors is over a wide range of movement velocities (slow- versus fast-movement velocity) and intensities (30% 1-RM versus 80% 1-RM) that reflect the interindividual variability during resistance exercise. Objective In this work, we examined whether the manipulation of velocity or intensity would disrupt an algorithmic extraction of single repetitions, contraction-phase specific and total TUT. Methods Twenty-seven participants performed four sets of three repetitions of their 30% and 80% 1-RM with velocities of 1 s, 2 s, 6 s and 8 s per repetition, respectively. An algorithm extracted the number of repetitions, single repetition, contraction-phase specific and total TUT. All exercises were video-recorded. The video recordings served as the gold standard to which algorithmically-derived TUT was compared. The agreement between the methods was examined using Limits of Agreement (LoA). The Pearson correlation coefficients were used to calculate the association, and the intraclass correlation coefficient (ICC 2.1) examined the interrater reliability. Results The calculated error rate for the algorithmic detection of the number of single repetitions derived from two smartphones accelerometers was 1.9%. The comparison between algorithmically-derived, contraction-phase specific TUT against video, revealed a high degree of correlation (r > 0.94) for both exercise machines. The agreement between the two methods was high on both exercise machines, intensities and velocities and was as follows: LoA ranged from -0.21 to 0.22 seconds for single repetition TUT (2.57% of mean TUT), from -0.24 to 0.22 seconds for concentric contraction TUT (6.25% of mean TUT), from -0.22 to 0.24 seconds for eccentric contraction TUT (5.52% of mean TUT) and from -1.97 to 1.00 seconds for total TUT (5.13% of mean TUT). Interrater reliability for single repetition, contraction-phase specific TUT was high (ICC > 0.99). Conclusion Neither intensity nor velocity disrupts the proposed algorithmic data extraction approach. Therefore, smartphone accelerometers can be used to extract scientific mechano-biological descriptors of dynamic resistance exercise with intensities ranging from 30% to 80% of the 1-RM with velocities ranging from 1 s to 8 s per repetition, respectively, thus making this simple method a reliable tool for resistance exercise mechano-biological descriptors extraction.

SARS-CoV-2 infection induces sustained humoral immune responses in convalescent patients following symptomatic COVID-19

Long-term antibody responses and neutralizing activities in response to SARS-CoV-2 infection are not yet clear. Here we quantify immunoglobulin M (IgM) and G (IgG) antibodies recognizing the SARS-CoV-2 receptor-binding domain (RBD) of the spike (S) or the nucleocapsid (N) protein, and neutralizing antibodies during a period of 6 months from COVID-19 disease onset in 349 symptomatic COVID-19 patients who were among the first be infected world-wide. The positivity rate and magnitude of IgM-S and IgG-N responses increase rapidly. High levels of IgM-S/N and IgG-S/N at 2-3 weeks after disease onset are associated with virus control and IgG-S titers correlate closely with the capacity to neutralize SARS-CoV-2. Although specific IgM-S/N become undetectable 12 weeks after disease onset in most patients, IgG-S/N titers have an intermediate contraction phase, but stabilize at relatively high levels over the 6 month observation period. At late time points, the positivity rates for binding and neutralizing SARS-CoV-2-specific antibodies are still >70%. These data indicate sustained humoral immunity in recovered patients who had symptomatic COVID-19, suggesting prolonged immunity.

Modulating the mechanokinetics of spontaneous contractions of the myometrium of rats using calix[4]arene C-90 – plasma membrane calcium ATPase inhibitor

Introduction. Plasma membrane calcium ATPase is a constitutive structure of cells that functions as a high affinity system of releasing Са2+ ions from the cytoplasm and ensures a long-term maintenance of the basal concentration of these cations in the state of dormancy. Currently, there are no satisfactory means for the pharmacological correction of plasma membrane calcium ATPase function. Thus, elaboration, synthesis, and study of substances with the targeted impact on plasma membrane calcium ATPase are topical issues. Previously, we determined the ability of this calix[4]arene in the concentration of 10 µM to inhibit the contractive activity and to slow down the relaxation of smooth muscle of the myometrium in the NO-dependent way, which considerably decreases the normalized maximal velocity of the relaxation phase. Materials and Methods. The tenzometric methods and mechanokinetic analysis were used to investigate the impact of the cumulative increase in the concentration of calix[4]arene С-90 (10 nM – 100 µM) on the spontaneous contractive activity of the myometrium of rats. The complete profile of spontaneous cycles of contractions-relaxa­tions was studied by the empirical multiparameter method of complex mechanokinetic analysis, elaborated by us (with the consideration of the parameters of time (τ0, τC and τR), force (Fmax, FC and FR), velocity (VC and VR), and impulse (Іmax, ІC and ІR). Results. Calix[4]arene C-90 evoked the dose-dependent inhibition of spontaneous contractive activity of the myometrium preparations. Its high concentrations caused a change in the structure of the contraction act, such as an increase in the duration of the contraction phase, while the duration of the relaxation phase did not show any changes. The multiparameter method of the complex mechanokinetic analysis demonstrated that in the whole range of the investigated concentrations, substance С-90 considerably decreases the indices of force parameters (Fmax, FC and FR) and the values of impulses of force Іmax, IC and IR of the spontaneous contractions of the myometrium. On the background of all the applied concentrations (10-7–10-4 М), calix[4]arene С-90 conditioned the slowing down of the relaxation of spontaneous contractions in uterine muscle prepa­rations of rats, which was reflected in a reliable decrease in the parameter for the maxi­mal velocity of the relaxation phase (VR). Conclusions. The results of the study demonstrate that calix[4]arene С-90 inhibits the processes of Са2+ extrusion from smooth muscle cells myoplasm, probably, impacting plasma membrane calcium ATPase molecules directly. It is noteworthy that C-90 is also likely to inhibit the processes of the intake of these cations to cells from the extracellular medium, causing a decrease in the velocity of force intensification during the contraction phase, and reducing the frequency and force of the spontaneous contractions in the myometrium.

Bounce and Stability in the Early Cosmology with Anomaly-Induced Corrections

An extremely fast exponential expansion of the Universe is typical for the stable version of the inflationary model, based on the anomaly-induced action of gravity. The total amount of exponential e-folds could be very large, before the transition to the unstable version and the beginning of the Starobinsky inflation. Thus, the stable exponential expansion can be seen as a pre-inflationary semiclassical cosmological solution. We explore whether this stable phase could follow after the bounce, subsequent to the contraction of the Universe. Extending the previous consideration of the bounce, we explore both stable expansion and the bounce solutions in the models with non-zero cosmological constant and the presence of background radiation. The critical part of the analysis concerns stability for small perturbations of the Hubble parameter. It is shown that the stability is possible for the variations in the bounce region, but not in the sufficiently distant past in the contraction phase.

Evaluation of the local atrial function by regional speckle tracking imaging using intracardiac echocardiography

Background It has been reported that low voltage areas and conduction abnormalities detected by electrophysiology catheters in the left atrium (LA) represent regional degeneration and fibrosis of the atrium and are related to a poor atrial fibrillation (AF) ablation outcome. Assessment of the local atrial function is clinically useful because atrial degeneration does not occur uniformly throughout the atrium. Though evaluating the global atrial function using speckle tracking imaging (STI) by transthoracic echocardiography (TTE) has been attempted, TTE does not have a sufficient image quality to assess local atrial STI. Purpose To evaluate the local atrial function by STI using intracardiac echocardiography (ICE) and to elucidate the characteristics of the STI in normal and abnormal voltage regions in the LA. Methods We included 9 patients undergoing AF ablation with written informed consent for this prospective observational study. After pulmonary vein isolation, we performed voltage mapping of the LA in sinus rhythm using a CARTO system (Biosense). Abnormal regions and normal regions were defined as those with low voltage areas (<0.5 mV) and those with normal voltages, respectively. Echo images were recorded by an ACUSON SC2000 (Siemens) and SOUNDSTAR catheter (Biosense). We inserted the SOUNDSTAR catheter into the LA to obtain clear images, recorded the STI of the anterior and inferior wall, and performed an offline analysis of the atrial strain with an eSie VVI work station (Siemens) and the LA voltage data with CARTO system at each site simultaneously (left figure). We compared the strain during the atrial contraction phase (Sct) between the normal and abnormal regions. Results Among the study population, 5 patients had low voltage areas in the LA. We evaluated the STI at 26 normal regions and 44 abnormal regions. The typical regional speckle tracking waveform in the normal region was similar to a jugular vein pressure waveform (right figure). There was a difference in the amplitude of the Sct between the groups; it was significantly smaller in the abnormal regions (normal and abnormal regions, 9.8±5.0% and 5.6±3.8%, p=0.0001). The duration of the Sct was significantly more prolonged in the abnormal regions than normal regions (98.8±26.3ms and 118.2±33.9ms, p=0.015). Conclusions This pilot study demonstrated that the local atrial function was evaluable by STI using ICE and that the regional strain tracking waveform during the atrial contraction phase in abnormal voltage regions was smaller and more prolonged than that in normal regions. An evaluation of the regional STI with an ICE may be useful to detect regional abnormalities of the atrium. Representative case Funding Acknowledgement Type of funding source: None

Estimation and interrater reliability of pupillography by digital mobile app: Digital movil pupillography app validity

Objective: The examination of pupillary light reflexes is widely employed to evaluate the autonomic system’s balance, ocular, and neurological conditions, typically evaluated by qualitative observation. To describe and evaluate the inter-rater reliability and agreement of pupillometric values obtained with a novel semi-automatic mobile pupillography app. Methods: Two examiners and two graders perform the measurements with an android app which corrects the device-face distance, measure the maximum contraction of the pupil, and calculates its slope, in a hospital room setting with three levels of environmental light intensity: <100, 101 to 200, and 201 to 300 lux, at 200, 400, 600, 900, 1200, and 1500 milliseconds. Results: Sixty healthy individuals, aged 18 to 45, were included; 85% had brown eyes. The reliability of the pupil/iris ratio had Ri = 70% to 88%, and bland Altman graphics show a uniform agreement. The pupillography curves show a similar slope at different light intensities, during the contraction phase. Conclusion: There were very good repeatability and inter-rater reproducibility of the measurements at average levels of illumination in examination rooms, even in dark-eyed people. This app provides a highly promising approach to pupillary measurements in clinical practice.

Evaluation of left atrial function in asymptomatic dogs with chronic myxomatous mitral valve disease: two-dimensional feature-tracking echocardiography and Simpson’s monoplanar methods

ABSTRACT: The present study evaluated the volume and function of the left atrium by two-dimensional echocardiographic feature-tracking imaging (2D-FTI) and Simpson’s monoplanar modeling in dogs with asymptomatic degenerative mitral valve disease (DMVD). The study consisted of 80 dogs that were divided into the following three groups: Group 1, 21 dogs (A); Group 2, 30 dogs (B1) and Group 3, 29 dogs (B2). The variable strain (contraction phase) was significantly lower in Group 3 than in Group 1 (12.92±4.54 x 16.69±5.74, p=0.014), and significant differences in the contraction strain index (CSI) were observed between all of the groups that were evaluated (1 = 46.82±8.10, 2 = 39.88±8.03, 3 = 35.25±5.64, p<0.0001). The atrial diastolic volume index (AdVi) that was measured by 2D-FTI was significantly higher in Group 3 than in Group 1 (1.31±0.95 x 0.96±0.31, p=0.038), and the atrial cardiac index (ACI) was also higher in Group 3 than in Group 1 (102.38±80.18 x 78.19±33.38, p=0.030). Atrial function was assessed by Simpson’s monoplanar method, which demonstrated an increase in the left atrial systolic volume, while the contractile function decreased with an increasing disease severity (Group 1 0.21±0.06; Group 2 0.25±0.06; Group 3 0.32±0.08, p<0.0001). The intraobserver and interobserver assessments showed low to moderate variability; most of the values for the coefficient of variation for the variables that were analysed with each method were below 25%. Thus, DMVD was determined to cause an alteration in atrial function, especially in the contraction phase, and even in asymptomatic animals, and the methods of 2D-FTI echocardiography and Simpson’s monoplanar evaluation are sensitive and early methods for the detection of left atrial dysfunction.