Differential motor unit changes after endurance or high-intensity interval training.

PURPOSE: Using a novel technique of high-density surface electromyography (HDEMG) decomposition and motor unit (MU) tracking, we compared changes in the properties of vastus medialis (VM) and vastus lateralis (VL) MUs following endurance (END) and high-intensity interval training (HIIT). METHODS: Sixteen men were assigned to an END or HIIT group (n=8 each) and performed six training sessions over 14 days. Each session consisted of 8-12×60s intervals at 100% peak power output (PPO) separated by 75s of recovery (HIIT) or 90-120min continuous cycling at ~65% VO2peak (END). Pre and post intervention, participants performed: 1) incremental cycling to determine VO2peak and PPO and 2) maximal (MVC), submaximal (10, 30, 50 and 70% MVC) and sustained (until task failure at 30% MVC) isometric knee extensions while HDEMG signals were recorded from the VM and VL. EMG signals were decomposed (submaximal contractions) into individual MUs by convolutive blind source separation. Finally, MUs were tracked across sessions by semi-blind source separation. RESULTS: After training, END and HIIT improved VO2peak similarly (by 5.0 and 6.7%, respectively). The HIIT group showed enhanced maximal knee extension torque by ~7% (p=0.02) and was accompanied by an increase in discharge rate for high-threshold MUs (≥50% knee extension MVC) (p0.05). CONCLUSIONS: HIIT and END induce different adjustments in MU discharge rate despite similar improvements in cardiopulmonary fitness. Moreover, the changes induced by HIIT are specific for high-threshold motor units. For the first time we show that HIIT and END induce specific neuromuscular adaptations, possibly related to differences in exercise load intensity and training volume

Tracking motor units longitudinally across experimental sessions with high-density surface electromyography.

KEY POINTS: Classic motor unit (MU) recording and analysis methods do not allow the same MUs to be tracked across different experimental sessions, and therefore, there is limited experimental evidence on the adjustments in MU properties following training or during the progression of neuromuscular disorders. We propose a new processing method to track the same MUs across experimental sessions (separated by weeks) by using high-density surface electromyography. The application of the proposed method in two experiments showed that individual MUs can be identified reliably in measurements separated by weeks and that changes in properties of the tracked MUs across experimental sessions can be identified with high sensitivity. These results indicate that the behaviour and properties of the same MUs can be monitored across multiple testing sessions. The proposed method opens new possibilities in the understanding of adjustments in motor unit properties due to training interventions or the progression of pathologies. ABSTRACT: A new method is proposed for tracking individual motor units (MUs) across multiple experimental sessions on different days. The technique is based on a novel decomposition approach for high-density surface electromyography and was tested with two experimental studies for reliability and sensitivity. Experiment I (reliability): ten participants performed isometric knee extensions at 10, 30, 50 and 70% of their maximum voluntary contraction (MVC) force in three sessions, each separated by 1 week. Experiment II (sensitivity): seven participants performed 2 weeks of endurance training (cycling) and were tested pre-post intervention during isometric knee extensions at 10 and 30% MVC. The reliability (Experiment I) and sensitivity (Experiment II) of the measured MU properties were compared for the MUs tracked across sessions, with respect to all MUs identified in each session. In Experiment I, on average 38.3% and 40.1% of the identified MUs could be tracked across two sessions (1 and 2 weeks apart), for the vastus medialis and vastus lateralis, respectively. Moreover, the properties of the tracked MUs were more reliable across sessions than those of the full set of identified MUs (intra-class correlation coefficients ranged between 0.63-0.99 and 0.39-0.95, respectively). In Experiment II, ∼40% of the MUs could be tracked before and after the training intervention and training-induced changes in MU conduction velocity had an effect size of 2.1 (tracked MUs) and 1.5 (group of all identified motor units). These results show the possibility of monitoring MU properties longitudinally to document the effect of interventions or the progression of neuromuscular disorders

Non-traumatic chronic shoulder pain is not associated with changes in rotator cuff interval tendon thickness

To determine whether the thickness of the rotator interval tendons is different when comparing both symptomatic and non-symptomatic sides in people with chronic shoulder pain, and to those free of pain. Furthermore, to calculate the level of association between the rotator interval tendon thicknesses and perceived shoulder pain-function. A cross-sectional, observational study. The supraspinatus, subscapularis and biceps brachii tendon thickness of sixty two patients with chronic shoulder pain were determined from standardized ultrasonography measures performed on both shoulders, whereas only the dominant arm was measured for the control subjects. Supraspinatus, subscapularis and biceps brachii tendon thickness was comparable between sides in the symptomatic group and was also comparable between the symptomatic and asymptomatic participants. In addition, the correlation between the tendon thickness and shoulder pain-function was non-significant. Tendon thickness was unaltered in people with chronic shoulder pain. These findings do not rule out the possibility that other changes in the tendon are present such as changes in the elastic properties and cell population and this should be explored in future studies

A theorem on the photographic process in Special Relativity. The train paradox revisited

The purpose of this letter is to show, on the one hand, how the so-called train paradox could be resolved directly without appealing to non-linear Lorentz transformations. The resolution is established in the most general case of curvilinear motion with a variable speed train. On the other hand, we formulate a theorem on the photographic process of two moving objects with relativistic effects.Comment: 7 pages, 1 figur

Immune Activation in Amyloid-β-Related Angiitis Correlates with Decreased Parenchymal Amyloid-β Plaque Load

Background: Primary angiitis of the central nervous system (PACNS) is a rare but serious condition. A fraction of patients suffering from PACNS concurrently exhibit pronounced cerebral amyloid angiopathy (CAA) which is characterized by deposits of amyloid-β (Aβ) in and around the walls of small and medium-sized arteries of the brain. PACNS with CAA has been identified as a distinct disease entity, termed Aβ-related angiitis (ABRA). Evidence points to an immune reaction to vessel wall Aβ as the trigger of vasculitis. Objective: To investigate whether the inflammatory response to Aβ has (1) any effect on the status of immune activation in the brain parenchyma and (2) leads to clearance of Aβ from brain parenchyma. Methods: We studied immune activation and Aβ load by quantitative immunohistochemical analysis in brain parenchyma adjacent to affected vessels in 11 ABRA patients and 10 matched CAA controls. Results: ABRA patients showed significantly increased immune activation and decreased Aβ loads in the brain parenchyma adjacent to affected vessels. Conclusion: Our results are in line with the hypothesis of ABRA being the result of an excessive immune response to Aβ and show that this can lead to enhanced clearance of Aβ from the brain parenchyma by immune-mediated mechanisms

Profiling the location and extent of musicians’ pain using digital pain drawings

Background and aims: According to the existing literature, musicians are at risk to experience a range of musculoskeletal painful conditions. Recently, digital technology has been developed to investigate pain location and pain extent. The aim of this study was to describe pain location and pain extent in musicians using a digital method for pain drawing analysis. Additionally, the association between pain drawing (PD) variables and clinical features in musicians with pain were explored. Materials and methods: One hundred fifty-eight musicians (90 women and 68 men; age 22.4±3.6 years) were recruited from Swiss and UK conservatoires. Participants were asked to complete a survey including both background musical information and clinical features, the Quick Dash (QD) questionnaire and the digital PDs. Results: Of the 158 participants, 126 musicians (79.7%) reported having pain, with higher prevalence in the areas of the neck and shoulders, the lower back and the right arm. The mean of pain extent was 3.1% ±6.5. The mean of QD was larger for musicians showing the presence of pain than for those without pain. Additionally, the results indicated a positive correlation between QD score and pain extent, and there were significant correlations between age and pain intensity, as well as between pain extent and pain intensity. Conclusions: The high prevalence of pain among musicians has been confirmed using a digital PD. In addition, positive correlations between pain extent and upper limb disability has been demonstrated. Our findings highlight the need for effective prevention and treatment strategies for musicians. *** For a video summary of this article please see http://researchonline.rcm.ac.uk/id/eprint/1807/ **

Lower Neutrino Mass Bound from SN1987A Data and Quantum Geometry

A lower bound on the light neutrino mass $m_\nu$ is derived in the framework of a geometrical interpretation of quantum mechanics. Using this model and the time of flight delay data for neutrinos coming from SN1987A, we find that the neutrino masses are bounded from below by $m_\nu\gtrsim 10^{-4}-10^{-3}$eV, in agreement with the upper bound $m_\nu\lesssim$ $({\cal O}(0.1) - {\cal O} (1))$ eV currently available. When the model is applied to photons with effective mass, we obtain a lower limit on the electron density in intergalactic space that is compatible with recent baryon density measurements.Comment: 22 pages, 3 figure

A pilot study using Tissue Velocity Ultrasound Imaging (TVI) to assess muscle activity pattern in patients with chronic trapezius myalgia

<p>Abstract</p> <p>Background</p> <p>Different research techniques indicate alterations in muscle tissue and in neuromuscular control of aching muscles in patients with chronic localized pain. Ultrasound can be used for analysis of muscle tissue dynamics in clinical practice.</p> <p>Aim</p> <p>This study introduces a new muscle tissue sensitive ultrasound technique in order to provide a new methodology for providing a description of local muscle changes. This method is applied to investigate trapezius muscle tissue response – especially with respect to specific regional deformation and deformation rates – during concentric shoulder elevation in patients with chronic trapezius myalgia and healthy controls before and after pain provocation.</p> <p>Methods</p> <p>Patients with trapezius myalgia and healthy controls were analyzed using an ultrasound system equipped with tissue velocity imaging (TVI). The patients performed a standardized 3-cm concentric shoulder elevation before and after pain provocation/exercise at a standardized elevation tempo (30 bpm). A standardized region of interest (ROI), an ellipsis with a size that captures the upper and lower fascia of the trapezius muscle (4 cm width) at rest, was placed in the first frame of the loop registration of the elevation. The ROI was re-anchored frame by frame following the same anatomical landmark in the basal fascia during all frames of the concentric phase. In cardiac measurement, tissue velocities are measured in the axial projection towards and against the probe where red colour represents shortening and red lengthening. In the case of measuring the trapezius muscle, tissue deformation measurements are made orthogonally, thus, indirectly. Based on the assumption of muscle volume incompressibility, blue represents tissue contraction and red relaxation. Within the ROI, two variables were calculated as a function of time: <it>deformation </it>and <it>deformation rate</it>. Hereafter, max, mean, and quadratic mean values (RMS) of each variable were calculated and compared before and after pain provocation/exercise.</p> <p>Results</p> <p>This new methodology seems valuable when looking at local muscle changes and studying the mechanism behind chronic muscle pain. The univariate analyses indicate that patients with chronic trapezius myalgia after pain provocation due to exercise at group level showed decreased strain and unchanged strain rate while healthy controls had unchanged strain and increased strain rate. However, the multivariate analysis indicates that most patients showed lower levels according to both strain and strain rate after exercise compared to most controls.</p> <p>Conclusion</p> <p>Tissue velocity imaging can help describe musculoskeletal tissue activity and dynamics in patients with chronic pain conditions. An altered muscle tissue dynamic after pain provocation/exercise among the majority of trapezius myalgia patients compared with the healthy controls was found.</p

Evidence of beta amyloid independent small vessel disease in familial Alzheimer\u27s disease

\ua9 2022 The Authors. Brain Pathology published by John Wiley &amp; Sons Ltd on behalf of International Society of Neuropathology. We studied small vessel disease (SVD) pathology in Familial Alzheimer\u27s disease (FAD) subjects carrying the presenilin 1 (PSEN1) p.Glu280Ala mutation in comparison to those with sporadic Alzheimer\u27s disease (SAD) as a positive control for Alzheimer\u27s pathology and Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) bearing different NOTCH3 mutations, as positive controls for SVD pathology. Upon magnetic resonance imaging (MRI) in life, some FAD showed mild white matter hyperintensities and no further radiologic evidence of SVD. In post-mortem studies, total SVD pathology in cortical areas and basal ganglia was similar in PSEN1 FAD and CADASIL subjects, except for the feature of arteriosclerosis which was higher in CADASIL subjects than in PSEN1 FAD subjects. Further only a few SAD subjects showed a similar degree of SVD pathology as observed in CADASIL. Furthermore, we found significantly enlarged perivascular spaces in vessels devoid of cerebral amyloid angiopathy in FAD compared with SAD and CADASIL subjects. As expected, there was greater fibrinogen-positive perivascular reactivity in CADASIL but similar reactivity in PSEN1 FAD and SAD groups. Fibrinogen immunoreactivity correlated with onset age in the PSEN1 FAD cases, suggesting increased vascular permeability may contribute to cognitive decline. Additionally, we found reduced perivascular expression of PDGFRβ AQP4 in microvessels with enlarged PVS in PSEN1 FAD cases. We demonstrate that there is Aβ-independent SVD pathology in PSEN1 FAD, that was marginally lower than that in CADASIL subjects although not evident by MRI. These observations suggest presence of covert SVD even in PSEN1, contributing to disease progression. As is the case in SAD, these consequences may be preventable by early recognition and actively controlling vascular disease risk, even in familial forms of dementia