Central motor control failure in fibromyalgia: a surface electromyography study

<p>Abstract</p> <p>Background</p> <p>Fibromyalgia (FM) is characterised by diffuse musculoskeletal pain and stiffness at multiple sites, tender points in characteristic locations, and the frequent presence of symptoms such as fatigue. The aim of this study was to assess whether the myoelectrical manifestations of fatigue in patients affected by FM are central or peripheral in origin.</p> <p>Methods</p> <p>Eight female patients aged 55.6 ± 13.6 years (FM group) and eight healthy female volunteers aged 50.3 ± 9.3 years (MCG) were studied by means of non-invasive surface electromyography (s-EMG) involving a linear array of 16 electrodes placed on the skin overlying the biceps brachii muscle, with muscle fatigue being evoked by means of voluntary and involuntary (electrically elicited) contractions. Maximal voluntary contractions (MVCs), motor unit action potential conduction velocity distributions (mean ± SD and skewness), and the mean power frequency of the spectrum (MNF) were estimated in order to assess whether there were any significant differences between the two groups and contraction types.</p> <p>Results</p> <p>The motor pattern of recruitment during voluntary contractions was altered in the FM patients, who also showed fewer myoelectrical manifestations of fatigue (normalised conduction velocity rate of changes: -0.074 ± 0.052%/s in FM vs -0.196 ± 0.133%/s in MCG; normalised MNF rate of changes: -0.29 ± 0.16%/s in FM vs -0.66 ± 0.34%/s in MCG). Mean conduction velocity distribution and skewnesses values were higher (p < 0.01) in the FM group. There were no between-group differences in the results obtained from the electrically elicited contractions.</p> <p>Conclusion</p> <p>The apparent paradox of fewer myoelectrical manifestations of fatigue in FM is the electrophysiological expression of muscle remodelling in terms of the prevalence of slow conducting fatigue-resistant type I fibres. As the only between-group differences concerned voluntary contractions, they are probably more related to central motor control failure than muscle membrane alterations, which suggests pathological muscle fibre remodelling related to altered suprasegmental control.</p

Screening, diagnosis and monitoring of sarcopenia:When to use which tool?

Background & aims: Sarcopenia is a muscle disorder associated with loss of muscle mass, strength and function. Early screening, diagnosis and treatment may improve outcome in different disease conditions. A wide variety of tools for estimation of muscle mass is available and each tool has specific technical requirements. However, different investigational settings and lack of homogeneity of populations influence the definition of gold standards, proving it difficult to systematically adopt these tools. Recently, the European Working Group on Sarcopenia in Older People (EWGSOP) published a revised recommendation (EWGSOP-2) and algorithm for using tools for screening and diagnosing sarcopenia. However, agreement of the EWGSOP2 criteria with other classifications is poor and although an overview of available tools is valuable, for the purpose of clinical decision-making the reverse is useful; a given scenario asks for the most suitable tools. Results: Tools were identified for screening, diagnostics and longitudinal monitoring of muscle mass. For each of these clinical scenarios the most appropriate tools were listed and for each technique their usability is specified based on sensitivity and specificity. Based on this information a specific recommendation is made for each clinical scenario. Conclusion: This narrative review provides an overview of currently available tools and future developments for different clinical scenarios such as screening, diagnosis and longitudinal monitoring of alterations in muscle status. It supports clinical decision-making in choosing the right tools for muscle mass quantification depending on the need within a given clinical scenario as well as the local availability and expertise. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of European Society for Clinical Nutrition and Metabolism

The assessment of neuromuscular fatigue during 120 min of simulated soccer exercise

Purpose This investigation examined the development of neuromuscular fatigue during a simulated soccer match incorporating a period of extra time (ET) and the reliability of these responses on repeated test occasions. Methods Ten male amateur football players completed a 120 min soccer match simulation (SMS). Before, at half time (HT), full time (FT), and following a period of ET, twitch responses to supramaximal femoral nerve and transcranial magnetic stimulation (TMS) were obtained from the knee-extensors to measure neuromuscular fatigue. Within 7 days of the first SMS, a second 120 min SMS was performed by eight of the original ten participants to assess the reliability of the fatigue response. Results At HT, FT, and ET, reductions in maximal voluntary force (MVC; −11, −20 and −27%, respectively, P ≤ 0.01), potentiated twitch force (−15, −23 and −23%, respectively, P < 0.05), voluntary activation (FT, −15 and ET, −18%, P ≤ 0.01), and voluntary activation measured with TMS (−11, −15 and −17%, respectively, P ≤ 0.01) were evident. The fatigue response was robust across both trials; the change in MVC at each time point demonstrated a good level of reliability (CV range 6–11%; ICC2,1 0.83–0.94), whilst the responses identified with motor nerve stimulation showed a moderate level of reliability (CV range 5–18%; ICC2,1 0.63–0.89) and the data obtained with motor cortex stimulation showed an excellent level of reliability (CV range 3–6%; ICC2,1 0.90–0.98). Conclusion Simulated soccer exercise induces a significant level of fatigue, which is consistent on repeat tests, and involves both central and peripheral mechanisms

Between-day repeatability of lower limb EMG measurement during running and walking

There are minimal data describing the between-day repeatability of EMG measurements during running. Furthermore, there are no data characterising the repeatability of surface EMG measurement from the adductor muscles, during running or walking. The purpose of this study was to report on the consistency of EMG measurement for both running and walking across a comprehensive set of lower limb muscles, including adductor magnus, longus and gracilis. Data were collected from 12 lower limb muscles during overground running and walking on two separate days. The coefficient of multiple correlation (CMC) was used to quantify waveform similarity across the two sessions for signals normalised to either maximal voluntary isometric contraction (MVIC) or mean/peak signal magnitude. For running, the data showed good or excellent repeatability (CMC=0.87-0.96) for all muscles apart from gracilis and biceps femoris using the MVIC method. Similar levels of repeatability were observed for walking. Importantly, using the peak/mean method as an alternative to the MVIC method, resulted in only marginal improvements in repeatability. The proposed protocol facilitated the collection of repeatable EMG data during running and walking and therefore could be used in future studies investigating muscle patterns during gait

Stable isotope and fluid inclusion study of sediment-hosted stratiform copper deposits from the Neuquén Basin, Argentina

The Los Chihuidos and El Porvenir deposits of the Neuquén Basin are examples of sediment-hosted stratiform Cu deposits generated by interaction of hydrocarbons and formation water with host red beds and metal-charged basinal brines. During early diagenesis of red beds precipitated hematite, kaolinite at 60 °C from meteoric water followed by calcite 1 (δ13C − 8 to − 3.3‰) and barite (δ34S + 4.1‰) with increasing temperature (75–85 °C) from an evolved surface fluid (δ18Ofluids + 0.9 to + 2.7‰). During the Tertiary Andean orogeny, hydrocarbons and formation water migrated and reacted with the red beds resulting in bleaching of the sandstone. Smectite (fluid δ18O − 2.2‰ and δD − 73.7‰), chlorite-smectite mixed-layer minerals (fluid δ18O − 6.9‰ and δD − 84‰), pyrite (δ34S + 10.2‰), and calcite 2 (δ13C − 12.9 to − 6.8‰) formed as by-product of the redox reactions. Calcite 2 formed from low-salinity fluids (0.4 to 5.9 wt% NaCl equiv.) at slightly higher temperatures (125–145 °C) at El Porvenir and at Los Chihuidos deposit (80–105 °C). During subsequent uplift, metal-charged basinal brines flowed into the bleached sandstone and precipitated chalcopyrite-bornite (δ34S + 12.3‰) followed by chalcocite-spionkopite (δ34S − 64 to + 4.1‰). Calcites 3a (δ13C − 19 to − 10.1‰) and 3b (δ13C − 31.4 to − 9.5‰) that accompanied Fe-Cu and Cu sulfides, respectively, formed from saline fluids (up to 21.3 wt% NaCl equiv.) at temperatures of 159–70 °C. The δ18O values (+ 5.6 to + 11.4‰) of fluids in equilibrium with calcite 3a are similar to oilfield and basinal brines. Fluids in equilibrium with calcite 3 in Los Chihuidos and calcite 3b in El Porvenir show much lighter δ18O values (− 7.3 to − 4.6‰ and − 0.6 to + 2.3‰, respectively), which suggests the involvement of methane as the main reductant and possibly meteoric water interaction

Genesis of the Loma Galena Pb-Ag deposit, Navidad District, Patagonia, Argentina: a unique epithermal system capped by an anoxic lake

Loma Galena (978,852 t Pb, 206 Moz Ag) is one of eight epithermal deposits in the world-class Navidad Pb + Ag ± (Zn, Cu) district located in the Cañadón Asfalto continental foreland basin, northern Patagonia, Argentina. This basin formed during the Jurassic in an extensional tectonic regime during the breakup of Gondwana. Host rocks comprise major listric faulted and tilted blocks of K-rich andesite to dacite lava flows (173.9–170.8 Ma; U-Pb ages for zircon) unconformably overlain by mudstone interbedded with stromatolitic and pisolitic limestones, sandstone, coal, and an Sr-rich evaporite layer deposited in a lacustrine environment. The mineralization occurs as disseminations in the organic-rich sedimentary rocks, in veins and hydrothermal breccia dikes in the hanging walls and footwalls of NW- and NE-striking normal faults, in volcanic autobreccias, and in a phreatic breccia at the contact of volcanic and sedimentary rocks. The earliest hydrothermal minerals consist of veins of colloform, crustiform, and cockade calcite 1 (δ13Cfluid –4.7 to 0.8‰; δ18Ofluid 4.8–11.6‰) and siderite. The precipitating fluids were likely basement-exchanged basinal brines having salinities of 9.5 to 16.4 wt % NaCl equiv and temperatures of 154.7° to 212°C. The interaction of these fluids with the host volcanic rocks formed calcite, albite, adularia, and celadonite-glauconite-group minerals followed by chlorite and siderite as fO2 decreased. Fluids intermittently boiled, as evidenced by bladed (platy) texture in calcite 1. Subsequent mineralizing stages contributed to the metal endowment of Loma Galena. The abundance of organic-rich mudstone and δ34S from –15.4 to 12.9‰ for sulfides suggests that the bottom waters of the lake were anoxic and the loci of microbial sulfate reduction (evaporites have δ34S 35‰). Mixing of upflowing metal-rich basinal fluids carrying some S from depth with this H2S-rich connate water efficiently precipitated Ag-bearing framboidal pyrite, colloform pyrite-marcasite, chalcopyrite, bornite, tennantite-tetrahedrite, sphalerite, and galena as veins, breccias, and disseminations in host rocks. The highest grade and tonnage of the ores are found in autobreccias at the junction of the uppermost lava flow and in the overlying mudstone, where the addition of a strong microbial signature is recorded in sulfides. This event also led to partial dissolution of magmatic and hydrothermal feldspar and calcite 1 in the altered volcanic rocks. Mineralization was followed by hydrothermal brecciation and successive precipitation of chalcedony (δ18Ofluid 2.6–4.8‰), barite (δ34S 15.7–22‰; 160.9°–183.8°C; 7.7–9.7 wt % NaCl equiv), calcite 2 (δ18Ofluid –10.2 to –3.7‰, 58°–95°C; 1.9–7.0 wt % NaCl equiv), strontianite, and quartz in brecciated veins and breccias; kaolinite (δ18Ofluid 2–6.2‰), illite-smectite, smectite, and carbonates with minor chalcedony and barite in the volcanic rocks; and calcite, chalcedony, and barite in the sedimentary rocks. A trend of decreasing salinity with decreasing temperature and lowering δ18O of the fluids with time suggests dilution of the basinal fluids by mixing with Jurassic meteoric water (δ18O −9 to −5.2‰). Loma Galena is a unique example of a polymetallic epithermal system formed in a sublacustrine anoxic environment that promoted the efficient deposition and preservation of Ag-bearing sulfides, thereby contributing to the large size and relatively high grade of the deposit