The effects of persistent articholinesterase action at the neuromuscular junction

The effects of organophosphorus compounds which form a rapidly-ageing complex with acetylcholinesterase (AChE) (e.g. pinacolyl S-(2- trimethylaminoethyl)methylphosphonothioate (BOS)) and hence exert a persistent anticholinesterase (anti-ChE) action have been compared with other compounds with a shorter time course of inhibition (e.g. ecothiopate iodide (ECO)). Although the inhibition of AChE produced by BOS lasted longer than that seen with ECO, the time course of the myopathy appeared very similar. BOS also possessed a number of properties which have been seen with other anti-ChEs. BOS and ECO produced significant increases in neuromuscular "jitter" 5 days after injection, not only in the diaphragm but also in the soleus and extensor digitorum longus muscles. Increases in "jitter" produced by ECO could be prevented by pyridostigmine prophylaxis or rapid treatment with pyridine-2- aldoxime methiodide. Some protection from the BOS-induced increases in "jitter" could be gained by repeated treatment with pyridine-2-aldoxime methiodide, an effect which could not be accounted for simply by enzyme reactivation. From experiments performed in Rej 129 mice it was determined that increases in "jitter", although demonstrated in some dystrophic muscles, could not be used as an early diagnostic tool. Because sequalae of inhibition were present some time after intoxication, by which time AChE appeared biochemically normal, experiments were performed to investigate inactivation of physiologically important AChE. The time course of extracellular MEPPs was utilised as an indicator of physiologically important AChE and compared with the AChE activity measured by the technique of Ellman et al. (1961). It was concluded that the degree of persistence of anti-ChE action was unimportant for the induction of myopathy with a time course of 3-24 hours, but had some importance in events of longer duration.

The neurotoxic effects of enzyme inhibitors at the neuromuscular junction

Current knowledge of the long-term, low dose effects of carbamate (CB) anti-cholinesterases on skeletal muscle or on the metabolism and regulation of the molecular forms of acetylcholinesterase (AChE) is limited. This is largely due to the reversible nature of these inhibitors and the subtle effects they induce which has generally made their study difficult and preliminary investigations were conducted to determine suitable study methods. A sequential extraction technique was used to rapidly analyse AChE molecular form activity at the mouse neuromuscular junction and also in peripheral parts of muscle fibres. AChE in the synaptic cleft involved in the termination of cholinergic transmission was successfully assessed by the assay method and by an alternative method using a correlation equation which represented the relationship between synaptic AChE and the prolongation of extra-cellular miniature endplate potentials. It was found that inhibition after in vivo Carbamate (CB) dosing could not be maintained during tissue analysis because CB-inhibited enzyme complexes decarbamoylated vary rapidly and could not be prevented even when maintained on ice. The methods employed did not therefore give a measure of inhibition but presented a profile of metabolic responses to continual, low dose CB treatment. Repetitive and continual infusion with low doses of the CBs: pyridostigmine and physostigmine induced a variety of effects on mouse skeletal muscle. Both compounds induced a mild myopathy in the mouse diaphragm during continual infusion which was characterised by endplate deformation without necrosis; such deformation persisted on termination of treatment but had recovered slightly 14 days later. Endplate and non-endplate AChE molecular forms displayed selective responses to CB treatment. During treatment endplate AChE was reduced whereas non-endplate AChE was largely unaffected, and after treatment, endplate AChE recovered, whereas non-endplate AChE was up-regulated. The mechanisms by which these responses become manifest are unclear but may be due to CB-induced effects on nerve-mediated muscle activity, neurotrophic factors or morphological and physiological changes which arise at the neuromuscular junction. It was concluded that, as well as inhibiting AChE, CBs also influence the metabolism and regulation of the enzyme and induce persistent endplate deformation; possible detrimental effects of long-term, low-dose determination requires further investigation.

Neuromuscular response to whole body vibration treatment during static and dynamic squat exercises

The impact of whole body vibrations (vibration stimulus mechanically transferred to the body) on muscular activity and neuromuscular response has been widely studied but without standard protocol and by using different kinds of exercises and parameters. In this study, we investigated how whole body vibration treatments affect electromyographic signal of rectus femoris during static and dynamic squat exercises. The aim was the identification of squat exercise characteristics useful to maximize neuromuscular activation and hence progress in training efficacy. Fourteen healthy volunteers performed both static and dynamic squat exercises without and with vibration treatments. Surface electromyographic signals of rectus femoris were recorded during the whole exercise and processed to reduce artifacts and to extract root mean square values. Paired t-test results demonstrated an increase of the root mean square values (p<0.05) in both static and dynamic squat exercises with vibrations respectively of 63% and 108%. For each exercise, subjects gave a rating of the perceived exertion according to the Borg's scale but there were no significant changes in the perceived exertion rate between exercises with and without vibration. Finally, results from analysis of electromyographic signals identified the static squat with WBV treatment as the exercise with higher neuromuscular system response. © 2012 IEEE.

Acute Effects of Neuromuscular-Training with Handheld-Vibration on Elbow Joint Position Sense

Context: Clinicians use exercises in rehabilitation to enhance sensorimotor-function, however evidence supporting their use is scarce. Objective: To evaluate acute effects of handheld-vibration on joint position sense (JPS). Design: A repeated-measure, randomized, counter-balanced 3-condition design. Setting: Sports Medicine and Science Research Laboratory. Patients or Other Participants: 31 healthy college-aged volunteers (16-males, 15-females; age=23+3y, mass=76+14kg, height=173+8cm). Interventions: We measured elbow JPS and monitored training using the Flock-of-Birds system (Ascension Technology, Burlington, VT) and MotionMonitor software (Innsport, Chicago, IL), accurate to 0.5°. For each condition (15,5,0Hz vibration), subjects completed three 15-s bouts holding a 2.55kg Mini-VibraFlex dumbbell (Orthometric, New York, NY), and used software-generated audio/visual biofeedback to locate the target. Participants performed separate pre- and post-test JPS measures for each condition. For JPS testing, subjects held a non-vibrating dumbbell, identified the target (90°flexion) using biofeedback, and relaxed 3-5s. We removed feedback and subjects recreated the target and pressed a trigger. We used SPSS 14.0 (SPSS Inc., Chicago, IL) to perform separate ANOVAs (p<0.05) for each protocol and calculated effect sizes using standard-mean differences. Main Outcome Measures: Dependent variables were absolute and variable error between target and reproduced angles, pre-post vibration training. Results: 0Hz (F1,61=1.310,p=0.3) and 5Hz (F1,61=2.625,p=0.1) vibration did not affect accuracy. 15Hz vibration enhanced accuracy (6.5±0.6 to 5.0±0.5°) (F1,61=8.681,p=0.005,ES=0.3). 0Hz did not affect variability (F1,61=0.007,p=0.9). 5Hz vibration decreased variability (3.0±1.8 to 2.3±1.3°) (F1,61=7.250,p=0.009), as did 15Hz (2.8±1.8 to 1.8±1.2°) (F1,61=24.027, p<0.001). Conclusions: Our results support using handheld-vibration to improve sensorimotor-function. Future research should include injured subjects, functional multi-joint/multi-planar measures, and long-term effects of similar training.

Neuromuscular Changes in Older Adults during the Lateral Step Task

Older adults may have trouble when performing activities of daily living due to decrease in physical strength and degradation of neuromotor and musculoskeletal function. Motor activation patterns during Lateral Step Down and Step Up from 4-inch and 8-inch step heights was assessed in younger (n=8, 24.4 years) and older adults (n=8, 58.9 years) using joint angle kinematics and electromyography of lower extremity muscles. Ground reaction forces were used to ascertain the loading, stabilization and unloading phases of the tasks. Older adults had an altered muscle activation sequence and significantly longer muscle bursts during loading for the tibialis anterior, gastrocnemius, vastus medialis, bicep femoris, gluteus medius and gluteus maximus muscles of the stationary leg. They also demonstrated a significantly larger swing time (579.1 ms vs. 444.8 ms) during the step down task for the moving leg. The novel data suggests presence of age-related differences in motor coordination during lateral stepping.

Efeito do kinesio taping® no desempenho neuromuscular do quadríceps e no equilíbrio em sujeitos submetidos à reconstrução do ligamento cruzado anterior: ensaio clínico e randomizado

Objetivo: Investigar os efeitos imediatos do Kinesio Taping® no desempenho neuromuscular do Quadríceps Femoral (QF) de indivíduos submetidos à reconstrução do Ligamento Cruzado Anterior (LCA). Metodologia: trata-se de um ensaio clínico e randomizado composto por 45 indivíduos do sexo masculino que se encontravam entre 12ª e 17ª semanas após reconstrução do LCA. Todos foram submetidos a uma avaliação inicial composta pela análise do equilíbrio postural, através da baropodometria; determinação do Senso de Posição Articular (SPA), seguidas das avaliações isocinéticas excêntricas e concêntricas a 600/s, concomitante com a captação do sinal eletromiográfico do músculo Vasto Lateral (VL). Posteriormente foram alocados de forma aleatória em Grupo Controle (GC), Grupo Placebo (GP) e Grupo Experimental (GE). Os indivíduos do GE foram submetidos ao protocolo sugerido (aplicação do Kinesio Taping® no QF do membro acometido), enquanto os do GP utilizaram a aplicação do Kinesio Taping® sem as recomendações propostas pelo método. Já os indivíduos do GC permaneceram em repouso por dez minutos, sendo todos os indivíduos submetidos a uma reavaliação de forma idêntica à primeira. Foram analisadas as seguintes variáveis: pico de torque médio, pico de torque/peso corporal, potência muscular e erro absoluto do SPA para a dinamometria; amplitude ântero-posterior e médio-lateral para a baropodometria; e a amplitude de ativação muscular (Root Means Square - RMS) por meio da eletromiografia de superfície. Resultados: Nenhuma das variáveis analisadas apresentou diferenças intergrupo ou intragrupo. Conclusão: O Kinesio Taping® não altera o desempenho neuromuscular do quadríceps femoral de indivíduos submetidos à reconstrução do LCA para nenhuma das variáveis analisadas.

Efeito tardio do kinesio taping na função do membro inferior e no desempenho neuromuscular do quadríceps femoral de mulheres saudáveis: ensaio clínico e randomizado

Introduction: Kinesio Taping (KT) has been used in healthy people to improve neuromuscular performance, however, few studies have evaluated its chronic effects, despite being suggested. Objective: To analyze the chronic effects of KT on neuromuscular performance of the quadriceps, the oscillation of the center of pressure and lower limb function in healthy women. Methods: blinded, randomized, controlled trial, composed of 60 women (mean age 21.9 ± 3.3 years and BMI 22.3 ± 2.2 kg / m2) submitted to the evaluation of oscillation of the center of pressure through the baropodometry, the lower limb function by the hop test, isokinetic knee performance, the electromyographic activity of the vastus lateralis (VL) and joint position sense of the knee (JPS). Then, participants were randomly divided into three groups of twenty: control - did not apply the KT; placebo - application of KT without tension on the quadriceps; Kinesio Taping - application of KT with tension in the same muscle group. The evaluations were conducted in five moments: prior to application of KT, immediately after the application, 24h, 48h after application and 24 hours after its removal (72h). SPSS 20.0 was used for statistical analysis. The KS test was used to verify the data normality, the Levene test for homogeneity of variances and a mixed-model ANOVA 3x5 to check intra and inter-group differences. Results: there was no difference in peak torque, the power, nor the electromyographic activity or SPA (p> 0.05) between groups. The displacement speed of center of pressure reduced immediately after the application on kinesio taping group (p <0.001), but with no differences between the groups (p = 0.28). There was a reduction in the time of peak torque among the three groups in the evaluations after KT application (p <0.001) and an increase in single hop in all groups (p <0.001), but with no differences between them. Conclusion: KT can not change, in a chronic way, the lower limb function, the oscillation of the center of pressure, the isokinetic performance, the JPS of the knee and the electromyographic activity of VL muscle in healthy women.

Efeitos imediatos da plataforma vibratória no desempenho neuromuscular do quadríceps femoral, após reconstrução do LCA: ensaio controlado, randomizado e cego

Objective: to investigate the immediate effect of the vibrating platform on the neuromuscular performance of the quadriceps femoris and on the postural oscillation of subjects submitted to Anterior Cruciate Ligament (ACL) reconstruction. Materials and methods: this study is a randomized and blind clinical trial. Forty-four male volunteers (average age of 27,4 ±6,2 IMC of 26,85± 3,8 Kg/m² and post surgery timeframe of 17± 1,4 weeks) were randomized into two groups: OFF platform (n=22, protocol of exercise over the vibrating platform off) and ON platform (n=22 protocol of exercise over the vibrating platform on, 50Hz frequency and 4mm of amplitude). All volunteers were submitted to assessment the isokinetic evaluation of the quadriceps femoris (isometric and isokinetic at 60°/s) and of the electromyography activity of the muscles Vasto Lateralis (VL) and Vasto Medialis (VM), besides the postural oscillation (baropodometry) in two distinct moments: before and immediately after the intervention protocol. The data was analyzed through the SPSS 20.0 software, with a 5% significance level. To verify the homogeneity of the groups it was used an ANOVA one way, and a ANOVA mixed model to compare the intra and inter groups. Results: it was observed differences between the pre and the post, to latero lateral velocity, isometric torque peak and total work in comparison with intragroup. However, it wasn’t verified any difference in comparing the intergroup in the preevaluation and in the post-evaluation protocol over the vibrating platform. Conclusion: the use of the vibrating platform doesn’t change as an immediate manner the isokinetic performance of the quadriceps femoris, the electromyography activity of the VL and the VM, also doesn’t interfere with the postural oscillation of individuals that were submitted to the ACL reconstruction.