Level Of Muscle Tone Research Articles

Insights into The Prenatal and Postnatal Knowledge & Critical Observations of Parents with Children who Have Down Syndrome: A Single Center Study

Introduction: Down syndrome (DS) is one of the many genetic syndromes commonly confronted by pediatricians. These people commonly share a few features which include a low level of muscle tone (hypotonia), learning disabilities, and abnormalities of the cranium and facial parts. Aims and Objectives: To assess the pre and postnatal knowledge, of parents with Down syndrome children. Place and Duration of study: This descriptive cross-sectional study was conducted in Shifa International Hospital (SIH), by Final year medical students, in association with the Cytogenetics Department. between December 2019 to September 2021 Material and Methods: All the chidren diagnosed with Down Syndrome at the SIH and their parents were invited to participate in our study. Convenience sampling was used depending solely on the number of parents who had accepted our invitation. A total sample size of 35 was included, of which 15 agreed to participate. A detailed questionnaire having both close ended and open questions in English and Urdu was filled out by those parents who consented. Data was entered and analysed using SPSS version 24.0. pvalue ?0.05 was taken as significant. Results: Our results showed that 11 of the 15 DS children i.e., 73.3% were male and 4 out of 15 i.e., 26.6% were females. None of these children had siblings with the same disorder. 13 of the 15 cases (86.6%) were diagnosed post- natally only 2 cases (13.3%) pre-natally. All the cases i.e., 100% were diagnosed by a pediatrician and none were diagnosed by an obstetrician. Surprisingly increasing age of either parent seemed to increase the incidence of DS offspring. 60.0% (9 of the 15) of parents did not know the condition could be diagnosed prenatally. While 10 of 15 (66.6%) of them were aware of its general complications. Answering open ended questions parents identified the lack of awareness, special educational institutes, and presence of communication gap between them and doctors as some of the factors that hindered the welfare of DS children. Conclusion: Only one parent knew about DS complications pre-natally and only a few were aware that a pre-natal diagnosis could be formed. Postnatal knowledge of parents was sketchy also, especially regarding the future complications faced by DS children, Parents critically observed insufficient public awareness, societal taboos, paucity of local DS data and prenatal medical DS training, and consequently lack of govermnnental support required by special needs DS children in our country.

Immortal orexin cell transplants restore motor-arousal synchrony during cataplexy

Waking behaviors such as sitting or standing require suitable levels of muscle tone. But it is unclear how arousal and motor circuits communicate with one another so that appropriate motor tone occurs during wakefulness. Cataplexy is a peculiar condition in which muscle tone is involuntarily lost during normal periods of wakefulness. Cataplexy therefore provides a unique opportunity for identifying the signaling mechanisms that synchronize motor and arousal behaviors. Cataplexy occurs when hypothalamic orexin neurons are lost in narcolepsy; however, it is unclear if motor-arousal decoupling in cataplexy is directly or indirectly caused by orexin cell loss. Here, we used genomic, proteomic, chemogenetic, electrophysiological, and behavioral assays to determine if grafting orexin cells into the brain of cataplectic (i.e., orexin-/-) mice restores normal motor-arousal behaviors by preventing cataplexy. First, we engineered immortalized orexin cells and found that they not only produce and release orexin but also exhibit a gene profile that mimics native orexin neurons. Second, we show that engineered orexin cells thrive and integrate into host tissue when transplanted into the brain of mice. Next, we found that grafting only 200-300 orexin cells into the dorsal raphe nucleus-a region densely innervated by native orexin neurons-reduces cataplexy. Last, we show that real-time chemogenetic activation of orexin cells restores motor-arousal synchrony by preventing cataplexy. We suggest that orexin signaling is critical for arousal-motor synchrony during wakefulness and that the dorsal raphe plays a pivotal role in coupling arousal and motor behaviors.

Increase in muscle tone promotes the use of ankle strategies during perturbed stance.

To maintain an upright standing posture against external disturbances, the human body mainly employs two types of postural control strategies: "ankle strategy" and "hip strategy." While it has been reported that the magnitude of the disturbance alters the use of postural control strategies, it has not been elucidated how the level of muscle tone, one of the crucial parameters of bodily function, determines the use of each strategy. We have previously confirmed using forward dynamics simulations of human musculoskeletal models that an increased muscle tone promotes the use of ankle strategies. The objective of the present study was to experimentally evaluate a hypothesis: an increased muscle tone promotes the use of ankle strategies. Do changes in the muscle tone affect the use of ankle strategies? Participants were asked to maintain their standing posture on a movable platform sliding horizontally at several accelerations. Postural reactions for support surface translations were examined under three instructions with or without handgrips: relax state, squeezing a handgrip, and an increased muscle tone of the whole body. Surface-electromyography and marker locations of joints were measured to calculate the index of muscle tone and postural control strategies. The relationship of the indexes was evaluated based on correlation coefficients. In half of the conditions, weak negative correlations were noted between the muscle tone index and postural control strategy index. In other words, an increased muscle tone rather promoted the use of the ankle strategy than the hip strategy. These findings are consistent with our previous simulation results. The results recognized a positive response to the research question. This suggests that it is crucial to take muscle tone into account to understand postural control strategies.

REM Sleep Without Atonia and Gait Impairment in People with Mild-to-Moderate Parkinson's Disease.

Subtle gait deficits can be seen in people with idiopathic rapid eye movement (REM) sleep behavior disorder (RBD), a prodromal stage of Parkinson's disease (PD) and related alpha-synucleinopathies. It is unknown if the presence and level of REM sleep without atonia (RSWA, the electromyographic hallmark of RBD) is related to the severity of gait disturbances in people with PD. We hypothesized that gait disturbances in people with mild-to-moderate PD would be greater in participants with RSWA compared to those without RSWA and matched controls, and that gait impairment would correlate with measures of RSWA. Spatiotemporal characteristics of gait were obtained from 41 people with PD and 21 age-matched controls. Overnight sleep studies were used to quantify muscle activity during REM sleep and group participants with PD into those with RSWA (PD-RSWA+, n = 22) and normal REM sleep muscle tone (PD-RSWA-, n = 19). Gait characteristics were compared between groups and correlated to RSWA. The PD-RSWA+ group demonstrated significantly reduced gait speed and step lengths and increased stance and double support times compared to controls, and decreased speed and cadence and increased stride velocity variability compared to PD-RSWA- group. Larger RSWA scores were correlated with worse gait impairment in the PD group. The presence and level of muscle tone during REM sleep is associated with the severity of gait disturbances in PD. Pathophysiological processes contributing to disordered gait may occur earlier and/or progress more rapidly in people with PD and RBD.

Muscle Tone Level Classification Based on Upper-Limb Impedance Model

Many tools have been developed for the assessment of muscle tone of impaired limbs. Despite, having the appropriate knowledge, therapists still face with challenge in the assessment due to the subjective evaluation of muscle tone during training sessions. Moreover, the training has become more-costly and time consuming since the subjects have to face the therapists over a long period of time. By deploying robot-assisted system, some of these problems could have been addressed but the aspect of proper assessment of subjects’ muscle tone levels still remain. Assessment of subjects’ muscle tones allows proper prescription of task during training session. Recent studies have established links between muscle tone and upper-limb mechanical impedance. However the development of adequate estimation algorithm for subjects’ upper-limb impedance parameters and the prediction of muscle tone level in a more objective manner is still a subject of many research works. This study proposes an appropriate strategy for the estimation of upper-limb mechanical impedance parameters as a mean for the assessment of subjects’ muscle tone levels. Both simulation and experimental results show that the upper-limb impedance parameters can be estimated to a good accuracy level, while the subjects’ muscle tone level can be consistently predicted.

The Sublaterodorsal Tegmental Nucleus Functions to Couple Brain State and Motor Activity during REM Sleep and Wakefulness.

Appropriate levels of muscle tone are needed to support waking behaviors such as sitting or standing. However, it is unclear how the brain functions to couple muscle tone with waking behaviors. Cataplexy is a unique experiment of nature in which muscle paralysis involuntarily intrudes into otherwise normal periods of wakefulness. Cataplexy therefore provides the opportunity to identify the circuit mechanisms that couple muscle tone and waking behaviors. Here, we tested the long-standing hypothesis that muscle paralysis during cataplexy is caused by recruitment of the brainstem circuit that induces muscle paralysis during REM sleep. Using behavioral, electrophysiological, and chemogenetic strategies, we found that muscle tone and arousal state can be decoupled by manipulation of the REM sleep circuit (the sublaterodorsal tegmental nucleus [SLD]). First, we show that silencing SLD neurons prevents motor suppression during REM sleep. Second, we show that activating these same neurons promotes cataplexy in narcoleptic (orexin-/-) mice, whereas silencing these neurons prevents cataplexy. Most importantly, we show that SLD neurons can decouple motor activity and arousal state in healthy mice. We show that SLD activation triggers cataplexy-like attacks in wild-type mice that are behaviorally and electrophysiologically indistinguishable from cataplexy in orexin-/- mice. We conclude that the SLD functions to engage arousal-motor synchrony during both wakefulness and REM sleep, and we propose that pathological recruitment of SLD neurons could underlie cataplexy in narcolepsy.

Method for Muscle Tone Monitoring During Robot-Assisted Therapy of Hand Function: A Proof of Concept.

Robot-assisted rehabilitation of hand function is becoming an established approach to complement conventional therapy after stroke, particularly in view of its possible unsupervised use to promote an increase in therapy dose. Given their intensive therapy regime, robots may promote a temporary increase in hand muscle tone and spasticity, which may cause pain and negatively affect recovery. To integrate hand muscle tone monitoring into an assessment-driven robot-assisted therapy concept, an online assessment of muscle tone is proposed and incorporated into an exercise. The exercise was preliminarily tested in a pilot study with five chronic stroke survivors (non-spastic at rest) and five healthy participants to identify the range of potential physiological muscle tone change that can happen also in a non-spastic population during a single exercise session. In both groups, the muscle tone level during hand opening was higher in fast 20 mm ramp-and-hold perturbations (150 ms) compared to slow (250 ms) perturbations, and corresponded to a force change of approximately 4-5 N. Despite not being statistically significantly different, in the stroke group the force change (and the speed dependency) increased with exercise time. This information could serve as a basis to develop strategies to continuously adapt the difficulty and activity level required in robot-assisted rehabilitation and to monitor or even control the muscle tone evolution over time.

Efficacy and Safety of Botulinum Toxin Type A for Limb Spasticity after Stroke: A Meta-Analysis of Randomized Controlled Trials.

Background Inconsistent data have been reported for the effectiveness of intramuscular botulinum toxin type A (BTXA) in patients with limb spasticity after stroke. This meta-analysis of available randomized controlled trials (RCTs) aimed to determine the efficacy and safety of BTXA in adult patients with upper and lower limb spasticity after stroke. Methods An electronic search was performed to select eligible RCTs in PubMed, Embase, and the Cochrane library through December 2018. Summary standard mean differences (SMDs) and relative risk (RR) values with corresponding 95% confidence intervals (CIs) were employed to assess effectiveness and safety outcomes, respectively. Results Twenty-seven RCTs involving a total of 2,793 patients met the inclusion criteria, including 16 and 9 trials assessing upper and lower limb spasticity cases, respectively. For upper limb spasticity, BTXA therapy significantly improved the levels of muscle tone (SMD=-0.76; 95% CI -0.97 to -0.55; P<0.001), physician global assessment (SMD=0.51; 95% CI 0.35-0.67; P<0.001), and disability assessment scale (SMD=-0.30; 95% CI -0.40 to -0.20; P<0.001), with no significant effects on active upper limb function (SMD=0.49; 95% CI -0.08 to 1.07; P=0.093) and adverse events (RR=1.18; 95% CI 0.72-1.93; P=0.509). For lower limb spasticity, BTXA therapy was associated with higher Fugl-Meyer score (SMD=5.09; 95%CI 2.16-8.01; P=0.001), but had no significant effects on muscle tone (SMD=-0.12; 95% CI -0.83 to 0.59; P=0.736), gait speed (SMD=0.06; 95% CI -0.02 to 0.15; P=0.116), and adverse events (RR=1.01; 95% CI 0.71-1.45; P=0.949). Conclusions BTXA improves muscle tone, physician global assessment, and disability assessment scale in upper limb spasticity and increases the Fugl-Meyer score in lower limb spasticity.

Long-term results of chronic intrathecal baclofen treatment in patients with spasticity and secondary dystonia

To estimate the efficacy of intrathecal treatment with baclofen (ITB) in spasticity and dystonia. Two groups of patients have been operated: 19 patients with spinal spasticity and 33 patients with cerebral spasticity (cerebral palsy). After baclofen screening test, the Synchromed2 (Medtronic) was implanted. The level of muscle tone was assessed by the Ashworth scale. The locomotion was assessed by GMFM 88 and Arens scale. The dystonia was assessed by the BFM scale. Follow-up was performed 3, 6 and 12 months after the operation and yearly after that. The duration of the follow-up ranged from 2 to 9 years. ITB led to a significant decrease in leg spasticity in both groups of patients (p<0.001). The dynamics of spasticity was more significant in the first group compared to the second group (2.77 and 2.07 points, respectively (p<0.0031)). The dynamics of muscle tone in arms was lesser then in legs (p<0.0022). The positive clinical dynamics in patients with secondary dystonia was minimal (BFM from 65±17 to 60±19). Increasing of ITB daily dose was required to maintenance the clinical effect in most patients. The loss of ITB effect was noted in 5% of patients. ITB was more effective in patients with spinal spasticity. The influence of ITB on the secondary dystonia was lesser then on the spasticity. The dynamic of the muscle tone was more significant in legs than in arms. The loss of ITB effect can be observed in some cases after the operation despite the positive result of baclofen screening-test.

Interaction between muscle tone, short-range stiffness and increased sensory feedback gains explains key kinematic features of the pendulum test in spastic cerebral palsy: A simulation study.

The pendulum test is a sensitive clinical assessment of spasticity where the lower leg is dropped from the horizontal position and features of limb motion are recorded. Three key kinematic features are associated with the degree of severity of spasticity in children with cerebral palsy: decreased initial limb excursion, reduced number of limb oscillations, and a non-vertical resting limb angle. While spasticity is attributed to increased velocity-dependent resistance to motion, prior models simulating increased sensorimotor feedback of muscle velocity fail to explain the key pendulum test kinematic outcomes in spastic individuals. Here we hypothesized that increased muscle tone, causing a transient increase in muscle force, i.e. short-range stiffness, could account for reduced first swing excursion and non-vertical resting limb angle. We further hypothesized that hyperreflexia modeled based on muscle fiber force, and not velocity, feedback would be necessary to reduce the number of oscillations because of its interaction with transiently increased muscle force due to short-range stiffness. We simulated the lower leg as a torque-driven single-link pendulum. Muscle tone was modeled as a constant baseline joint torque, short-range stiffness torque was dependent on the level of muscle tone, and delayed sensory feedback torque to simulate reflex activity was based on either muscle velocity or force. Muscle tone and transient short-range stiffness were necessary to simulate decreased initial swing excursion and non-vertical resting leg angle. Moreover, the reduction in the number of oscillations was best reproduced by simulating stretch reflex activity in terms of force, and not velocity, feedback. Varying only baseline muscle torque and reflex gain, we simulated a range of pendulum test kinematics observed across different levels of spasticity. Our model lends insight into physiological mechanisms of spasticity whose contributions can vary on an individual-specific basis, and potentially across different neurological disorders that manifest spasticity as a symptom.

Analysis of the effects of the upper limb improvement programme in patients after ischemic stroke treated with botulinum toxin

Introduction: Stroke is not only a medical problem, but also - due to the permanent disability of the injured person - a significant social problem. A significant number of patients after a neurological event develop increased muscle tone. Upper motoneuron damage syndrome promotes pain, stiffness, muscle contracture and weakness, which can potentially delay or prevent success in the rehabilitation process. In the upper limb, the spastic pattern is most often expressed through adduction and internal rotation of the glenohumeral joint, combined with flexion in the elbow, radiocarpal joint and interphalangeal joints. The specificity of spasticity-type increased tension makes rehabilitation of patients suffering from this disorder one of the most difficult tasks of neurological rehabilitation. Aim: The aim of the study was to assess muscle tone and range of motion of the inferior limb in patients after ischemic stroke subjected to 4 cycles of intramuscular injections of a botulinum toxin preparation and subjected to motor rehabilitation. Research Project: Pilot experimental study. Methodology: The study was carried out in the Neurological Unit with Stroke Sub-unit and Sub-Department of Neurological Rehabilitation at John Paul II Specialist Hospital in Krakow in the period from September 2014 to November 2015. The study group consisted of 20 patients after ischemic stroke (13 men, 7 women), age 30 to 72. All patients completed a 4-cycle study, which included injections of the botulinum toxin preparation, combined with a 15-day cycle of individual rehabilitation exercises. Each training session lasted 90 minutes. In order to verify the therapeutic process, active and passive mobility was measured according to the SFTR method and the assessment of muscle tone level was done using the Modified Ashworth Scale. Results: The taken therapeutic actions caused a positive increase in mobility, mostly passive, in the glenohumeral-scapular, elbow and forearm as well as the radiocarpal joints. There was also a slight increase in active mobility of the upper limb joints. In the course of obtaining results, it was shown that the use of botulinum toxin, combined with the rehabilitation exercise programme, significantly reduced pathological muscle tone both within the elbow, radiocarpal joint, and the interphalangeal joints of the hands. Conclusions: The presented results showed that the use of the botulinum toxin combined with medical rehabilitation allows local treatment of spasticity without exposing patients to adverse systemic reactions associated with oral medication. In addition, it has a positive effect on the increase in passive and - to a lesser extent - active range of motion in the joints of the inferior limb.

Triaxial MMG investigation during FES-induced cycle movements

Spinal cord injury is damage to the spinal cord that results in loss of functions, causes muscle, joint and bone deficits, moreover it increases the muscle tone level. FEScycling is an alternative rehabilitation process to conserve the musculoskeletal system affected by the injury in the functional state. The aim of this study is to get the legs bilaterally synchronized by FES and compare MMG signal responses. The preliminary protocol consists of five consecutive contractions. The first and the last contractions were discarded and the three intermediate contractions were analyzed. A ratio between MMG values of muscle responses during propulsion and return of pedalling phases was calculated for each cycle and each leg. The applied FES profile consisted of pulse and burst on time of 250 us and 5 ms and frequencies of 1000 Hz and 20 Hz, respectively. Results showed that greater MMG RMS values tend to occur during the propulsion phase than in the return phase. MMG Z axis of RLL and MMG X axis of LLL were the axes that presented the greatest ratios. The MMG RMS signal showed that greater values tend to occur during the propulsion phase than in the return phase of the same thigh.

Complications of Laryngeal Masks in Children

Complications of Laryngeal Masks in Children

Pharmacogenetic inhibition of the subcoeruleus region influences rem sleep and cataplexy in narcoleptic mice

Cataplexy – the sudden involuntary loss of skeletal muscle tone – is a defining feature of narcolepsy. A longstanding, but untested, hypothesis is that cataplexy results from intrusion of REM sleep paralysis into wakefulness. This hypothesis is built on the assumption that cataplexy and REM sleep paralysis share a common neural mechanism. The current study aimed to determine if cataplexy is influenced by direct manipulation of REM sleep circuitry. We did this by pharmacogenetically inhibiting cells in the subcoeruleus – a region important for REM paralysis – while monitoring REM sleep and cataplexy in narcoleptic mice. Virally-mediated transduction of hM4D-Gi/o was bilaterally targeted to the subcoeruleus (Sub-C) in hypocretin knockout mice ( n = 7). Standard electrophysiological (i.e., EEG/EMG) and behavioural criteria were used to characterize cataplexy and REM sleep. Intraperitoneal administration of clozapine-n-oxide (CNO, 10 mg/kg) was used to inhibit Sub-C cells expressing hM4D-Gi/o. Saline injections served as controls for CNO administration. Histological and immunohistochemistry were used to verify hM4D-Gi/o expression in the left/right Sub-C. Sub-C inhibition markedly influenced REM sleep and cataplexy. Compared to saline, Sub-C inhibition increased REM sleep amounts by increasing both the number ( p = 0.001) and duration of REM episodes ( p < 0.0001). This intervention also triggered increases in basal levels of muscle tone during REM sleep, i.e., it blocked REM sleep paralysis ( p < 0.05). Silencing Sub-C cells also lead to marked sleep fragmentation by increasing the number of NREM to REM transitions. Sub-C inhibition lead to an 88% decrease ( p = 0.04) in time spent in cataplexy as well as 75% fewer cataplexy episodes ( p = 0.025). There were no measureable changes in the duration of cataplectic events ( p > 0.05 for all variables). Pharmacogenetic manipulation of the Sub-C influences REM sleep expression as well as cataplexy expression in narcoleptic mice. At first glance, these preliminary data suggest that REM sleep paralysis and cataplexy may be mediated by a similar neural mechanism.

Influences of Chronic Shoulder Pain on Muscle Tone Changes in Trunk Muscles

The purpose of this study was to examine the influences of chronic shoulder pain on the muscle tone in trunk muscles. The study's subjects were 40 men and women in their 30 to 50s, which were divided into two groups. A chronic shoulder pain group consisted of 20 subjects who had been diagnosed with chronic shoulder pain by doctors, and a painless group consisted of 20 subjects who had experienced no such pain. An analysis was performed using electromyography on the muscle tone in the rectus abdominalis, external oblique, internal oblique, and erector spinae muscles under the same conditions between the two groups. The analysis results were as follows. The chronic shoulder pain group exhibited an overall high level of trunk muscle tone than the painless group, along with a statistically significant difference in the rectus abdominalis(p<.05). Moreover, the chronic shoulder pain group showed differences in the trunk muscle tone depending on the affected side. The chronic left shoulder pain group yielded higher levels of muscle tone in the right-side trunk muscles. In particular, the group revealed statistically significant differences in the rectus abdominalis and internal oblique(p<.05). The chronic right shoulder pain group exhibited higher levels of muscle tone in the left-side trunk muscles with a statistically significant difference in the internal oblique(p<.05). The above results suggested that chronic shoulder pain influences increases in the muscle tone in the trunk muscles on the opposite side to the affected shoulder.

Measurement of muscle stiffness using robotic assisted gait orthosis in children with cerebral palsy: a proof of concept

Purpose. To evaluate the feasibility and reliability of a novel stiffness assessment tool implemented in the driven gait orthosis Paediatric Lokomat; to investigate the influence of single robotic-assisted gait training (RAGT) on muscle stiffness in children with cerebral palsy (CP).Methods. Ten children with spastic CP conducted a single standard RAGT session and stiffness was assessed before and after the RAGT. Nine of the ten subjects were tested twice on the same day to investigate test–retest reliability, intraclass correlation coefficients (ICCs), standard error of measurement (SEM), coefficient of variation of the method error (CVME) and resistive torques during passive leg movements (stiffness in Nm/°) were calculated.Results. ICCs showed high reliability (0.83–0.97) for hip and knee movements. SEM and CVME indicated 0.028–0.085 Nm/°, 9.5–23.0% of test–retest variability in hip and 0.018–0.064 Nm/°, 13.3–43.5% in knee measures. Using the assessment tool, a significant decrease in muscle stiffness in participants, especially in children with high levels of muscle tone, could be shown after a single session of RAGT.Conclusions. The assessment tool L-STIFF is a feasible tool for automated measurement of stiffness in children with CP, but it is not sensitive enough to record small changes in muscle tone.

Balance control under different passive contributions of the ankle extensors: quiet standing on inclined surfaces

Human bipedal stance is often modeled as a single inverted pendulum that pivots at the ankle joints in the sagittal plane. Because the center of body mass is usually maintained in front of the ankle joints, ankle extensor torque is continuously required to prevent the body from falling. During quiet standing, both passive and active mechanisms contribute to generate the ankle extensor torque counteracting gravity. This study aimed to investigate the active stabilization mechanism in more detail. Eight healthy subjects were requested to stand quietly on three different surfaces of 1) toes-up, 2) level, and 3) toes-down. Surface electromyogram (EMG) was recorded from the medial head of the gastrocnemius (MG), soleus (SOL), and tibialis anterior muscles. Inclination angle of the body was simultaneously measured. As a result, we found that EMG activities of MG and SOL were lowest during the toes-up standing and highest during the toes-down, indicating that increased (decreased) passive contribution required less (more) extensor torque generated by active muscle contraction. Frequency domain analysis also revealed that sway-related modulation of the ankle extensor activity (0.12-4.03 Hz) was unchanged among the three foot inclinations. On the other hand, isometric contraction strength of these muscles increased as the slope declined (toes-up < level < toes-down). These results support the idea that by regulating the isometric contraction strength, the CNS maintains a constant level of muscle tone and resultant ankle stiffness irrespective of the passive contribution. Such control scheme would be crucial when we consider the low bandwidth of the intermittent controller.

Assessment of firefighters-rescuers' work severity in relation with interaction between physical and mental load

Assessment of firefighters-rescuers' work severity in relation with interaction between physical and mental load The present work is focused on occupational health problems caused by ergonomic risk in firefighting, which is one of the most hazardous occupations. The aim was to evaluate the work heaviness degree and to estimate the muscle fatigue for a study group consisting of 12 firefighters-rescuers. Applying qualitative ergonomic analyses (OWAS a.o.) and clinical experiments to determine consumed metabolic energy using heart rate monitoring, the following work hardness categories were observed: firefighter-rescuer — category III (hard work, 8.2 ± 1.2 kcal/min); commanding officers — category II (moderate work, 6.0 ± 1.6 kcal/min). Assessment of muscle strain and functional state (tone) using myotonometric measurements showed several muscle tone levels, allowing subdivision of firefighters into different conditional categories basing on muscle tone and fatigue: I — a state of equilibrium when muscles are able to adapt to the work load and are partly able to relax; and II — muscle fatigue and increased tone. It was also found that the increase of muscle tone and fatigue mainly depended on workers physical preparedness and length of service, and less on their age. Assessment interaction of mental and physical load using NASA-TLX method indicated that the highest degree of total workload was for several firemen, especially, commanding officers when temporary demands, task performance, effort and frustration were taken into consideration.

Assessment of skeletal muscle fatigue of road maintenance workers based on heart rate monitoring and myotonometry

ObjectiveThis research work is dedicated to occupational health problems caused by ergonomic risks. The research object was road building industry, where workers have to work very intensively, have long work hours, are working in forced/constrained work postures and overstrain during the work specific parts of their bodies. The aim of this study was to evaluate the work heaviness degree and to estimate the muscle fatigue of workers after one week work cycle. The study group consisted of 10 road construction and maintenance workers and 10 pavers aged between 20 and 60 years.MethodsPhysical load were analyzed by measuring heart rate (HR), work postures (OWAS) and perceived exertion (RPE). Assessments of the muscles strain and functional state (tone) were carried out using myotonometric (MYO) measurements. The reliability of the statistical processing of heart rate monitoring and myotonometry data was determined using correlating analysis.ResultsThis study showed that that road construction and repairing works should be considered as a hard work according to average metabolic energy consumption 8.1 ± 1.5 kcal/min; paving, in its turn, was a moderately hard work according to 7.2 ± 1.1 kcal/min. Several muscle tone levels were identified allowing subdivision of workers into three conditional categories basing on muscle tone and fatigue: I – absolute muscle relaxation and ability to relax; II – a state of equilibrium, when muscles are able to adapt to the work load and are partly able to relax; and III – muscle fatigue and increased tone. It was also found out that the increase of muscle tone and fatigue mainly depend on workers physical preparedness and length of service, and less – on their age.ConclusionWe have concluded that a complex ergonomic analysis consisting of heart rate monitoring, assessment of compulsive working postures and myotonometry is appropriate to assess the work heaviness degree and can provide prognosis of occupational pathology or work-related musculoskeletal disorders for the workers under different workload conditions. These results can also be used when deciding on necessary rest time and its periodicity.

Interaction between spontaneous and neurally mediated regulation of smooth muscle tone in the rabbit corpus cavernosum

Interaction between spontaneous and neurally mediated regulation of tone in the corpus cavernosum smooth muscle (CCSM) of the rabbit was investigated. Changes in isometric muscle tension, intracellular Ca2+ concentration ([Ca2+]i) and membrane potential were recorded. CCSM developed spontaneous contractions, transient increases in [Ca2+]i (Ca2+ transients) and depolarizations. This spontaneous activity was abolished by blocking L-type Ca2+ channels (nicardipine, 1 mum), sarcoplasmic reticulum Ca2+ pump activity (cyclopiazonic acid, 10 microm), Ca2(+)-activated Cl- channels (niflumic acid, 10 mum) or cyclooxygenase-2 (COX-2; NS-398, 1 microm). Transmural nerve stimulation initiated either alpha-adrenergic contractions or nitrergic relaxations of CCSM depending on the level of muscle tone. NS-398 suppressed nerve-evoked contractions by about 70% but caused only a 40% reduction in the corresponding Ca2+ transient. Blocking nitric oxide synthase with N(omega)-nitro-l-arginine (LNA, 100 microm) reinforced nerve-evoked Ca2+ transients by about 150%, whilst increasing the corresponding Ca2+ transients by only 20%. In CCSM preparations that had been pre-contracted with either noradrenaline (0.3 microm) or prostaglandin F(2alpha) (0.1 microm), nerve stimulation inhibited about 70% of the contraction and caused only a 20% decrease in [Ca2+]i. Fluorescent immunohistochemistry with COX-2 antibodies and the reverse transcriptase-polymerase chain reaction (RT-PCR) method showed that the enzyme and its mRNA were highly expressed in the CCSM. These results suggest that spontaneously produced prostaglandins (PGs) not only contribute to the generation of spontaneous contractions but also facilitate nerve-evoked contractions. Conversely, spontaneously released nitric oxide (NO) suppresses excitation. Thus, interaction between spontaneous and neurally mediated regulation of CCSM tone may be fundamental to maintaining the muscle contractility. In addition, both PGs and NO appear to alter CCSM tone with only small changes in [Ca2+]i.