Impact of 10-Min Daily Yoga Exercises on Physical and Mental Discomfort of Home-Office Workers During COVID-19.

OBJECTIVE: Evaluate the effects of 10 min/day of yoga for 1 month on musculoskeletal discomfort and mood disturbance of home-office workers. BACKGROUND: The COVID-19 pandemic forced many people to switch to teleworking. The abrupt change from an office setting to an improvised home-office may negatively affect the musculoskeletal and emotional health of workers. By providing mental and physical exercises, yoga may be effective in reducing adverse effects. METHOD: Fifty-four participants (42 women, 12 men) followed a 1-month yoga program, while 40 participants (26 women, 14 men) continued with their common work routine. The Cornell Musculoskeletal Discomfort Questionnaire was used to evaluate severity, interference with work and frequency of pain, and to obtain a total discomfort score for 25 body areas. Mood disturbance was evaluated with the Profile of Mood States questionnaire. Both groups completed both questionnaires, before and after the experimentation period. RESULTS: After 1 month, for the yoga group only, significant reductions were observed in the discomfort of eyes, head, neck, upper and lower back, right wrist, and hips/buttocks, as well as reductions in discomfort severity, frequency and interference for the neck, upper and lower back. Total mood disturbance was also significantly reduced for the yoga group only. No favorable changes occurred for the control group. CONCLUSION: The yoga intervention program appears to reduce musculoskeletal discomfort and mood disturbance of home-office workers. APPLICATION: Sedentary workers may benefit from 10 min/day of yoga during the workday to attenuate potential physical and emotional discomfort during the current pandemic and beyond.

Comparison of Physiological Effects Induced by Two Compression Stockings and Regular Socks During Prolonged Standing Work.

OBJECTIVE: The goal of this study was to evaluate and compare lower-leg muscle fatigue, edema, and discomfort induced by the prolonged standing of security guards wearing regular socks and those wearing 15-20 or 20-30 mmHg compression stockings as intervention. BACKGROUND: Compression stockings are sometimes used by individuals standing all day at work. However, quantitative evidence showing their potential benefits for lower-leg health issues in healthy individuals during real working conditions is lacking. METHOD: Forty male security employees participated in the study. All were randomly assigned to the control or one of the two intervention groups (I15-20 or I20-30). Lower-leg muscle twitch force, volume, and discomfort ratings were measured before and after their regular 12-hr standing work shift. RESULTS: Significant evidence of lower-leg long-lasting muscle fatigue, edema, and discomfort was observed after standing work for guards wearing regular socks. However, no significant changes were found for guards wearing either compression stockings. CONCLUSION: In healthy individuals, compression stockings seem to attenuate efficiently the tested outcomes in the lower leg resulting from prolonged standing. APPLICATION: Occupational activities requiring prolonged standing may benefit from 15-20 or 20-30 mmHg compression stockings. As similar benefits were observed for both levels of compression, the lower level may be sufficient.

Effect of Periodic Voluntary Interventions on Trapezius Activation and Fatigue During Light Upper Limb Activity.

OBJECTIVE: The effects of diverse periodic interventions on trapezius muscle fatigue and activity during a full day of computer work were investigated. BACKGROUND: Musculoskeletal disorders, including trapezius myalgia, may be associated with repeated exposure to prolonged low-level activity, even during light upper-extremity tasks including computer work. METHODS: Thirty healthy adults participated in a study that simulated two 6-hour workdays of computer work. One workday involved imposed periodic passive and active interventions aimed at disrupting trapezius contraction monotony (Intervention day), whereas the other workday did not (Control day). Trapezius muscle activity was quantified by the 3-dimensional acceleration of the jolt movement of the acromion produced by electrically induced muscle twitches. The spatio-temporal distribution of trapezius activity was measured through high-density surface electromyography (HD-EMG). RESULTS: The twitch acceleration magnitude in one direction was significantly different across measurement periods (p = 0.0156) on Control day, whereas no significant differences in any direction were observed (p > 0.05) on Intervention day. The HD-EMG from Intervention day showed that only significant voluntary muscle contractions (swing arms, Jacobson maneuver) induced a decrease in the muscle activation time and an increase in the spatial muscle activation areas (p < 0.01). CONCLUSION: Disruption of trapezius monotonous activity via brief voluntary contractions effectively modified the ensuing contraction pattern (twitch acceleration along one axis, active epochs reduction, and larger spatial distribution). The observed changes support an associated reduction of muscle fatigue. APPLICATION: This study suggests that disruptive intervention activity is efficient in reducing the impact of trapezius muscle fatigue.

Perceived Physical Discomfort and Its Associations With Home Office Characteristics During the COVID-19 Pandemic.

OBJECTIVE: The goal of this study was to evaluate the prevalence and change in perception of physical discomfort, including musculoskeletal discomfort, during the COVID-19 pandemic and to determine associations of demographic factors, telework activity, and home office characteristics with the highest prevalence of discomfort. BACKGROUND: The COVID-19 pandemic forced a substantial increase in telework in many countries. The sudden change from a regular workplace to an improvised "home office" may have an impact on working conditions and physical symptoms of office workers. However, investigations in this area remain limited. METHOD: A cross-sectional study design was used to compare self-reported complaints of physical discomfort perceived from before with those during the pandemic. Associations between complaints and home office characteristics were investigated from 150 faculty and 51 administrative staff of an academic institution with an age range of 41.16 ± 10.20 (59% female). RESULTS: A significant increase of physical discomfort was found during the pandemic period for head, eyes, hand, and upper back for both staff and faculty and neck, shoulders, elbows, and lower back for faculty only. Logistic regression analyses point to associations with the lack of a laptop stand, uncomfortable desk, poor lighting, and sitting time, among others. CONCLUSION: A high prevalence of physical discomfort was reported by teleworkers during the COVID-19 pandemic. Some home office characteristics were associated with these discomforts. APPLICATION: Some telework characteristics seem to be risk factors for physical discomfort. Consideration should be given to teaching best practices for workstation setup and/or conducting other preventive interventions in the work environment.

A PRELIMINARY ASSESSMENT OF PHYSICAL WORK EXPOSURES AMONG ELECTRONIC WASTE WORKERS AT AGBOGBLOSHIE, ACCRA GHANA.

Occupational exposure associated with unstructured, informal e-waste recycling has received very limited attention. This study aimed to quantify the occupational physical exposures among informal e-waste workers at the largest e-waste site in Africa. A cross-sectional field survey of 163 male e-waste workers was conducted using a self-report occupational physical activity questionnaire, along with direct work observations, and pedometer estimates of walking activity for a subset of workers (n = 42). Results indicated significant differences in self-reported 7-day work exposures among the three main e-waste job categories, namely, collectors (n = 70), dismantlers (n = 73) and burners (n = 20). Prolonged walking, sitting and standing on five or more days in the workweek was frequently reported by collectors (87%), dismantlers (82%) and burners (60%), respectively. Nearly 90% of collectors and burners and 60% of dismantlers reported lifting and carrying on five or more days in the workweek. The exposure combinations identified suggest a risk for musculoskeletal disorders (MSDs). Findings call attention to the need for research examining potential associations between physical exposures and MSDs affecting e-waste workers in Agbogbloshie. The high exposure variability both between and within workers has implications for future exposure assessments conducted in unregulated, informal work settings.

Physiological and neuromotor changes induced by two different stand-walk-sit work rotations.

The potential of rotating postures to alleviate the effects of prolonged standing and sitting postures has been advocated to attenuate the accumulation of muscle fatigue, considered a precursor to musculoskeletal disorders. We aimed to evaluate the effects of two posture rotations, both including standing, walking, sitting, on physiological and neuromotor measures. Twenty-two participants followed two posture rotations, with different rest-break distributions, for 5.25 h. Lower-leg muscle twitch force, volume, force control and discomfort perception were evaluated during and after work exposure on two non-consecutive days. Significant changes in all measures indicate a detrimental effect in lower-leg long-lasting muscle fatigue, oedema, performance and discomfort after 5 h for both exposures. However, for both exposures recovery was significant 1 h and 15 h post-workday. Differences between the two rotation schedules were not significant. Hence, stand-walk-sit posture rotation promotes recovery of the tested measures and is likely to better prevent muscle fatigue accumulation. Practitioner summary: Lower-leg muscle twitch force, volume, force control, and discomfort were quantified during and after 5 h of stand-walk-sit work rotations with two different rest-break distributions. Measures revealed similar significant effects of work exposures regardless of rotation; which did not persist post-work. This beneficial recovery contrasts with the standing only situations. Abbreviations: MSDs: musculoskeletal disorders; MTF: muscle twitch force; RMSE: root mean square error; MVC: maximum voluntary contraction; M: mean; SE: standard error.

Physiological changes during prolonged standing and walking considering age, gender and standing work experience.

Occupational standing is associated with musculoskeletal and venous disorders. The aim was to investigate whether lower leg oedema and muscle fatigue development differ between standing and walking and whether age, gender and standing work habituation are factors to consider. Sixty participants (15 young females, 15 young males, 15 older males, and 15 young males habituated to standing work) were included and required to stand/walk for 4.5 hours in three periods with two seated breaks. Waterplethysmography/bioelectrical impedance, muscle twitch force and surface electromyography were used to assess lower leg swelling (LLS) and muscle fatigue as well as gastrocnemius muscle activity, respectively. While standing led to LLS and muscle fatigue, walking did not. Low-level medial gastrocnemius activity was not continuous during standing. No significant influence of age, gender and standing habituation was observed. Walking can be an effective prevention measure to counteract the detrimental effects of quasi-static standing.Practitioner summary: Prolonged standing leads to lower leg oedema and muscle fatigue while walking does not. The primary cause of fatigue may be in other muscles than the medial gastrocnemius. Walking may be an effective prevention measure for health risks of occupational standing when included intermittently.Abbreviation: BI: bioelectrical impedance; LLS: lower leg swelling; SEMG: surface electromyography; MTF: muscle twitch force; WP: waterplethysmography; Bsl: Baseline; L: Lunch; E: Evening; MTM: method times measurement; EA: electrical activity; IQR: interquartile range; p: percentile; M: mean; SE: standard error; Adj: adjusted.

Pneumococcal Competence Coordination Relies on a Cell-Contact Sensing Mechanism.

Bacteria have evolved various inducible genetic programs to face many types of stress that challenge their growth and survival. Competence is one such program. It enables genetic transformation, a major horizontal gene transfer process. Competence development in liquid cultures of Streptococcus pneumoniae is synchronized within the whole cell population. This collective behavior is known to depend on an exported signaling Competence Stimulating Peptide (CSP), whose action generates a positive feedback loop. However, it is unclear how this CSP-dependent population switch is coordinated. By monitoring spontaneous competence development in real time during growth of four distinct pneumococcal lineages, we have found that competence shift in the population relies on a self-activated cell fraction that arises via a growth time-dependent mechanism. We demonstrate that CSP remains bound to cells during this event, and conclude that the rate of competence development corresponds to the propagation of competence by contact between activated and quiescent cells. We validated this two-step cell-contact sensing mechanism by measuring competence development during co-cultivation of strains with altered capacity to produce or respond to CSP. Finally, we found that the membrane protein ComD retains the CSP, limiting its free diffusion in the medium. We propose that competence initiator cells originate stochastically in response to stress, to form a distinct subpopulation that then transmits the CSP by cell-cell contact.

RecFOR is not required for pneumococcal transformation but together with XerS for resolution of chromosome dimers frequently formed in the process.

Homologous recombination (HR) is required for both genome maintenance and generation of diversity in eukaryotes and prokaryotes. This process initiates from single-stranded (ss) DNA and is driven by a universal recombinase, which promotes strand exchange between homologous sequences. The bacterial recombinase, RecA, is loaded onto ssDNA by recombinase loaders, RecBCD and RecFOR for genome maintenance. DprA was recently proposed as a third loader dedicated to genetic transformation. Here we assessed the role of RecFOR in transformation of the human pathogen Streptococcus pneumoniae. We firstly established that RecFOR proteins are not required for plasmid transformation, strongly suggesting that DprA ensures annealing of plasmid single-strands internalized in the process. We then observed no reduction in chromosomal transformation using a PCR fragment as donor, contrasting with the 10,000-fold drop in dprA- cells and demonstrating that RecFOR play no role in transformation. However, a ∼1.45-fold drop in transformation was observed with total chromosomal DNA in recFOR mutants. To account for this limited deficit, we hypothesized that transformation with chromosomal DNA stimulated unexpectedly high frequency (>30% of cells) formation of chromosome dimers as an intermediate in the generation of tandem duplications, and that RecFOR were crucial for dimer resolution. We validated this hypothesis, showing that the site-specific recombinase XerS was also crucial for dimer resolution. An even higher frequency of dimer formation (>80% of cells) was promoted by interspecies transformation with Streptococcus mitis chromosomal DNA, which contains numerous inversions compared to pneumococcal chromosome, each potentially promoting dimerization. In the absence of RecFOR and XerS, dimers persist, as confirmed by DAPI staining, and can limit the efficiency of transformation, since resulting in loss of transformant chromosome. These findings strengthen the view that different HR machineries exist for genome maintenance and transformation in pneumococci. These observations presumably apply to most naturally transformable species.

Muscular and Vascular Issues Induced by Prolonged Standing With Different Work-Rest Cycles With Active or Passive Breaks.

OBJECTIVE: The aim of this study was to evaluate the long-lasting motor, behavioral, physiological, and perceptual effects of prolonged standing work in three work-rest cycle conditions including passive or active rest breaks. BACKGROUND: Muscle fatigue has been evidenced after prolonged standing work through physiological and neuromotor measures. It has been postulated that muscle fatigue induced by prolonged work could be attenuated by appropriate scheduling of work and rest periods. However, investigations in this domain remain limited. METHOD: Thirty participants simulated standing work for 5 hr with work-rest cycles of short, medium, or long standing periods including passive or active breaks. Lower-leg muscle twitch force (MTF), muscle oxygenation, lower-leg volume, postural stability, force control, and discomfort perception were quantified on 2 days. RESULTS: Prolonged standing induced significant changes in all measures immediately after 5 hr of work, indicating a detrimental effect in long-lasting muscle fatigue, performance, discomfort, and vascular aspects. Differences in the measures were not significant between work cycles and/or break type. CONCLUSION: Similar physiological and motor alterations were induced by prolonged standing. The absence of difference in the effects induced by the tested work-rest cycles suggests that simply altering the work-rest cycle may not be sufficient to counteract the effects of mainly static standing work. Finally, standing for 3 hr or more shows clear detrimental effects. APPLICATION: Prolonged standing is likely to contribute to musculoskeletal and vascular symptoms. A limitation to less than 3 hr of mostly static standing in occupational activities could avoid alterations leading to these symptoms.

Shoulder muscular activity in individuals with low back pain and spinal cord injury during seated manual load transfer tasks.

This study aimed to compare the activity of four shoulder muscles in individuals with low back pain (LBP), spinal cord injuries (SCI) and a control group, during one-handed load transfer trials. Nine individuals with minimum one-year of LBP, eleven with thoracic/lumbar SCI and nine healthy controls participated in this study. The activations of anterior deltoid, upper trapezius, infraspinatus and pectoralis major were recorded by surface EMG during one-handed transferring of a cylinder from a home shelve to six spatially distributed target shelves. The integrated EMG values were compared using repeated measure ANOVA. Both LBPs and SCIs had higher anterior deltoid activation and LBPs required more upper trapezius activation than controls (p < 0.05). The spatial position of the targets also significantly influenced demands for these two muscles. The anterior deltoid and upper trapezius in LBP and SCI individuals are under higher demand during occupational load transfer tasks. Practitioner Summary: This study aimed to compare the activation of four shoulder muscles in individuals with low back pain, spinal cord injuries and healthy condition. EMG analysis showed that the injured groups required more upper trapezius and anterior deltoid activation during load transfer tasks, which may predispose them to muscle overexertion.

Fine-tuning of choline metabolism is important for pneumococcal colonization.

The human pathogen Streptococcus pneumoniae (the pneumococcus) is rare in having a strict requirement for the amino alcohol choline, which decorates pneumococcal teichoic acids. This process relies on the lic locus, containing the lic1 and lic2 operons. These operons produce eight proteins that import and metabolize choline, generate teichoic acid precursors and decorate these with choline. Three promoters control expression of lic operons, with Plic1P1 and Plic1P2 controlling lic1 and Plic2 controlling lic2. To investigate the importance of lic regulation for pneumococci, we assayed the activity of transcriptional fusions of the three lic promoters to the luciferase reporter gene. Plic1P1 , whose activity depends on the response regulator CiaR, responded to fluctuations in extracellular choline, with activity increasing greatly upon choline depletion. We uncovered a complex regulatory mechanism controlling Plic1P1 , involving activity driven by CiaR, repression by putative repressor LicR in the presence of choline, and derepression upon choline depletion mediated by LicC, a choline metabolism enzyme. Finally, the ability to regulate Plic1P1 in response to choline was important for pneumococcal colonization. We suggest that derepression of Plic1P1 upon choline depletion maximizing choline internalization constitutes an adaptive response mechanism allowing pneumococci to optimize growth and survival in environments where choline is scarce.

Effect of bit wear on hammer drill handle vibration and productivity.

The use of large electric hammer drills exposes construction workers to high levels of hand vibration that may lead to hand-arm vibration syndrome and other musculoskeletal disorders. The aim of this laboratory study was to investigate the effect of bit wear on drill handle vibration and drilling productivity (e.g., drilling time per hole). A laboratory test bench system was used with an 8.3 kg electric hammer drill and 1.9 cm concrete bit (a typical drill and bit used in commercial construction). The system automatically advanced the active drill into aged concrete block under feed force control to a depth of 7.6 cm while handle vibration was measured according to ISO standards (ISO 5349 and 28927). Bits were worn to 4 levels by consecutive hole drilling to 4 cumulative drilling depths: 0, 1,900, 5,700, and 7,600 cm. Z-axis handle vibration increased significantly (p<0.05) from 4.8 to 5.1 m/s2 (ISO weighted) and from 42.7-47.6 m/s2 (unweighted) when comparing a new bit to a bit worn to 1,900 cm of cumulative drilling depth. Handle vibration did not increase further with bits worn more than 1900 cm of cumulative drilling depth. Neither x- nor y-axis handle vibration was effected by bit wear. The time to drill a hole increased by 58% for the bit with 5,700 cm of cumulative drilling depth compared to a new bit. Bit wear led to a small but significant increase in both ISO weighted and unweighted z-axis handle vibration. Perhaps more important, bit wear had a large effect on productivity. The effect on productivity will influence a worker's allowable daily drilling time if exposure to drill handle vibration is near the ACGIH Threshold Limit Value. [1] Construction contractors should implement a bit replacement program based on these findings.

Vibrotactile cuing revisited to reveal a possible challenge to sensorimotor adaptation.

Motor responses to unexpected external perturbations require the adjustment of the motor commands driving the ongoing activity. Strategies can be learned with practice to compensate for these unpredictable perturbations (e.g., externally induced slips and trips). It has been hypothesized that response improvements reflect the adaptation of motor commands through updates of an internal model. This hypothesis may be nuanced when a pre-existing motor response could be used. In that case, since a relatively adequate response is known, only the timing of the command needs to be determined. If so, then it could be inferred that the timing of movement initiation and the specific sequence of motor commands can be dissociated. Previously, we quantified the benefits of cuing vs. learning on recovery motor responses resulting from a trip induced by the abrupt stop of one side of a split belt treadmill. Trip occurrence was randomized within a series of strides. Two groups of young adults participated to two distinct experiments (learning, cuing). In the learning experiment, trip recovery improved progressively from the 4th to the 8th trial to reach an "adapted response". In the cuing experiment, trip recovery was immediate (from 1st trial). Expanding from these results, the aim of the present work was to differentiate the processes underlying the generation of motor compensation strategies in response to an external perturbation under time uncertainty. A supplementary analysis revealed that "cued" responses were kinematically similar to the "adapted response" and remained invariant regardless of cue lead time (250, 500 ms before trip) and application location of the cue (arm, trunk, lower leg). It is posited that all responses (cued and non-cued) are the expression of a pre-existing motor program derived from life experiences. Here, the cue significantly reduces time uncertainty and adaptation consists primarily in resolving time uncertainty based on the trial-by-trial learning of the stochastic property of trip occurrence in order to reduce the response delay. Hence, response time delay and motor program parameters appear to stem from two distinct processes.

Natural genetic transformation generates a population of merodiploids in Streptococcus pneumoniae.

Partial duplication of genetic material is prevalent in eukaryotes and provides potential for evolution of new traits. Prokaryotes, which are generally haploid in nature, can evolve new genes by partial chromosome duplication, known as merodiploidy. Little is known about merodiploid formation during genetic exchange processes, although merodiploids have been serendipitously observed in early studies of bacterial transformation. Natural bacterial transformation involves internalization of exogenous donor DNA and its subsequent integration into the recipient genome by homology. It contributes to the remarkable plasticity of the human pathogen Streptococcus pneumoniae through intra and interspecies genetic exchange. We report that lethal cassette transformation produced merodiploids possessing both intact and cassette-inactivated copies of the essential target gene, bordered by repeats (R) corresponding to incomplete copies of IS861. We show that merodiploidy is transiently stimulated by transformation, and only requires uptake of a ~3-kb DNA fragment partly repeated in the chromosome. We propose and validate a model for merodiploid formation, providing evidence that tandem-duplication (TD) formation involves unequal crossing-over resulting from alternative pairing and interchromatid integration of R. This unequal crossing-over produces a chromosome dimer, resolution of which generates a chromosome with the TD and an abortive chromosome lacking the duplicated region. We document occurrence of TDs ranging from ~100 to ~900 kb in size at various chromosomal locations, including by self-transformation (transformation with recipient chromosomal DNA). We show that self-transformation produces a population containing many different merodiploid cells. Merodiploidy provides opportunities for evolution of new genetic traits via alteration of duplicated genes, unrestricted by functional selective pressure. Transient stimulation of a varied population of merodiploids by transformation, which can be triggered by stresses such as antibiotic treatment in S. pneumoniae, reinforces the plasticity potential of this bacterium and transformable species generally.

Direct involvement of DprA, the transformation-dedicated RecA loader, in the shut-off of pneumococcal competence.

Natural bacterial transformation is a genetically programmed process allowing genotype alterations that involves the internalization of DNA and its chromosomal integration catalyzed by the universal recombinase RecA, assisted by its transformation-dedicated loader, DNA processing protein A (DprA). In Streptococcus pneumoniae, the ability to internalize DNA, known as competence, is transient, developing suddenly and stopping as quickly. Competence is induced by the comC-encoded peptide, competence stimulating peptide (CSP), via a classic two-component regulatory system ComDE. Upon CSP binding, ComD phosphorylates the ComE response-regulator, which then activates transcription of comCDE and the competence-specific σ(X), leading to a sudden rise in CSP levels and rendering all cells in a culture competent. However, how competence stops has remained unknown. We report that DprA, under σ(X) control, interacts with ComE∼P to block ComE-driven transcription, chiefly impacting σ(X) production. Mutations of dprA specifically disrupting interaction with ComE were isolated and shown to map mainly to the N-terminal domain of DprA. Wild-type DprA but not ComE interaction mutants affected in vitro binding of ComE to its promoter targets. Once introduced at the dprA chromosomal locus, mutations disrupting DprA interaction with ComE altered competence shut-off. The absence of DprA was found to negatively impact growth following competence induction, highlighting the importance of DprA for pneumococcal physiology. DprA has thus two key roles: ensuring production of transformants via interaction with RecA and competence shut-off via interaction with ComE, avoiding physiologically detrimental consequences of prolonged competence. Finally, phylogenetic analyses revealed that the acquisition of a new function by DprA impacted its evolution in streptococci relying on ComE to regulate comX expression.

The effects of attractive vs. repulsive instructional cuing on balance performance.

BACKGROUND: Torso-based vibrotactile feedback has been shown to improve postural performance during quiet and perturbed stance in healthy young and older adults and individuals with balance impairments. These systems typically include tactors distributed around the torso that are activated when body motion exceeds a predefined threshold. Users are instructed to "move away from the vibration". However, recent studies have shown that in the absence of instructions, vibrotactile stimulation induces small (~1°) non-volitional responses in the direction of its application location. It was hypothesized that an attractive cuing strategy (i.e., "move toward the vibration") could improve postural performance by leveraging this natural tendency. FINDINGS: Eight healthy older adults participated in two non-consecutive days of computerized dynamic posturography testing while wearing a vibrotactile feedback system comprised of an inertial measurement unit and four tactors that were activated in pairs when body motion exceeded 1° anteriorly or posteriorly. A crossover design was used. On each day participants performed 24 repetitions of Sensory Organization Test condition 5 (SOT5), three repetitions each of SOT 1-6, three repetitions of the Motor Control Test, and five repetitions of the Adaptation Test. Performance metrics included A/P RMS, Time-in-zone and 95 % CI Ellipse. Performance improved with both cuing strategies but participants performed better when using repulsive cues. However, the rate of improvement was greater for attractive versus repulsive cuing. CONCLUSIONS: The results suggest that when the cutaneous signal is interpreted as an alarm, cognition overrides sensory information. Furthermore, although repulsive cues resulted in better performance, attractive cues may be as good, if not better, than repulsive cues following extended training.

Long-Lasting Changes in Muscle Twitch Force During Simulated Work While Standing or Walking.

OBJECTIVE: The aim of this study was to evaluate the long-lasting effects of prolonged standing work on a hard floor or floor mat and slow-pace walking on muscle twitch force (MTF) elicited by electrical stimulation. BACKGROUND: Prolonged standing work may alter lower-leg muscle function, which can be quantified by changes in the MTF amplitude and duration related to muscle fatigue. Ergonomic interventions have been proposed to mitigate fatigue and discomfort; however, their influences remain controversial. METHOD: Ten men and eight women simulated standing work in 320-min experiments with three conditions: standing on a hard floor or an antifatigue mat and walking on a treadmill, each including three seated rest breaks. MTF in the gastrocnemius-soleus muscles was evaluated through changes in signal amplitude and duration. RESULTS: The significant decrease of MTF amplitude and an increase of duration after standing work on a hard floor and on a mat persisted beyond 1 hr postwork. During walking, significant MTF metrics changes appeared 30 min postwork. MTF amplitude decrease was not significant after the first 110 min in any of the conditions; however, MTF duration was significantly higher than baseline in the standing conditions. CONCLUSION: Similar long-lasting weakening of MTF was induced by standing on a hard floor and on an antifatigue mat. However, walking partially attenuated this phenomenon. APPLICATION: Mostly static standing is likely to contribute to alterations of MTF in lower-leg muscles and potentially to musculoskeletal disorders regardless of the flooring characteristics. Occupational activities including slow-pace walking may reduce such deterioration in muscle function.

Programmed protection of foreign DNA from restriction allows pathogenicity island exchange during pneumococcal transformation.

In bacteria, transformation and restriction-modification (R-M) systems play potentially antagonistic roles. While the former, proposed as a form of sexuality, relies on internalized foreign DNA to create genetic diversity, the latter degrade foreign DNA to protect from bacteriophage attack. The human pathogen Streptococcus pneumoniae is transformable and possesses either of two R-M systems, DpnI and DpnII, which respectively restrict methylated or unmethylated double-stranded (ds) DNA. S. pneumoniae DpnII strains possess DpnM, which methylates dsDNA to protect it from DpnII restriction, and a second methylase, DpnA, which is induced during competence for genetic transformation and is unusual in that it methylates single-stranded (ss) DNA. DpnA was tentatively ascribed the role of protecting internalized plasmids from DpnII restriction, but this seems unlikely in light of recent results establishing that pneumococcal transformation was not evolved to favor plasmid exchange. Here we validate an alternative hypothesis, showing that DpnA plays a crucial role in the protection of internalized foreign DNA, enabling exchange of pathogenicity islands and more generally of variable regions between pneumococcal isolates. We show that transformation of a 21.7 kb heterologous region is reduced by more than 4 logs in dpnA mutant cells and provide evidence that the specific induction of dpnA during competence is critical for full protection. We suggest that the integration of a restrictase/ssDNA-methylase couplet into the competence regulon maintains protection from bacteriophage attack whilst simultaneously enabling exchange of pathogenicicy islands. This protective role of DpnA is likely to be of particular importance for pneumococcal virulence by allowing free variation of capsule serotype in DpnII strains via integration of DpnI capsule loci, contributing to the documented escape of pneumococci from capsule-based vaccines. Generally, this finding is the first evidence for a mechanism that actively promotes genetic diversity of S. pneumoniae through programmed protection and incorporation of foreign DNA.

Midcell recruitment of the DNA uptake and virulence nuclease, EndA, for pneumococcal transformation.

Genetic transformation, in which cells internalize exogenous DNA and integrate it into their chromosome, is widespread in the bacterial kingdom. It involves a specialized membrane-associated machinery for binding double-stranded (ds) DNA and uptake of single-stranded (ss) fragments. In the human pathogen Streptococcus pneumoniae, this machinery is specifically assembled at competence. The EndA nuclease, a constitutively expressed virulence factor, is recruited during competence to play the key role of converting dsDNA into ssDNA for uptake. Here we use fluorescence microscopy to show that EndA is uniformly distributed in the membrane of noncompetent cells and relocalizes at midcell during competence. This recruitment requires the dsDNA receptor ComEA. We also show that under 'static' binding conditions, i.e., in cells impaired for uptake, EndA and ComEA colocalize at midcell, together with fluorescent end-labelled dsDNA (Cy3-dsDNA). We conclude that midcell clustering of EndA reflects its recruitment to the DNA uptake machinery rather than its sequestration away from this machinery to protect transforming DNA from extensive degradation. In contrast, a fraction of ComEA molecules were located at cell poles post-competence, suggesting the pole as the site of degradation of the dsDNA receptor. In uptake-proficient cells, we used Cy3-dsDNA molecules enabling expression of a GFP fusion upon chromosomal integration to identify transformed cells as GFP producers 60-70 min after initial contact between DNA and competent cells. Recording of images since initial cell-DNA contact allowed us to look back to the uptake period for these transformed cells. Cy3-DNA foci were thus detected at the cell surface 10-11 min post-initial contact, all exclusively found at midcell, strongly suggesting that active uptake of transforming DNA takes place at this position in pneumococci. We discuss how midcell uptake could influence homology search, and the likelihood that midcell uptake is characteristic of cocci and/or the growth phase-dependency of competence.