Forearm EMG response activity during motor performance in individuals prone to increased stress reactivity

Mind over body: A neuroergonomic approach to assessing motor performance under stress in older adults

Stress impairs motor performance, which is exacerbated with age. Stress also impairs brain activity in the prefrontal cortex, which communicates with the motor areas of the brain to regulate exercise and motor performance. To develop ergogenic strategies for the aging workforce, mind (brain)-body mechanisms behind the effect of stress on neuromuscular performance need to be well understood. This study investigated the influence of social stress on motor performance and information flow between the frontal and motor regions of the brain during intermittent handgrip contractions among older adults. Thirty older adults, balanced by gender, performed intermittent handgrip contractions at 30% of maximum strength before and after being subjected to a social stressor. Force steadiness, strength loss, root mean square electromyogram (EMG) activity, activation of the brain regions, and functional and effective connectivity between the frontal and motor brain regions were computed for pre- and post-stressor handgrip contractions. Older men exhibited improved motor performance after the stressor and concomitant reduction in functional connectivity between the frontal-motor brain regions ipsilateral to the contracting hand. Additionally, while both sexes exhibited significant causal information flow, i.e., effective connectivity, from the frontal to the motor regions of the brain, irrespective of the stressor, older women exhibited a bidirectional effective connectivity between the frontal-motor brain regions after the stressor. Stress had a facilitative effect on the motor performance of older men through compensatory brain network reorganization. Older women exhibited comparable motor performance pre/post stress, despite showing an increase in bidirectional information flow between the frontal-motor areas. Employing brain hemodynamics can facilitate better understanding of the impact of stress on neuromuscular performance and its differential impacts on brain network reorganization between the sexes.

Sex-specific muscle activation and oxygenation kinetics during a repetitive forward pointing task

We compared the minute-by-minute muscle activity and oxygenation responses to a repetitive arm motion-induced fatiguing task between the sexes in order to address the literature gap on these time-dependent fatigue responses. Twenty-six (13 females) healthy adults performed a repetitive pointing task (RPT) with the arm moving forward/backward at shoulder height until reaching 8/10 (Borg CR10) for neck/shoulder perceived exertion (RPE). Neck/shoulder RPE, oxygenation and electromyography were recorded every minute and compared between first and second half of the task and between the sexes. Greater changes in oxygen supply and activation amplitude occurred during the second half of the task. Despite similar time to fatigue-terminal (p > 0.05), females showed greater anterior deltoid activation amplitude at all time points than males, and only the males showed increases in anterior and posterior deltoid activation amplitudes. In females, middle (ρ = -0.34, p = 0.04) and posterior (ρ = -0.44, p = 0.01) deltoid amplitudes were negatively correlated with perceived exertion during the first half of the task. Results suggest that reduced modulation of anterior deltoid activation amplitude in females may reflect a sub-optimal fatigue-mitigation mechanism compared with males and may help explain their greater susceptibility to neck/shoulder musculoskeletal disorders. Novelty: Despite similar fatigability and trapezius oxygenation, females showed greater deltoid activation throughout the task. Deltoid activation increased in males but not in females. The results support the important role of the deltoid in sex-specific neck/shoulder injury mechanisms.

A Methodological Framework to Capture Neuromuscular Fatigue Mechanisms Under Stress

Neuromuscular fatigue is exacerbated under stress and is characterized by shorter endurance time, greater perceived effort, lower force steadiness, and higher electromyographic activity. However, the underlying mechanisms of fatigue under stress are not well-understood. This review investigated existing methods of identifying central mechanisms of neuromuscular fatigue and the potential mechanisms of the influence of stress on neuromuscular fatigue. We found that the influence of stress on the activity of the prefrontal cortex, which are also involved in exercise regulation, may contribute to exacerbated fatigue under stress. We also found that the traditional methods involve the synchronized use of transcranial magnetic stimulation, peripheral nerve stimulation, and electromyography to identify the contribution of supraspinal fatigue, through measures such as voluntary activation, motor evoked potential, and silent period. However, these popular techniques are unable to provide information about neural alterations upstream of the descending drive that may contribute to supraspinal fatigue development. To address this gap, we propose that functional brain imaging techniques, which provide insights on activation and information flow between brain regions, need to be combined with the traditional measures of measuring central fatigue to fully understand the mechanisms behind the influence of stress on fatigue.

Important gender differences in psychosomatic and school-related complaints in relation to adolescent weight status

Underweight or overweight in adolescence is linked to several adverse health outcomes. Less evidence exists about the association between weight status and school-related psychosocial characteristics in high income countries. We sought to investigate the relationship between weight status and psychosomatic and school-related complaints with a focus on gender differences. The study is a cohort of 18,462 adolescents (12-19 years; 51% girls) conducted in Sweden. The associations between weight status and psychosomatic and school-related complaints were estimated by binary logistic regression adjusted for several potential confounders. After correction for multiple testing, being underweight or overweight/obese was adversely associated with several psychosomatic and school-related complaints with significant differences between boys and girls. Specifically, underweight boys had higher odds to have psychosomatic complaints than normal-weight boys, while no such associations were observed among underweight girls. Overweight/obese (vs. normal-weight) boys had higher odds to complain about headache, pain in the back/hips, and feeling low. Overweight/obese (vs. normal-weight) girls were more likely to complain about feeling low, anxious/worried and having difficulty in falling asleep (P ≤ 0.01). In relation to school-related complaints (e.g., being bullied at school and academic failure), greater associations were observed for overweight/obese girls and boys than for underweight adolescents compared with normal-weight peers.

A Systematic Review of EMG Applications for the Characterization of Forearm and Hand Muscle Activity during Activities of Daily Living: Results, Challenges, and Open Issues

The role of the hand is crucial for the performance of activities of daily living, thereby ensuring a full and autonomous life. Its motion is controlled by a complex musculoskeletal system of approximately 38 muscles. Therefore, measuring and interpreting the muscle activation signals that drive hand motion is of great importance in many scientific domains, such as neuroscience, rehabilitation, physiotherapy, robotics, prosthetics, and biomechanics. Electromyography (EMG) can be used to carry out the neuromuscular characterization, but it is cumbersome because of the complexity of the musculoskeletal system of the forearm and hand. This paper reviews the main studies in which EMG has been applied to characterize the muscle activity of the forearm and hand during activities of daily living, with special attention to muscle synergies, which are thought to be used by the nervous system to simplify the control of the numerous muscles by actuating them in task-relevant subgroups. The state of the art of the current results are presented, which may help to guide and foster progress in many scientific domains. Furthermore, the most important challenges and open issues are identified in order to achieve a better understanding of human hand behavior, improve rehabilitation protocols, more intuitive control of prostheses, and more realistic biomechanical models.

Tracking stress via the computer mouse? Promises and challenges of a potential behavioral stress marker

Computer mouse tracking offers a simple and cost-efficient way to gather continuous behavioral data and has mostly been utilized in psychological science to study cognitive processes. The present study extends the potential applicability of computer mouse tracking and investigates the feasibility of using computer mouse tracking for stress measurement. Drawing on first empirical results and theoretical considerations, we hypothesized that stress affects sensorimotor processes involved in mouse usage. To explore the relationship between stress and computer mouse usage, we conducted a between-participant field experiment in which N = 994 participants worked on four mouse tasks in a high-stress or low-stress condition. In the manipulation check, participants reported different stress levels between the two conditions. However, frequentist and machine learning data analysis approaches did not reveal a clear and systematic relationship between mouse usage and stress. These findings challenge the feasibility of using straightforward computer mouse tracking for generalized stress measurement.

Perfectionistic Concerns are Detrimental to Skill Learning for Minimally Invasive Surgery

BACKGROUND

The pursuit of high standards and continuous self-improvement are important aspects of a professional attitude in medicine. However, when identity and self-esteem are dependent on flawless performance, healthy striving can become perfectionism. The present study examines the influence of perfectionism on the learning process of basic instrument handling for minimally invasive surgery (MIS).

METHODS

Thirty medical students volunteered to participate in the study (19 females, 11 males). The mean age was 19.8 years (SD = 1.8). The Perfectionism Inventory was used to determine the degree of perfectionist characteristics in two main factors: Self-evaluative perfectionism and Conscientious perfectionism. Participants practiced with the loops and wire task on a surgical simulator and were tested for skill retention within 48 hours. During practice instrument movement was captured in three-dimensional space using a Leap Motion controller. Performance was assessed by time and total path length travelled by the instruments.

RESULTS

Self-evaluative perfectionism was negatively related to skill retention with regard to movement efficiency, but did not predict change in average time on task. The Conscientious perfectionism factor was not a predictor of skill retention with regard to path length or completion time.

RESULTS

Self-evaluative perfectionism was a significant predictor of change in average pathlength between sessions but did not predict change in average time. The Conscientious perfectionism factor was not a predictor of changes in path length or completion time.

CONCLUSIONS

Overly negative self-evaluation during MIS skill practice undermined the learning process. Trainees with self-critical perfectionistic tendencies may not optimally benefit from their efforts during practice.

Neuromuscular fatigue profiles depends on seat feature during long duration driving on a static simulator

Prolonged driving could induce neuromuscular fatigue and discomfort since drivers have little opportunity to adjust their position. However, better car seat design could play a major role in limiting these effects. This study compared the effect of two different seats (S - soft and F - firm) on neuromuscular fatigue and driver's perceived discomfort during prolonged driving, also assessing the effect of different road types on neuromuscular activity. Twenty participants performed two 3-h driving sessions, one for each seat, on a static simulator. Every 20 min, participants self-evaluated their level of whole-body and individual body-area discomfort. Surface electromyography (sEMG) was recorded for eight muscles including Trapezius descendens (TD), Erector spinae longissimus (ESL), Multifidus (MF), Vastus lateralis (VL) and Tibialis anterior (TA) throughout the driving sessions. Moreover, an endurance static test (EST) was performed prior to and after each driving session. Whole-body discomfort increased with time with both seats, but no difference in discomfort scores was observed between seats throughout the driving sessions. The highest discomfort scores were for neck and lower back areas with both seats. Neuromuscular fatigue was revealed by a shorter endurance time in post-driving EST for both seats. EMG recordings showed different neuromuscular fatigue profiles for the two seats, with earlier onset of fatigue for S. Despite the lack of difference in perceived discomfort level, the two seats have different impacts: the softness of S induces greater activity of the lower back muscles, while F offers greater support for the lower back.

Performance anxiety and the plasticity of emotional responses

Current psychological theories of performance anxiety focus heavily on relating performers' physiological and mental states to their abilities to maintain focus and execute learned skills. How task-specific expertise and past experiences moderate the degree to which individuals become anxious in a given performance context are not well accounted for within these theories. This review considers how individual differences arising from learning may shape the psychobiological, emotional, and cognitive processes that modulate anxious states associated with the performance of highly trained skills. Current approaches to understanding performance anxiety are presented, followed by a critique of these approaches. A connectionist model is proposed as an alternative approach to characterising performance anxiety by viewing performers' anxious states at a specific time point as jointly determined by experience-dependent plasticity, competition between motivational systems, and ongoing cognitive and somatic states. Clarifying how experience-dependent plasticity contributes to the emergence of socio-evaluative anxiety in challenging situations can not only help performers avoid developing maladaptive emotional responses, but may also provide new clues about how memories of past events and imagined future states interact with motivational processes to drive changes in emotional states and cognitive processing.

Cognitive stress changes the attributes of the three heads of the triceps brachii during muscle fatigue

INTRODUCTION

Cognitive stress (CS) changes the peripheral attributes of a muscle, but its effect on multi-head muscles has not been investigated. The objective of the current research was to investigate the impact of CS on the three heads of the triceps brachii (TB) muscle.

METHODS

Twenty-five young and healthy university students performed a triceps push-down exercise at 45% one repetition maximum (1RM) with and without CS until task failure, and the rate of fatigue (ROF), endurance time (ET) and number of repetitions (NR) for both exercises were analyzed. In addition, the first and last six repetitions of each exercise were considered non-fatiguing (NF) and fatiguing (Fa), respectively, and the root mean square (RMS), mean power frequency (MPF) and median frequency (MDF) for each exercise repetition were evaluated.

RESULTS

The lateral and long head showed significant differences (P<0.05) in the ROF between the two exercises, and all the heads showed significant (P<0.05) differences in the RMS between the two exercises under NF conditions. Only the long head showed a significant difference (P<0.05) in the MPF and MDF between the two exercises. CS increases the ET (24.74%) and NR (27%) of the exercise. The three heads showed significant differences (P<0.05) in the RMS, MPF and MDF under all exercise conditions.

CONCLUSION

A lower ROF was obtained with CS. In addition, the RMS was found to be better approximator of CS, whereas MPF and MDF were more resistant to the effect of CS. The results showed that the three heads worked independently under all conditions, and the non-synergist and synergist head pairs showed similar behavior under Fa conditions. The findings from this study provide additional insights regarding the functioning of each TB head.

Full-shift and task-specific upper extremity muscle activity among US large-herd dairy parlour workers

US large-herd dairy parlour workers experience a high prevalence of musculoskeletal symptoms in the upper extremity. The purpose of this study was to estimate and compare full-shift and task-specific muscle activity of the upper extremity among parlour workers. Surface electromyography data were recorded continuously throughout a full work shift for each participant (n = 60). For a subset of participants (n = 33), muscular effort was estimated for milking task cycles. Lower muscle activity levels and higher per cent muscular rest was observed among rotary parlour participants as compared to herringbone and parallel parlour participants for anterior deltoid, forearm flexor and forearm extensor muscles. These findings suggest rotary parlours may offer workstation designs or work organisational dynamics which may be more beneficial to the health and performance of the worker, as compared to parallel or herringbone parlours. Practitioner Summary: Study findings suggest milking parlour configurations present different biomechanical demands on workers which may influence worker health and performance. Our findings will enable more informed decisions regarding both engineering (e.g. parlour configuration or milking equipment) and administrative (e.g. work organisation) control strategies for large-herd milking parlours.

Age-specific neural strategies to maintain motor performance after an acute social stress bout

Stress due to cognitive demands and fatigue have shown to impair motor performance in older adults; however, the effect of social stress and its influence on prefrontal cortex (PFC) functioning in older adults during upper extremity motor performance tasks is not known. The present study explored the after-effects of an acute social stress bout on neural strategies, measured using PFC and hand/arm muscle activation, and adopted by younger and older adults to maintain handgrip force control. Nine older [74.1 (6.5) years; three men, six women] and ten younger [24.2 (5.0) years, four men, six women] adults performed handgrip force control trials at 30% maximum voluntary contractions before and after the Trier Social Stress Test (TSST). PFC activity was measured using functional near infrared spectroscopy and muscle activity from the flexor and extensor carpi radialis (FCR/ECR) was measured using electromyography. In general, aging was associated with decreased force steadiness and force complexity with a concomitant increase in bilateral PFC activity. While motor performance remained comparable before and after the TSST stress session in both age groups, the associated neural strategies differed between groups. While the stress condition was associated with lower FCR and ECR activity in younger adults despite no change in the PFC activation, stress was associated with increases in FCR activity in older adults. This stress-related compensatory neural strategy of increasing hand/arm muscle activation, potentially via the additional recruitment of the stress-motor neural circuitry, may have played a role in maintaining motor performance in older adults.

Objective Evaluation of Performance Stress in Musicians With Focal Hand Dystonia: A Case Series

Five musicians suffering from focal dystonia participated in a pilot study that examined the feasibility of an experimental protocol designed to assess musicians' motor performance under stress. Electrocardiography, free cortisol levels, and subjective assessments were used to monitor alterations of the hypothalamic-pituitary-adrenal axis. As measures of motor outcome, temporal variability of finger movements and muscular cocontraction of the wrist flexor and extensor were assessed. Findings suggest that the specific experimental design could be successfully applied. Several methodological issues such as carryover effects, the use of free cortisol, the inclusion of a double baseline, and the classification of dystonic patients into stress responders and nonresponders are analyzed and discussed.

Biomechanical analyses of prolonged handwriting in subjects with and without perceived discomfort

Since wrist-joint position affects finger muscle length and grip strength, we studied its biomechanical relevance in prolonged handwriting. We recruited participants from young adults, aged 18-24, and separated them into control (n=22) and in-pain (n=18) groups, based whether or not they experience pain while handwriting. The participants then performed a writing task for 30 min on a computerized system which measured their wrist-joint angle and documented their handwriting kinematics. The in-pain group perceived more soreness and had a less-extended wrist joint, longer on-paper time, and slower stroke velocity compared to control group. There was no significant difference in handwriting speed and quality between the two groups. The wrist extension angle significantly correlated with perceived soreness. Ergonomic and biomechanical analyses provide important information about the handwriting process. Knowledge of pen tip movement kinematics and wrist-joint position can help occupational therapists plan treatment for individuals with handwriting induced pain.

Interaction between physical and psychosocial risk factors on the presence of neck/shoulder symptoms and its consequences

This study aimed to quantify the interaction between physical and psychosocial factors on the presence of neck/shoulder symptoms (NSS) and its consequences (reduced activities and absenteeism) among 1294 coal mining workers in Indonesia. A self-administered questionnaire was used to obtain information on current workplace exposure and NSS and its consequences. Participants were grouped into one of four combination exposure groups: low physical and low psychosocial (as the reference group); low physical and high psychosocial; high physical and low psychosocial, and high physical and high psychosocial (HPhyHPsy). The attributable proportion (AP) due to interaction between both factors was examined. Individuals in the HPhyHPsy group were most likely to report NSS [odds ratio (OR) 4.83, 95% confidence interval (CI) 2.43-9.58], reduced activities (OR 3.90, 95% CI 2.36-6.43), and absenteeism (OR 3.91, 95% CI 2.11-7.25). This study has shown an interaction between physical and psychosocial factors that increases the OR of NSS (AP 0.49, 95% CI 0.08-0.89). Practitioner Summary: Although physical and psychosocial factors are known to be predictors for NSS, little is known about their interaction. Self-reported questionnaire was used to obtain information about physical and psychosocial factors at work. This study found an interaction between the physical and psychosocial risk factors that increases the odds ratio of NSS.

Subjective evaluation of physical and mental workload interactions across different muscle groups

Both physical and mental demands, and their interactions, have been shown to increase biomechanical loading and physiological reactivity as well as impair task performance. Because these interactions have shown to be muscle-dependent, the aim of this study was to determine the sensitivity of the NASA Task Load Index (NASA TLX) and Ratings of Perceived Exertion (RPE) to evaluate physical and mental workload during muscle-specific tasks. Twenty-four participants performed upper extremity and low back exertions at three physical workload levels in the absence and presence of a mental stressor. Outcome measures included RPE and NASA TLX (six sub-scales) ratings. The findings indicate that while both RPEs and NASA TLX ratings were sensitive to muscle-specific changes in physical demand, only an additional mental stressor and its interaction with either physical demand or muscle groups influenced the effort sub-scale and overall workload scores of the NASA TLX. While additional investigations in actual work settings are warranted, the NASA TLX shows promise in evaluating perceived workload that is sensitive not only to physical and mental demands but also sensitive in determining workload for tasks that employ different muscle groups.

The combined effect of physical, psychosocial/organisational and/or environmental risk factors on the presence of work-related musculoskeletal symptoms and its consequences

This study assessed the combined effect of physical and psychosocial/organisational and/or environmental factors on the presence of musculoskeletal symptoms (MSS) and its consequences (reduced activities and absenteeism due to MSS) in a random sample of 3003 workers in New Zealand. By telephone interview, participants reported their current workplace exposures and MSS (neck/shoulder, arm/elbow, wrist and low back) and its consequences. Data were analysed using multivariable logistic regression. Combined exposure to physical and psychosocial/organisational and/or environmental factors increased the odds of MSS in the neck/shoulder (OR 3.14, 95% CI 1.79-5.52), arms/elbow regions (OR 4.14, 95% CI 2.21-7.76) and low back (OR 1.74, 95% CI 1.28-2.37) and its consequences, i.e. reduced activities due to neck/shoulder symptoms (OR 5.45, 95% CI 2.28-13.00), absenteeism due to neck/shoulder symptoms (OR 5.19, 95% CI 2.24-12.01) and absenteeism due to low back symptoms (OR 4.37, 95% CI 2.92-6.53). In contrast, favourable psychosocial/organisational work conditions reduced the odds of wrist symptoms due to poor physical work conditions (OR 2.19, 95% CI 1.44-3.34). We conclude that to reduce MSS and its consequences, employers need to adopt a multifaceted approach: concentrate on improving physical conditions as well as the psychosocial/organisational and environmental aspects of the working environment.

Perceived distance during golf putting

This study examined the effect of anxiety states on the relationship between golf-putting distance and performance in an environment requiring high movement accuracy. Twenty-three amateur golfers attempted 15 putts at each of three putting distances, 1.25, 1.50, and 1.75m, under conditions characterized by both control demands and pressure. All attempts were recorded, and kinematic features were analyzed. Under conditions involving an audience and a monetary reward, the mean score on the State-Trait Anxiety Inventory Y-1 and the mean heart rate increased by 14 points and 11bpm, respectively. We grouped participants on an a posteriori basis using the median split. The backswing of high-anxiety performers shortened, the downswing speed declined, and the relative time to peak club-head velocity changed when putting under pressure from 1.25m. In contrast, no change in backswing or relative time to peak velocity was observed in low-anxiety performers, although impact velocity increased under this condition. These results indicate that the degree to which both low- and high-anxiety golfers were anxious about failure affected motor control at the 1.25-m distance, suggesting that a distortion in perceived distance may result from the interaction between putting distance and anxiety related to failure during golf putting.

The influence of mental load on muscle tension

We examined the differences in muscle tension and in physiological measures depending on the type of mental task. Fifteen participants performed tests for sustained attention, vigilance and maintaining posture only. We analysed electromyogram (EMG) measures of extensor digitorum (ED), flexor carpi ulnaris (FU), deltoideus (DE) and trapezius (TR), and heart rate (HR) and respiratory frequency (RF). Measures indicated higher values for mental tasks than for maintained posture only with significant differences in all measures. The following relationships were also significant: between DE and physiological measures (HR and RF), between ED and the amplitude of EMG of the other three muscles, between FU and TR and between HR and RF. The results of this study showed that the relationship between mental demands and muscle tension was mostly reflected by tension in the arm and shoulder girdle muscles and, to a lesser degree, in forearm muscles.

PRACTITIONER SUMMARY

We focused on physiological and muscle tension measures differentiating work according to the level of mental demands. Differences in sustained attention, vigilance and maintaining posture only proved that mental demands were mostly reflected by tension in arm and shoulder girdle muscles and, to a lesser degree, in forearm muscles.

A prospective study of the relationship between musculoskeletal or psychological complaints and muscular responses to standardized cognitive and motor tasks in a working population

The present study sought to determine the relationship between musculoskeletal or psychological complaints and muscular responses to standardized cognitive and motor tasks. The prospective study design examined (i) whether complaint severity predicts muscular responses during standardized tasks and (ii) whether the muscular responses predict changes in complaint severity over one year. Musculoskeletal and psychological complaints were recorded by monthly reports the four months preceding and 12 months succeeding a work session in the laboratory; complaint-severity indices were computed from complaint-severity scores (intensity scorexduration score). Surface electromyography (EMG) was recorded bilaterally from the upper trapezius, middle deltoid, and forearm extensor muscles in 45 post-office workers (30 women) during two identical task series. Between the series, exhausting submaximal muscle contractions (25% of peak torque) were performed. In adjusted regression models, no relations between musculoskeletal complaints the last four months and muscle activity during the task series were found. However, psychological complaints the last four months predicted higher muscle activity levels and a steeper rise in muscle activity in the muscles not engaged in motor task performance. Sleep disturbance was the strongest individual predictor of increased muscle responses. In contrast, psychological complaints the last four months predicted lower EMG levels in the task-engaged muscle during the complex-choice-reaction-time tasks. None of the muscle-activity responses to the standardized tasks predicted changes in severity of musculoskeletal or psychological complaints over the subsequent one-year period. In conclusion, psychological complaints predict different responses in task-engaged and non-involved muscles during cognitive and motor tasks. Musculoskeletal complaints did not predict responses to the tasks.

Gender differences in work-related risk factors associated with low back symptoms

The prevalence of low back symptoms (LBS) in many working populations is high and differences in prevalence between genders are inconsistent. However, gender-specific risk factors for LBS have seldom been examined. Hence, the aim of the present study was to indicate gender-specific LBS risk factors. A sample of 3003 people was interviewed by telephone to get information about current workplace exposure and LBS. The risk of LBS for the whole population increased with work in awkward/tiring positions (OR 1.37, 95% CI 1.12-1.68) and very/extremely stressful jobs (OR 1.46, 95% CI 1.05-2.03). None of the explanatory variables were significantly associated with LBS for males but working in awkward/tiring positions (OR 1.51, 95% CI 1.04-2.20), dissatisfaction with contact and cooperation with management (OR 1.68, 95% CI 1.02-2.78) and finding their job to be very/extremely stressful (OR 2.27, 95% CI 1.46-3.52) were significantly associated with LBS for females. Interventions to reduce LBS in workplaces should focus on reducing working in awkward/tiring positions, improving contact and cooperation with management, and reducing stressful jobs, especially amongst females.

PRACTITIONER SUMMARY

Strategies to prevent or reduce LBS should focus on reducing exposure to awkward or tiring positions at work, improving contact and cooperation with management, and reducing stressful jobs, especially for females.

Neurophysiological and Dynamical Control Principles Underlying Variable and Stereotyped Movement Patterns During Motor Skill Acquisition

While novices who are unfamiliar to a new motor skill typically show variable and unstable movements, highly skilled experts show a stable and accurate performance. These distinct differences in motor control between experts and novices have led researchers to hypothesize that neuromotor noise is reduced in the process of motor skill acquisition. On the other hand, it should be noted that novices’ movements have other characteristics; they are habituated and stereotyped. In this review, we discuss the principles governing spatiotemporal organization of movements in novices and experts while solving specific motor problems under varied conditions, by introducing experimental and theoretical studies that use neurophysiological techniques such as electromyography, functional magnetic resonance imaging, and transcranial magnetic stimulation, and mathematical models such as stochastic and dynamical models. On the basis of the findings from a variety of perceptual-motor skills (e.g., ballthrowing, badminton smash, long-distance running, piano and drum performance, street dance, a popular hand game of rock-paper-scissors, and temporal order judgement task), we argue that the novices’ characteristic movement patterns were organized under specific constraints and typical strategy, without which the variability would increase even more, while experts’ movements were organized with functional and compensatory variability that can drive out erroneous noise variability. We also showed that in a particular type of interlimb coordination, skilled and unskilled movement patterns could be seamlessly described as the time evolution of nonlinear and self-organized dynamical systems, suggesting that the dynamical systems approach is a major candidate for understanding the principle underlying organization of experts’ and novices’ movements.

Effects of physical and mental task demands on cervical and upper limb muscle activity and physiological responses during computer tasks and recovery periods

The present study examined the effects of physical and mental workload during computer tasks on muscle activity and physiological measures. Activity in cervical postural muscles and distal forearm muscles, heart rate and blood pressure were compared among three tasks and rest periods of 15 min each in an experimental study design. Fourteen healthy pain-free adults participated (7 males, mean age = 23.2 ± 3.0 years) and the tasks were: (1) copy-typing ("typing"), (2) typing at progressively faster speed ("pacing"), (3) mental arithmetic plus fast typing ("subtraction"). Typing task was performed first, followed by the other two tasks in a random order. Median muscle activity (50th percentile) was examined in 5-min intervals during each task and each rest period, and statistically significant differences in the "time" factor (within task) and time × task factors was found in bilateral cervical erector spinae and upper trapezius muscles. In contrast, distal forearm muscle activity did not show any significant differences among three tasks. All muscles showed reduced activity to about the baseline level within first 5 min of the rest periods. Heart rate and blood pressure showed significant differences during tasks compared to baseline, and diastolic pressure was significantly higher in the subtraction than pacing task. The results suggest that cervical postural muscles had higher reactivity than forearm muscles to high mental workload tasks, and cervical muscles were also more reactive to tasks with high physical demand compared to high mental workload. Heart rate and blood pressure seemed to respond similarly to high physical and mental workloads.

Effect of tryptophan-rich egg protein hydrolysate on brain tryptophan availability, stress and performance

BACKGROUND & AIMS

Reduced brain serotonin function is involved in stress-related disturbances and may particularly occur under chronic stress. Although serotonin production directly depends on the availability of its plasma dietary amino acid precursor tryptophan (TRP), previously described effects of tryptophan-rich food sources on stress-related behavior are rather modest. Recently, an egg protein hydrolysate (EPH) was developed that showed a much greater effect on brain TRP availability than pure TRP and other TRP-food sources and therefore may be more effective for performance under stress. The aim of the present study was to investigate the effects of EPH compared to placebo protein on plasma amino acids, stress coping and performance in subjects with high and low chronic stress vulnerabilities.

METHODS

In a placebo-controlled, double-blind, crossover study, 17 participants with high and 18 participants with low chronic stress vulnerabilities were monitored for mood and performance under acute stress exposure either following intake of EPH or placebo.

RESULTS

EPH significantly increased plasma TRP availability for uptake into the brain, decreased depressive mood in all subjects and improved perceptual-motor and vigilance performance only in low chronic stress-vulnerable subjects.

CONCLUSIONS

The acute use of a TRP-rich egg protein hydrolysate (EPH) is an adequate method to increase plasma TRP for uptake into the brain and may be beneficial for perceptual-motor and vigilance performance in healthy volunteers.

Participation during major technological change and low back pain

The development of IT involves major changes in many work settings. Theories of organizational change predict negative consequences of change-related work load on back pain to be less when employees participate in the planning and implementation of change. In a longitudinal field study the effects of participation in the introduction of a new internet service were tested. 29 employees (16 f, 13 m) of a municipal office were studied before, at the end of, and 6 months after implementation of an electronic service. Their participation in the planning and implementation of the project, psychosocial working conditions and back pain were assessed using standardized validated questions. 15 employees said that they had no influence on the project or were only informed of it, while 14 employees said that they could make suggestions, or even take part in decision-making. The two groups did not differ in experience of back pain six months before the project was started, but the group with low participation possibilities had significantly more back pain after the implementation of the project (p=0.021). There was no change in back pain in those employees who had sufficient possibilities of participation. Prevention of work related back pain during phases of technological change should involve employees in planning and implementation.

Music performance anxiety in skilled pianists: effects of social-evaluative performance situation on subjective, autonomic, and electromyographic reactions

Music performance anxiety (MPA), or stage fright in music performance, is a serious problem for many musicians, because performance impairment accompanied by MPA can threaten their career. The present study sought to clarify on how a social-evaluative performance situation affects subjective, autonomic, and motor stress responses in pianists. Measurements of subjective state anxiety, heart rate (HR), sweat rate (SR), and electromyographic (EMG) activity of upper extremity muscles were obtained while 18 skilled pianists performed a solo piano piece(s) of their choice under stressful (competition) and non-stressful (rehearsal) conditions. Participants reported greater anxiety in the competition condition, which confirmed the effectiveness of stress manipulation. The HR and SR considerably increased from the rehearsal to competition condition reflecting the activation of sympathetic division of the autonomic nervous system. Furthermore, participants showed higher levels of the EMG magnitude of proximal muscles (biceps brachii and upper trapezius) and the co-contraction of antagonistic muscles in the forearm (extensor digitorum communis and flexor digitorum superficialis) in the competition condition. Although these responses can be interpreted as integral components of an adaptive biological system that creates a state of motor readiness in an unstable or unpredictable environment, they can adversely influence pianists by disrupting their fine motor control on stage and by increasing the risk of playing-related musculoskeletal disorders.

Yoga ameliorates performance anxiety and mood disturbance in young professional musicians

Yoga and meditation can alleviate stress, anxiety, mood disturbance, and musculoskeletal problems, and can enhance cognitive and physical performance. Professional musicians experience high levels of stress, performance anxiety, and debilitating performance-related musculoskeletal disorders (PRMDs). The goal of this controlled study was to evaluate the benefits of yoga and meditation for musicians. Young adult professional musicians who volunteered to participate in a 2-month program of yoga and meditation were randomized to a yoga lifestyle intervention group (n = 15) or to a group practicing yoga and meditation only (n = 15). Additional musicians were recruited to a no-practice control group (n = 15). Both yoga groups attended three Kripalu Yoga or meditation classes each week. The yoga lifestyle group also experienced weekly group practice and discussion sessions as part of their more immersive treatment. All participants completed baseline and end-program self-report questionnaires that evaluated music performance anxiety, mood, PRMDs, perceived stress, and sleep quality; many participants later completed a 1-year followup assessment using the same questionnaires. Both yoga groups showed a trend towards less music performance anxiety and significantly less general anxiety/tension, depression, and anger at end-program relative to controls, but showed no changes in PRMDs, stress, or sleep. Similar results in the two yoga groups, despite psychosocial differences in their interventions, suggest that the yoga and meditation techniques themselves may have mediated the improvements. Our results suggest that yoga and meditation techniques can reduce performance anxiety and mood disturbance in young professional musicians.

Physiological and psychological reactions to work in men and women with identical job tasks

Differences in physiological functioning in the hypothalamus-pituitary-adrenal cortex axis and the autonomic nervous system have been suggested to contribute to many of the health differences that may be observed between men and women as well as being relevant for the development of musculoskeletal pain. To clarify whether men and women with identical work tasks reacted differently when doing work known to induce musculoskeletal pain, ratings and physiological measurements were obtained at work start (15:30) and at the end of the workshift (22:30) on 17 men and 20 women. Men showed a larger decrease in perceived energy levels during the workshift but there were no differences between men and women as regards cortisol, adrenaline, noradrenaline, heart-rate activation, perceived stress, pain and physical exertion. In conclusion, differential physiological activation during the workshift seem to be an unlikely mechanism for explaining gender differences in pain associated with exposure to awkward and repetitive movements.

The effect of forearm posture on wrist flexion in computer workers with chronic upper extremity musculoskeletal disorders

Background

Occupational computer use has been associated with upper extremity musculoskeletal disorders (UEMSDs), but the etiology and pathophysiology of some of these disorders are poorly understood. Various theories attribute the symptoms to biomechanical and/or psychosocial stressors. The results of several clinical studies suggest that elevated antagonist muscle tension may be a biomechanical stress factor. Affected computer users often exhibit limited wrist range of motion, particularly wrist flexion, which has been attributed to increased extensor muscle tension, rather than to pain symptoms. Recreational or domestic activities requiring extremes of wrist flexion may produce injurious stress on the wrist joint and muscles, the symptoms of which are then exacerbated by computer use. As these activities may involve a variety of forearm postures, we examined whether changes in forearm posture have an effect on pain reports during wrist flexion, or whether pain would have a limiting effect on flexion angle.

Methods

We measured maximum active wrist flexion using a goniometer with the forearm supported in the prone, neutral, and supine postures. Data was obtained from 5 subjects with UEMSDs attributed to computer use and from 13 control subjects.

Results

The UEMSD group exhibited significantly restricted wrist flexion compared to the control group in both wrists at all forearm postures with the exception of the non-dominant wrist with the forearm prone. In both groups, maximum active wrist flexion decreased at the supine forearm posture compared to the prone posture. No UEMSD subjects reported an increase in pain symptoms during testing.

Conclusion

The UEMSD group exhibited reduced wrist flexion compared to controls that did not appear to be pain related. A supine forearm posture reduced wrist flexion in both groups, but the reduction was approximately 100% greater in the UEMSD group. The effect of a supine forearm posture on wrist flexion is consistent with known biomechanical changes in the distal extensor carpi ulnaris tendon that occur with forearm supination. We infer from these results that wrist extensor muscle passive tension may be elevated in UEMSD subjects compared to controls, particularly in the extensor carpi ulnaris muscle. Measuring wrist flexion at the supine forearm posture may highlight flexion restrictions that are not otherwise apparent.

Thinking activates EMG in scalp electrical recordings

OBJECTIVE

Fast electrical rhythms in the gamma range (30-100Hz) in scalp (but not intracranial) recordings are predominantly due to electromyographic (EMG) activity. We hypothesized that increased EMG activity would be augmented by mental tasks in proportion to task difficulty and the requirement of these tasks for motor or visuo-motor output.

METHODS

EEG was recorded in 98 subjects whilst performing cognitive tasks and analysed to generate power spectra. In four other subjects, neuromuscular blockade was achieved pharmacologically providing EMG-free spectra of EEG at rest and during mental tasks.

RESULTS

In comparison to the paralysed condition, power of scalp electrical recordings in the gamma range varied in distribution, being maximal adjacent to cranial or cervical musculature. There were non-significant changes in mean gamma range activity due to mental tasks in paralysed subjects. In normal subjects, increases in scalp electrical activity were observed during tasks, without relationship to task difficulty, but with tasks involving limb- or eye-movement having higher power.

CONCLUSIONS

Electrical rhythms in the gamma frequency range recorded from the scalp are inducible by mental activity and are largely due to EMG un-related to cognitive effort. EMG varies with requirements for somatic or ocular movement more than task difficulty.

SIGNIFICANCE

Severe restrictions exist on utilizing scalp recordings for high frequency EEG.

Effects of a vertical keyboard design on typing performance, user comfort and muscle tension

To circumvent the awkward pronated hand position inherent to conventional horizontal keyboards, a vertical, split keyboard was designed with flexible cushions supporting the wrists, allowing relaxed hand and arm postures. During eight twice-weekly 30-min training sessions, the performance and subjective comfort of nine experienced typists were tested. Typing speed and error percentage, and surface electromyographic activity of six forearm muscles and two postural muscles were recorded in separate sessions at the end of each week. Typing speed rapidly recovered to the preset rate of 300 keystrokes/min and error percentages were similar for the two keyboards. The vertical keyboard caused lower muscular activity in especially finger extensor muscles, did not increase postural muscle activity, and self-reported comfort was higher. Thus, the vertical keyboard was easily mastered, was experienced as comfortable, and caused less stress on muscles sensitive to repetitive strain injuries.

The effects of shoulder load and pinch force on electromyographic activity and blood flow in the forearm during a pinch task

The object of the current study was to determine whether static contraction of proximal musculature has an effect on the blood flow more distally in the upper extremity. Static contractions of muscles in the neck shoulder region at three levels (relaxed, shoulders elevated and shoulders elevated loaded with 4.95 kg each) were combined with intermittent pinch forces at 0, 10 and 25% of the maximum voluntary contraction (MVC). Blood flow to the forearm was measured with Doppler ultrasound. Myoelectric activity of the forearm and neck-shoulder muscles was recorded to check for the workload levels. Across all levels of shoulder load, blood flow increased significantly with increasing pinch force (21% at 10% MVC and by 44% at 25% MVC). Blood flow was significantly affected by shoulder load, with the lowest blood flow at the highest shoulder load. Interactions of pinch force and shoulder load were not significant. The myoelectric activity of forearm muscles increased with increasing pinch force. The activation of the trapezius muscle decreased with increasing pinch force and increased with increasing shoulder load. The precise mechanisms accounting for the influence of shoulder load remains unclear. The results of this study indicate that shoulder load might influence blood flow to the forearm.

Epidemiology of work related neck and upper limb problems: psychosocial and personal risk factors (part I) and effective interventions from a bio behavioural perspective (part II)

Work related neck and upper limb symptoms have a multi-factorial origin. Possible risk factors are of a physical, psychosocial or personal origin. These factors can reinforce each other and their influence can also be mediated by cultural or societal factors. Initially, most research on neck and upper limb symptoms focused on work-related physical exposure. Nowadays, psychosocial work characteristics are recognized as important risk factors. Various models have been developed to offer frameworks for possible pathways, but their empirical support is still not conclusive. In part I of this paper an overview is presented of the results of recent epidemiological studies on work related psychosocial and personal risk factors for neck and upper limb symptoms. In addition, the interplay between these factors and the possible intermediate role of an individuals work style in this process is explored. In contrast to previous reviews, it is now possible to base the conclusions on the effect of work related psychosocial factors on neck and upper limb symptoms on quite a few longitudinal studies. These studies show that high work demands or little control at work are often related to these symptoms. However, this relationship is neither very strong nor very specific. Perceived stress is studied in not as many studies but more consistently related to neck and upper limb symptoms. This also applies to general distress or other pain (co-morbidity). Job dissatisfaction does not contribute to neck and upper limb symptoms. Too little research on personal characteristics is available to draw any conclusions. It is plausible that behavioural aspects, such as work style, are of importance in the etiology of work related upper limb symptoms. However, studies concerning these factors are promising but too scarce to draw conclusions. Future studies should address these behavioural aspects. In part II, the recent studies on the effectiveness of preventive measures for work related neck and upper limb problems are discussed. Few randomised or non randomised controlled trials have been carried out to evaluate the effectiveness of individual or organisational interventions to improve work related psychosocial factors. Very few have reported on the preventive effect for work related neck and upper limb symptoms. Therefore, there is a great need for additional high quality trials before any conclusions on effectiveness of bio-behavioural interventions for reduction of neck and upper limb problems and return to work after these symptoms can be made. From the low back pain intervention research can be learned that interventions should best be targeted to both the worker and the organisation and that interventions will only be successful when all stakeholders are involved.

Pathophysiology of upper extremity muscle disorders

A review of the literature on the pathophysiology of upper extremity muscle disorders (UEMDs) was performed. An overview is given of clinical findings and hypotheses on the pathogenesis of UEMDs. The literature indicates that disorders of muscle cells and limitations of the local circulation underlie UEMDs. However, these disorders identified do not necessarily lead to symptoms. The following mechanisms have been proposed in the literature: (1) selective recruitment and overloading of type I (Cinderella) motor units; (2) intra-cellular Ca(2+) accumulation; (3) impaired blood flow; (3b) reperfusion injury; (3.3c) blood vessel-nociceptor interaction; (4a) myofascial force transmission; (4b) intramuscular shear forces; (5) trigger points; (6) impaired heat shock response. The results of the review indicate that there are multiple possible mechanisms, but none of the hypotheses forms a complete explanation and is sufficiently supported by empirical data. Overall, the literature indicates that: (1) sustained muscle activity, especially of type I motor units, may be a primary cause of UEMDs; (2) in UEMDs skeletal muscle may show changes in morphology, blood flow, and muscle activity; (3) accumulation of Ca(2+) in the sarcoplasm may be the cause of muscle cell damage; (4) it seems plausible that suboptimal blood flow plays a role in pathogenesis of UEMDs; (5) since the presence of fiber disorders is not a sufficient condition for the development of UEMSDs additional mechanisms, such as sensitization, are assumed to play a role.

Differential effects of mental load on proximal and distal arm muscle activity

Work-related upper extremity disorders (WRUEDs) that result from keyboarding tasks are prevalent and costly. Although the precise mechanisms causing the disorder are not yet fully understood, several risk factors have been proposed. These include the repetitive nature of the motor task and the associated sustained static working postures, but also more psychological factors such as mental load. Epidemiological surveys have shown that WRUEDs are more prone to develop in the postural muscles of the neck/shoulder area than in the executive muscles controlling the hand. The present study investigated whether the activation patterns of these two muscle types are differentially affected by an additional mental load during the performance of a repetitive tapping task. Participants tapped various keying patterns with their dominant index finger at two prescribed tempi. Mental load was manipulated by means of an auditory short-term memory task. We recorded the EMG activity of two neck/shoulder muscles (trapezius and deltoid), two upper arm muscles (biceps and triceps), and four forearm muscles (flexor digitorum superficialis, extensor digitorum, extensor carpi radialis longus and extensor carpi ulnaris) and analyzed the kinematics and impact forces of the index finger. The results confirmed that the upper limb has two functions. Specifically, activity of the executive distal musculature was increased during tapping at the higher pace, while the activity of the postural upper limb musculature was elevated due to the memory task. We argue that continuously increased muscular activity can lead to fatigue and thus eventually cause musculoskeletal complaints. The results are discussed with respect to biomechanical adaptation strategies that deal with the consequences of increased noise in the neuromotor system due to enhanced mental processing.

Muscular co-contraction covaries with task load to control the flow of motion in fine motor tasks

This study focuses on the relationship between movement-time fluctuations in fine motor tasks and changing levels of muscular co-contraction. Based on a recent neuromotor noise theory, we expected that increased task stress would increase muscular co-contraction and prolong movement times. Ten right-handed adults performed a graphic task, which elicited local movement-time prolongations. In half the trials, a distracting sound was presented as an external stressor. Besides pen-tip kinematics, two estimates of muscular co-contraction were obtained from the surface EMG measurements of eight arm and hand muscles. The results confirm the presumed co-variation of movement time and co-contraction. We conclude that muscular co-contraction forms a strategic means to adapt the flow of motion to central information processing demands.

The form of augmented force-feedback fields and the efficiency and satisfaction in computer-aided pointing tasks

This study investigates operation efficiency and user satisfaction for spatial and temporal shapes of augmented force-feedback fields to be used with computer pointing devices in target acquisition tasks. In an experiment, three different force-field shapes at two different mean force levels were compared, with an electromechanical force-feedback trackball as control device and with efficiency and user satisfaction as dependent variables. Efficiency was measured by the time required to perform a certain task, and user satisfaction was measured through a subjective rating procedure. Satisfaction results indicate that to a rough approximation, participants can be grouped into those who prefer high and those who prefer low force levels. Members of the former group were most satisfied with force fields with a gradual start and an abrupt ending. This force-field shape also proved to be the most efficient for both groups. When all participants were considered as a single group, none of the effects was found to be statistically significant. A gender effect was also found; in both preference groups women achieved significantly shorter task completion times than men. Actual or potential applications of this research include enabling computer interaction for people prone to repetitive strain injuries and the increment of efficiency and satisfaction in human-computer interaction in general.

Group Training with Healthy Computing Practices to Prevent Repetitive Strain Injury (RSI): A Preliminary Study

This pilot study investigated whether group training, in which participants become role models and coaches, would reduce discomfort as compared to a nontreatment Control Group. Sixteen experimental participants participated in 6 weekly 2-hr group sessions of a Healthy Computing program whereas 12 control participants received no training. None of the participants reported symptoms to their supervisors nor were they receiving medical treatment for repetitive strain injury prior to the program. The program included training in ergonomic principles, psychophysiological awareness and control, sEMG practice at the workstation, and coaching coworkers. Using two-tailed t tests to analyze the data, the Experimental Group reported (1) a significant overall reduction in most body symptoms as compared to the Control Group and (2) a significant increase in positive work-style habits, such as taking breaks at the computer, as compared to the Control Group. This study suggests that employees could possibly improve health and work style patterns based on a holistic training program delivered in a group format followed by individual practice.

Effect of Preparation on Dual-Task Performance in Postural Control

The authors applied an overlapping-task design to study the interaction between postural control and cognitive task processes in young (n = 10) and older (n = 10) adults. A rapid destabilizing floor translation was followed at specific time intervals by a simple auditory reaction time (RT) task. The translations were preceded by either an informational cue or no cue. Interference between postural task demands and the RT task was found only in the first 50 ms. Cueing also had an effect on both the onset of the postural recovery response and RT performance. The results suggest (a) only a brief interference between postural and cognitive processing demands in relatively easy tasks, (b) competition for a common central mechanism, possibly a response-selection mechanism, and (c) no differential impact of aging on that interaction.

Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks

The objective of the present study was to gain insight into the effects of precision demands and mental pressure on the load of the upper extremity. Two computer mouse tasks were used: an aiming and a tracking task. Upper extremity loading was operationalized as the myo-electric activity of the wrist flexor and extensor and of the trapezius descendens muscles and the applied grip- and click-forces on the computer mouse. Performance measures, reflecting the accuracy in both tasks and the clicking rate in the aiming task, indicated that the levels of the independent variables resulted in distinguishable levels of accuracy and work pace. Precision demands had a small effect on upper extremity loading with a significant increase in the EMG-amplitudes (21%) of the wrist flexors during the aiming tasks. Precision had large effects on performance. Mental pressure had substantial effects on EMG-amplitudes with an increase of 22% in the trapezius when tracking and increases of 41% in the trapezius and 45% and 140% in the wrist extensors and flexors, respectively, when aiming. During aiming, grip- and click-forces increased by 51% and 40% respectively. Mental pressure had small effects on accuracy but large effects on tempo during aiming. Precision demands and mental pressure in aiming and tracking tasks with a computer mouse were found to coincide with increased muscle activity in some upper extremity muscles and increased force exertion on the computer mouse. Mental pressure caused significant effects on these parameters more often than precision demands. Precision and mental pressure were found to have effects on performance, with precision effects being significant for all performance measures studied and mental pressure effects for some of them. The results of this study suggest that precision demands and mental pressure increase upper extremity load, with mental pressure effects being larger than precision effects. The possible role of precision demands as an indirect mental stressor in working conditions is discussed.

Patients suffering from nonspecific work-related upper extremity disorders exhibit insufficient movement strategies

The purpose of this research was to investigate whether patients experiencing nonspecific complaints of the forearm caused by sustained use of the personal computer exhibit deviant movement strategies as compared to healthy participants. Patients (N=10) and controls (N=24) performed a graphical aiming task combined with an auditory memory task. Force production (pen pressure), kinematic- and performance variables were recorded. During a trial, the control group gradually increased pen pressure from the stationary phases to the dynamic phase. The patients increased their pen pressure much more abruptly and to such a degree that the final pressure during real-time movement far exceeded that of the controls. Memory load led to a greater increase of pen pressure from the stationary phase to the dynamic phase in the patient group. Patients further displayed longer reaction times. The results are discussed within the framework of our recent theory on the role of neuromotor noise in the regulation of task performance under conditions of stress.

Biobehavioral Mechanisms of Work-Related Upper Extremity Disorders. Proceedings of a symposium. 6-7 November 2000, Washington, DC, USA

BACKGROUND

Epidemiological studies provide support for the role of organizational and individual psychosocial stressors in work-related upper extremity disorders (WRUEDs). Despite this evidence, the biological plausibility of a relationship between exposure to various psychosocial and work organizational stressors and WRUEDs remains unclear

METHODS

The Georgetown Symposium on Biobehavioral Mechanisms of Work-Related Upper Extremity Disorders was held in Washington D.C. on November 6-7, 2000 to improve the understanding of potential biobehavioral mechanisms, identify future areas for research and discuss the implications of this body of knowledge for intervention. This meeting involved presentations and discussions by researchers and clinicians from a number of disciplines (epidemiology, occupational medicine, rheumatology, orthopedics, surgery, internal medicine, psychoneuroimmunology, occupational health psychology, behavioral medicine, psychophysiology and experimental and organizational psychology).

RESULTS

The symposium generated several papers addressing the following topics: definitions and job stress models; epidemiological foundations; musculoskeletal and biomechanical models; central nervous system models of recurrent and persistent clinical pain; psychophysiology of work; and implications for intervention. These papers comprise this special issue.

DISCUSSION

The present paper summarizes the various contributions to this special issue and provides direction for future research on potential biobehavioral pathways.