Effects of a ball-backrest chair on the muscles associated with upper crossed syndrome when working at a VDT

This study examined the effect of a ball-backrest chair on the weakness and tightness of muscles associated with upper crossed syndrome when working at a visual display terminal (VDT). The surface electromyography (EMG) was recorded from the serratus anterior, middle trapezius, and upper trapezius muscles of 20 adults as they performed VDT work, which are known as the weakened and tightened muscles of upper crossed syndrome. The recorded signals were averaged and normalized to the mean amplitude of the EMG signal obtained during submaximal reference voluntary contractions. The significance of differences between the use of a general-purpose backrest and a ball backrest was tested by paired t-test, with the significance cutoff set at alpha=0.05. The activities of the serratus anterior and middle trapezius muscles increased and that of the upper trapezius muscle decreased when sitting in a ball-backrest chair compared to when sitting in a chair with a general-purpose backrest (p<0.05). These results indicate that the use of a ball-backrest chair reduces the risk of patients with upper crossed syndrome developing muscles soreness or injury related to overuse when working at a VDT.     

Temporal aspects of increases in eye-neck activation levels during visually deficient near work

In an experimental study two levels of oculomotor load were induced via optical trial lenses. Trapezius muscle activity was measured with bipolar surface electromyography and normalized to a submaximal contraction. Sixty-six subjects with a median age of 36 (range 19-47, std 8) viewed a black and white Gabor grating (5 c/deg) for two 7-min periods monocularly through a 0 D lens or binocularly through -3.5 D lenses. The effect of time was separately regressed to EMG in two different subgroups of responders: a High-Oculomotor-Load (HOL) and a Low-Oculomotor-Load (LOL) group. A linear regression model was fitted on group level with exposure time on the x-axis and normalized trapezius muscle EMG (%RVE) on the y-axis. The slope coefficient was significantly positive in the -D blur condition for only the HOL subgroup of responders: 0.926 + Time(min 1-7) × 0.088 (p = 0.002, r(2)=0.865). There was no obvious sign of this activity to level off or to stabilize. These results suggest that professional information technology users that are exposed to a high level of oculomotor load, during extended times, are at an increased risk of exhibiting an increased trap.m. activity.     

Stationarity test of electromyographic signals during isokinetic trunk exertions

The aim of this study is to investigate the stationarity of the electromyographic (EMG) signals during isokinetic exertions of the trunk muscle. Six healthy subjects participated in this study. The erector spinae muscles were used to collect the signals. In order to simulate the isokinetic exercises of the trunk, a Cybex system with a trunk modular component was used. All subjects performed sustained exertions with a combination of load (25%, 50% MVC) and angular velocity (0, 15, 30 degree/s). The stationarity of the signals was tested by the reverse arrangements test and modified reverse arrangements test. In the results, the signal stationarity was high in all conditions in the reverse arrangements test. However, in the modified reverse arrangements test it was relatively low at about the 30 degree/s angular velocity. In the analysis of variance, the effect of angular velocity was statistically significant at the 0.05 significance level in the modified reverse arrangements test and Tukey's HSD grouping showed that the stationarity of 30 degree/s angular velocity was significantly different from 0, 15 degree/s condition. These results indicate that the stationarity of the EMG signals showed no difference between isometric and isokinetic conditions when the angular velocity was equal to 15 degree/s.     

Principle component analysis of exposure variation analysis during computer work at presence of delayed onset muscle soreness

Eleven healthy volunteers took part in three sessions where computer work was performed for 10 min in each session. The recordings were made on two consecutive days. After the first session, the subjects underwent a series of high intensity eccentric exercises of shoulder elevation to induce muscle soreness. The second session was performed immediately after the exercises and third session 24 hours after the exercise. Surface electromyography (EMG) of descending and ascending trapezius, deltoideus anterior and serratus anterior was recorded. Exposure variation analysis (EVA) centroid and marginal distribution was computed. Principle component analysis (PCA) was performed on both cases. Describing more than 80% of variance, first eight components for EVA marginal distributions and first four ones for EVA centroid were picked to be investigated. The sole EVA amplitude levels played a practically significant role to describe the variation in EVA marginal distribution. However, a significant pattern of load redistribution to superficial muscles was not found. This may suggest investigating the role of deep muscles in redistribution of load during computer work in response to high level eccentric contractions.     

The effect of Video Display Terminal (VDT) mouse use on muscle contractions in the neck and forearm

This study used surface electromyography (EMG) to examine the percent of maximum voluntary contraction (%MVC) of the upper trapezius, the flexors of the wrist/fingers and extensors of the wrist/fingers during Video Display Terminal (VDT) mouse use with the mouse positioned either next to the computer or on a lapdesk. Thirty participants, between the ages of 18 and 40, used a VDT mouse to follow a prescribed pattern for three trials at each location. Although there was a trend towards the lapdesk location producing lower %MVC than the computer location for the trapezius and wrist/finger flexors (lapdesk: trapezius M 4.71%, wrist/finger flexors M 3.53%; computer: trapezius M 5.74%, wrist/finger flexors M 3.94%) a two way ANOVA controlling for sequence and order found no significant difference between the means. There was no trend for the effects of location for the wrist/finger extensors. These results suggest that changing the position of the mouse may not significantly reduce muscle contractions.     

Level of self-reported neck/shoulder pain and biomechanical workload in cleaners

The aim of the present study was to investigate the relation between self-reported pain, muscular activity and postural load during cleaning tasks. Eighteen cleaners performed usual cleaning tasks in both a laboratory and a lecture room. The level of perceived pain in the neck-shoulder region during the last 7 days was recorded. Bipolar surface electromyography (SEMG) was recorded bilaterally from upper trapezius and erector spinae muscles during cleaning. Root mean square (RMS) and permutation entropy (PE) values representing amplitude and complexity of SEMG time-series were estimated. A tri-axial accelerometer package was mounted on the low back (L5-S1) to measure postural changes during cleaning tasks. The 10th, 50th and 90th percentiles of the angular distributions were computed to characterize postures and movements. Pain tended to play a significant role on RMS of left/right trapezius and left erector spinae muscles (P≤0.08). Cleaners with low pain level exhibited higher muscular activity during cleaning. Pain played or tended to play a significant role on PE of left and right erector spinae muscles (P≤0.08). Pain played a significant role on the 10th, 50th and 90th percentile (P<0.05) of lateral flexion angle (side bending). The present study emphasizes biomechanical adaptations occurring in presence of neck-shoulder pain during cleaning tasks.     

Spatially Specific Changes in Infants' Muscle Coactivity as They Learn to Reach

Infants first reach out and touch objects between the ages of 3 and 5 months. This article reports changes in muscle coactivity associated with this transition. A group of 4 infants were observed weekly from 3 to 30 weeks and every 2 weeks from 30 to 52 weeks. Hand kinematics of both prereaching and reaching movements were collected, as was electromyographic activity from the trapezius, deltoid, biceps, and triceps. Before infants first reached for toys presented at midline, they used biceps and triceps to move their hands near the toy in front of them and 45° to the side of midline. After the transition, they used trapezius and deltoid to move the hand toward the toy and combinations of multiple muscles when their arms were high and extended near the toy. Thus, infants showed a dramatic change in which muscles worked together across the transition to reaching, even though their hands moved in similar spatial regions.     

Reliability of normalisation methods for EMG analysis of neck muscles

Acceptable reliability of normalisation contractions in electromyography (EMG) is paramount for testing conducted over a number of days or if normal laboratory strength testing equipment is unavailable. This study examined the reliability of maximal voluntary isometric contractions (MVIC) and sub-maximal (60%) isometric contractions for use in neck muscle EMG studies. Surface EMG was recorded bilaterally from eight sites around the neck at C4/5 level from five healthy male subjects. Subjects performed MVIC and sub-maximal normalisation contractions using an isokinetic dynamometer (ID) and a portable cable dynamometer with attached strain gauge (PCD) in addition to a MVIC against a manual resistance (MR). Subjects were tested in flexion, extension, left and right lateral bending and were retested by the same tester within a two-week period. Intra class correlation co-efficients (ICC) were calculated for each testing method and contraction direction and a mean ICC was calculated across all contraction directions. All normalisation methods produced excellent within-day reliability (mean ICC >0.80) but only the MVICs using the ID and PCD had acceptable reliability when assessed between-days. This study confirmed the validity of using MVICs elicited using the ID and PCD as reliable reference contractions for the normalisation of neck EMG.     

Developing a framework for assessing muscle effort and postures during computer work in the field: the effect of computer activities on neck/shoulder muscle effort and postures

The present study, a part of the PROOF (PRedicting Occupational biomechanics in OFfice workers) study, aimed to determine whether trapezius muscle effort was different across computer activities in a field study of computer workers, and also investigated whether head and shoulder postures were different across computer activities. One hundred twenty participants were measured continuously for two hours each while performing their own computer work. Keyboard activities were associated with the highest intensity of left and right trapezius muscle efforts, and mouse activities were associated with the smallest variability in left and right trapezius muscle efforts. Corresponding trends in head and shoulder postures included that the greatest head flexion and left and right shoulder internal rotation was observed during keyboard activities, and that the smallest variability in head flexion, head lateral tilt, and right shoulder internal rotation was observed during mouse activities. Identifying which muscle efforts and postures are different across computer activities is the first essential step for developing prediction rules for muscle efforts and postures, which can be used to link muscle efforts and postures to musculoskeletal symptoms in epidemiological studies.     

Multiple Lenses

ABSTRACT

Cross-cultural contacts between child welfare practitioners and client families must be examined for sensitivity to race and ethnicity. However, these contacts also occur in the context of the differences in role and power inherent in involuntary transactions and often involve difficulties with use of drugs or alcohol. Using a case example, this article applies overlapping lenses to help understand this complicated context Each lens broadens the view and sharpens the focus on what is happening and how to act to help.     

Correlation between pelvic floor strength and physical activity level in healthy men

The male pelvic floor muscles comprise a pair of compound muscle layers referred to as the levator ani. Studies have shown that pelvic floor muscle strength is affected by physical activity. This study aimed to assess male pelvic floor muscle strength through manometry of the external anal sphincter and evaluation of its association with physical activity level, BMI, and rectal pressure in healthy men. To assess physical activity level over the previous week, we used the International Physical Activity Questionnaire 8 (IPAQ). Pelvic floor muscle strength was assessed via anorectal manometry. The results shows a negative correlation between resting pressure and MET, a positive correlation between rectal pressure and resting and maximum pressure. The novel finding of this study is a negative correlation between walking and pelvic floor strength. This study raises new questions about the understanding of the interaction among physical activity, intraabdominal pressure, and pelvic floor strength in the physiology of continence in men.     

The influence of an abdominal support for a dental stool in the distributions and electrical activity of the longissimus and the superior trapezius muscle in dentists

This study evaluated the influence an abdominal support attached to a traditional stool, of those used by dentists, has on the body's distribution of the electrical activity of the superior trapezius and the longissimus thoracic muscles of dental students during the execution of a clinical procedure. The results showed no significant difference in the body's distribution in the seat and backrest, but did reveal there was a weight discharge of 3.1 ± 1.9% of dentist's body weight in the abdominal support. The 9 o'clock position proved to be the best position to perform clinical procedures. It was also observed that the position was closer to the body's axis.     

Visual ergonomics interventions in mail sorting facilities

This study was performed between 2004 and 2011 at mail sorting facilities in Sweden. During this time, different interventions were performed. The first was a lighting intervention that had a positive impact on the postal workers, especially those with eyestrain. A new lighting system also improved the illuminance and gave better light distribution. The second intervention involved new personal spectacles for the postal workers who needed them and this had a positive effect on eyestrain. The third intervention involved a specific type of sorting spectacles for the postal workers who already used progressive lenses privately. The reading distances that the postal workers had while sorting the mail was inverted to the distances in their regular progressive lenses. The new sorting spectacles had a positive effect on head postures and on muscular activity.     

TIME PREFERENCE AND THE DISTRIBUTIONS OF WEALTH AND INCOME

This paper examines the connection between time preference heterogeneity and economic inequality in a deterministic environment. Specifically, we extend the standard neoclassical growth model to allow for (1) heterogeneity in consumers' discount rates, (2) direct preferences for wealth, and (3) human capital formation. The second feature prevents the wealth distribution from collapsing into a degenerate distribution. The third feature generates a strong positive correlation between earnings and capital income across consumers. A calibrated version of the model is able to generate patterns of wealth and income inequality that are very similar to those observed in the United States. (JEL D31, E21, O15)     

Red light,green light: Color priming in financial decisions

Colors are widely present in the financial decision making arena: at firms’ and data providers’ websites; television reports; newspaper publications; advertizements; security market displays, with colors such as red and green prominently employed. Our experimental analysis involves a between subject design exposing subjects to financial substance on colored backgrounds and exploring the effect on their investment decisions. We focus on financial decisions under uncertainty about probability, examining subjects’ investment valuations and the probabilities they assign to the possible outcomes.This study explores the role of color exposure as a priming factor in financial decision making. Priming is a process of activating particular connections or associations in memory prior to carrying out an action or task. The associations occur when a certain stimulus or event increases the availability of specific information categories and, as a result, affect decision making.The results indicate that red color priming emphasizes value losses of the underlying asset. To wit, subjects who were exposed to red (R) assigned higher valuations and probabilities to events involving the loss domain, than to events involving the gain domain, relatively to the valuations assigned by subjects who were exposed to green (G). The aggregated evaluation given by the R subjects when the investment payback was subject to negative (positive) underlying asset returns was higher (lower) than that of the G subjects by roughly 15% (19%) of the invested amount.     

An analysis of the encoding and decoding of spontaneous and posed smiles: The use of facial electromyography

Twenty subjects judged 80 video segments containing brief episodes of smiling behavior for expression intensity and happiness of the stimulus person. The video records were produced under instructions to (a) pose, (b) experience a happy feeling or (c) to both experience and show a happy feeling. An analysis of the integrated facial electromyogram (EMG), recorded over four muscle regions (zygomaticus major, depressor anguli oris, corrugator supercilii, andmasseter), showed that judgments of happiness and of intensity of expression could be predicted in a multiple regression analysis (multipleR = .64 for perceived happiness and .79 for perceived expression intensity). The perception of happiness was affected by EMG activity in regions other thanzygomaticus major. The use of parameters other than the mean of the integrated EMG, namely variance, skewness, kurtosis and properties of the amplitude distributions across time, provided accurate classification of the elicitation conditions (pose happiness versus experience happiness) in a discriminant analysis. For the discrimination of posed and felt smiles variables describing aspects of facial activity in the temporal domain were more useful than any of the other measures. It is suggested that facial EMG can be a useful tool in the analysis of both the encoding and decoding of expressive behavior. The results indicate the advantage of using multiple-site EMG recordings as well as of using amplitude and temporal characteristics of the facial EMG measures.The research was supported in part by funds associated with the John Sloan Dickey Third Century Professorship (Kleck) and in part by grant BNS-8507600 from the National Science Foundation (Lanzetta). Ursula Hess and Arvid Kappas were supported by stipends from the Deutscher Akademischer Austauschdienst (German Academic Exchange Service).     

Establishing a mutual reality.

Nursing stories are a vehicle for sharing the uniqueness of the nurse-patient relationship. In this article, a nurse-patient engagement within an acute mental health inpatient unit is described and viewed through various lenses. Consideration is given to literature on reflective thinking. Each lens lends itself to exploring the reflective thinking that occurred for the author. The author's personal perspective on an ethic of care is presented.     

Does traffic noise alter calling time in frogs and toads? A case study of anurans in Eastern Ontario,Canada

In habitats disturbed by anthropogenic noise, acoustically communicating species may develop behavioral responses that help them transmit information and overcome signal masking. We studied four anuran species breeding in wetlands, ponds, and ditches near a highway in eastern Ontario, Canada, to test whether they called more often when traffic noise intensity was lower, and stopped calling when the noise intensity increased (i.e., gap calling behavior). We made call recordings between April and July 2011, and compared the traffic noise intensity (sound pressure level) between times when the anurans were calling and times when they were not calling. We found that the two species with the highest call peak frequency (American toad, gray treefrog) called randomly with regard to traffic noise intensity. In contrast, the two species with the lowest call peak frequency (green frog, bullfrog) called more often when traffic noise intensity was low. The behavioral response in the two latter species likely represents a short-term strategy that enhances their signal-to-noise ratio thereby increasing the chance of effective communication. Our results support predictions derived from the acoustic adaptation hypothesis: low-frequency signals are more prone to be masked by anthropogenic noise and therefore require behavioral adjustments (in this study gap-calling behavior) to ameliorate this effect.     

Stair-ascent performance in elderly women: effect of explosive strength training

Explosive-type strength training may alter kinetics and neuromuscular activity during stair ascent in elderly women. This may improve functional ability. Nineteen women (69.7 ± 3.4 yr) were randomly allocated to strength training (TG; twice per wk, 12 wk) or a control group (CG). Stair ascent was assessed at self-chosen (AFV), standardized (ASV), and maximal velocity (AMV) pre- and posttraining. Ground-reaction force (GRF) and EMG quantified kinetics and neuromuscular activity. After training, TG increased AMV and AFV velocity by 8% (p = .02) and 17% (p= .007), respectively (TG vs. CG; p< .05). This was accompanied by elevated rectus femoris EMG (from 21% to 48%, p< .047). At AFV, TG increased GRF first peak force 4% (p= .047), and CG increased second peak force 5% (p = .036). Muscle coactivation remained unaltered in both groups. Explosive-type strength training led to enhanced stair-climbing performance at maximal and self-chosen speed, reflecting an improved functional ability.     

Mere religiosity is not enough! Spirituality strengthens the relations between religiosity and positive youth development

Although prior research shows that either religiosity or spirituality facilitates well-being, the interaction of both constructs in predicting positive youth development (PYD) in collectivistic contexts remains unknown. This study examined the moderating role of spirituality on the link between religiosity and PYD, including each of its Cs (i.e., competence, confidence, connection, character, and caring) among 1116 Filipino adolescents. Results demonstrate that both religiosity and spirituality are positively correlated with PYD and its dimensions. Furthermore, there is a significant interaction between religiosity and spirituality for the overall PYD construct and the socio-emotional Cs (i.e., connection, character, and caring). This study highlights the importance of young people's sense of connection with something beyond than themselves (i.e., spirituality) in promoting adolescent thriving.