The effects of backpack load carrying on dynamic balance as measured by limits of stability

PURPOSE: The purpose of this research was to determine if standing dynamic balance was affected by carrying a backpack. SUBJECTS: Data was obtained from 50 healthy college students. MATERIALS AND METHODS: Limits of stability was assessed using the Smart Equitest Balance Master System(R). Reaction time, movement velocity, end point excursion, maximum excursion, and directional control were measured to evaluate movement, with and without a loaded backpack. DATA ANALYSIS: Reliability was established using an Intra-Class Correlation Coefficient (2,1). MANOVA was utilized to analyze the effect of the backpack. SUMMARY DATA: Movement velocity significantly decreased during backpack loaded trials (p=0.004). Directional control was significantly different with respect to direction (p=0.006). No significant difference in reaction time, maximum excursion, or end point excursion was observed with backpack loading (p=0.10-0.93). CONCLUSION: This study concludes that backpack load carrying has an effect on movement velocity and directional control.     

Designing an ergonomics backpack for student aged 7-9 with user centred design approach

Researches explored that backpacks are the most common means of carrying school supplies for students. Carrying heavy backpacks causes a wide range of disorders such as musculoskeletal disorders and postural malfunction. User Centered Design has proven its suitability to produce high efficient products with the most adaptability to consumer demands. This approach combined with consideration of normal standards and ergonomics features, with the recognition of children's needs and requirements, has been used in this research to prepare an initial design of a backpack. After that, its prototype was manufactured. The backpack was tested by 120 elementary students in three steps of form, ergonomics and load sense. A redesign was performed that has applied the results of the test run. Results showed that this new backpack can considerably reduce the effective loads on the shoulders, back and neck.     

Assessment of cognitive workload of in-vehicle systems using a visual peripheral and tactile detection task setting

The increase of driver information and infotainment systems includes also interaction technologies like speech interaction that minimize visual-manual demand and put the focus to cognitive demand. The question is whether this could lead to distraction effects and decreased traffic safety. This study presents an evaluation method for cognitive demand based on different detection paradigms in a dual task setting. A listening and a backward counting task are realized on three difficulty levels as simulations of cognitively loading secondary tasks and investigated using a visual versus a tactile detection paradigm. The results show that both detection paradigms are able to discriminate the task levels and that subjects successfully apply compensation strategies in the dual task setting especially during the listening task.     

Effectiveness of a school-based backpack health promotion program: Backpack Intelligence

A prominent school health issue in the United States is the use of backpacks, however, there is a paucity of literature on the effectiveness of backpack safety programs. The purpose of this paper is to describe a school-based backpack health promotion program: Backpack Intelligence, report on its effectiveness, and suggest avenues for future research. Three-hundred-seventy-two 6th and 7th grade students participated in the program which was integrated into their physical education curriculum. Of those students, 242 completed post-education surveys to assess its effectiveness. Pre-education, 44% reported that their backpack was uncomfortable to carry, and 61% reported two or more warning signs that their backpack was too heavy. Only 57% wore their backpack properly and less than half organized the contents in their backpack correctly. Post-education, 63% reported the program worthwhile. Forty-two percent changed the way they used their backpack, and 93% felt knowledgeable about backpack safety, a 24% increase. Both grade and gender differences were found. Areas identified in the literature as fruitful for future research were suggested. Until we have definitive research on the link between backpack use and injury, interventions may be imperfect, but as a society we are compelled to safeguard the health of our children.     

Biomechanical analysis of loading/unloading a ladder on a truck

Loading/unloading a ladder on vehicles are frequent tasks and involve overhead handling that may expose workers to risk factors of shoulder musculoskeletal disorders. The objective of the present study was to evaluate posture, forces required and perceived exertion when loading and unloading the ladder on a utility truck. Thirteen male overhead line workers from an electric utility in Brazil participated in this study. Shoulder elevation angle was measured using inclinometers. The required force to load/unload the ladder was measured by dynamometer. Subjective assessment of the perceived exertion was recorded to compare the exertion reported during the test conditions to the field conditions. The task of loading/unloading the ladder presented risks of shoulder musculoskeletal disorders (MSDs) to workers because it requires high levels of force (approximately 60% of the maximal force) combined with overhead posture of the shoulders (more than 100° from the neutral posture). Age and height presented to interfere in biomechanical risks presented in load/unload task. There was no significant difference between the subjective exertion during the test conditions and handling the ladder in the field. Ergonomic intervention is recommended to reduce these risks for shoulder MSDs.     

Carrying loads and postural sway in standing: the effect of load placement and magnitude

This study investigated the effect that load magnitude, load location, and the dimensions that the base of support have on postural sway in standing while wearing a backpack, single strapped bag, briefcase, or purse. Subjects were instructed to carry a load of 10% or 20% of their body weight with either their feet spaced shoulder width apart or together for a period of 45 seconds. Medial/lateral and anterior/posterior center of pressure (COP) displacement and COP velocity were calculated. Overall, it was found that an increase in load magnitude produced an increase in postural sway and velocity of COP. In addition, a large increase in the medial/lateral COP velocity was observed when subjects carried a briefcase, single strapped bag, or purse. Additionally, a larger COP sway was recorded in conditions of standing with decreased base of support (feet together). These findings suggest the importance of considering the way we carry loads in order not only to place less strain on the body and to minimize our efforts, but to optimize postural control as well.     

The effects of back belts and load on selected lifting kinematics during a simulated patient transfer

This study used two dimensional biomechanical analysis to examine the effects of back belts and lifting load on selected lifting kinematics during a simulated patient transfer. A human manikin placed in a sitting position was attached to a customized lifting apparatus which controlled the lifting load and direction of the manikin. Eighteen female participants, between the age of 21 and 27, completed six lifts (sit to stand transfers) of the manikin. Three lifts were completed at the 30 lb load condition (no belt, belt 1 and belt 2) and three lifts were completed at the 50 lb load condition (no belt, belt 1 and belt 2). A doubly two way ANOVA found a significant main effect for the belt condition, F(12,6)=10.06, P=0.002. There was no significant effect for load and no interaction existed between belt and load. The results revealed a significant decrease in trunk flexion when participants wore the wider (nine inch) belt during the 30~lb lifts when compared to the no belt trials. No significant differences were found in trunk flexion means with the narrower width (six inch) belt. No significant differences were found in trunk spinal flexion with either belt condition during the 50 lb lifts. There were no significant differences found in either of the belts in the means of lifting time, knee flexion, elbow flexion, forward displacement of the lifter's center of mass, and the lifter's maximum center of mass velocity. The results suggest that wider back belts may be more effective at reducing spinal flexion during patient lifting under moderate load conditions when compared to narrower back belts and to no-belted controls.     

Investigating the effects of physical and cognitive demands on the quality of performance under different pacing levels

The study was undertaken to investigate the effects of pacing on aspects of performance at an assembly task and on the operators' responses related to work behaviour, perceived workload and perceived stress. A particular objective of the study was to investigate whether physical and cognitive demands may interact in their influences on these effects. An assembly task was simulated in the laboratory and the level of pacing imposed, work height and memory load within the task were all varied. The results showed that the type of pacing commonly imposed (as is common with a lean manufacturing Takt time system in industry) can significantly affect both performance and perceived workload and stress. Physical demands (through work height affecting posture) and mental demand (through memory load) were also found to have significant effects, as would be expected from the many studies of these in the literature. More importantly, some interactions were found between pacing and work height in their effects on quality of assembly and the operator's own rating of performance, and between work height and memory load in their effects on errors. These findings will need to be taken into account by companies when implementing Takt time systems.     

Contribution of mental workload to job stress in industrial workers

This study's central objective is to determine how several individual, organizational and ergonomic factors influence the relationship between job stress and mental workload for workers in an electronics company. A cross-sectional study was made as a test of hypotheses regarding that relationship. The sample is composed of 95 workers, of both sexes, from the electronics industry in the metropolitan zone of Guadalajara, Jalisco, Mexico. Ergonomic conditions were evaluated with the Ergonomic Evaluation List, stress was evaluated by administering the SWS-Survey to groups of subjects, and mental workload was evaluated with the NASA-TLX Workload Index. Using Cochran's and Mantel-Haenzsel statistics, the odds ratio for each of the independent variables was {e}stimated as a risk factor for job stress, and analysis was later conducted by means of logistic regression for those risks found to be significant. Of the 95 worker participants, 26.3% presented a high level of job stress and 17.9% of the workers were found to present high levels of mental workload. The results show that working hours, mental demand, temporal demand, and frustration when faced with a given task may be considered risk factors for job stress.     

Effects of Cognitive Demand and Judgment Strategy on Person Perception Accuracy

The present study examined the effects of cognitive demand and judgment strategy in performance on the Interpersonal Perception Task (Costanzo & Archer, 1989). The Interpersonal Perception Task (IPT) contains 30 brief, real-life scenes on videotape for which there are objectively correct answers to questions about status, intimacy, kinship, competition, and deception. A total of 142 participants were run in a 2 (high vs. low cognitive demand) × 2 (first impression vs. nonverbal cues strategy) × 2 (audiovisual vs. visual only modality) design. A significant Cognitive Demand × Judgment Strategy interaction supported the hypothesized benefit of a first impression strategy when participants experienced high, rather than low, cognitive demand. In contrast, participants receiving the nonverbal cues strategy had higher accuracy under low, rather than high, cognitive demand. The conditional effects of cognitive demand on person perception are considered and the larger role of cognitive resources in interaction is discussed.     

Brain Electrical Activity Associated With Cognitive Processing During a Looking Version of the A‐Not‐B Task

This work was designed to investigate individual differences in brain electrical activity during a looking version of the A‐not‐B task. It was proposed that this spatial task required the cognitive skills of working memory and inhibitory control, each associated with frontal lobe function. Electroencephalograms (EEGs) were recorded from 54 8‐month‐old infants during baseline and task. Only high performers on the looking task exhibited increases in 6‐ to 9‐Hz EEG power from baseline to task. These task‐related changes were evident at frontal and posterior scalp locations. High performers on the looking task exhibited lower EEG coherence values at right hemisphere frontal locations relative to the low performers. These lower coherence values were evident during baseline and task. All infants showed increased frontal‐parietal coherence during the spatial working memory task relative to baseline values. These data confirm previous cognitive neuroscience work associating frontal lobe function with cognitive performance levels during infancy.     

Does transformational leadership predict group emotional intelligence in work settings? / ¿Es el liderazgo transformacional un predictor de la inteligencia emocional grupal en los contextos laborales?

Contagion of emotions is a widely accepted characteristic of transformational leaders. However, the impact they may have on the Emotional Intelligence of their subordinates is an open question. In this paper, we analyse whether Transformational Leadership (LTF) perceptions influence the Emotional Intelligence of their groups (GEI). This is a novel approach within the actual interest on emotional intelligence and its role in group results. The participants were 272 subordinates from 52 groups that belonged to different private and public organizations in Spain. They completed a questionnaire including the variables of interest. Our study helps to clarify the relations between TFL perceptions and GEI, showing that TFL and GEI relate at the group level and that TFL is one of the predictors of the perception of GEI in work settings. Thus, the development of emotionally competent transformational leaders will produce emotionally competent groups that might increase their performance, efficiency and other processes (i.e., engagement).     

Power Eliminates the Influence of Body Posture on Facial Emotion Recognition

We investigated how power priming affects facial emotion recognition in the context of body postures conveying the same or different emotion. Facial emotions are usually recognized better when the face is presented with a congruent body posture, and recognized worse when the body posture is incongruent. In our study, we primed participants to either low, high, or neutral power prior to their performance in a facial-emotion categorization task in which faces were presented together with a congruent or incongruent body posture. Facial emotion recognition in high-power participants was not affected by body posture. In contrast, low-power and neutral-power participants were significantly affected by the congruence of facial and body emotions. Specifically, these participants displayed better facial emotion recognition when the body posture was congruent, and worse performance when the body posture was incongruent. In a following task, we trained the same participants to categorize two sets of novel checkerboard stimuli and then engaged them in a recognition test involving compounds of these stimuli. High, low, and neutral-power participants all showed a strong congruence effect for compound checkerboard stimuli. We discuss our results with reference to the literature on power and social perception.     

The effect of task differences,attention and personality on the frequency of body-focused hand movements

A hypothesized relationship between apparently irrelevant self or object manipulatory hand movements and attentional demand was investigated by observing the frequency of these hand movements during the performance of three tasks: a monologue, mental arithmetic, and rest. The attentional demand of each task was assessed by means of a simultaneous reaction time probe task. The monologue task had both the highest frequency of hand movements and the highest level of attentional demand. However, correlations between these measures were not significant for any of the tasks. The influence of the task differences on movement frequencies was much greater than the effect of individual differences. Correlations of trait anxiety and field dependence measures with movement frequencies varied markedly with task differences. The nature and significance of these movements is considered by reference to similar observations in nonhuman species.     

Global healthy backpack initiatives

Schoolbag use by children is a global common concern.. Children carry school books and other amenities in their school bags. Global evidence indicates that daily load carried by school children may have negative health implications. Backpack as a school bag model, is the healthiest way of load carriage for school children. Several initiatives have been launched world over to minimize unhealthy consequences resulting from schoolbags. Based on a situation analysis, Sri Lanka implemented a national healthy schoolbag campaign by joint efforts of Ministries of Health and Education. Actions were contemplated on; strategies for bag weight reduction, introduction of an ergonomically modeled schoolbag and bag behaviour change. New strategies were introduced with awareness campaigns to policy makers, bag manufacturers, parents, teachers and children. Four million schoolchildren benefitted. In 2000, the backpack strategy of "Pack it Light, Wear it Right" was started as a public health initiative in the United States by the American Occupational Therapy Association (AOTA). Over the last eleven years, thousands of occupational therapy practitioners and students participated in educational programs and outreach activities. In 2004, modeled after the success AOTA initiative, the Icelandic Occupational Therapy Association launched a national backpack awareness initiative. This article shares examples of practices that could be implemented in any context to the promote health of children.     

Examining the impact of age and multitasking on motorcycle conspicuity

This poster presents a study to assess one's ability to detect motorcycles under different conditions of conspicuity while performing a secondary visual load task. Previous research in which participants were required to detect motorcycles revealed differences in age (young adults/older adult) as well as differences associated with motorcycle conspicuity conditions. Past research has specifically found motorcycles with headlights ON and modulating headlights (flashing) to be more conspicuous than motorcycles with headlights OFF within traffic conditions. The present study seeks to provide more information on the effects of multitasking on motorcycle conspicuity and safety. The current study seeks to determine the degree to which multitasking limits the conspicuity of a motorcycle within traffic. We expect our results will indicate main effects for distraction task, age, gender, motorcycle lighting conditions, and vehicular DRLs on one's ability to effectively detect a motorcycle. The results have implications for motorcycle safety in general and through this research, a better understanding of motorcycle conspicuity can be established so as to minimize the risk involved with motorcycle operation.     

Effect of Sexual Arousal on Cortical Coupling During Performance of the Tower of Hanoi Task in Young Men

Sexual arousal affects cognitive processing, which depends on the coordinated functioning among cortical areas. The aim of this research was to determine whether previous observation of videos with sexual content affects the degree of cortical electroencephalographic (EEG) coupling during performance of an executive task. Cortical EEG correlations were calculated in three groups of heterosexual men under three conditions: at rest; during observation of a video with neutral, aggressive, or erotic content; and while performing the Tower of Hanoi task (TOH). Based on self-reports, it was shown that the erotic video induced general and sexual arousal, while the aggressive video affected valence and general arousal. Task performance was similar in all three groups. During performance of TOH, only the erotic group showed a decreased correlation between prefrontal areas with an increased correlation between parietal and prefrontotemporal areas, specifically in the slow bands. It is likely that these changes in the degree of cortical coupling could be associated with the cognitive strategies or functional adaptations that participants require to adequately solve the task during a state of sexual arousal. These data could contribute to improving our understanding of the central nervous mechanisms that underlie the effect of sexual arousal on the cognitive processes involved in tasks like TOH.     

It does (not) get better: Reference income violation and altruism

We experimentally test whether the gap between reference and actual income impacts subsequent altruism. Participants first perform a real-effort task for a fixed wage and then play a dictator game. Between conditions, we vary the level and the timing of the revelation of the wage. In some conditions, participants know the wage before the real effort task and are not informed of the other potential levels. In some other conditions, they are informed of the distribution of wages before the real effort task, but the actual wage is only revealed afterward. Participants in the latter conditions can form references that may be higher or lower than their actual wage. Our hypothesis is that the gap between the reference and the actual wage impacts transfers in the subsequent dictator game, either because participants want to compensate their recent losses, or because of the emotional reaction to gains and losses. The results support this hypothesis: participants who get the low wage transfer less and are less likely to transfer when they are informed of the other potential levels than when they are not. Conversely, participants who get the high wage are more likely to transfer positive amounts when they are informed of the other potential levels. We use physiological (skin conductance response) and declarative data to discuss the role of emotions in our treatment effects.     

Analyzing Web pages visual scanpaths: between and within tasks variability

In this paper, we propose a new method for comparing scanpaths in a bottom-up approach, and a test of the scanpath theory. To do so, we conducted a laboratory experiment in which 113 participants were invited to accomplish a set of tasks on two different websites. For each site, they had to perform two tasks that had to be repeated ounce. The data were analyzed using a procedure similar to the one used by Duchowski et al. [8]. The first step was to automatically identify, then label, AOIs with the mean-shift clustering procedure [19]. Then, scanpaths were compared two by two with a modified version of the string-edit method, which take into account the order of AOIs visualizations [2]. Our results show that scanpaths variability between tasks but within participants seems to be lower than the variability within task for a given participant. In other words participants seem to be more coherent when they perform different tasks, than when they repeat the same tasks. In addition, participants view more of the same AOI when they perform a different task on the same Web page than when they repeated the same task. These results are quite different from what predicts the scanpath theory.     

An Implementation of Protocol Analysis and the Silent Dog Method in the Area of Behavioral Safety

Recent research has demonstrated that conducting safety observations increases the safety performance of the observer. The purpose of this study was to help determine whether observers make self-verbalizations regarding their own safety performance and whether these reports are functionally related to safety performance. In order to answer these questions two experiments were conducted using both protocol analysis and the silent dog method. The objective of Experiment 1 was (a) to determine whether safety performance with continuous, concurrent talk-aloud procedures is functionally equivalent to safety performance without talk-aloud reports, and (b) to determine whether that safety performance is altered when participants are presented with a distracter task. The goal of Experiment 2 was to determine whether the safety-related verbalizations made by Experiment 1 participants were task-relevant and functionally related to safety performance. The results from both Experiments 1 and 2 provide support for the existence of a functional relationship between safety-related verbalizations and increases in safety performance.