Comparison between static maximal force and handbrake pulling force

The measurement of maximum pulling force is important not only for specifying force limit of industrial workers but also for designing controls requiring high force. This paper presents a comparison between maximal static handbrake pulling force (FST) and force exerted during normal handbrake pulling task (FDY). These forces were measured for different handle locations and subject characteristics. Participants were asked to pull a handbrake on an adjustable car mock-up as they would do when parking their own car, then to exert a force as high as possible on the pulled handbrake. Hand pulling forces were measured using a six-axes force sensor. 5 fixed handbrake positions were tested as well as a neutral handbrake position defined by the subject. FST and FDY were significantly correlated. Both were found to be dependent on handbrake position, age and gender. As expected, women and older subjects exerted lower forces. FST was significantly higher than FDY. The ratio FmR (FDY divided by FST) was also analyzed. Women showed higher FmR than men meaning that the task required a higher amount of muscle capability for women. FmR was also influenced by handbrake location. These data will be useful for handbrake design.     

Quantification of hand grasp force using a pressure mapping system

The goal of this study was to use a pressure sensor to measure the force distribution and contact area of the hand when gripping, pushing, and pulling a cylinder. Data was collected from 10 subjects with no hand impairments and from 1 subject with rheumatoid arthritis (RA). Subjects grasped an aluminum cylinder wrapped with a Tekscan pressure sensor and performed each trial at 25%, 50%, and 100% maximum voluntary exertion. A relationship was found between increasing exertion and increasing hand area with increasing hand contact area. The force distribution maps showed the thenar region of the hand exerts the most force during pushing while the metacarpal joint line exerts the highest force during pulling. The third and fourth phalange were found to exert the highest phalange force during gripping. The force distribution maps from the RA subject showed higher thumb forces and distal phalange forces, relative to the entire phalange, compared to the non-impaired subjects. This suggests that the RA subject compensates for the lack of phalange function with the regions of the hand that still function. Future studies should sample individuals with a larger hand area range and sample more individuals with RA.     

Effects of pushing height on trunk posture and trunk muscle activity when a cart suddenly starts or stops moving

Unexpected sudden (un)loading of the trunk may induce inadequate responses of trunk muscles and uncontrolled trunk motion. These unexpected perturbations may occur in pushing tasks, when the cart suddenly starts moving (unloading) or is blocked by an obstacle (loading). In pushing, handle height affects the user's working posture, which may influence trunk muscle activity and trunk movement in response to the perturbation. Eleven healthy male subjects pushed a 200 kg cart with handles at shoulder and hip height in a start condition (sudden release of brakes) and a stop condition (bumping into an obstacle). Before the perturbation, the baseline of the trunk inclination, internal moment and trunk extensor muscle activity were significantly higher when pushing at hip height than at shoulder height. After the perturbation, the changes in trunk inclination and internal moment were significantly larger when pushing at shoulder height than at hip height in both conditions. The opposite directions of changes in trunk inclination and internal moment suggest that the unexpected perturbations caused uncontrolled trunk motion. Pushing at shoulder height may impose a high risk of low-back injury due to the low trunk stiffness and large involuntary trunk motion occurring after carts suddenly move or stop.     

The evaluation of team lifting on physical work demands and workload in ironworkers

Lifting and carrying heavy loads occur frequently among ironworkers and result in high prevalence and incidence rates of low back complaints, injuries and work-disability. From a health perspective, little information is available on the effect of team lifting on work demands and workload. Therefore, the objective of this study was to compare the effects of team lifting of maximally 50 kg by two ironworkers (T50) with team lifting of maximally 100 kg by four ironworkers (T100). This study combined a field and laboratory study with the following outcome measures: duration and frequency of tasks and activities, energetic workload, perceived discomfort and maximal compression forces (Fc peak) on the low back. The physical work demands and workload of an individual iron worker during manual handling of rebar materials of 100 kg with four workers did not differ from the manual handling of rebar materials of 50 kg with two workers, with the exception of low back discomfort and Fc peak. The biomechanical workload of the low back exceeded for both T50 and T100 the NIOSH threshold limit of 3400N. Therefore, mechanical transport or other effective design solutions should be considered to reduce the biomechanical workload of the low back and the accompanying health risks among iron workers.     

Finnish Seniors’ Move to a Senior House: Examining the Push and Pull Factors

The purpose of this article is to explore the factors influencing residential decisions of Finnish seniors. Analysis draws on qualitative data gathered from in-depth interviews and open-ended survey questions completed by 37 seniors living in three independent living facilities in Finland. Content analysis was used to identify key factors pushing residents out of their former living situations and pulling them into their respective independent living facility. Analysis indicates that different senior houses attract different types of residents. Nevertheless, as a group, they reported similar motivational factors relating to community, physical, and social environments and to their personal circumstances.     

Near-Misses and Stop Buttons in Slot Machine Play: An Investigation of How They Affect Players,and May Foster Erroneous Cognitions

In modern casinos, multiline slot machines are becoming increasingly popular compared to traditional, three-reel slot machines. A paucity of research has examined how the unique presentation of near-misses and the use of a stop button in multiline slot machines impact erroneous cognitions related to the perception of skill and agency during play. Our goal therefore was to determine the prevalence of erroneous cognitions pertaining to near-miss outcomes and the usage of a stop button and then to see whether the stop button affected players’ experiences of winning, losing and near-miss outcomes. We recruited 132 gamblers from a casino in Ontario. They played two versions of a slot machine simulator: one with a stop button and one without a stop button. We measured player’s arousal [skin conductance responses (SCRs), pressure on the spin-button), and behavioural responses (post-reinforcement pauses (PRPs)] to wins, losses and near-misses during play. We predicted more robust physiological SCRs and longer PRPs to wins in the stop button game. We also predicted that near-misses encountered in the stop button game would trigger greater levels of arousal and frustration in players, as indexed by larger SCRs, and greater force applied to the spin button to initiate the next spin. Erroneous cognitions pertaining to the stop button and near-misses respectively were assessed following play. Results showed that a small but meaningful percentage of players held erroneous cognitions about the stop button (13.6%) and near-misses (16%). Players depressed the spin button harder, and had larger SCRs for all outcomes when using the stop button. Players also paused longer for near-misses in the game involving the stop button. Our findings converge to suggest that the stop button encourages an erroneous perception of skill in some players, and consequentially impacts how such players perceive their outcomes in multiline slot machines.     

Race/Ethnicity and Stop‐and‐Frisk: Past,Present, Future

Scholarly debates surrounding stop‐and‐frisk typically assess the effectiveness and lawfulness of stop‐and‐frisk. Notwithstanding these efforts, recent reviews have excluded some recent research that addresses its impact on racial and ethnic immigrants. Understanding how the practice of stop‐and‐frisk affects racial and ethnic immigrants is worth including in reviews of these policies, considering the recent growth of research involving crime and immigrants that largely finds that immigration does not result in higher levels of crime. This review includes recent work showing that overall enforcement – stops and arrests – is higher in immigrant communities despite their lower levels of criminal involvement and recent work exploring differences among first‐generation and second‐generation immigrants in perceptions of police stops. Finally, some suggestions for the future of stop‐and‐frisk research are considered.     

Perseveration in Tool Use: A Window for Understanding the Dynamics of the Action‐Selection Process

Two experiments investigated how 3‐year‐old children select a tool to perform a manual task, with a focus on their perseverative parameter choices for the various relationships involved in handling a tool: the actor‐to‐tool relation and the tool‐to‐target relation (topology). The first study concerned the parameter value for the tool‐to‐target relation by asking how children use a cane for either pushing an object further away (exclosure; outside the hook) or pulling an object nearby (enclosure; inside the hook). The second study concerned the parameter value for the hand‐to‐tool relation by assessing the hand used for grasping a spoon to feed a puppet. Results from both studies showed that on the first trial, choices were driven by task information. However, when the task switched from pulling to pushing or from left hand to right hand, or vice versa, children persevered with the choice they made during the 4 previous trials. Results are discussed in terms of the dynamical field modeling work of Esther Thelen and her colleagues. Our findings underscore Thelen's hypotheses that: (a) the action‐selection process is a dynamic affair, affected by multiple influences at different time scales and its own intrinsic dynamics; and (b) that perseverative behavior is a general phenomenon that is neither indicative for a specific period in the development, nor for a particular task. Similarly, we argue that the presence (or absence) of causal understanding emerges from the action‐selection process, rather than determining this process.     

Impact of lightweight and conventional jackhammers on the operator

Jackhammer manufacturers have recently developed lightweight (45-60 lbs) jackhammers intended to reduce the required lifting and pushing forces during operation. However, the vibration characteristics of the lightweight jackhammers and their effect on muscle activity are currently unknown. The objective of this study was to compare the measured vibration and muscle activity between: (i) conventional (90 lb) and light weight (60 lb) jackhammers, (ii) different pavement type/thickness combinations, and (iii) pneumatic and hydraulic jackhammers. Five jackhammers were tested on 4 and 6 inch thick asphalt and concrete pavements by four experienced operators. Analysis of the results revealed that both weight classes averaged 9.7 m/s(2) at the 20 Hz weighted 1/3 octave band frequency, and the TLV of daily exposure for either weight class of jackhammer was less than 1.5 hours/per day. There was an approximately 33% difference in vibration measured on the hand of the operators due to pavement thickness, 30% due pavement type, and no difference due to power source. Conventional jackhammers overall produced higher muscle activity than lightweight jackhammers. Although selection of the correct jackhammer for the job involves many factors including pavement type and thickness, the results of this research can be used to assist in selecting the appropriate jackhammer.     

Early retirement differences between Denmark and The Netherlands: A cross-national comparison of push and pull factors in two small European welfare states

The goal of this study is to give a comprehensive empirical account of push and pull factors, situated at various societal levels, which may influence people's early retirement. Factors in two contrasting European countries have been analysed and compared: Denmark, where the rate of early exit/retirement is relatively low, and The Netherlands, where this rate is relatively high. Our analysis, looking into possible explanations for the difference in rates, includes factors that operate at the macro or institutional level of the labour market and the social security system, at the meso level of firms and companies, and at the micro level of individual workers. In addition, we not only look into the effects of structural, objective factors, which impacts are usually analysed from an incentive perspective, but also into the effects of cultural factors, i.e. of preferences, attitudes and values. Cultural factors related to early exit have not been the object of much international comparison thus far, although their possible significance is readily acknowledged. The differences in retirement behaviour in Denmark and The Netherlands are explained by the fact that Danish workers, at all three levels, are less experiencing structural and cultural factors pushing them out of the labour market, as well as experiencing factors pulling them into retirement, compared to workers in The Netherlands.     

Physical variation in low-load work - physiological effects during exposure & recovery

Trends in industry are leaning towards jobs that are more stereotyped at lower workloads. Physical variation is a potential ergonomic intervention. However, little is known of physiological response to different kinds of variation. To investigate this issue, three kinds of isometric contraction patterns with the same mean amplitude, cycle time, and duty cycle were compared. Fatigue responses were measured by multiple biomechanical and physiological approaches. In exercise, sustained and intermittent contractions with zero force had a greater number of statistically significant differences in fatigue responses. Intermittent contractions with amplitude ? and 1? of mean force had effects intermediate but close to the sustained contraction. In recovery, sustained contractions led to decreased twitch forces 24 hours post-exercise whereas both intermittent contractions recovered within 60 minutes. This suggests that time varying forces, even without complete muscular rest, may be a useful intervention to reduce local and perceived fatigue in workers performing low-load tasks.     

Cut-points to prevent low back injury due to force exertion at work

Force exertion is related to low back injuries (LBI). This paper critically reviews the literature concerning cut-points for back force exertion, presents available guidelines in a concise manner, and identifies areas that need further research. The studies reviewed were grouped according to the criteria used to set the cut-point values. Most often cut-points differ than concur. The approach considering physiological, psychophysical, epidemiological, and biomechanical aspects of back force exertion meets the most known criteria and presents the lowest common denominator of instantaneous load for lifting tasks. Further experimental and epidemiological studies in peak load and cumulative exposure are necessary. Compound indices should also be developed for pushing, pulling, and carrying. Future indices should consider electromyographically determined fatigue, differential viscoelastic properties of tissues, aging, and the cross sectional area of back muscles. We hope that this paper contributes to a more systematic appraisal of back force exertion at work.     

Six‐Month‐Old Infants Prefer Speech with Raised Formant Frequencies

Voices can be characterized by their fundamental frequency as well as by speech timbre characteristics, such as formant frequencies. While infants' responses to fundamental frequency characteristics are well established, very little is known about how infants respond to changes in formant frequencies. This study tested whether 6‐month‐old infants prefer listening to speech with raised formant frequencies over speech with lowered formant frequencies. Naturally spoken utterances were acoustically manipulated to render raised‐formant and lowered‐formant stimuli that only differed in the formant frequencies, while keeping fundamental frequency and other acoustic characteristics constant. Infants in an infant‐controlled listening procedure listened longer to the raised‐formant than to the lowered‐formant stimuli. These results provide the first evidence that infants distinguish and show preferences for variations in formant frequencies in adult speech.     

Predictors of foster care exits to permanency: A competing risks analysis of reunification, guardianship, and adoption

Although foster care is intended to be temporary, and policy explicitly requires permanency outcomes, many children experience lengthy stays and exit foster care without a permanent family. This study sought to identify which child and placement characteristics were important predictors of exit to three types of permanency outcomes: reunification, guardianship, and adoption. A sample of 3351 children who entered foster care in 2006 was observed for 30 to 42 months. Permanency outcomes were analyzed using competing risks survival analysis. Children exited foster care to different types of permanency at different rates and frequencies. Reunification occurred most quickly and frequently. Guardianship was second in terms of median duration but third in frequency. Adoption was the second most common exit but had the longest median duration. One in four children remained in foster care or exited without permanency. While patterns varied by type of permanency, three major categories of important predictors were identified: 1) demographic characteristics of age at entry and race, 2) clinical needs related to children's disabilities and mental health problems, and 3) continuity and connections represented by kin placements, sibling placements, early stability, and absence of runaway events. Implications for practice, policy, and research are discussed.     

Long Hours and Longings: Australian Children's Views of Fathers' Work and Family Time

Using two waves of paired data from a population sample of 10‐ to 13‐year‐old Australian children (5,711 father–child observations), the authors consider how the hours, schedules, intensity, and flexibility of fathers' jobs are associated with children's views about fathers' work and family time. A third of the children studied considered that their father works too much, one eighth wished that he did not work at all, and one third wanted more time with him or did not enjoy time together. Logistic regression modeling revealed that working on weekends, being time pressured, being unable to vary start and stop times, and working long hours generated negative views in children about fathers' jobs and time together. The time dilemmas generated by fathers' work devotions and demands are salient to and subjectively shared by their children.     

Trajectories of positive youth development and promotive factors among adolescents during the transition to high school in China

Within the framework of positive youth development (PYD) and life course theory, this study was designed to examine patterns of PYD and promotive factors over the first semester of Chinese high school with a sample of 480 students (boys, 43.96%). The growth mixture model identified four trajectories of PYD, labeled high start–fast decreasing, high start–low decreasing, low start–low increasing, and mid–persistent. Results also showed that membership in a PYD trajectory is significantly related to three promotive factors: parental involvement, teacher involvement, and intentional self-regulation. These findings have important theoretical and practical insights for a deeper understanding of the underlying mechanisms of positive development in adolescents following the critical period surrounding the transition to high school.     

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.     

10‐Month‐Olds Visually Anticipate an Outcome Contingent on Their Own Action

It is known that young infants can learn to perform an action that elicits a reinforcer, and that they can visually anticipate a predictable stimulus by looking at its location before it begins. Here, in an investigation of the display of these abilities in tandem, I report that 10‐month‐olds anticipate a reward stimulus that they generate through their own action: .5 sec before pushing a button to start a video reward, they increase their rate of gaze shifts to the reward location; and during periods of extinction, reward location gaze shifts correlate with bouts of button pushing. The results are consistent with the hypothesis that the infants have an expectation of the outcome of their actions: several alternative hypotheses are ruled out by yoked controls. Such an expectation may, however, be procedural, have minimal content, and is not necessarily sufficient to motivate action.     

GENDER-COHORT SUCCESSION AND RETIREMENT AMONG OLDER MEN AND WOMEN, 1951 TO 1984

Long-term trends in occupational change and retirement policy have influenced the relative labor force participation and retirement patterns of subgroups of the older population. Structural changes in the economy have had a large impact on older men and women, pushing the former out of the labor force while pulling the latter in. Meanwhile, the expansion of pension programs for the aged has generally increased the early retirement of men under age 65. Time-series analyses of these trends between 1951 and 1984 point to the specific influences of these factors on gender-cohorts.