Pulling Tasks Research Articles

An Investigation of Leaning Behaviors During One-Handed Submaximal Exertions with Extended Reaches

OCCUPATIONAL APPLICATIONSThe purpose of this study was to investigate hand leaning forces and the preferred leaning postures when completing tasks with various task hand locations, force demands, and effort directions. Twenty female participants completed a variety of different exertions with a leaning surface available. The hand leaning force magnitude changed as task hand location, force direction, and force level changed. These forces were significantly higher during pulling tasks and increased with increasing task hand load. The leaning hand height was slightly higher when task locations were at shoulder height, compared to the umbilical height. The findings are important, as current ergonomic tools neglect to consider that different task characteristics may change how and when a worker leans with their hands. These findings are of particular use to industry, as ergonomists now have representative forces and heights, to help guide leaning estimates during proactive risk assessments.TECHNICAL ABSTRACT Background: Leaning occurs in many automotive manufacturing tasks and provides various benefits to the worker. Leaning may allow for a more effective posture for task completion or reduce loading on the spine. Ergonomic assessments of tasks with leaning can be problematic because there is not sufficient data to predict leaning hand forces or the location of the leaning hand. Therefore, this study was completed to investigate leaning hand forces to help ergonomists make better predictions of how a leaning hand might be used during various industrial tasks. Purpose: The purpose of this study was to investigate hand leaning characteristics and the preferred leaning postures when completing tasks with constrained reaches. Methods: Twenty female participants completed exertions with 24 combinations of load (27.5 and 55 N), force direction (push, pull, and down), horizontal reach (95% and 120% of arm length), and vertical height (shoulder and umbilical height). A large leaning surface was available to use while completing the task. Results: The height of the leaning hand ranged between 106.6 and 116.3 cm across all conditions. The leaning hand force was affected by task hand location, force direction, and force demand. Leaning hand forces increased with increasing task hand load and ranged from 13.8 to 79.6 N of force. Task hand pulls had higher leaning hand forces compared to push and down exertion directions, regardless of task hand location or force demand. Conclusion: The findings of this study will be of particular use to industry as ergonomists now have representative leaning forces and heights to help guide leaning estimates during proactive risk assessments.

Determinants and magnitudes of manual force strengths and joint moments during two-handed standing maximal horizontal pushing and pulling

Pushing and pulling are common occupational exertions that are increasingly associated with musculoskeletal complaints. This study focuses on the sensitivity of shoulder capacity to gender, handle height, exertion type (push or pull) and handle orientation for these tasks. All factors except for handle orientation influenced unilateral and total manual force strength (p < 0.01), with exertion type being the most influential. Interaction effects also existed between handle height and exertion type. Additionally, joint moments at the shoulders and low back were influenced by all factors studied (p < 0.01), with exertion type again being most influential. Knowledge of the relative influence of multiple factors on shoulder capacity can provide guidance regarding these factors when designing or evaluating occupational pushing and pulling tasks for a diverse population.Practitioner Summary: pushing and pulling comprise nearly half of all manual materials handling tasks. Practitioners often assess, design or modify these tasks while incorporating constraints, including manual force direction and handle interface. This study provides guidance to aid design of pushing and pulling tasks in the context of shoulder physical capacity.

Cooperation in wild Barbary macaques: factors affecting free partner choice.

A key aspect of cooperation is partner choice: choosing the best available partner improves the chances of a successful cooperative interaction and decreases the likelihood of being exploited. However, in studies on cooperation subjects are rarely allowed to freely choose their partners. Group-living animals live in a complex social environment where they can choose among several social partners differing in, for example, sex, age, temperament, or dominance status. Our study investigated whether wild Barbary macaques succeed to cooperate using an experimental apparatus, and whether individual and social factors affect their choice of partners and the degree of cooperation. We used the string pulling task that requires two monkeys to manipulate simultaneously a rope in order to receive a food reward. The monkeys were free to interact with the apparatus or not and to choose their partner. The results showed that Barbary macaques are able to pair up with a partner to cooperate using the apparatus. High level of tolerance between monkeys was necessary for the initiation of successful cooperation, while strong social bond positively affected the maintenance of cooperative interactions. Dominance status, sex, age, and temperament of the subjects also affected their choice and performance. These factors thus need to be taken into account in cooperative experiment on animals. Tolerance between social partners is likely to be a prerequisite for the evolution of cooperation.

Study of Hamadryas Baboons (Papio Hamadryas) Ability to Solve Object Manipulation Tasks.

Cognitive ability to solve object manipulation tasks was evaluated by "string pulling" and "transparent tube" tests. The string pulling task was solved by 7 of 11 animals. The task of object extraction from the tube was too difficult, not a single animal solved it. The authors conclude that Hamadryas baboons demonstrated rather poor ability to solve object manipulation tasks.

Investigation of Work-related Musculoskeletal Disorders (MSDs) in Warehouse Workers in Saudi Arabia

In many field organizations, such as those in the industrial and service sectors, poor working posture is a common issue that can lead to various human body problems, particularly musculoskeletal disorders (MSDs) and physiological stress. Numerous tasks in the workplace, particularly in the industrial sector (i.e., manual material handling tasks), require an individual to perform in poor working conditions to meet task demands. The purpose of the current study was to evaluate musculoskeletal disorders and identify ergonomic factors related to lower back, shoulder and lower arm pain in two types of manual tasks: lifting and pulling objects in supermarket warehouses. A total of 92 male workers (ages 26–38) participated; 45 workers performed lifting tasks (first posture) and 47 workers performed a task that involved pulling heavy objects (second posture). Rapid Upper Limb Assessment (RULA) and a pain self-report chart were used. The heart rate (HR) was continuously recorded to evaluate the physiological stresses of each task posture. The results showed that lifting task highly significantly impacted low back pain among all participants. In addition, the results found a significant correlation existed between trunk, upper arm and lower arm scores and all self-report charts of pain and discomfort in the lower back, upper arm and lower arm region for all participants. Also, the pulling heavy object task posture significantly affected the lower arm score and reflected a highest prevalence of MSDs on wrist body part. The results presented a significant association existed between lower arm and wrist scores and all self-report charts of pain and discomfort in the lower arm and wrist body parts of all participants. The higher HR value was associated with the lifting task posture. There was a significant difference between both task postures overall. The results of the study proved that the RULA method was a useful tool to assess the MSDs on body regions in manual lifting and pulling tasks.

Ergonomic task reduction prevents bone osteopenia in a rat model of upper extremity overuse.

We evaluated the effectiveness of ergonomic workload reduction of switching rats from a high repetition high force (HRHF) lever pulling task to a reduced force and reach rate task for preventing task-induced osteopenic changes in distal forelimb bones. Distal radius and ulna trabecular structure was examined in young adult rats performing one of three handle-pulling tasks for 12 wk: 1) HRHF, 2) low repetition low force (LRLF); or 3) HRHF for 4 wk and than LRLF thereafter (HRHF-to-LRLF). Results were compared to age-matched controls rats. Distal forelimb bones of 12-wk HRHF rats showed increased trabecular resorption and decreased volume, as control rats. HRHF-to-LRLF rats had similar trabecular bone quality as control rats; and decreased bone resorption (decreased trabecular bone volume and serum CTX1), increased bone formation (increased mineral apposition, bone formation rate, and serum osteocalcin), and decreased osteoclasts and inflammatory cytokines, than HRHF rats. Thus, an ergonomic intervention of HRHF-to-LRLF prevented loss of trabecular bone volume occurring with prolonged performance of a repetitive upper extremity task. These findings support the idea of reduced workload as an effective approach to management of work-related musculoskeletal disorders, and begin to define reach rate and load level boundaries for such interventions.

Role of combined tactile and kinesthetic feedback in minimally invasive surgery

Haptic feedback is of critical importance in surgical tasks. However, conventional surgical robots do not provide haptic feedback to surgeons during surgery. Thus, in this study, a combined tactile and kinesthetic feedback system was developed to provide haptic feedback to surgeons during robotic surgery. To assess haptic feasibility, the effects of two types of haptic feedback were examined empirically - kinesthetic and tactile feedback - to measure object-pulling force with a telesurgery robotics system at two desired pulling forces (1 N and 2 N). Participants answered a set of questionnaires after experiments. The experimental results reveal reductions in force error (39.1% and 40.9%) when using haptic feedback during 1 N and 2 N pulling tasks. Moreover, survey analyses show the effectiveness of the haptic feedback during teleoperation. The combined tactile and kinesthetic feedback of the master device in robotic surgery improves the surgeon's ability to control the interaction force applied to the tissue. Copyright © 2014 John Wiley & Sons, Ltd.

Upper Extremity Forces Generated During Activities of Daily Living

Purpose: Activity restrictions are typically imposed on patients following median sternotomy. Among common sternal precautions (SP) are limitations in upper extremity (UE) force production. The purpose of this study was to measure peak forces during UE activities of daily living and to examine the effect of force production by varying the temporal components of task completion. Methods: Fifteen participants between 22 and 59 years of age performed 19 lifting, pushing, or pulling tasks. For each task, participants performed 3 trials at their preferred speed and 3 trials at a slow speed. Peak forces were measured using a digital dynamometer. Mean percentage change in force produced during preferred and slow movements was recorded for each task. Descriptive statistics were calculated, and paired Student t tests were used to determine differences in force between preferred and slow speeds. Results: Mean peak force generated during preferred speed was less than 10 pounds (a common SP weight limit) for only 6 of the 19 tasks. Peak force exceeded 20 pounds for 5 tasks. Forces were less for all tasks performed at a slow speed as compared with a preferred speed, except 1; the percentage reduction in force ranged from 8% to 61%. Conclusions: Many daily tasks generate UE peak forces in excess of 10 pounds. Performing UE movements at slower than normal speeds reduces peak forces. Optimally, SP should be individualized and functionally based, with consideration for the UE forces produced during activities patients are likely to perform.

Does effort influence inequity aversion in cotton-top tamarins (Saguinus oedipus)?

The human sense of fairness entails sensitivity not just to equality, the equal division of resources, but also to merit, the relationship between an individual's share of resources and how hard they worked for their share. Recent evidence suggests that our sensitivity to equality has deep phylogenetic roots: several nonhuman animal species show an aversion to unequal reward distributions. However, the extent to which nonhuman animals share sensitivity to merit remains poorly understood, largely because previous studies have failed to properly manipulate work effort in inequity aversion tasks. Here, we tested whether cotton-top tamarins (Saguinus oedipus) would exhibit a differential response to inequity when acquiring rewards was either (1) effortful or (2) effortless. Subjects engaged in a pulling task in which they had an opportunity to deliver a disadvantageously unequal distribution of food to themselves and a partner (one piece for self, four pieces for partner). We made delivery effortful by adding a weight to the pulling handle. Critically, effort was calibrated to each individual. Results show that individuals varied markedly in their response to effort, highlighting the importance of manipulating work effort at the individual level. Overall, subjects showed little aversion to inequity. However, subjects were slightly less likely to accept inequity when doing so was effortful, although this effect was pronounced in only one individual. Our findings suggest a new method for capturing individual variation in effort and for studying the roots of the concept of merit in nonhuman animals.

Dogs (Canis familiaris) can learn to attend to connectivity in string pulling tasks.

String pulling tasks are commonly used to investigate recognition of means-end connections. Previous studies suggested that dogs base their choice on proximity rather than connectivity (Osthaus, Lea, & Slater, 2005), nonetheless, dogs performed successfully in the related support problem (Range, Hentrup, & Virányi, 2011). To reinvestigate dogs' means-end understanding, we tested 34 Border collies in string pulling tasks in which the proximity of the reward to the connected string's end was varied. First, subjects were presented with a four-string task (four parallel perpendicular strings, one baited, with the reward in line with the correct string's end). Dogs that performed above chance in this task were tested with a curved string task, involving one straight and one curved string. When the reward was attached to the curved string, it was equidistant from both strings' ends so that choosing by proximity was not possible. Although group level performance was significantly above chance, only three of 20 dogs met criterion individually, of which one dog subsequently solved a broken string task upon its first presentation. However, the dogs seemed to be unable to overcome their proximity bias in a parallel diagonal string task where proximity of the unconnected string's end to the reward was misleading. We conclude that although dogs may not demonstrate means-end understanding spontaneously, some can learn to pay attention to connectivity when proximity is not a confounding factor. This study supports the notion that animals may apply several alternative strategies to solve physical problems, which are influenced by the test-setup.

Patterned-String Tasks: Relation between Fine Motor Skills and Visual-Spatial Abilities in Parrots

String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla) and the cockatiel (Nymphicus hollandicus), forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.

Kinematics of cart pushing and pulling under different loads and surface gradient conditions

Background: Manual material handling incidents are responsible for a large portion of lost work days annually. With the transition to e-commerce, cart pushing and pulling tasks have become more common. Objective: This research explored the effects of surface gradient and load on full body kinematics during cart pushing and pulling tasks. Methods: Ten participants were recruited to complete two sets of tasks. Participants performed cart pushing tasks on three surface gradients and three load masses and downhill cart pulling tasks on two surface gradients and three load masses while being recorded with an optical motion capture system. Full body, three-dimensional joint angles were calculated for each task, and peak angles of the major body joints were analyzed using general linear models to determine the effects of the dependent variables. Results: During the cart pushing tasks, increased load mass and surface gradient both caused a significant increase in the peak joint angles of most body joints with surface gradient having the larger effect. When cart pushing and pulling tasks were compared with 5° and 10° surface gradients and three load masses, cart pushing resulted in significantly higher joint angles. Conclusion: During manual material handling tasks involving a cart, surface gradients and load masses should be minimized.

Will food-handling time influence agonistic behaviour in sub-adult common ravens (Corvus corax)?

Discovering a food source may invoke either competition or cooperation, depending on many factors such as divisibility and accessibility. We experimentally investigated the influence of effort to procure food on the tolerance towards others during feeding. Nine sub-adult captive ravens were tested in different foraging contexts that differed in foraging effort, namely three string-pulling conditions and two without pulling requirement. We expected that the effort to gain access to food would positively affect the tolerance towards others at feeding. As predicted, we found fewer agonistic interactions, fewer displacements of subordinates from food and prolonged feeding bouts in the three string-pulling conditions compared to the two conditions when no pulling was involved. Further, in the string pulling tasks interactions occurred mostly on the perch before pulling and only rarely was pulling interrupted by agonistic interactions. The rate of interactions did not change over trials. Our data suggests that perceived effort influences social behaviour.

Grip force control during simple manipulation tasks in non-neuropathic diabetic individuals

ObjectiveTo assess hand function and grip force (GF) control in non-neuropathic diabetic individuals using traditional hand function tests and instrumented handles that provide information about the underlying neural mechanisms controlling simple manipulation tasks. MethodsTwelve diabetic individuals (31–60years-old) without neuropathy and 12 controls performed traditional functional tests (i.e., nine hole peg test, Jebsen–Taylor test, and maximum grip strength test) and were tested for GF control in two situations: holding a free moving instrumented handle and isometrically pulling fixed handles. Task performance in the tests and safety margin (SM – percentage of GF above the minimum needed to hold the handle) were the main dependent variables assessed. ResultsThere was no difference between diabetics and controls in any functional test and in SM in isometric pulling task. However, diabetics presented around twice lower SM than controls in the free holding task. ConclusionsDiabetics showed no impairment in functional manipulation tasks. However, they presented a lower SM than healthy controls. SignificanceThis lower SM suggests that diabetics may present sensory impairment that could put them at risk of losing objects during its manipulation. Also, it suggests that the applied experimental procedure is sensitive to detect mild sensory impairment in diabetics.

Psychophysical basis for maximum pushing and pulling forces: A review and recommendations

The objective of this paper was to perform a comprehensive review of psychophysically determined maximum acceptable pushing and pulling forces. Factors affecting pushing and pulling forces are identified and discussed. Recent studies show a significant decrease (compared to previous studies) in maximum acceptable forces for males but not for females when pushing and pulling on a treadmill. A comparison of pushing and pulling forces measured using a high inertia cart with those measured on a treadmill shows that the pushing and pulling forces using high inertia cart are higher for males but are about the same for females. It is concluded that the recommendations of Snook and Ciriello (1991) for pushing and pulling forces are still valid and provide reasonable recommendations for ergonomics practitioners. Regression equations as a function of handle height, frequency of exertion and pushing/pulling distance are provided to estimate maximum initial and sustained forces for pushing and pulling acceptable to 75% male and female workers.At present it is not clear whether pushing or pulling should be favored. Similarly, it is not clear what handle heights would be optimal for pushing and pulling. Epidemiological studies are needed to determine relationships between psychophysically determined maximum acceptable pushing and pulling forces and risk of musculoskeletal injuries, in particular to low back and shoulders. Relevance to industryThis article provides a concise discussion of important factors relevant to designing and analyzing pushing/pulling tasks. Regression equations to estimate initial and sustained pushing and pulling forces acceptable to 75% male and female workers are provided and can be used to design and analyze pushing and pulling tasks common in industry.

Push/Pull Risk Factors at Workstations: A Case-Control Study of Mexican Industrial Workers

The objective of this study was to quantify and assess whether push/pull tasks in the workplace are risk factors for lower back pain etiology. A case-control study was conducted of 231 industrial workers 18-55 years old who were insured by the Mexican Social Security Institute MSSI in the Guadalajara Metropolitan Area of Jalisco, Mexico. Exposure was evaluated via a questionnaire. Multivariate analysis using conditional logistic regression showed risks for push/pull tasks odds ratio = 5.7, 95% confidence interval, 1.4-23.1 adjusted for lifting, carrying, and driving work. The fraction attributable to push/pull tasks was 0.58, suggesting that the risk of developing lumbar spondyloarthrosis might be reduced by 58% with ergonomic redesign for pushing and pulling tasks at workstations. Additional research is needed to confirm this relationship and will ideally incorporate a greater number of subjects to assure detailed analyses of exposure categories and facilitate new comparisons with the results of the present study. © 2012Wiley Periodicals, Inc.

Biomechanical analysis of primary upper limb muscle contributors to a functional pulling movement

Better understanding of the muscles that are dominant contributors to upper limb functional tasks may inform rehabilitation in older individuals at risk for disability. Our aim was to determine the muscles primarily responsible for hand movement during pulling. We used an upper limb musculoskeletal computer model that incorporated upper limb joints, physiologic force‐generating properties for all muscles crossing the shoulder, elbow, and forearm, and delays associated with neural activation. A horizontal pulling task was performed by a 50th percentile adult male (5′11″, 180lbs) against 6lb resistance; joint kinematics and EMG were recorded. In the computer simulation, contributions of 32 individual muscles in the measured movement were determined using induced acceleration analysis, which calculates the effect of each muscle's force, applied in isolation, on hand movement. The simulation successfully replicated experimental kinematics (mean error 0.0003°; max 0.06°) and muscle activations. Of the 12 muscles identified as substantial contributors to pulling, 8 cross the shoulder. Our novel simulations suggest that shoulder muscles play an important role in successful functional pulling and are more influential to this upper limb task than elbow and forearm muscles; they may warrant more attention in strengthening programs in at‐risk groups. NIH #5R24HD050821‐02, NSF CBET‐0828115, WFU SRF and CCCRF.

Spatial dependency of shoulder muscle demands in horizontal pushing and pulling

Pushing and pulling account for nearly half of all manual material handling tasks. The purpose of this investigation was to develop a 3-D spatial muscle activity map for the right upper extremity during pushing and pulling tasks. Nineteen males performed 140 ramped directional hand exertions (70 push; 70 pull) at locations along three axes aligned with the anatomical planes. Electromyography (EMG) of 14 sites on the right upper extremity was recorded. Two directional 3-way repeated measures ANOVAs assessed the influence of hand position on EMG. Hand position and exertion direction influenced total and individual muscle demand. During pulling exertions, all three hand location parameters influenced total muscle activity (p < 0.001) and similarly in pushing exertions (p < 0.002), though less pronounced than in pulling. Data were used to create equations to predict the muscle activity of untested hand locations for novel work design scenarios.

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.

The biomechanical characteristics and physiological cost of three standardized pulling tasks

Purpose: The purpose of this study was to investigate the biomechanical characteristics and physiological cost of three standardized pulling tasks. 12 female and 17 male subjects participated in the study. The subjects were instructed to pull a load at three different heights (hip, shoulder, eye – anatomical landmarks defined the end of a pull) at a rate of ten pulls per minute, for a period of ten minutes (one hundred total pulls). The pulls were sub-maximal and chosen to represent a task during a typical 8 hour workday. Statistics: ANOVA statistical analyses with Bonferroni pairwise comparisons were performed to determine significance. Results: Statistical significance was obtained for energy expenditure (Ė), sagittal displacement and twisting velocity. Hip pulling Ė was lower than shoulder pulling Ė (p=0.046) and eye pulling Ė (p=0.002) by 7% and 11%, respectively. Hip pulling involves less sagittal displacement than shoulder (p=0.004) and eye (p=0.001) by 37% and 46%, respectively. Finally, twisting velocity at hip (p=0.042) and shoulder (p=0.006) pulling were 30% and 36% higher than twisting velocity at eye pulling. Conclusion: Physiological data combined with biomechanical data provide a comprehensive description of the demands associated with this standardized pulling task. This combined information assists in risk factor identification and intervention design for tasks involving repetitive upper limb movements.