Psychophysical basis for maximum pushing and pulling forces: A review and recommendations (original) (raw)
Related papers
Applied Ergonomics, 2010
Using psychophysics, the maximum acceptable forces for pushing have been previously developed using a magnetic particle brake (MPB) treadmill at the Liberty Mutual Research Institute for Safety. The objective of this study was to investigate the reproducibility of maximum acceptable initial and sustained forces while performing a pushing task at a frequency of 1 min À1 both on a MPB treadmill and on a highinertia pushcart. This is important because our pushing guidelines are used extensively as a ergonomic redesign strategy and we would like the information to be as applicable as possible to cart pushing. On two separate days, nineteen female industrial workers performed a 40-min MPB treadmill pushing task and a 2-hr pushcart task, in the context of a larger experiment. During pushing, the subjects were asked to select a workload they could sustain for 8 h without ''straining themselves or without becoming unusually tired, weakened, overheated or out of breath.'' The results demonstrated that maximum acceptable initial and sustained forces of pushing determined on the high inertia pushcart were 0.8% and 2.5% lower than the MPB treadmill. The results also show that the maximum acceptable sustained force of the MPB treadmill task was 0.5% higher than the maximum acceptable sustained force of . Overall, the findings confirm that the existing pushing data developed by the Liberty Mutual Research Institute for Safety still provides an accurate estimate of maximal acceptable forces for the selected combination of distance and frequency of push for female industrial workers.
International Journal of Industrial Ergonomics, 2007
The purpose of this experiment was to replicate a previous psychophysical experiment . Maximum acceptable forces of dynamic pushing: comparison of two techniques. Ergonomics 42, 32-39] which investigated maximum acceptable initial and sustained forces while performing a 7.6 m pushing task at a frequency of 1 min À1 on a magnetic particle brake treadmill versus pushing on a high-inertia pushcart. Fourteen male industrial workers performed both a 40-min treadmill pushing task and a 2-h pushcart task, with a unique water loading system, in the context of a larger experiment. During pushing, the subjects were asked to select a workload they could sustain for 8 h without ''straining themselves or without becoming unusually tired, weakened, overheated or out of breath.'' The results revealed that similar to the previous study maximum acceptable sustained forces of pushing determined on the high inertia cart were significantly higher (21%) than the forces determined from the magnetic particle brake treadmill. These results were countered by an 18% decrease in maximum acceptable forces for the criterion magnetic particle brake treadmill task, perhaps due to secular changes in the industrial population. Based on the present findings, it is concluded that the existing pushing data [Snook, S.H., Ciriello, V.M., 1991. The design of manual tasks: revised tables of maximum acceptable weights and forces. Ergonomics 34, 1197-1213] still provides an accurate estimate of maximal acceptable forces for this pushing distance and frequency.
Ergonomics, 2012
The objective of this study was to investigate potential associations between an individual's psychophysical maximum acceptable force (MAF) during pushing tasks and biomechanical tissue loads within the lumbar spine. Ten subjects (eight males, two females) pushed a cart with an unknown weight at one push every two minute for a distance of 3.9 m. Two independent variables were investigated, cart control and handle orientation while evaluating their association with the MAF. Dependent variables of hand force and tissue loads for each MAF determination and preceding push trial were assessed using a validated, electromyography-assisted biomechanical model that calculated spinal load distribution throughout the lumbar spine. Results showed no association between spinal loads and the MAF. Only hand forces were associated with the MAF. Therefore, MAFs may be dependent upon tactile sensations from the hands, not the loads on the spine and thus may be unrelated to risk of low back injury.
Safety and Health at Work, 2016
The purpose of this review is to name and describe the important factors of musculoskeletal strain originating from pushing and pulling tasks such as cart handling that are commonly found in industrial contexts. A literature database search was performed using the research platform Web of Science. For a study to be included in this review differences in measured or calculated strain had to be investigated with regard to: (1) cart weight/ load; (2) handle position and design; (3) exerted forces; (4) handling task (push and pull); or (5) task experience. Thirteen studies met the inclusion criteria and proved to be of adequate methodological quality by the standards of the Alberta Heritage Foundation for Medical Research. External load or cart weight proved to be the most influential factor of strain. The ideal handle positions ranged from hip to shoulder height and were dependent on the strain factor that was focused on as well as the handling task. Furthermore, task experience and subsequently handling technique were also key to reducing strain. Workplace settings that regularly involve pushing and pulling should be checked for potential improvements with regards to lower weight of the loaded handling device, handle design, and good practice guidelines to further reduce musculoskeletal disease prevalence.
Observational Assessment of Forceful Exertion and the Perceived Force Demands of Daily Activities
Journal of Occupational Rehabilitation, 2004
The primary objective of this study was to assess the accuracy and precision with which analysts observe and estimate the force produced as subjects performed exertions on a work simulator. Eight analysts observed 32 subjects and estimated force as a percent of subjects' maximum voluntary contraction (% MVC). Analysts exhibited bias toward the mean, as high force exertions (>67% MVC) were underestimated (mean: 11.6% MVC) and low force exertions (<34% MVC) were overestimated (mean: 6.7% MVC). Average error for medium force exertions (34-67% MVC) was not statistically different from zero (2.1% MVC). For all force levels, precision of the estimate was very poor (standard deviation range: 16.2-20.7% MVC). Experience of the analyst in performing ergonomic analysis did not affect accuracy. A secondary objective of the study was to conduct a survey in which subjects identified activities of daily living they perceived as equivalent to controlled force levels. A total of 59 different activities ranging from minimal force required to near maximum were listed by at least 5% of the participants. This list may be used to assist health care practitioners and patients convey the force demands required of occupational tasks as well as for evaluating the diminished strength of the patient.
International Journal of Industrial Ergonomics, 2010
The purpose of this study was to compare psychophysiological responses between healthy men and women workers during dynamic pushing on two frictional floor surfaces. First, using a psychophysical approach 27 participants chose a cart weight that they could push for 8 h ''without strain or becoming unusually tired, weakened, overheated or out of breath'' on Plywood (coefficient of friction ¼ 0.68) and Teflon (coefficient of friction ¼ 0.26) walkways. Second, cardiopulmonary and muscle metabolic measurements were collected simultaneously on two separate days while participants pushed the highinertia cart over a 7.6 m distance at a frequency of 1 push/min at the psychophysically chosen workload for 2 h on each walkway. Muscle responses, Tissue Hemoglobin Index (THI) and Tissue Oxygenation Index (TOI), from the right and left gastrocnemius medialis, were obtained using near-infrared spectroscopy.
The load-velocity profiles of three upper-body pushing exercises in men and women
Sports Biomechanics, 2019
This study aimed to explore the differences in the load-velocity profile between three upper-body pushing exercises in men and women. The load-velocity profiles (from 20% to 100% of the onerepetition maximum [1RM] in 5% increments) of 24 sport sciences students (12 men) were randomly tested during the horizontal bench press (HBP), inclined bench press (IBP) and seated military press (SMP) exercises. The 1RM was higher for the HBP (men: 94.2 ± 14.6 kg; women: 45.4 ± 10.1 kg), followed by the IBP (men: 87.7 ± 11.6 kg; women: 41.6 ± 6.6 kg), and finally the SMP (men: 67.4 ± 7.8 kg; women: 37.3 ± 6.3 kg). The mean test velocity (i.e., averaged velocity of all loads) and the slope of the loadvelocity profile were significantly different between exercises (SMP > IBP > HBP) and sexes (men > women). The correlations between the exercises were very high for the individual 1RM values (r range = 0.714-0.982), but lower correlations were observed for the mean test velocity (r range = 0.237-0.766) slope of the load-velocity profile (r range = 0.018-0.721), and velocity of the 1RM (r range = 0.004-0.446). These results confirm that men present higher velocities at low relative loads (i.e., %1RM) compared to women during upper-body pushing exercises.
An analysis of load transmission within the human body during pushing and pulling
2004
Central to the study was an investigation of the influence of the three groups of muscles representing and surrounding the joints: (1) arm and the shoulder, (2) trunk muscles and the spine, (3) lower extremity and the pelvis, on the maximum acceptable force applied to the hand during pushing and pulling when an arm was elevated at 5 degrees in a frontal plane. In this paper we report a detailed numerical simulation model that allowed us to quantify the limiting factors in each joint. The calculations were carried out for different arm positions during the right hand pushing and pulling.
Journal of Applied Biomechanics, 29:285-291
This study examined the influence of frequency and direction of force application on psychophysically acceptable forces for simulated work tasks. Fifteen male participants exerted psychophysically acceptable forces on a force transducer at 1, 3 or 5 repetitions per minute by performing both a downward press and a pull towards the body. These exertions were shown previously to be strength and balance limited, respectively. Workers chose acceptable forces at a lower percentage of their maximum voluntary force capacity during downward (strength limited) exertions than during pulling (balance limited) at all frequencies (4-11%, p = 0.035). Frequency modulated acceptable hand force; however only during downward exertions, where forces at five repetitions per minute were 13% less (p = 0.005) than those at one exertion per minute. This study provides insight into the relationship between biomechanically limiting factors and the selection of acceptable forces for unilateral manual tasks.
Effect of the Gender and Personal Characteristics Impact on One-Handed Isometric Push-Pull Exertions
International journal of occupational hygiene, 2019
Pushing/pulling activities are known as usual and high frequent tasks in industrial sectors, especially in developing countries. Nearly, half of all manual material handling tasks is comprised of push/pull exertions, so it is essential to determine the maximum value of push/pull force exertions by Iranian workers to design the workplace optimally. A total number of 31 volunteer students (19 males and 12 females) were participated in a one-handed maximum push/pull force measurement test in standing posture. The results were measured using the Isometric Push-Pull Dynamometer. Height and weight were also recorded through interviews. Data analysis showed that the pull/push forces of women were 72% and 52% of men, but the data variation for men was higher than women. Using linear regression and Pearson correlation coefficient, it was found that there were only two strong correlations between the push force of women with body mass index (R-Sq = 75.55%) and weight (R-Sq = 74.8%) and men's pull strength was almost independent of individual characteristics. The results of maximum push/pull can be used for improvement in workstations and push/pull tools' design in production and services industries, in which occupational health promotion will be achieved.