Changes in spine loading patterns throughout the workday as a function of experience, lift frequency, and personality (original) (raw)
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Does personality affect the risk of developing musculoskeletal discomfort?
Theoretical Issues in Ergonomics Science, 2006
Personality theory suggests that individuals can react differently to the same situation. The primary objective of this research was to study employees' personality preferences as they related to manual materials handing jobs. The hypothesis tested was that those whose work preferences did not match the nature of their job requirements would report more psychosocial, physiological or psychological stress and strain compared with those whose personality preferences did match their jobs. A total of 133 employees from two distribution centres completed the Myers-Briggs Type Indicator and other inventories pertaining to their work environments. The results showed that, when employees' personalities were better matched with the nature of their work environment, they generally reported less anxiety and physical discomfort and more job satisfaction and social support than those having a mismatch. This relationship was more prominent in the less physically demanding jobs, suggesting an interaction between physical workload factors and psychosocial influences. This research suggests that integrating knowledge of one's personality preferences with the physical and psychosocial demands of a job may increase one's understanding of the causes of musculoskeletal discomfort in industrial workplaces and aid ergonomists in designing jobs to better match individuals' capabilities, limitations and work preferences.
2019
In spite of strong prevalence of neck and shoulder musculoskeletal disorders among health care workers, the effect of their routine work activities, which demands physical exertion and high cognitive load, on the loading of neck-shoulder musculatures is not clearly understood. Additionally, it is currently unknown as to how the internal loading of the neck-shoulder musculature caused by the external work-related factors is affected by the individual personality. The purpose of this study was to evaluate the musculoskeletal loading of neck-shoulder musculature when human participants performed physically and cognitively demanding exertions. The loading of neck-shoulder musculature was evaluated using objective and subjective assessment methods. Electromyography (EMG) of the neck-shoulder musculature was used as the objective assessment method, whereas NASA-TLX scores were used as the subjective assessment method. Individual personality types were determined using MBIT personality test. Twenty (18 males and 2 females) participants were recruited for data collection. Each participant performed two experimental sessions: Session 1-physical exertion, participant performed 10 maximum static pulling exertions in semi standing posture simulating a bed-tostretcher patient transfer task. Session 2-physical and cognitive exertion, during this session, in addition to 10 static pulling exertions (same as session 1), the participant performed mentally demanding tasks such as memorizing and recalling a list of words. The activities of three major neck-shoulder muscles: upper trapezius, sternocleidomastoid, and cervical trapezius, were studied. Muscle activity data showed that the neck-shoulder muscles worked harder while performing a combination of physical and cognitive exertions than purely physical exertions. The effect of the loading of neck-shoulder muscles was found sensitive to the individual personality. In general for all the muscles, among the participants with feeling personalities, a higher increase in the activation level of muscles was observed. The knowledge gained from this study imply that investigations viewing the entire work system (the interaction of physical and psychosocial workplace issues, as well as individual factors) will most likely to derive the root causes of neck-shoulder MSDs among healthcare occupations. iii Acknowledgements I would like to express my sincere gratitude and deep appreciation to Dr. Ashish Nimbarte, my major advisor, for his guidance, invaluable recommendation, encouragement, understanding and wisdom. He was never lacking in kindness and support. He believed in me and gave me this opportunity at a crucial time in my life. Without his support this thesis would not have been a reality. I would also like to extend my appreciation to my committee members, Dr. Steve Guffey and Dr. Warren Myers, for their valuable suggestion on improving the quality of this thesis and for their teaching and advice during my graduate studies at West Virginia University. I wish to thank all my participants for their time, patience and cooperation. I am indebted to my wife Rabab for her love, encouragement and support which inspired me to reach this goal. Finally, I dedicate this thesis to my lovely kids Rakan and Ghassan. They have always provided me love and are indubitably the source of my strength and confidence.
Spine loading as a function of lift frequency, exposure duration, and work experience
Clinical Biomechanics, 2006
Background. Physiological and psychophysical studies of the effects of lifting frequency have focused on whole-body measurements of fatigue or subjective acceptance of the task and have not considered how spine loads may change as a function of lift frequency or lift time exposure. Our understanding of biomechanical spine loading has been extrapolated from short lifting bouts to the entire work day and may have led us to incorrect assumptions. The objective of this project was to document how spine loading changes as a function of experience, lift frequency, and lift duration while repetitively lifting over the course of an 8-h workday.
The Spine Journal, 2003
BACKGROUND CONTEXT: The role of biomechanical workplace factors in spine loading has been well documented. However, our understanding of the role of psychosocial and individual factors in producing spine loads is poorly understood. Even less is understood about the relative contribution of these factors with respect to kinematic, kinetic and muscle activity responses, as well as spine loading. PURPOSE: To explore the relative contribution of biomechanical and psychosocial workplace factors and individual characteristics on the biomechanical responses and spine loading. STUDY DESIGN/SETTING: The contribution of various levels of workplace factors to spine loading was monitored under laboratory conditions. PATIENT SAMPLE: Sixty (30 male and 30 female) college-age individuals who were asymptomatic to low back pain. OUTCOME MEASURES: Trunk kinematics and kinetics, muscle activity and the three-dimensional spinal loads.
Spine, 2001
Study Design. A repeated-measures in vivo experiment. Objective. To describe within-subject variability of spinal compression in repetitive lifting. Summary of Background Data. Epidemiology and failure mechanics suggest that peak loads may be more predictive of injury than average loads. Nevertheless, biomechanical studies usually focus on the latter. Methods. Ten healthy males performed 360 lifts in 1 hour of a 45-L crate, weighted with a stable 10-kg mass on 1 day and with an unstable mass (10 kg of water) on another day. The maximum compression force in each lift was estimated, using a simple inverse dynamics model and a single equivalent muscle model. Results. The individual distributions of maximum compression force were slightly skewed to the right (average skewness 0.67). Median and 95th percentile values were used to characterize the distribution. The median (50th percentile) compression ranged from 3375 to 6125 N, and from 3632 to 6298 N in the stable and unstable load conditions, respectively. The within-subjects peak (95th percentile) compression forces were from 405 to 1767 N and from 526 to 2216 N, respectively, higher than the median values. The peak values differed significantly between conditions, whereas the difference in medians did not reach significance. Only a limited trendwise (fatigue-related) variance could be demonstrated. Conclusion. Peak spinal compression by far exceeds median compression in repetitive lifting and can be affected by task conditions independently from the median. Therefore, the variability of spinal loads needs to be taken into consideration when analyzing and redesigning tasks that can cause spinal injuries.
International Archives of Occupational and Environmental Health, 2003
Objectives To determine the different cognitive strategies adopted by workers in assessing the effects of lifting-task parameters on effort, and to validate workers' assessments. Methods Questionnaires were administered to 217 male workers with varied levels of experience in manual handling. Workers were asked to assess the effects of lifting on perceived effort, using linguistic descriptors (e.g., light, heavy), and to determine the physical meaning of such descriptors. In addition, each worker assessed on-the-job effort, perceived risk of injury and work dissatisfaction, and musculoskeletal outcomes in a cross-sectional design. Results Perceived physical effort was significantly associated with lifting variables. Results indicated that the three-cluster strategy is the best performer. Weight of load emerged as the most influential factor that impacted on effort in the most dominant cluster (close to 50% of the observations). The second cluster (25% of the observations) demonstrated that weight, horizontal distance, and twisting angle, contributed equally to effort, and the third cluster had weight and vertical travel distance as the most important variables (with travel distance being more important). Perceived effort was significantly associated with objective indices (i.e., biomechanical lifting equivalent and NIOSH lifting index), and musculoskeletal symptoms in eight body parts. Conclusions Cognitive reasoning of experienced workers may be used as an active device for the evaluation of strenuous physical activities such as lifting tasks. Lifting activities are significantly associated with musculoskeletal symptoms, not only in the lower-back region, but also in seven other body parts; and effort may integrate the effects of both physical (lifting tasks) and non-physical (i.e., work dissatisfaction) factors, as well as perception of risk.
Psychophysiological responses to manual lifting of unknown loads
PLOS ONE, 2021
Background The handling of unknown weights, which is common in daily routines either at work or during leisure time, is suspected to be highly associated with the incidence of low back pain (LBP). Objectives To investigate the effects of knowledge and magnitude of a load (to be lifted) on brain responses, autonomic nervous activity, and trapezius and erector spinae muscle activity. Methods A randomized, within-subjects experiment involving manual lifting was conducted, wherein 10 participants lifted three different weights (1.1, 5, and 15 kg) under two conditions: either having or not having prior knowledge of the weight to be lifted. Results The results revealed that the lifting of unknown weights caused increased average heart rate and percentage of maximum voluntary contraction (%MVC) but decreased average inter-beat interval, very-low-frequency power, low-frequency power, and low-frequency/high-frequency ratio. Regardless of the weight magnitude, lifting of unknown weights was a...
Gender influences on spine loads during complex lifting
The Spine Journal, 2003
Background context: Previous research has documented differences in spine loading between genders when the imposed load is normalized relative to the size of the person. However, under realistic work conditions the magnitude of the load handled is seldom adjusted relative to worker anthropometry. Thus, there is a void in our knowledge in that we do not understand how material handling influences spine loading and potential risk of injury as a function of gender under realistic lifting situations. Purpose: To evaluate the differences in spine loading between men and women when exposed to similar workplace demands. Study design: A laboratory study was conducted to investigate the biomechanical responses during realistic free-dynamic lifting tasks when subjects lifted from origins and destinations that were either fixed or set relative to the subject's anthropometry. Patient sample: Twenty men and 20 women asymptomatic for low back pain were recruited to participate in the study. Outcome measures: The three-dimensional spine loads were predicted from a well-established electromyography-assisted model. Methods: Both genders completed a series of symmetric and asymmetric (60-degree clockwise) lifts that originated from two shelf heights ("relative" to knee height and "set" at 35 cm from floor) and terminated at one of two destination heights ("relative" to waist and "set" 102 cm from the floor). Three levels of box weight were investigated (6.8, 13.6 and 22.7 kg). Results: Men had significantly greater compression forces than women (about 640 N). Loading differences between genders were further magnified by several of the workplace factors. The differences between men and women were even greater when lifting either of the heavier loads from the lower fixed shelf (more than 50% greater). Conclusions: It is apparent that men produce the greater loads on their spines during lifting. However, engineering controls, such as adjustable workplace layout or less weight lifted, may reduce or eliminate gender-specific differences in spine loads. Furthermore, the differences in spine loads appear to be a result of kinematic trade-offs and muscle coactivity differences in combination with unequal body masses between genders. However, when the loads were put into context of the expected tolerances of the spine, women were found to be at increased risk of injury, especially when lifting heavy loads or under asymmetric lifting conditions. Collectively, the results indicate the need to account for differences between the genders when designing the workplace.
Variation in spinal load and trunk dynamics during repeated lifting exertions
Clinical Biomechanics, 1999
Objectives. To quantify the variability in lifting motions, trunk moments, and spinal loads associated with repeated lifting exertions and to identify workplace factors that in¯uence the biomechanical variability. Design. Measurement of trunk dynamics, moments and muscle activities were used as inputs into EMG assisted model of spinal loading. Background. Traditional biomechanical models assume repeated performance of a lifting task produces little variability in spinal load because the assessments overlook variability in lifting dynamics and muscle coactivity. Methods. Five experienced and seven inexperienced manual materials handlers performed 10 repeated lifts at each combination of load weight, task asymmetry and lifting velocity. Results. Box weight, task asymmetry and job experience in¯uenced the magnitude and variability of spinal load during repeated lifting exertions. Surprisingly, experienced subjects demonstrated signi®cantly greater spinal loads and within-subject variability in spinal load than inexperienced subjects. Trial-to-trial variability accounted for 14% of the total variation in compression overall and 32% in lateral shear load. Although the mean spinal load was safely below the NIOSH recommended limit; due to variability about the mean, more than 20% of the lifts exceeded the recommended limit. Conclusion. Spinal load changed markedly from one exertion to the next despite identical task requirements. Trial-to-trial variability in kinematics, kinetics, and spinal load were in¯uenced by workplace factors, and may play a role in the risk of low-back pain. Relevance Ergonomic assessments considering only the mean value of spinal load overlook the fact that a large fraction of the lifts may exceed recommended levels.