Gender influences on spine loads during complex lifting (original) (raw)
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Spine Loading as a Function of Gender
Spine, 2002
In vivo laboratory studies were conducted to investigate the spine loads imposed on men and women during a series of lifting tasks that varied in the degree of lifting control required by the subject.
The effects of sex and handedness on lumbar kinetics during asymmetric lifting tasks: A pilot study
Proceedings of the 7th International Digital Human Modeling Symposium (DHM 2022) and Iowa Virtual Human Summit 2022 -
Manual material handling such as box lifting is a very common task that is used in the industrial and medical fields. It is widely accepted that manual lifting can potentially lead to low back injury. Asymmetric lifting, which involves twisting of the trunk, shifts trunk muscle activation and can increase the lower back loading on the spine thus further increasing the likelihood of injury. Other researchers have explored asymmetric lifting but have not considered the effects of handedness. Sex has also been considered as a factor related to low back injury, but majority of research work include only male subjects in literature. This work aims to examine the effects of sex, handedness, box load, and box origin on the maximum lumbar flexion/extension L5-S1 joint moments generated during two-handed box lifting so that safer lifting recommendations can be made for those tasks. Eight participants (sex: 4 women, 4 men; age:
The effect of load and posture on load estimations during a simulated lifting task in female workers
International Journal of Industrial Ergonomics, 2003
The objectives of this study were: (1) to determine the effects of posture and load on relative load estimates (RLE) and absolute load estimates (ALE) of a one hand-lifting task within female checkout operators; (2) to quantify the magnitude of the over-and underestimations of the absolute load estimates in three different postures; and (3) to compare the RLE and ALE responses with respect to correct, under-and overestimations of the load. Eighteen experienced, healthy female checkout operators lifted standardized containers of three different weights (28.9, 33.4, 37.8 N) in three different postures (normal, maximum, extreme) for two trials. For each condition, the weight of the test container was estimated in relative and absolute terms. A binary logistic regression for the RLE and a balanced ANOVA with repeated measures was used to test the main effects and interactions for the ALE. An a ¼ 0:05 was used for all tests of the RLE and ALE. These results showed a statistically significant interaction for posture and load, indicating that different combinations of load and posture affected load estimation differently. It was observed that overestimation of the load occurred in the maximum and extreme postures while handling the heavier loads, whereas underestimation occurred in the normal posture lifting the lightest load. In general, individuals were better able to correctly identify the relative effect of the load than to estimate the weight of the load in absolute terms.
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.
The Spine Journal, 2006
BACKGROUND CONTEXT: Psychosocial stressors have been associated with low back pain reporting. However, response to psychosocial risk factors may be dependent on the individual's personality type that, in turn, can affect muscle recruitment and spine loading. This study explores how personality might be associated with spine loading during repetitive lifting performed throughout an entire work shift. PURPOSE: Assess spine loading as a function of an individual's personality type during repetitive, long-term exposure to a materials handling tasks. STUDY DESIGN: Laboratory experiment where experienced and inexperienced participants performed repetitive, asymmetric lifts at various load and lift frequency levels throughout a series of 8-hour exposure periods. Spine loads were monitored throughout the work period. PATIENT SAMPLE: Twelve novice and 12 experienced materials handlers who were asymptomatic for back pain. OUTCOME MEASURES: Spine compression, anterior-posterior (A/P) shear, and lateral shear at the L5-S1 level. METHODS: Participants were categorized into personality types based upon the Myers-Briggs personality type indicator. An electromyography-assisted biomechanical model was used to assess spine compression, A/P shear, and lateral shear throughout the exposure period. RESULTS: The results indicate that intuitors had higher shear spinal loading regardless of moment exposure, lift frequency, and time through the work period, compared with the sensor personality type. In addition, higher spine compressive and shear forces occurred in the perceiver personality compared with the judgers' personality trait, regardless of moment and, often, lift frequency. Novice lifters typically experienced greater spine loading. CONCLUSIONS: The results suggest that when there exists a personality-job environment mismatch, spinal loading increases via an increase in antagonistic co-contraction. The trends suggest that inherent personality characteristics may play a role in one's motor control strategies when performing a repetitive lifting task.
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.
International Archives of Occupational and Environmental Health, 2011
Purpose In the year 1991, manual materials handling guidelines were published by Liberty Mutual Research Institute for Safety. In these guidelines, maximum acceptable weights (MAWs) and forces (MAFs) for lifting, lowering, pushing, pulling, and carrying were derived from studies conducted in a 20 year span before the above publication date. The question is whether the present generation of workers has retained the same gender differences and absolute values in psychophysically determined MAWs and MAFs as those reflected in the guideline. Methods Twenty-four female industrial workers performed 20 variations of lifting, lowering, pushing, pulling, and carrying. A psychophysical methodology was used whereby the workers chose a workload they could sustain for 8 h without ''straining themselves or without becoming unusually tired, weakened, overheated or out of breath.'' Results In females, MAWs of lifting, lowering, and carrying averaged 53% of the present-day male values, similar to the 55% in the guideline. MAFs of pushing and pulling were 83 and 86% of the present-day male values but slightly higher than the 73 and 78% in the guideline, respectively for initial and sustained forces. Conclusions The similarity of gender differences between the guideline and the present findings was coupled with dramatic decreases in MAWs of lifting, lowering, and carrying. Such decreases may reflect a new psychophysical set point; however, considerations about adjusting existing guidelines on lifting, lowering, and carrying may not be appropriate until additional data from other sources inside and outside the US confirm the present findings.
Evaluation of spinal loading during lowering and lifting
Clinical Biomechanics, 1998
Objective. To estimate the three-dimensional spinal loads during various lifting and lowering tasks. Design. The in viva measurements of the trunk dynamics, moments, and myoelectric activity were used as inputs into an electromyographic-assisted model used to predict the three-dimensional spinal loads. Background. Previous studies of eccentric motions have investigated muscle activity, trunk strength, and trunk moments. A void in the body of knowledge exists in that none of these studies investigated spinal loading. Methods. Ten subjects lifted (40" of flexion to 00) and lowered (0" of flexion to 40") boxes while positioned in a structure that restrained the pelvis and hips. The tasks were performed under isokinetic trunk velocities of 5, 10, 20, 40, and 80 deg s-l while holding a box with weights of 9.1, 18.2, and 27.3 kg. Results. Lowering strength was found to be 56% greater than lifting strength. The lowering tasks produced significantly higher compression forces but lower anterior-posterior shear Forces than the lifting tasks. The differences in the spinal loads produced by the two lifting tasks were attributed to differences in coactivity and unequal lifting moments (i.e. holding the box farther away from the body). Conclusions. The nature of the spinal loads that occur during lowering and lifting were significantly different. The difference in spinal loads may be explained by different lifting styles. Relevance This study revealed the importance of investigating lowering as well as lifting since these types of motions result in drastically different EMG-torque relationships and, ultimately, different spinal loading patterns. Furthermore, this study indicates the importance of taking into account differences in lifting style (trunk moments) and the coactivity of the trunk muscles when estimating loads on the spine.