Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lifting”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed1999

Object size effects on initial lifting forces under microgravity conditions.

Individuals usually report for two objects of equal mass but different volume that the larger object feels lighter. This so-called size-weight illusion has been investigated for more than a century. The illusion is accompanied by increased forces, used to lift the larger object, resulting in a higher initial lifting speed and acceleration. The illusion holds when subjects know that the mass of the two objects is equal and it is likely that this also counts for the enlarged initial effort in lifting a larger box. Why should this happen? Under microgravity, subjects might be able to eliminate largely the weight-related component of the lifting force. Then, if persistent upward scaling of the weight-related force component had been the main cause of the elevated initial lifting force under normal gravity, this elevated force might disappear under microgravity. On the other hand, the elevated initial lifting effort in the large box would be preserved if it had been caused mainly by a persistent upward scaling of the force component, necessary to accelerate the object. To test whether the elevated initial lifting effort either persists or disappears under microgravity, a lifting experiment was carried out during brief periods of microgravity in parabolic flights. Subjects performed whole-body lifting movements with their feet strapped to the floor of the aircraft, using two 8-kg boxes of different volume. The subjects were aware of the equality of the box masses. The peak lifting forces declined almost instantaneously with approx. a factor 9 in the first lifting movements under microgravity compared with normal gravity, suggesting a rapid adaptation to the loss of weight. Though the overall speed of the lifting movement decreased under microgravity, the mean initial acceleration of the box over the first 200 ms of the lifting movement remained higher (P=0.030) in the large box (1.87+/-0.127 m/s2) compared with the small box (1.47+/-0.122 m/s2). Under normal gravity these accelerations were 3.30+/-0.159 m/s2 and 2.67+/-0.159 m/s2, respectively (P=0.008). A comparable trend was found in the initial lifting forces, being significant in the pooled gravity conditions (P=0.036) but not in separate tests on the normal gravity (P=0.109) and microgravity (P=0.169) condition. It is concluded that the elevated initial lifting effort with larger objects holds during short-term exposure to microgravity. This suggests that upward scaling of the force component, required to accelerate the larger box, is an important factor in the elevated initial lifting effort (and the associated size-weight illusion) under normal gravity.

Adult↗
PubMed2005

Spine loading as a function of lift frequency, exposure duration, and work experience.

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. METHODS: Twelve novice and twelve experienced manual materials handlers performed repetitive, asymmetric lifts at different load and lift frequency levels throughout an 8-h exposure period. Compression, anterior-posterior shear, and lateral shear were evaluated over the lifting period using an EMG-assisted biomechanical model. RESULTS: Spinal loads increased after the first 2 h of lifting exposure regardless of the lift frequency. Loading was also greater for the inexperienced subjects compared to experienced lifters. The greatest spine loads occurred at those lift frequencies and weights to which the workers were unaccustomed. INTERPRETATION: Increases in spine loading were tracked back to the changes in muscle recruitment patterns that typically involved increased muscle coactivation. The results emphasize the importance of previous motor programming in defining spine loads during repetitive lifting. These results indicate a very different influence of frequency and lift time exposure compared to physiologic and psychophysical assessments. This study has shown that it is not sufficient to extrapolate from short lift periods to extended exposure periods if the biomechanical loading implications of the task are of interest.

Adult↗
PubMed2005

Devastating injuries in healthcare workers: description of the crisis and legislative solution to the epidemic of back injury from patient lifting.

The purpose of this report is to describe a crisis in healthcare, disabling back injuries in US healthcare workers. In addition, outlined is the proven solution of safe, mechanized, patient lifting, which has been shown to prevent these injuries. A "Safe Patient Handling--No Manual Lift" policy must be immediately instituted throughout this country. Such a policy is essential to halt hazardous manual patient lifting, which promotes needless disability and loss of healthcare workers, pain and risk of severe injury to patients, and tremendous waste of financial resources to employers and workers' compensation insurance carriers. Healthcare workers consistently rank among top occupations with disabling back injuries, primarily from manually lifting patients. Back injury may be the single largest contributor to the nursing shortage. Reported injuries to certified nursing assistants are three to four times that of registered nurses. A national healthcare policy for "Safe Patient Handling--No Manual Lift" is urgently needed to address this crisis. Body mechanics training is ineffective in prevention of back injury with patient lifting. Mandated use of mechanical patient lift equipment has proven to prevent most back injury to nursing personnel and reduce pain and injury to patients associated with manual lifting. With the national epidemic of morbid obesity in our country, innovative devices are available for use in emergency medical systems and hospitals for patient lifting and transfer without injury to hospital personnel. The US healthcare industry has not voluntarily taken measures necessary to reduce patient handling injury by use of mechanical lift devices. US healthcare workers who suffer disabling work-related back injuries are limited to the fixed, and often inadequate, relief which they may obtain from workers' compensation. Under workers' compensation law, healthcare workers injured lifting patients may not sue their employer for not providing mechanical lift equipment. Discarding healthcare workers disabled by preventable back injuries is an abuse which legislators must remedy. In addition, Medicare reimbursement policies must also be updated to allow the disabled community to purchase electrically operated overhead ceiling lifts. The US lags far behind countries with legislated manual handling regulations and "No Lifting" nursing policies. England and Australia have had "No Lifting" nursing policies in place since 1996 and 1998, respectively. The National Occupational Research Agenda (NORA) recognized a model in 2003 for reduction of back injuries to nursing staff in US healthcare facilities. Also in 2003, the American Nurses Association called for elimination of manual patient handling because it is unsafe and causes musculoskeletal injuries to nurses. The first state legislation for safe patient handling passed both houses in California but was vetoed by the Governor in September 2004. California and other states are preparing to (re)introduce legislation in January 2005. A national, industry-specific policy is essential to quell the outflow of nursing personnel to disability from manual patient lifting.

Adult↗
PubMed1989

Occupational lifting by nursing aides and warehouse workers.

Nursing aides (18 women and six men) at one traditional and one modern geriatric ward, and warehouse workers (16 men) at two different types of warehouse departments were studied during occupational work. The vertical load during manual handling was measured using strain gauges built into wooden shoes. The warehouse workers performed four times as many lifts as the nursing aides and transferred five times as great a mass per unit time. Less than 25% of the lifts were carried out with the load evenly distributed on both feet during both the upward lift and lowering. In the warehouses the lifts were short, while the nursing aides were exposed both to lifts of longer duration and to carrying, as well as a greater frequency of unexpected, sudden and high peak load. The heart rate and oxygen uptake values recorded were relatively low, and both groups utilized approximately 25% of their maximum aerobic power. According to official occupational injury statistics, both warehouse workers and nursing aides belong to risk groups with a high frequency of reported back injuries. However, more injuries are reported by nursing aides than by warehouse workers. Greater muscle strength in male workers may partly explain this difference. Qualitative differences in the design of the lifting work, with more lifts of long duration in awkward work postures, more carrying, more exertion of horizontal forces and a greater frequency of unexpected rapid lifts in the nursing aides may also contribute to the differences in risk of injury between these occupational groups. Considerable differences were found between the two hospital wards as regards lifting frequency, force, duration and the proportion of lifts with an even distribution of load on both feet during upward lift. The lifting work was approximately 50% less in the modern ward, which has easily maneuvered electric overhead hoists, spacious premises and better work organization than in the traditional ward, even though the patient handling needs were equivalent. In the warehouse department at which the wares were stored with easy access, the frequency of lifts with an even distribution of load on both feet was approximately 25%, compared to 7% in the other warehouse department. In conclusion, evaluations of occupational lifting work should include a quantitative assessment of the duration and load distribution of lifting, as well as of postures. Workstation design, technical aids and work organization have a profound effect on the lifting work load even in jobs with equal manual handling demands.

Accidents, Occupational↗
PubMed1993

Physiological and subjective responses to maximal repetitive lifting employing stoop and squat technique.

To establish safe levels for physical strain in occupational repetitive lifting, it is of interest to know the specific maximal working capacity. Power output, O2 consumption, heart rate and ventilation were measured in ten experienced forestry workers during maximal squat and stoop repetitive lifting. The two modes of repetitive lifting were also compared with maximal treadmill running. In addition, electromyogram (EMG) activity in four muscles was recorded and perceived central, local low-back and thigh exertion were assessed during the lifting modes. No significant difference was found in power output between the two lifting techniques. Despite this the mean O2 consumption was significantly greater during maximal squat lifting [38.7 (SD 5.8) ml.kg-1.min-1] than maximal stoop lifting [32.9 (SD 5.7) ml.kg-1.min-1] (P < 0.001). No significant correlation was found between O2 consumption (in millilitres per kilogram per minute) during maximal treadmill running and maximal stoop lifting, while O2 consumption during maximal squat lifting correlated highly with that of maximal treadmill running (r = 0.928, P < 0.001) and maximal stoop lifting (r = 0.808, P < 0.01). While maximal heart rates were significantly different among the three types of exercise, no such differences were found in the central rated perceived exertions. Perceived low-back exertion was rated significantly lower during squat lifting than during stoop lifting. The EMG recordings showed a higher activity for the vastus lateralis muscle and lower activity for the biceps femoris muscle during squat lifting than during stoop lifting. Related to the maximal voluntary contraction, the erector spinae muscle showed the highest activity irrespective of lifting technique.

Back↗
PubMed2000

Relationship between lifting capacity and anthropometric measures.

STUDY DESIGN: Prospective analysis of relationship between lifting capacity and multiple anthropometric variables. OBJECTIVES: To determine the relationship between lifting capacity and anthropometric variables and to model this relationship quantitatively. BACKGROUND: Low-back injuries commonly occur in individuals who perform lifting tasks. Objective data are needed to determine preinjury lifting capacity that, in turn, might be used to guide decisions during rehabilitation of these injuries. METHODS AND MEASURES: We recorded age and sex and measured the following variables for 35 men and 23 women between the ages of 22 and 40: height, weight, percentage of body fat, torso height, pelvic width, pelvic girth, arm length, thigh girth, and calf girth. Variables were selected for the study on the basis of theoretical modeling or previous research regarding the relationship between study variables and lifting capacity. Subjects also were tested to determine their maximum lifting capacity by using a lordotic lumbar spine lifting technique. RESULTS: Stepwise regression analysis indicated that the combination of sex, age, thigh girth, pelvic girth, and percentage body fat was significantly related to maximum lift capacity (multiple R2 = 0.76). The mean absolute difference (+/- SD) between lifted amount predicted by the regression model and the actual amount lifted was 118.6 +/- 86 N (26 +/- 19.3 lb), which corresponded to an average absolute error of 16% (SD = 14%) of the actual weight lifted. CONCLUSION: The results may be useful in estimating 1 aspect of preinjury lifting capacity. Similar studies are needed to model the requirements of frequency of lift, duration of lifting efforts, variety of hand-object coupling, and combined lifting and reaching.

Adolescent↗
PubMed2000

Metabolic and cardiorespiratory responses to continuous box lifting and lowering in nonimpaired subjects.

STUDY DESIGN: A within-subject experimental design. OBJECTIVES: To compare the magnitude of metabolic and cardiorespiratory changes produced during box lifting and lowering among combinations of lift technique (leg lift and leg-torso lift) and lift weight (10.8 and 15.4 kg). BACKGROUND: Continuous box lifting and lowering can be used as an exercise in a low-back rehabilitation program. Awareness of the possible cardiovascular stress of this activity is important to the clinician because some patients may have existing cardiovascular pathologies or possess unknown risk factors for cardiovascular disease. METHODS AND MEASURES: A group of 17 nonimpaired men 26 +/- 8 years of age (mean +/- SD) performed the 4 experimental trials on different days in a counterbalanced order determined by a Latin Square design. Lifting and lowering was performed for 6 continuous minutes at a rate of 12 cycles per minute. Physiologic variables were oxygen uptake, minute ventilation, heart rate, systolic blood pressure, diastolic blood pressure, metabolic equivalent, and rate-pressure product. RESULTS: There were stepwise increases in the values for oxygen uptake, minute ventilation, heart rate, metabolic equivalent, and rate-pressure product from the leg-torso lift to the leg lift and from 10.8 to 15.4 kg of weight within each lift technique (with the exception that minute ventilation and heart rate did not differ between the leg-torso lift at 15.4 kg and the leg lift at 10.8 kg). For the 4 lifts, values (mean +/- SD) varied from 20.3 +/- 5.4 to 28.8 +/- 5.8 mL x kg x min(-1) for oxygen uptake, 42.2 +/- 11.1 to 66.4 +/- 15.2 L x min(-2) for minute ventilation,129 +/- 20.6 to 156 +/- 16.5 beats x min(-1) for heart rate, 5.8 +/- 1.6 to 8.2 +/- 1.6 for metabolic equivalent, and 197 +/- 49.4 to 245 +/- 41.2 for rate-pressure product (x10(-2)). CONCLUSION: The leg lift with the 15.4-kg weight produced the greatest physiologic stress. Because of the magnitude of the increase in the variables measured for all 4 types of lifts, clinicians should closely monitor patients' response to this type of exercise.

Adult↗
PubMed1995

A study of different postures on isometric lifting strength in normal college students.

The purpose of this study was to describe norms of isometric lifting strength for normal college students and to investigate the effects of gender, body weight, height, and upper and lower limb length on lifting strength. Three types of lifting (i.e., arm, back, and leg lifting) were measured in a sample of 104 college students aged between 18 and 26 years. A Force Evaluation and Testing System (FET 5000) was used for strength measurements with three standard lifting positions. The average of three trials for each lifting strength test was used as the subject's test score. The results showed that the highest mean lifting strength was recorded for leg lifting in both males and females. Both groups also had the lowest score in arm lifting. Of the total sample, there was a difference of strength of nearly three- times between leg and arm lifting. Males were stronger than females in all lifting patterns. In addition, lifting strengths were significantly affected by such variables as sex, weight and height. Body weight was an effective predictor of arm lifting strength, and height an effective predictor of leg lifting strength. Finally, we found that strength in one position had positive relations with strength in other positions. These findings and the establishment of data base can in future provide therapists with an objective evaluation regarding lifting strength of individuals for clinical use.

Adolescent↗
PubMed1995

The psychophysical lifting capacities of Chinese subjects.

The psychophysical lifting capacity (MAWL) of twelve subjects was determined in this study. The subjects were all young Chinese males who performed lifting tasks in three lifting ranges (floor to knuckle, floor to shoulder, and knuckle to shoulder) and four lifting frequencies (one-time maximum, 1 lift/min, 4 lifts/min, and 6 lifts/min). The oxygen uptake (1/min) and heart rate (beats/min) were recorded while subjects were lifting. Upon completion of each lifting task, the subjects were required to rate their perceived exertion levels. The statistical analyses results indicated the following. Chinese subjects have smaller body size and MAWLs compared with past studies using the US population. The MAWLs decreased with an increase in lifting frequencies. The decrements of MAWL due to lifting frequencies were in agreement with the results of past studies. However, there were larger decreases due to lifting ranges. The MAWLs of the floor to knuckle height lift were the largest, followed by the MAWLs of the floor to shoulder height lift, and the MAWLs of the knuckle to shoulder height lift. The measured physiological responses were considered similar to those obtained in past studies. Subjects' perceived stress levels increased with the lifting frequency and the upper extremities received the most stress for the total range of lifting tasks. The comparisons of the Chinese MAWLs with the NIOSH lifting guidelines for limits (AL and MPL) indicated that the vertical discounting factor in the guidelines should be modified before the NIOSH limits can be applied to non-Western populations.

Adult↗
PubMed1996

The influence of task resistance on the characteristics of maximal one- and two-handed lifting exertions in men and women.

Dynamic lifting strength was assessed at lift velocities ranging from 0 to 1 m.s-1 using a hydrodynamometer in which the viscous resistance to motion could be preset. Nine men and nine women performed one- and two-handed dynamic exertions against low, medium, and high resistances. The subjects were required to lift as forcefully and as fast as possible from a height of 400 mm to just above head height. The instantaneous forces recorded at knee, knuckle, hip, shoulder, elbow, and head heights were compared with those obtained during maximal one- and two-handed isometric lifts performed at the same heights. The position of peak force relative to stature was lower for one-handed lifts (35.9% of stature) than for two-handed lifts (38.4% of stature) (P < 0.005), but was unaffected by lift resistance (P > 0.05) and subject sex (P > 0.05). Lifting forces during two-handed exertions were on average 1.5 times greater than for one-handed exertions (P < 0.0001). However, the difference in the strength of one- and two-handed lifts was highly dependent on hand height (P < 0.0001) and task resistance (P < 0.005), and was greater for the men than for the women (P < 0.001). When static lifting strength was measured at heights relative to stature and normalized by dividing by body weight, there was no significant difference in performance between the men and the women [mean normalized female:male: (f:m) strength ratio = 0.76, P > 0.05]. Under dynamic conditions the sex difference in lifting performance was pronounced (mean normalized f:m strength ratio = 0.68, P < 0.01), especially for power output (mean f:m power.unit body weight-1 ratio = 0.52, P < 0.005). The proportion of generality (r2 x 100) between dynamic and static lifting strength was found to range between 63% and 87%. These data suggest that the dynamic and static tests of lifting strength measured a common, intrinsic ability to produce maximal lifting forces. The finding that sex differences in strength are dependent on whether the exertion is static or dynamic has important implications for biomechanical models of human strength.

Adult↗
PubMed2004

The role of back muscle endurance, maximum force, balance and trunk rotation control regarding lifting capacity.

Evaluation of lifting capacity is widely used as a reliable instrument in order to evaluate maximal and safe lifting capacity. This is of importance in regard to planning rehabilitation programs and determining working ability. The aim of this study was to investigate the influence of basic functions on the lifting capacity measured by the progressive isoinertial lifting evaluation (PILE) and the functional capacity evaluation (FCE) tests in a lower (floor to waist) and an upper (waist to shoulder) setting and compare the two test constructs. Seventy-four female subjects without acute low back pain underwent an examination of their lifting capacities and the following basic functions: (1) strength and endurance of trunk muscles, (2) cardiovascular endurance, (3) trunk mobility and (4) coordination ability. A linear regression model was used to predict lifting capacity by means of the above-mentioned basic functions, where the F statistics of the variables had to be significant at the 0.05 level to remain in the model. Maximal force in flexion showed significant influence on the lifting capacity in both the PILE and the FCE in the lower, as well as in the upper, lifting task. Furthermore, there was a significant influence of cardiovascular endurance on the lower PILE and also of endurance in trunk flexion on the lower FCE. Additional inclusion of individual factors (age, height, weight, body mass index) into the regression model showed a highly significant association between body height and all lifting tasks. The r (2) of the original model used was 0.19/0.18 in the lower/upper FCE and 0.35/0.26 in the lower/upper PILE. The model r (2) increased after inclusion of these individual factors to between 0.3 and 0.4. The fact that only a limited part of the variance in the lifting capacities can be explained by the basic functions analyzed in this study confirms the assumption that factors not related to the basic functions studied, such as lifting technique and motor control, may have a strong influence on lifting capacity. These results give evidence to suggest the inclusion of an evaluation of lifting capacity in clinical practice. Furthermore, they raise questions about the predictive value of strength and endurance tests in regard to lifting capacity and work ability.

Back↗
PubMed2004

Foot positioning instruction, initial vertical load position and lifting technique: effects on low back loading.

This study investigated the effects of initial load height and foot placement instruction in four lifting techniques: free, stoop (bending the back), squat (bending the knees) and a modified squat technique (bending the knees and rotating them outward). A 2D dynamic linked segment model was combined with an EMG assisted trunk muscle model to quantify kinematics and low back loading in 10 subjects performing 19 different lifting movements, using 10.5 kg boxes without handles. When lifting from a 0.05 m height with the feet behind the box, squat lifting resulted in 19.9% (SD 8.7%) higher net moments (p < 0.001) and 17.0% (SD 13.2%) higher compression forces (p < 0.01) than stoop lifting. This effect was reduced to 12.8% (SD 10.7%) for moments and a non-significant 7.4% (SD 16.0%) for compression forces when lifting with the feet beside the box and it disappeared when lifting from 0.5 m height. Differences between squat and stoop lifts, as well as the interaction with lifting height, could to a large extent be explained by changes in the horizontal L5/S1 intervertebral joint position relative to the load, the upper body acceleration, and lumbar flexion. Rotating the knees outward during squat lifts resulted in moments and compression forces that were smaller than in squat lifting but larger than in stoop lifting. Shear forces were small ( < 300 N) at the L4/L5 joint and substantial (1100 - 1400 N) but unaffected by lifting technique at the L5/S1 joint. The present results show that the effects of lifting technique on low back loading depend on the task context.

Adult↗
PubMed1999

Evaluation of the revised NIOSH lifting equation. A cross-sectional epidemiologic study.

STUDY DESIGN: A cross-sectional study of the 1-year prevalence of low back pain was conducted in workers employed in manual lifting jobs. OBJECTIVES: To provide epidemiologic data to determine the correlation between the prevalence of low back pain and exposure to manual lifting stressors, measured with the lifting index component of the revised lifting equation from the National Institute for Occupational Safety and Health (NIOSH). SUMMARY OF BACKGROUND DATA: The NIOSH lifting equation has been proposed as a practical, yet valid tool for assessing the risks of low back pain caused by manual lifting. To date, however, there have been few studies in which the effectiveness of the equation to identify jobs with elevated rates of low back pain has been evaluated. METHODS: Fifty jobs from four industrial sites were evaluated with the NIOSH lifting equation. A symptom and occupational history questionnaire was administered to 204 people employed in lifting jobs and 80 people employed in nonlifting jobs. Regression analysis was used to determine whether there was a correlation between the lifting index and reported low back pain. RESULTS: As the lifting index increased from 1.0 to 3.0, the odds of low back pain increased, with a peak and statistically significant odds ratio occurring in the 2 < lifting index < or = 3 category (odds ratio = 2.45). For jobs with a lifting index higher than 3.0, however, the odds ratio was lower (odds ratio = 1.45). CONCLUSIONS: Although low back pain is a common disorder, the lifting index appears be a useful indicator for determining the risk of low back pain caused by manual lifting.

Adult↗
PubMed2002

The influence of weight and starting height on lifting mechanics in lower extremity amputees.

This study compares the lifting mechanics of lower extremity amputees to controls and describes the influence of weight lifted and starting height on lifting style. Subjects included three individuals with transtibial amputation (TTA), two individuals with transfemoral amputation (TFA), and three able-bodied controls (CO). Amputee subjects performed six repetitions of six weights, randomly ordered, from two starting heights. TTA lifted from 30 cm and knee height, TFA from knee and thigh height, and controls from all three heights. Data were obtained from a work simulator, force plate, and a motion analysis system, with starting posture index, lateral sway index, lift duration, synchrony index, and hip moments and elbow moments as dependent measures. The results for each lifting height were analyzed using a mixed model repeated measures MANOVA to test for group and weight differences and post hoc tests were applied when appropriate. Results suggest that healthy lower extremity amputees who have had a number of years to adjust to their prosthesis and develop compensatory strategies can complete a repetitive lifting task at a performance level very similar to able-bodied controls. The most consistent group differences detected were in the timing parameters: synchrony and duration. TTA and TFA tended to lift with less synchronization of hip and knee movements than able-bodied controls and to initiate the lift with their upper bodies. In contrast, able-bodied controls tended to move their upper and lower bodies more synchronously during the lift. TTA had longer lift durations than CO. In terms of stability and moments generated, TTA lifted very similarly to controls. TFA used a different lifting style that involved higher moments and more use of the upper body, particularly for lifts of heavier weights. TFA appeared to be less stable than CO, while TTA did not appear to be less stable than CO.

Adaptation, Biological↗
PubMedDate not supplied

Psychophysical capacity of industrial workers for lifting symmetrical and asymmetrical loads symmetrically and asymmetrically for 8 h work shifts.

This paper presents comprehensive maximum acceptable weight of lift (psychophysical lifting capacity) database for male and female industrial workers for lifting symmetrical and asymmetrical loads symmetrically and asymmetrically for 8 h work shifts. The experimental data collected in previous studies on experienced (industrial) and inexperienced (non-industrial) materials handlers (Mital 1984a, Mital and Fard 1986) and the patterns of responses between the two populations (Mital 1985, 1987) were used to generate this database. Since previous work (Mital 1985, 1987) showed that responses of both experienced and inexperienced materials handlers to task variables are similar and also provided multipliers relating the psychophysical lifting capacities of the two populations, it was possible: (1) to convert psychophysical capacity data for asymmetrical lifting of symmetrical and asymmetrical loads, collected on inexperienced workers to reflect psychophysical lifting capacity of experienced workers for asymmetrical lifting; and (2) to take psychophysical lifting capacity data of experienced industrial workers for symmetrical lifting of symmetrical loads and generate from it their psychophysical lifting capacity for symmetrical and asymmetrical lifting of symmetrical and asymmetrical loads by using the response patterns of inexperienced workers to lifting symmetrical and asymmetrical loads symmetrically and asymmetrically. Both approaches were used and, as expected, provided almost identical values for the psychophysical lifting capacity of industrial workers for symmetrical and asymmetrical lifting of symmetrical and asymmetrical loads. Therefore, the final database tables provided in this paper used combined values generated by the two methods.

Databases, Bibliographic↗
PubMed2003

Endoscopic brow lift: a retrospective review of 628 consecutive cases over 5 years.

Since its introduction in 1992, endoscopic brow lift has gained tremendous recognition because it has been promoted as a novel technique to correct brow ptosis as well as glabella rhytids in a minimally invasive manner with fewer complications than the classic coronal brow lift method. In this retrospective study, 628 endoscopic brow lift procedures performed over a 5-year period (1997-2001) at Manhattan Eye Ear and Throat Hospital were reviewed. The number of endoscopic brow lift procedures performed at this institution has declined 70 percent. The purpose of this study was to elucidate the causes of this striking trend by soliciting the opinions of 21 New York plastic surgeons on their current brow ptosis management. The response rate was 84 percent (21 of 25 surgeons contacted). Currently, 25 percent of the interviewed plastic surgeons perform endoscopic brow lift regularly, 50 percent of the plastic surgeons perform endoscopic brow lift occasionally, and 25 percent of the participants no longer perform endoscopic brow lift. While most patients (70 percent) were satisfied with their results, only 50 percent of the plastic surgeons were pleased with the long-term results (after more than 2 years of follow-up). Observed postsurgical complications of endoscopic brow lift included alopecia, hairline changes, infected hardware, brow asymmetry requiring surgical revision, prolonged forehead/brow paresthesia, frontal branch nerve paralysis, and scalp dysesthesia. These complications were similar to those resulting from open brow lifts. Seventy-one percent of the surveyed New York plastic surgeons routinely administered botulinum toxin type A (Botox) within 6 months of the endoscopic brow lift procedure. Possible explanations for the decline in the overall number of endoscopic brow lift procedures include the following: (1) the selection criteria for the ideal endoscopic brow lift patients are currently more limited; (2) other techniques equal or surpass endoscopic brow lift in effectiveness and predictability; and (3) endoscopic brow lift is ineffective in the majority of patients. There is no single superior surgical procedure for brow ptosis management available at this time.

Adult↗
PubMed2006

Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads.

Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were performed on healthy subjects to collect segmental rotations during lifts needed as input data in subsequent model studies. The model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles to take curved paths in flexion and trunk dynamic characteristics (inertia and damping) while subject to measured kinematics and gravity/external loads. A dynamic kinematics-driven approach was employed accounting for the spinal synergy by simultaneous consideration of passive structures and muscle forces under given posture and loads. Results satisfied kinematics and dynamic equilibrium conditions at all levels and directions. Net moments, muscle forces at different levels, passive (muscle or ligamentous) forces and internal compression/shear forces were larger in stoop lifts than in squat ones. These were due to significantly larger thorax, lumbar and pelvis rotations in stoop lifts. For the relatively slow lifting tasks performed in this study with the lowering and lifting phases each lasting approximately 2 s, the effect of inertia and damping was not, in general, important. Moreover, posterior shift in the position of the external load in stoop lift reaching the same lever arm with respect to the S1 as that in squat lift did not influence the conclusion of this study on the merits of squat lifts over stoop ones. Results, for the tasks considered, advocate squat lifting over stoop lifting as the technique of choice in reducing net moments, muscle forces and internal spinal loads (i.e., moment, compression and shear force).

Adult↗
PubMed2003

Maximum acceptable weights for asymmetric lifting of Chinese females.

This study used the psychophysical approach to evaluate the effects of asymmetric lifting on the maximum acceptable weight of lift (MAWL) and the resulting heart rate, oxygen uptake and rating of perceived exertion (RPE). A randomized complete block factorial design was employed. Twelve female college students lifted weights at three different lifting frequencies (one-time maximum, 1 and 4 lifts/min) in the sagittal plane and at three different asymmetric angles (30 degrees, 60 degrees, and 90 degrees ) from the floor to a 68-cm height pallet. This lifting experiment was conducted for a 1-h work period using a free-style lifting technique. The MAWLs for asymmetric lifting were significantly lower than those for symmetric lifting in the sagittal plane. The MAWL decreased with the increase in the angle of asymmetry. However, the heart rate, oxygen uptake and RPE remained unchanged. Though the MAWL decreased significantly with lifting frequency, both the physiological costs (heart rate and oxygen uptake) and rating of perceived exertion increased with the increase in lift frequency. The most stressed body part was the arm. Lifting frequency had no significant effect on the percentage decrease in MAWL from the sagittal plane values. On average, decreases of 5%, 9% and 14% for MAWL at 30 degrees, 60 degrees and 90 degrees asymmetric lifting, respectively, were revealed. This result was in agreement with the findings of Chinese males studied by Wu [Int. J. Ind. Ergonom. 25 (2000) 675]. The percentage decrease in MAWL with twisting angle for the Chinese participants was somewhat lower than those for Occidental participants. In addition, even though there was an increase in heart rate and RPE with the increase in the symmetrical lift angle for Occidental participants, it was different from the Chinese participants. Lastly, the 1991 NIOSH equation asymmetry multiplier is more conservative in comparison with the results of the present study.

Adult↗