Parental knowledge of school backpack weight and contents. (33/202)

Parental knowledge of their students' backpack weight and contents was assessed by identifying 188 students who carried backpacks weighing at least 10% of their body weights through a survey of 745 students in three elementary schools. Most parents (96%) had never checked their child's backpack weight; 34% had never checked the backpack contents.  (+info)

Reposition sense of lumbar curvature with flexed and asymmetric lifting postures. (34/202)

STUDY DESIGN: Reposition sense of lumbar curvature was assessed as a function of trunk flexion, trunk asymmetry, and target lumbar curvature using a repeated-measures design and an active-active proprioception paradigm. OBJECTIVE: The objectives of the research were to measure the ability of the subjects to sense and control the lumbar curvature in different lifting postures and to see if error in the lumbar curvature would increase in high-risk postures. SUMMARY OF BACKGROUND DATA: The risk of low back disorders (LBDs) is related to trunk posture, with greater risk reported in flexed and asymmetric trunk positions. Spinal posture, including trunk position and lumbar lordosis, influences spinal stability. Hence, the ability to accurately sense and control spinal curvature may be an important factor in the control of LBD risk. METHODS: Eleven subjects were trained to assume specified lumbar curvatures using visual feedback. The ability of the subjects to reproduce this curvature without feedback was then assessed. This procedure was repeated for different trunk postures, including flexion and asymmetry, and with different target lumbar curvatures. RESULTS: These measurements demonstrated reposition error was increased in flexed trunk positions but was unchanged with trunk asymmetry. This increase in reposition error with flexion was diminished when the target posture and lumbar curvature were highly flexed and kyphotic. CONCLUSIONS: This research suggests that it may be difficult to control spinal curvature in flexed positions, leading to an increased risk of injury. For jobs in which flexed working postures are unavoidable, therefore, it is important to minimize potentially unstable events such as slipping or shifting loads to avoid injury.  (+info)

Sensorimotor memory for fingertip forces: evidence for a task-independent motor memory. (35/202)

When repetitively lifting an object with randomly varying mechanical properties, the fingertip forces reflect the previous lift. We examined the specificity of this "sensorimotor memory" by observing the effects of an isolated pinch on the subsequent lift of a known object. In this case, the pinch force was unrelated to the fingertip forces necessary to grip the object efficiently. The peak grip force used to lift the test object (4 N weight) depended on the preceding task. Compared with repetitively lifting the 4 N test object, the peak grip force was 2 N greater when a lift of the same object was preceded by a lift in which a hidden mass was attached to the object to increase the weight to 8 N. This 2 N increase in grip force also occurred when subjects lifted the 4 N test object after pinching a force transducer with a force of 8 N. Thus, similar grip forces were stored in sensorimotor memory for both tasks, and reflected subjects' use of 7.9 +/- 1.1 N to lift the 8 N object. Similar effects occurred when the preceding pinch or lift was performed with the opposite hand. The peak lift force was unaffected by the isolated pinch, suggesting that a generalized increase in fingertip and limb forces did not occur. We conclude that the sensorimotor memory is not specific for lifting an object. It is doubtful that this particular memory stores the physical properties of objects or reflects a forward internal model for predictively controlling fingertip forces.  (+info)

Impact of ergonomic intervention on back pain among nurses. (36/202)

OBJECTIVES: This study assessed the impact of ergonomic intervention on rates of low-back pain among hospital nurses. METHODS: Altogether 1239 female nurses from two hospitals in southern England completed a baseline postal questionnaire about low-back pain and associated risk factors. Between 18 and 28 months after the baseline survey, major intervention was implemented at one hospital to minimize unassisted patient handling and high-risk nursing tasks. At the other, no intervention was initiated, and efforts to improve patient handling were more limited. Thirty-two months after the baseline survey, a second postal survey was carried out in both hospitals (1,167 respondents) to reassess the prevalence of symptoms and risk factors. RESULTS: After adjustment for nonoccupational risk factors, prevalent low-back pain at baseline was associated with low job satisfaction and the performance of patient-handling activities without mechanical aids. After the intervention, the prevalence of occupational risk factors was somewhat lower, but similar improvements occurred at the comparison hospital. At the intervention site the prevalence of symptoms increased slightly (from 27% to 30%), whereas at the comparison site there was no change, the prevalence remaining constant at 27%. Calculations based on the association of risk factors with symptoms at baseline and the observed changes in their prevalence indicated that the change in risk factors was insufficient to produce a substantial reduction in back pain. CONCLUSIONS: These findings cast doubt on the means by which many hospitals are attempting to improve the ergonomics of nursing activities. More effective methods of implementing changes in work systems are needed.  (+info)

Control strategies correcting inaccurately programmed fingertip forces: model predictions derived from human behavior. (37/202)

When picking up a familiar object between the index finger and the thumb, the motor commands are predetermined by the CNS to correspond to the frictional demand of the finger-object contact area. If the friction is less than expected, the object will start to slip out of the hand, giving rise to unexpected sensory information. Here we study the correction strategies of the motor system in response to an unexpected frictional demand. The motor commands to the mononeuron pool are estimated by a novel technique combining behavioral recordings and neuromuscular modelling. We first propose a mathematical model incorporating muscles, hand mechanics, and the action of lifting an object. A simple control system sends motor commands to and receives sensory signals from the model. We identify three factors influencing the efficiency of the correction: the time development of the motor command, the delay between the onset of the grip and load forces (GF-LF-delay), and how fast the lift is performed. A sensitivity analysis describes how these factors affect the ability to prevent or stop slipping and suggests an efficient control strategy that prepares and corrects for an altered frictional condition. We then analyzed fingertip grip and load forces (GF and LF) and position data from 200 lifts made by five healthy subjects. The friction was occasionally reduced, forcing an increase of the GF to prevent the object being dropped. The data were then analyzed by feeding it through the inverted model. This provided an estimate of the motor commands to the motoneuron pool. As suggested by the sensitivity analysis the GF-LF-delay was indeed used by the subjects to prevent slip. In agreement with recordings from neurons in the primary motor cortex of the monkey, a sharp burst in the estimated GF motor command (NGF) efficiently arrested any slip. The estimated motor commands indicate a control system that uses a small set of corrective commands, which together with the GF-LF-delay form efficient correction strategies. The selection of a strategy depends on the amount of tactile information reporting unexpected friction and how long it takes to arrive. We believe that this technique of estimating the motor commands behind the fingertip forces during a precision grip lift can provide a powerful tool for the investigation of the central control of the motor system.  (+info)

Reasons for applying innovations for scaffolding work. (38/202)

In this paper reasons for applying and for not applying technical and organisational innovations in scaffolding work are studied. In a participatory ergonomic approach these innovations were developed to reduce problems concerning physical load of scaffolders. In this study reasons for the adoption of the innovations in the scaffolding sector are evaluated in 2 studies, in 48 companies. More than half of the scaffolding sector in the Netherlands adopted the innovations. Reasons for applying innovations concerned improvement of work and health and satisfaction with usage. The reason for not applying the innovations concerned specific situations, such as offshore work, in which innovations were not applicable.  (+info)

Intervention strategies to reduce musculoskeletal injuries associated with handling patients: a systematic review. (39/202)

AIMS: To report, analyse, and discuss the results of a systematic review looking at intervention strategies to reduce the risk factors associated with patient handling activities. METHODS: A search strategy was devised to seek out research between 1960 and 2001. Inclusion/exclusion criteria limited the entry of papers into the review process. A checklist was selected and modified to include a wide range of study designs. Inter-rater reliability was established between six reviewers before the main review process commenced. Each paper was read by two reviewers and given a quality rating score, with any conflicts being resolved by a third reviewer. Papers were grouped by category: multifactor, single factor, and technique training based interventions. RESULTS: A total of 2796 papers were found, of which 880 were appraised. Sixty three papers relating to interventions are reported in this paper. The results are reported as summary statements with the associated evidence level (strong, moderate, limited, or poor). CONCLUSION: There is strong evidence that interventions predominantly based on technique training have no impact on working practices or injury rates. Multifactor interventions, based on a risk assessment programme, are most likely to be successful in reducing risk factors related to patient handling activities. The seven most commonly used strategies are identified and it is suggested that these could be used to form the basis of a generic intervention programme, with additional local priorities identified through the risk assessment process. Health care providers should review their policies and procedures in light of these findings.  (+info)

The relative importance of whole body vibration and occupational lifting as risk factors for low-back pain. (40/202)

AIMS: To explore the impact of occupational exposure to whole body vibration (WBV) on low back pain (LBP) in the general population and to estimate the burden of LBP attributable to occupational WBV in comparison with that due to occupational lifting. METHODS: A questionnaire including sections on WBV at work, LBP, and potential risk factors was mailed to a community sample of 22 194 men and women of working age. Sources and durations of exposure to occupational WBV were ascertained for the past week and personal vibration doses (eVDV) were estimated. Analysis was confined to subjects reporting exposures in the past week as typical of their work. Associations of LBP with eVDV, driving industrial vehicles, and occupational lifting were explored by logistic regression and attributable numbers were calculated. RESULTS: Significant associations were found between daily lifting of weights greater than 10 kg at work and LBP, troublesome LBP (which made it difficult to put on hosiery), and sciatica (prevalence ratios 1.3 to 1.7); but the risk of these outcomes in both sexes varied little by eVDV and only weak associations were found with riding on industrial vehicles. Assuming causal associations, the numbers of cases of LBP in Britain attributable to occupational WBV were estimated to be 444 000 in men and 95 000 in women. This compared with an estimated 940 000 male cases and 370 000 female cases of LBP from occupational lifting. CONCLUSIONS: The burden of LBP in Britain from occupational exposure to WBV is smaller than that attributable to lifting at work.  (+info)