Influence of back support conditions on the apparent mass of seated occupants under horizontal vibration

The response characteristics of seated human subjects exposed to fore-aft (x-axis) and lateral (y-axis) vibration are investigated through measurements of dynamic interactions between the seated body and the seat pan, and the upper body and the seat backrest. The experiments involved: (i) three different back support conditions (no back support, and upper body supported against a vertical and an inclined backrest); (ii) three different seat pan heights (425, 390 and 350 mm); and three different magnitudes (0.25, 0.5 and 1.0 m/s2 rms acceleration) of band limited random excitations in the 0.5-10 Hz frequency range, applied independently along the fore-aft and lateral directions in an uncoupled manner. The body force responses, measured at the seat pan and the backrest along the direction of motion, are applied to characterize the total body apparent mass (APMS) reflected on the seat pan, and those of the upper body reflected on the backrest. Unlike the widely reported responses of seated occupants under vertical vibration, the responses to horizontal vibration show strong effect of excitation magnitude. The large displacements at lower frequencies cause considerable rotations of the upper body, and the knees and ankles, particularly when seated without a back support, which encouraged the occupants to continually shift larger portion of the body weight towards their feet. This together with the strong dependence on the excitation magnitude resulted in considerable inter-subject variability of the data. The addition of a back support causes stiffening of the body to limit the low frequency rocking motion of the upper body under x-axis motion, while considerable dynamic interactions with the backrest occur. The mean apparent mass (APMS) responses measured at the seat pan and the backrest suggest strong contributions due to the back support condition, and the direction and magnitude of horizontal vibration, while the role of seat height is important only in the vicinity of the resonant frequencies. In the absence of a back support, the seat pan responses predominate at a lower frequency (near 0.7 Hz) under both directions of motion, while two secondary peaks in the magnitude also occur at relatively higher frequencies. The addition of back support causes the seat pan response to converge mostly to a single primary peak, resulting in a single-degree-of-freedom like behavior, with peak occurring in the 2.7-5.4 Hz range under x-axis, and 0.9-2.1 Hz range under y-axis motions, depending upon the excitation magnitude and the back support condition. This can be attributed to the stiffening of the body in the presence of the constraints imposed by the backrest. A relaxed posture with an inclined backrest, however, causes a softening effect, when compared to an erect posture with a vertical backrest. The backrest, however, serves as another source of vibration to the seated occupant, which tends to cause considerably higher magnitude responses. The considerable magnitudes of the apparent mass response measured at the seat back under fore-aft motions suggest strong interactions with the backrest. Such interactions along the side-to-side motions, however, are relatively small. The results suggest that the biodynamic characterization of seated occupants exposed to horizontal vibration requires appropriate considerations of the interactions with the backrest.     

Assessment of functional status, low back disability, and use of diagnostic imaging in patients with low back pain and radiating leg pain.

We analyzed data from outpatients with chronic low back pain (LBP) in the Veterans Health Study (n = 563) to examine the relationship between localized LBP intensity and radiating leg pain in assessing patient functional status, low back disability, and use of diagnostic imaging. Based on the localized LBP intensity, the study subjects were divided into tertiles (low, moderate, and high intensity). The study subjects were also stratified by the extent of radiating leg pain. Using analysis of variance and multiple regression analysis, we compared the relative importance of localized LBP intensity and radiating leg pain in explaining the variability in the means of the SF-36 scales and low back disability days, and in the proportion of patients who had used diagnostic imaging. The results of the study indicate that measures of localized LBP intensity and radiating leg pain contribute separately to the assessment of patient functional status, low back disability, and use of diagnostic imaging. These results suggest that localized LBP intensity and radiating leg pain may represent two different approaches in assessing back pain severity. Future epidemiological and health services research should consider both measures in assessing the impact of LBP on patient functional status, low back disability, and use of diagnostic imaging.     

高中生座位舒适度与脊椎疼痛的关系调查

目的 了解高中生课室座位舒适度,明确其与脊椎疼痛的关系,为高中生改善坐姿、预防脊椎疼痛提供依据.方法 采用多层整群抽样随机选取佛山市两所高中,发放调查问卷2 350份,调查学生课室座位舒适度及近一个月内的颈痛、背痛和腰痛的患病率,统计分析座位舒适度及其具体因素与颈痛、背痛和腰痛的相关性.结果 回收有效问卷2 212份,...     

Predictors of seat-belt use among school-aged children in two low-income Hispanic communities

OBJECTIVES: To examine the prevalence of seat belt use among school-aged children in low-income Hispanic communities. METHODS: We conducted unobtrusive observations of school-aged children (aged 5 to 12 years) traveling to and from nine elementary schools in two communities. We documented vehicle type, and belted status and seating position of children, driver, and other passengers. Results are presented as percentages with 95% confidence intervals (CIs). RESULTS: We observed 3651 children, of which restraint use could be determined for 2741. Overall, 29% of children were using seat belts. By seating location, 58% were in the front seat with 40% belted, and 42% were in the back seat with 14% belted. Children were most likely to be restrained when traveling in the front seat (40.0%, CI=37.6-42.5); traveling with a belted driver (42.4%, CI=40.0-44.8); or traveling without additional passengers (40.3%, CI=37.0-43.7) CONCLUSIONS: Seat belt use among children from this study population was below the national average and was alarmingly low among children in the back seat. While traveling, being belted in the back seat provides the most protection in a collision. Prevention efforts need to be based on an understanding of the barriers to restraint use for children traveling in the back seat.     

Effects of chair design on back muscle fatigue

The electromyographic activity of the paraspinal muscles were examined to investigate the effects of chair sitting on muscle activation patterns and muscle fatigue. Twenty-four subjects were studied on the Balans, Back Up, and standard office chairs during a seated writing task and standing while performing a standardized muscle fatigue assessment test. The results of the study indicate that in 87.5% of the comparisons at the L3 site, the Back Up chair has lower readings of muscular effort compared to the Balans and office chair. During the muscle fatigue testing, the greatest amount of fatigue was noted in those subjects who sat in the Back Up chair last. When the Back Up chair was first or second, the least amount of fatigue was observed. The sEMG results supports a biomechanical model. The ergonomics of the Balans and office chairs give the least amount of support to the low back, while the Back Up chair provides the greatest amount of support. It is suggested that adequate pelvic girdle support during seated tasks will lower the threshold of back fatigue and thus facilitate return to work for low back pain patients.     

孕期体操运动对不良症状改善的效果

目的 研究孕期体操运动对不良症状的改善作用,为开展孕期体操提供理论依据。方法 选择北京市5个孕妇学校的孕25～34周孕妇为研究对象,采用专家研发的孕期体操,观察孕期不良症状的改善效果。结果 孕妇通过体操干预,便秘症状改善率为81．2％,失眠改善率为82．8％,腿抽筋症状改善率为89．3％,浮肿症状改善率为53．3％,腰背疼痛感改善率为72．5％,血糖控制改善率为50％,髋关节打开程度改善率为90．6％。结论 孕期体操运动能够有效改善孕期便秘、失眠、腿抽筋、浮肿、腰背疼痛等不良症状,孕妇养生保健体操是安全有效,值得进一步研究和推广的。     

Influence of support conditions on vertical whole-body vibration of the seated human body

The vibration transmission to the lumbar and thoracic segments of seated human subjects exposed to whole body vibration of a vehicular nature have been mostly characterised without the back and hand supports, which is not representative of general driving conditions. This non-invasive experimental study investigated the transmission of vertical seat vibration to selected vertebrae and the head along the vertical and fore-aft axes of twelve male human subjects seated on a rigid seat and exposed to random vertical excitation in the 0.5-20 Hz range. The measurements were performed under four different sitting postures involving combinations of back support conditions and hands positions, and three difference magnitudes of vertical vibration (0.25, 0.5 and 1.0 m/s(2) rms acceleration). The results showed significant errors induced by sensor misalignment and skin effects, which required appropriate correction methodologies. The averaged corrected responses revealed that the back support attenuates vibration in the vertical axis to all the body locations while increasing the fore-aft transmissibility at the C7 and T5. The hands position generally has a relatively smaller effect, showing some influences on the C7 and L5 vibration. Sitting without a back support resulted in very low magnitude fore-aft vibration at T5, which was substantially higher with a back support, suggestive of a probable change in the body's vibration mode. The effect of back support was observed to be very small on the horizontal vibration of the lower thoracic and lumbar regions. The results suggest that distinctly different target body-segment biodynamic functions need to be defined for different support conditions in order to represent the unique contribution of the specific support condition. These datasets may then be useful for the development of biodynamic models.     

手法复位夹板外固定配合理疗对桡骨远端骨折患者腕关节功能恢复的影响

目的探讨手法复位夹板外固定配合理疗对桡骨远端骨折患者腕关节功能恢复的影响。方法 60例桡骨远端骨折患者随机分为两组各30例,对照组行手术切开复位钢板螺钉内固定,观察组行手法复位夹板外固定配合理疗,比较两组的治疗效果。结果观察组的腕关节功能优良率显著高于对照组,疼痛缓解时间、手背消肿时间及骨折愈合时间均显著短于对照组(P<0.05)。治疗后,两组的掌倾角及尺偏角均较治疗前显著升高(P<0.05),但两组间比较无统计学差异(P>0.05)。结论手法复位夹板外固定配合理疗治疗桡骨远端骨折患者可有效缩短疼痛时间、手背肿胀时间,促进骨折愈合,改善腕关节功能。     

Clinical diagnosis and decision in practice. A young woman with back pain

A woman aged 23 visited the GP because of nagging back pain at the level of L.2-L.3. In spite of the atypical symptom, the GP made the diagnosis of 'back pain of myogenic origin', possibly the result of camping in inclement weather. When the pain was still present after one week, the patient coughed, produced greyish-green mucus, was dyspnoeic, had 38.5 degrees C fever, while crepitations and reduced breathing sounds were heard in the right lower lung fields, the working diagnosis of 'pneumonia' was made. No laboratory studies were done; X-ray diagnostics and a good response to antibiotic treatment confirmed the diagnosis. After the symptoms recurred and patient's use of an oral contraceptive was established, she was examined for 'pulmonary embolism'. After this condition was shown to be likely, anticoagulant treatment was instituted, which led to rapid recovery.     

Risk factors for first-ever low back pain among workers in their first employment

BACKGROUND: Low back pain has been estimated to be the most costly ailment of people of working age. Both work characteristics and individual factors have been identified as risk factors. The first interaction between work characteristics and individual factors occurs when workers start in their first job. AIMS: To investigate work-related risk factors for first-ever low back pain in young workers in their first employment. METHODS: A cross-sectional analysis was performed on 278 young workers in their first employment and without a history of low back pain prior to working. Work-related physical factors, psychosocial work characteristics, individual variables and first-ever low back pain were queried by means of a questionnaire. RESULTS: About half of the workers who developed low back pain after job start did so in the first year of employment. An increased risk was observed for (i) long periods of seated work [relative risk (RR) = 3.2, 95% confidence interval (CI) = 1.6-6.4]; (ii) more than 12 flexion or rotation movements of the trunk per hour (RR = 3.0, 95%CI = 1.4-6.4); and (iii) more than 3 years seniority in a job involving lifting more than 25 kg at least once an hour (RR = 3.7, 95%CI = 1.4-9.4). As to psychosocial work characteristics, first-ever low back pain was associated with a combination of low psychological job demands and low supervisor support. CONCLUSION: Work-related physical factors and psychosocial work characteristics should be considered as risk factors for first-ever low back pain. First-ever episodes of low back pain are common in the first year of employment. This may reflect a lack of work experience or training.     

Seat inclination, use of lumbar support and low-back pain of taxi drivers

OBJECTIVES: Epidemiologic evidence supporting optimal seating is limited and inconsistent. This cross-sectional study was conducted to examine the association between seat inclination, use of lumbar support, and the prevalence of clinically significant low-back pain among taxi drivers METHODS: A digital inclinometer was used to measure inclinations of seat surfaces (theta(seat)) and backrests (theta(back)), and calculate the back-to-thigh angle (theta(back-thigh)). Structured interviews were conducted to gather information on the use of lumbar support and the prevalence of low-back pain that had led to medical attention or absence from driving in the past month. A multiple logistic regression analysis was used to estimate the prevalence odds ratio (OR) with adjustment for age, body mass index, professional seniority, monthly driving hours, and the intensity of exposure to whole-body vibration. RESULTS: Among 224 drivers, the mean theta(seat), and theta(backrest) were 14.5 (SD 9.6) and 95.1 (SD 2.7) degrees, respectively, resulting in theta(back-thigh) of 80.6 (SD 9.3) degrees. Fifty-five percent used a lumbar support regularly, but 25% reportedly had significant low-back pain. The prevalence of low-back pain was 23% among those with theta(back-thigh) <86 degrees, 37% for those with a theta(back-thigh) of 86 approximately 91 degrees, and 9% for a theta(back-thigh) of >91 degrees. The adjusted OR comparing those with a theta(back-thigh) of < or = 91 degrees to those with a theta(back-thigh) of >91 degrees was 5.11 [95% confidence interval (95% CI) 1.07 approximately 24.4]. For regularly using drivers versus those not using lumbar support, the prevalence of low-back pain was 18% versus 34%, with an adjusted OR of 0.33 (95% CI 0.16 approximately 0.68). Neither theta(seat) nor theta(backrest) alone was significantly associated with low-back pain. CONCLUSIONS: The epidemiologic observation of this study was consistent with the results of prior biomechanical studies on appropriate seat inclinations and the use of lumbar support. Prospective studies are needed to confirm the true beneficial effects of these seating parameters.     

Lumbar spine injection and interventional procedures in the management of low back pain

Lumbar spine injections play a role in the evaluation and treatment of low back pain and lumbar radiculopathy. These injection procedures have been demonstrated to be effective in determining the pain generator for low back pain. There is still debate as to the long-term pain relief from epidural and intra-articular facet joint injections, and no controlled studies have examined the long-term effects of SI joint injections. Additional investigation is certainly warranted to evaluate further the long-term benefits and determine with patients would benefit the most from these injections. Current evidence validates that these injections provide temporary relief of low back and radicular leg pain up to several months, if not longer. This duration of pain relief creates an opportunity to maximize rehabilitation efforts while symptoms are minimal.     

The relationship among back injury,pain and sexual functioning

Retrospective, self-reported frequencies of pre- and post-injury sexual intercourse were compared in four back injury diagnostic groups. Comparisons were made among groups, and the relation of self-reported pain was compared to the frequency of self-reported sexual intercourse. One hundred subjects were interviewed and their medical records reviewed two years, on average, post-injury. All subjects reported a reduction in sexual frequency post-injury. The surgery group was found to experience a greater reduction in sexual frequency than non-surgery back injured patients. In addition, all subjects reported experiencing some level of pain, and the degree of reported pain was significantly correlated with reduced frequency of sexual intercourse. However, this relationship was considered clinically insignificant. The implications of these findings for individuals with chronic back pain are discussed.Private Practice, Columbia, South Carolina.     

Low back pain and lumbar angles in Turkish coal miners

BACKGROUND: This study was designed to assess the incidence of low back pain among Turkish coal miners and to investigate the relationship between angles of the lumbar spine and low back pain in coal miners. METHODS: Fifty underground workers (Group I) and 38 age-matched surface workers (Group II) were included in the study. All the subjects were asked about low back pain in the past 5 years. The severity of low back pain was evaluated with 10 mm visual analog scale (VAS). Modified oswestry low back pain disability questionnaire (MOSW) was used to measure functional disability. Sacral horizontal angle (SHA), lumbosacral angle (LSA), and lumbar lordosis were measured through Cobb method. RESULTS: The prevalance of low back pain was higher in Group I than in Group II (78.0%, 32.4%, respectively, P < 0.001). The mean VAS score was higher in Group I than in Group II (P < 0.05). There was no difference in MOSW scores between the two Groups. The mean SHA was lower in Group I than in Group II (P = 0.02). No statistically significant difference was determined in lumbar angles of underground and surface workers with low back pain (P > 0.05). CONCLUSIONS: The results of the study showed that low back pain occurred in 78.0% of Turkish coal miners. Although the nature of the occupation may have influenced coal miners' lumbar spinal curvature, lumbar angles are not a determinant for low back pain in this population. Further extensive studies involving ergonomic measurements are needed to validate our results for Turkish coal mining industry.     

Risk factors for the development of low back pain in adolescence.

A previous history and earlier onset of low back pain are associated with chronic low back pain in adults, implying that prevention in adolescence may have a positive impact in adulthood. The study objectives were to determine the incidence of low back pain in a cohort of adolescents and to ascertain risk factors. A cohort of 502 high school students in Montreal, Canada, was evaluated during 1995-1996 at three separate times, 6 months apart. The outcome was low back pain occurrence at a frequency of at least once a week in the previous 6 months. Of the 377 adolescents who did not complain of low back pain at the initial evaluation, 65 developed low back pain over the year (cumulative incidence, 17 percent). Risk factors associated with development of low back pain were high growth (odds ratio = 3.09; 95 percent confidence interval (CI): 1.53, 6.01), smoking (odds ratio = 2.20; 95% CI: 1.38, 3.50), tight quadriceps femoris (odds ratio = 1.02; 95% CI: 1.00, 1.05), tight hamstrings (odds ratio = 1.04; 95% CI: 1.01, 1.06), and working during the school year (odds ratio = 1.33; 95% CI: 1.03, 1.71). Modifying such risk factors as smoking and poor leg flexibility may potentially serve to prevent the development of low back pain in adolescents.     

Risk of low back pain in people admitted to hospital for traffic accidents and falls.

STUDY OBJECTIVE--The aim was to assess the risk of back symptoms in people admitted to hospital because of traffic accidents and falls. DESIGN--The study was a cross sectional survey with information collected by postal questionnaire. Main outcome measures were associations between hospital admission for a traffic accident or fall and reported first onset of back symptoms at the same age and at later ages. SETTING--General practices in seven towns and one rural district. SUBJECTS--1172 men and 1495 women aged 20-59 years were selected from the age-sex registers of 136 general practitioners in the study areas. MAIN RESULTS--Low back pain was reported by 1556 subjects and hospital admission for a traffic accident or fall by 362. The incidence of low back pain was unusually high during the year of age at which subjects were first admitted to hospital for trauma (RR = 5.5, 95% CI 3.8-7.8). The risk of first developing symptoms in subsequent years was lower, but still significantly increased (RR = 1.3, 95% CI 1.1-1.6). Low back pain which started at the age of an accident tended to last longer than that occurring in other circumstances, and was more often ascribed to injury (56% of cases). However, this proportion was smaller than the calculated attributable proportion for traffic accidents and falls (82%). CONCLUSIONS--The data suggest that a person under age 60 years who is admitted to hospital for a traffic accident or fall has a 7% chance of developing low back pain as result of the injury. However, the link between the injury and subsequent symptoms is often not obvious to the patient.     

The debate on lower back pain and its relationship to work: a retrospective study of workers on sick leave

Lower back pain has a high prevalence among the Mexican working population, with extensive social and economic repercussions. Official figures show that lower back pain accounts for 10.0 to 15.0% of sick leave excuses. However, this fails to identify any relationship between lower back pain and job conditions, since such leave is only granted if it can be shown that the condition was not work-related. The present study shows that such a relationship does in fact exist. A retrospective study examined all cases (n = 210) in which workers were granted sick leave for lower back pain in an IMSS (Mexican Government Health Insurance) hospital in Mexico City during a seven-year period. The results show the association and interactions between debilitating lower back pain and several work-related variables: job position, time-on-the-job, and physical effort and weight-carrying associated with the position. Causes of lower back pain and the difficulty in obtaining accurate, precise back pain diagnosis are discussed. A number of clinical, epidemiological, and legal strategies for the study and prevention of back pain are suggested.     

Chronic low back pain: the failure of organic medicine

In this issue of the journal, a series of 67 patients is presented with persistent or recurrent chronic low back pain and leg pain after insertion of a lumbar-disc prosthesis in a private hospital in Germany. A relationship between degenerative changes in the vertebral column and chronic low back pain is often assumed but lacks a scientific basis. Psychosocial factors are much more important than biomechanical factors in determining the outcome, but the interaction between these determinants is far more complicated than just 'having problems'. Accordingly, a multidisciplinary approach is the most successful mode of treatment, while local measures aimed at the vertebral column are generally ineffective or of unproven value. Patients will continue to seek magic cures from 'quacks with a knife' as long as medical specialists are insufficiently trained to deal with unexplained somatic symptoms.     

Lower back pain in health insurance policyholders: prevalence and associated factors

A cross-sectional study was conducted with individuals of both sexes (20-59 years of age), all covered by the COOPERSINOS Health Care Plan of Vale do Rio dos Sinos University. The study aimed to determine the prevalence of lower back pain and associated factors in the previous three months. A self-applied questionnaire included socioeconomic, demographic, occupational, and lifestyle questions. Prevalence of lower back pain among the 775 individuals was 52.8% in the previous year (95%CI: 49.3-56.3) and 46% in the previous three months (95%CI: 42.5-49.5). Poisson regression for lower back pain in the previous 90 days showed an association with: (1) age 40-49 years; (2) self-reported strenuous or difficult work; and (3) smoking. Despite the high prevalence of lower back pain and difficulty in performing work activities, the pain was not disabling. Although 29.9% of workers reported some difficulty in performing their daily or work-related activities due to lower back pain, absenteeism was quite low.     

Evaluation of a swiveling seat to reduce the physical load on forklift drivers]

Many forklift drivers have musculoskeletal disorders such as low back pain related to poor work posture and whole-body vibration. With a forklift operator's seat capable of 45-degree swiveling, we evaluated the physical reduction in the load in 10 subjects working in a back-looking position by means of surface electromyography (EMG) and the angle of rotation of the trunk and neck regions. The amplitude of surface EMG on the trapezius, erector spinae, and latissimus dorsi muscles in looking back or maintaining a back-looking position decreased with a swiveling seat compared to the stationary seat. Nevertheless, there was little alleviation of the amplitude of surface EMG on the sternocleidomastoid muscle in maintaining a back-looking posture and no decrease in looking back. The angle of rotation of the trunk maintaining a back-looking position was decreased greatly with the swiveling seat, but no decrease in the rotation angle of the neck was seen. Our study suggests that a swiveling seat is effective in reducing the physical load on the forklift driver during back-looking operations, and this may lead to the prevention of low back pain.