Validation of a questionnaire for assessing physical work load.
OBJECTIVES: Reliable, valid, and compatible methods are required for exploring the complex interactive effects of psychosocial and physical stressors on complaints and disorders. An instrument for assessing physical work load that integrates information from a biomechanical model of lumbar load is presented and validated. METHODS: Four hundred and fifty-five people working in nursing homes for elderly people in Germany filled out the developed questionnaire 3 times within 1 year. Test-retest reliability was calculated, and validity was checked several times. Relationships with other, theoretically related and unrelated variables were examined. RESULTS: The test-retest reliability of the questionnaire measures was about 0.65. The convergent and discriminant validity was satisfactory, and the questionnaire was able to separate professional subgroups with different physical work loads. The Spearman rank-order correlations between physical load and musculoskeletal complaints were about 0.30. CONCLUSIONS: The method developed in this study is a reliable and valid instrument for assessing physical work load. The integration of statistical methods from psychological testing and theory in the development of methods exploring the effects of physical work load is advocated. (+info)
Back injury in municipal workers: a case-control study.
OBJECTIVES: The purpose of this study was to identify factors associated with acute low back injury among municipal employees of a large city. METHODS: For each of 200 injured case patients, 2 coworker controls were randomly selected, the first matched on gender, job, and department and the second matched on gender and job classification. In-person interviews were conducted to collect data on demographics, work history, work characteristics, work injuries, back pain, psychosocial and work organization, health behaviors, and anthropometric and ergonomic factors related to the job. Psychosocial work organization variables were examined with factor analysis techniques; an aggregate value for job strain was entered into the final model. Risk factors were examined via multivariate logistic regression techniques. RESULTS: High job strain was the most important factor affecting back injury (odds ratio [OR] = 2.12, 95% confidence interval [CI] = 1.28, 3.52), and it showed a significant dose-response effect. Body mass index (OR = 1.54, 95% CI = 1.08, 2.18) and a work movement index (twisting, extended reaching, and stooping) (OR = 1.42, 95% CI = 0.97, 2.08) were also significant factors. CONCLUSIONS: Results suggest that increasing workers' control over their jobs reduces levels of job strain. Ergonomic strategies and worksite health promotion may help reduce other risk factors. (+info)
Risk factors for back injury in 31,076 retail merchandise store workers.
Risk factors for work-associated strain or sprain back injuries were investigated in a cohort of 31,076 material handlers from 260 retail merchandise stores in the United States. The workers studied were those with significant material-handling responsibilities--daily lifting and movement of merchandise. Workers in jobs with the greatest physical work requirements had an injury rate of 3.64 per 100 person-years versus 1.82 in workers with lesser work requirements. The unadjusted injury rate for males was 3.67 per 100 person-years compared with 2.34 per 100 person-years for females, but the excess for males was confounded by higher physical work requirements for men in the stocker/receiver job category. The injury rate ratio for short versus long duration of employment was 3.53 (95% confidence interval: 2.90, 4.30); for medium versus long duration of employment, it was 1.38 (95% confidence interval: 1.18, 1.62). The elevated rate ratios were maintained when the data were stratified by subsets with different rates of turnover. The results suggest that workers with the greatest physical work requirements and those with the shortest duration of employment are at the highest risk of back injuries. However, selection forces causing worker turnover within this cohort of active workers are not well characterized and have the potential to bias the measures for time-related factors such as duration of employment. (+info)
Abdominal muscle response during curl-ups on both stable and labile surfaces.
BACKGROUND AND PURPOSE: With the current interest in stability training for the injured low back, the use of labile (movable) surfaces, underneath the subject, to challenge the motor control system is becoming more popular. Little is known about the modulating effects of these surfaces on muscle activity. The purpose of this study was to establish the degree of modulating influence of the type of surface (whether stable or labile) on the mechanics of the abdominal wall. In this study, the amplitude of muscle activity together with the way that the muscles coactivated due to the type of surface under the subject were of interest. SUBJECTS: Eight men (mean age=23.3 years [SD=4.3], mean height=177.6 cm [SD=3.4], mean weight=72.6 kg [SD=8.7]) volunteered to participate in the study. All subjects were in good health and reported no incidence of acute or chronic low back injury or prolonged back pain prior to this experiment. METHODS: All subjects were requested to perform 4 different curl-up exercises-1 on a stable surface and the other 3 on varying labile surfaces. Electromyographic signals were recorded from 4 different abdominal sites on the right and left sides of the body and normalized to maximal voluntary contraction (MVC) amplitudes. RESULTS: Performing curl-up exercises on labile surfaces increased abdominal muscle activity (eg, for curl-up on a stable surface, rectus abdominis muscle activity was 21% of MVC and external oblique muscle activity was 5% of MVC; for curl-up with the upper torso on a labile ball, rectus abdominis muscle activity was 35% of MVC and external oblique muscle activity was 10% of MVC). Furthermore, it appears that increases in external oblique muscle activity were larger than those of other abdominal muscles. CONCLUSION AND DISCUSSION: Performing curl-ups on labile surfaces changes both the level of muscle activity and the way that the muscles coactivate to stabilize the spine and the whole body. This finding suggests a much higher demand on the motor control system, which may be desirable for specific stages in a rehabilitation program. (+info)
Effects of squat lift training and free weight muscle training on maximum lifting load and isolinetic peak torque of young adults without impairments.
BACKGROUND AND PURPOSE: Manual lifting is a frequent cause of back injury, and there is no evidence as to which training mode can provide the best training effect for lifting performance and muscle force. The purpose of this study was to examine the effects of a squat lift training and a free weight muscle training program on the maximum lifting load and isokinetic peak torque in subjects without known neuromuscular or musculoskeletal impairments. SUBJECTS: Thirty-six adults (20 male, 16 female) without known neuromuscular or musculoskeletal impairments participated. The subjects' mean age was 21.25 years (SD=1.16, range=20-24). METHODS: Subjects were divided into 3 groups. Subjects in group 1 (n=12) performed squat lift training. Subjects in group 2 (n=12) participated in free weight resistance training of their shoulder abductors, elbow flexors, knee extensors and trunk extensors. Subjects in group 3 (n=12) served as controls. The maximum lifting load and isokinetic peak torques of the trunk extensors, knee extensors, elbow flexors, and shoulder abductors of each subject were measured before and after the study. Training was conducted on alternate days for 4 weeks, with an initial load of 80% of each subject's maximum capacity and with the load increased by 5% weekly. RESULTS: All groups were comparable for all measured variables before the study. After 4 weeks, subjects in groups 1 and 2 demonstrated more improvement in maximum lifting load and isokinetic peak torque of the back extensors compared with the subjects in group 3, but the 2 training groups were not different. CONCLUSION AND DISCUSSION: The findings demonstrate that both squat lift and free weight resistance training are equally effective in improving the lifting load and isokinetic back extension performance of individuals without impairments. (+info)
Misclassification of physical work exposures as a design issue for musculoskeletal intervention studies.
OBJECTIVES: This study determined the impact of misclassification due to using job titles as surrogate variables for physical work exposures to assess confounding in a study of the preventive effect of back belts on back injury. The authors present retail merchandise data that quantify misclassification from residual confounding by physical work exposures on injury rate ratios when available administrative job titles are used. METHODS: Job title and direct observation data on 134 workers were used to calculate the percentage to which the job-title-adjusted rate ratio for back injury accounts for confounding by the true physical work exposures, awkward postures, and heavy weight handling. Workers' compensation data, an estimate of the effect of back belts from the literature, and the percentage of adjustment of the rate ratio due to the job title variable were used to calculate the magnitude of bias from the rate ratio adjusted for job title. RESULTS: The job title variable was found to have sensitivities of 97% and 85% and specificities of 68% and 58% for awkward postures and heavy weight handling, respectively. The magnitude of confounding bias remaining for the back-injury rate ratio when the job title surrogate was used was 24% for postures and 45% for heavy weight handling. CONCLUSIONS: The administrative job title performed poorly in this setting; residual confounding was sufficient to bias the rate ratio from 2.0 to 1.3. The effect of additional sources of misclassification and the need for better exposure measures than job title are discussed. (+info)
Spine: posture, mobility and pain. A longitudinal study from childhood to adolescence.
A longitudinal study was undertaken to analyse the development of posture and spinal mobility during growth and its relationship to low back pain and sports activities. A total of 90 children were examined at 5-6 years of age and re-examined at 15-16. Sagittal configuration and mobility were measured using Debrunner's kyphometer. Information about pain and activities was acquired by interview with the parents of the 5- to 6-year-olds and by a questionnaire to the 15- to 16-year-olds. Posture changed significantly during the study period: thoracic kyphosis increased by 6 degrees and lumbar lordosis increased by 6 degrees. The relationship between kyphosis and lordosis was independent of gender at age 5-6, but kyphosis in relation to lordosis was significantly lower in girls among the 15- to 16-year-olds. The total sagittal mobility of the spine decreased significantly during the 10-year study period: in the thoracic spine by as much as 27 degrees and in the lumbar spine by 4 degrees. About one-third of the children at the age of 15-16 years stated that they had occasional low back pain. This complaint was more frequent in those stating they had suffered some type of back injury, but low back pain was not related to gender, regular physical training, posture or spinal mobility. The results of the study showed that kyphosis and lordosis increased and mobility decreased in the 90 children who were examined both at age 5-6 and 15-16 years. The relationship between kyphosis and lordosis decreased in girls but not in boys. Occasional low back pain was reported by 38% of the children at the age of 15-16 years, but back pain was not related to posture, spinal mobility or physical activity. (+info)
Propensity for osteoarthritis and lower limb joint pain in retired professional soccer players.
OBJECTIVE: To quantify the prevalence of osteoarthritis and the severity of pain in the lower limb joints of players retired from English professional soccer. METHOD: An anonymous self administered questionnaire was distributed to 500 former players registered with the English Professional Footballers' Association. The questionnaire was designed to gather information on personal details, physical activity loading patterns, history of lower limb joint injury, and current medical condition of the lower limb joints. RESULTS: Of 500 questionnaires distributed, 185 (37%) were returned. Nearly half of the respondents (79: 47%) retired because of injury; 42% (33) were acute injuries and 58% (46) chronic injuries. Most of the acute injuries that led to early retirement were of the knee (15: 46%), followed by the ankle (7: 21%) and lower back (5: 15%). Most of the chronic injuries that led to early retirement were also of the knee (17: 37%), followed by the lower back (10: 22%) and the hip (4: 9%). Of all respondents, 32% (59) had been medically diagnosed with osteoarthritis in at least one of the lower limb joints. More respondents had been diagnosed with osteoarthritis in the knee joints than either the ankle or the hip joints. Significantly (p<0.001) more respondents reported pain in one lower extremity joint during one or more daily activities than those who did not (joint pain: 137, 80%; no joint pain: 35, 20%). CONCLUSION: The risk for professional soccer players of osteoarthritis in at least one of the lower extremity joints is very high and significantly greater than for the general population. The results support the suggestion that professional soccer players should be provided with health surveillance during their playing career. (+info)