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PubMed2002

Self-reported sleep quality, strain and health in relation to perceived working conditions in females.

Self-reported sleep quality, strain and health in relation to perceived working conditions in females The aims of this study were to examine self-reported sleep quality, perceived strain and health in relation to working conditions; the prevalence and severity of sleep disturbances and daytime distress arising from poor sleep in women on different work shifts. Furthermore, to see whether females with gastrointestinal symptoms, joint-, back- or muscle-pain and who are dissatisfied with working hours differ with regard to the above aspects. Finally, degree of strain-related symptoms and sleep difficulties were tested as predictors of sleep quality and general health outcome. Important research questions are whether registered nurses and those on rotating work shifts have greater sleep problems than others. A total of 156 females, aged 20-59 years, working at three different casualty departments, answered structured questionnaires. The results showed a persistently high rate of psycho-physiological long-term effects of stress related to working conditions. Thirty-four per cent were dissatisfied with their working hours, and exhibited significantly more mental strain, fatigue/excessive tiredness and inability to relax after work because of involuntary thoughts, in relation to working conditions than others did. Sixty-two females (39.7%) complained of insufficient sleep. The sleep quality outcome was significantly predicted by difficulty falling asleep (odds ratio 8.4), difficulty in falling asleep after nocturnal awakening (odds ratio 3.4) and perceived exhaustion (odds ratio 2.6). Females suffering from gastrointestinal symptoms and joint-, back- and muscle symptoms for several days in a week or even everyday were especially sensitive to worse sleep quality. Independent of work shifts, registered nurses exhibited a higher degree of mental strain and prolonged recovery in comparison with others. In conclusions, sleep initiation difficulties, troubled sleep and exhaustion significantly predicted reduced sleep quality outcome with decreased resilience to stress and vulnerability to psycho-physiological disorders in females working within the health care system.

Adult↗
PubMed1994

Spectral analysis of electromyogram in lumbar muscles: fatigue induced endurance contraction.

In the last few years, epidemiological studies have shown correlations between the low endurance capacity of the erector spinae muscle and low back pain (LBP). In this study, the function of the erector spinae muscle and localized muscle fatigue in LBP were investigated in both LBP patients and control subjects without LBP, using surface multi-channel electromyograms (EMG). Four positions (L1, L2, L4, L5) were chosen as representative locations for the different functions of the erector spinae muscle. Median frequency (fm) parameters of an EMG power density spectrum were monitored to quantify localized muscle fatigue. This research indicated a statistically significant difference (P < 0.05) in fm parameters between the LBP patients and the control subjects. The integrated electromyogram (iEMG) signals of LBP patients were considerably higher than for the control subjects during endurance isometric contraction. Our research suggested that human fatiguing erector spinae muscle, in submaximal voluntary contractions tests, induced a different firing order of motor unit spikes between two groups.

Adult↗
PubMed2006

Physical capacity in relation to low back, neck, or shoulder pain in a working population.

AIMS: To investigate the longitudinal relation between physical capacity (isokinetic lifting strength, static endurance of the back, neck, and shoulder muscles, and mobility of the spine) and low back, neck, and shoulder pain. METHODS: In this prospective cohort study, 1789 Dutch workers participated. At baseline, isokinetic lifting strength, static endurance of the back, neck, and shoulder muscles, and mobility of the spine were measured in the pain free workers, as well as potential confounders, including physical workload. Low back, neck, and shoulder pain were self-reported annually at baseline and three times during follow up. RESULTS: After adjustment for confounders, Poisson generalised estimation equations showed an increased risk of low back pain among workers in the lowest sex specific tertile of performance in the static back endurance tests compared to workers in the reference category (RR = 1.42; 95% CI 1.19 to 1.71), but this was not found for isokinetic trunk lifting strength or mobility of the spine. An increased risk of neck pain was shown for workers with low performance in tests of isokinetic neck/shoulder lifting strength (RR = 1.31; 95% CI 1.03 to 1.67) and static neck endurance (RR = 1.22; 95% CI 1.00 to 1.49). Among workers in the lowest tertiles of isokinetic neck/shoulder lifting strength or endurance of the shoulder muscles, no increased risk of shoulder pain was found. CONCLUSIONS: The findings of this study suggest that low back or neck endurance were independent predictors of low back or neck pain, respectively, and that low lifting neck/shoulder strength was an independent predictor of neck pain. No association was found between lifting trunk strength, or mobility of the spine and the risk of low back pain, nor between lifting neck/shoulder strength or endurance of the shoulder muscles and the risk of shoulder pain.

Adult↗
PubMedDate not supplied

Trunk muscular strength in pre-pubertal children with and without back pain.

OBJECTIVE: While in adulthood there is no proven relationship between back pain and trunk muscle strength, in pre-pubertal subjects this topic has been poorly studied. The aim of the study was to evaluate isometric and isokinetic trunk muscle strength in children with or without previous back pain. METHODS: The recent occurrence of back pain (last 6 months) among 144 children (77 males, 67 females, age 11.9 +/- 0.3 years) was assessed using a questionnaire. Extensor and flexor trunk muscle strength was measured through isometric and isokinetic (60, 90, 120 degrees/s) tests. Peak torque (PT), PT angle, PT flexor/PT extensor ratio and intra-session coefficient of variation (COV) were determined. RESULTS: Flexor and extensor muscle PT, but not PT angle, were significantly higher in males than in females, irrespective of back pain occurrence. PT flexor/PT extensor ratio at 90 degrees angular velocities increased significantly only in males with back pain, compared with males without back pain. The COV trend was similar for flexor and extensor muscles. CONCLUSIONS: Isometric and isokinetic trunk muscle strength probably play a minor role in back pain occurrence in children. The isokinetic testing velocity may be important in determining trunk strength differences between children with and without back pain.

Abdominal Muscles↗
PubMed1994

Hip-spine movement interaction and muscle activation patterns during sagittal trunk movements in low back pain patients.

Profiles of hip-spine movement interaction and muscle activations were characterized in 10 low back pain patients and in 10 normal subjects during trunk forward bending and extension. Electrogoniometric recordings showed that patients performed the movements significantly more slowly than normal subjects when asked to choose a comfortable cadence. For movements performed at the same velocity and amplitude, only the movement profiles at the spine and activation patterns of the erector spinae (ES) muscle during flexion were found to be significantly different between the two groups. A detailed analysis revealed that a subgroup of six patients (SG2) with an abnormal hip-spine movement interaction showed a significant (P < 0.01) lack of relaxation in ES muscle at the end of flexion. Patients from SG2 had pain for a longer time (P < 0.01) compared to patients from SG1 with normal movement and electromyographic profiles. Given the small sample size, these results are not conclusive, but they suggest that the lack of relaxation of the ES muscle may be associated with perturbation of movement patterns and the duration of the symptoms.

Adult↗
PubMed2004

Trunk muscle strength and disability level of low back pain in collegiate wrestlers.

INTRODUCTION/PURPOSE: Low back pain (LBP) is a frequent injury in athletes. This study examined the relationship between isokinetic trunk muscle strength and the functional disability level of chronic LBP. We particularly focused on the existence of radiological abnormalities (RA) in the lumbar region. METHODS: Subjects were 53 collegiate wrestlers. Trunk extensor and flexor muscle strength was measured at three angular velocities (60, 90, and 120degrees x s(-1)). The examined parameters for trunk muscle strength were peak torque, work, average torque, and average power. The disability level of LBP was estimated by using two questionnaires. Based on the RA evaluation with x-ray and MRI, all 53 wrestlers were assigned to two groups as the RA group (N = 35, 66%) and the non-RA group (N = 18, 34%). Correlations between trunk muscle strength and the disability level of LBP in each group were analyzed with Spearman's rank test. RESULTS: Without considering the disability level, there were 14 subjects with LBP (40%) in the RA group and 8 (44%) in the non-RA. Significantly correlated parameters with the disability level of LBP could be observed only when the subjects were restricted to the non-RA group. The correlated parameters with the two questionnaires were peak torque at 120degrees x s(-1), work at 60degrees x s(-1) and 90degrees x s(-1), and average torque at 90degrees x s(-1) and 120degrees x s(-1). There were no significantly correlated parameters in the RA group. None of the trunk flexor parameters were significantly correlated with the disability level of LBP. CONCLUSION: The relatively low strength of trunk extensors may be one of the factors related to nonspecific chronic low back pain in collegiate wrestlers.

Adolescent↗
PubMed2002

Changes in the surface EMG signal and the biomechanics of motion during a repetitive lifting task.

The analysis of surface electromyographic (EMG) data recorded from the muscles of the back during isometric constant-force contractions has been a useful tool for assessing muscle deficits in patients with lower back pain (LBP). Until recently, extending the technique to dynamic tasks, such as lifting, has not been possible due to the nonstationarity of the EMG signals. Recent developments in time-frequency analysis procedures to compute the instantaneous median frequency (IMDF) were utilized in this study to overcome these limitations. Healthy control subjects with no history of LBP (n = 9; mean age 26.3 +/- 6.7) were instrumented for acquisition of surface EMG data from six electrodes on the thoraco-lumbar region and whole-body kinematic data from a stereo-photogrammetric system. Data were recorded during a standardized repetitive lifting task (load = 15% body mass; 12 lifts/min; 5-min duration). The task resulted in significant decreases in IMDF for six of the nine subjects, with a symmetrical pattern of fatigue among contralateral muscles and greater decrements in the lower lumbar region. For those subjects with a significant decrease in IMDF, a lower limb and/or upper limb biomechanical adaptation to fatigue was observed during the task. Increases in the peak box acceleration were documented. In two subjects, the acceleration doubled its value from the beginning to the end of the exercise, which lead to a significant increase in the torque at L4/L5. This observation suggests an association between muscle fatigue at the lumbar region and the way the subject manipulates the box during the exercise. Fatigue-related biomechanical adaptations are discussed as a possible supplement to functional capacity assessments among patients with LBP.

Adaptation, Biological↗
PubMed1992

CT-based geometric data of human spine musculature. Part I. Japanese patients with chronic low back pain.

Mechanical factors are considered to play a dominant role in low back problems. Various spinal structures, including muscles, act in unison to resist the external load, including the body segments. An estimation of the forces in these requires a knowledge of the orientation, location, and area of cross-section of the muscles to complete the information for the formulation of a truly three-dimensional biomechanical mathematical model of the spine in the lumbar region. Computed tomography scans of 10 Japanese patients suffering from chronic low back pain were obtained to determine the geometric data of the abdominal and back muscles from the 12th thoracic vertebral to the first sacral vertebral level. The mean age +/- 1 SD of the group was 40.1 +/- 14.12 years (range, 24-70), 573 +/- 88.5 N of body weight (range, 441-705), and 1.63 +/- 0.09 m tall (range, 1.44-1.74). The geometric parameters quantified were the line of action, and the centroid and physiologic area of cross-section of each muscle as a function of the spinal level. The effective/physiological area of cross-section of each muscle changed along the length of the spine because of the change in the line of action of the muscle. The centroidal approach adopted for quantifying the lines of action of various muscles was found unsuitable for the abdominal muscles, excluding the rectus abdominis, because of the associated anatomic complexities. Alternatives are proposed to complete the data base. The application of the data for the formulation of a truly three-dimensional biomechanical model of the spine at the L3-4 level is briefly presented. Application to nonlinear optimization-based force predictions in various spinal structures is discussed.

Adult↗
PubMed2004

Intermingling versus clonal coherence during skeletal muscle development: mosaicism in eGFP/nLacZ-labeled mouse chimeras.

To study the relative contributions of clonal coherence vs. myoblast intermingling to the formation of mammalian skeletal muscles, enhanced green fluorescent protein (eGFP) and nLacZ labels were used to analyze neonatal and adult mouse embryo aggregation chimeras. The eGFP marker allowed us to estimate absolute levels of the eGFP transgenic parental contributions as well as variances of levels within a chimeric individual; nLacZ served as a counter-label in neonatal chimeras. In mature chimeric muscle, free intracellular diffusion of eGFP led to an averaging of the eGFP level in individual myofibers. Chimerism, i.e., differing eGFP levels, was evident between corresponding right and left muscles, between adjacent back, body wall, limb (shank, foot), and extraocular muscles and among myofibers within these muscles. Inhomogeneities in muscles far from their somitic origin indicated unbalanced sampling from small founder pools. The results obtained with adult eGFP<-->0 chimeras were corroborated by neonatal chimeras with complementary eGFP<-->nLacZ labels.

Animals↗
PubMed2000

Motor control problems in patients with spinal pain: a new direction for therapeutic exercise.

Recent research into muscle dysfunction in patients with low back pain has led to discoveries of impairments in deep muscles of the trunk and back. These muscles have a functional role in enhancing spinal segmental support and control. The muscle impairments are not those of strength but rather problems in motor control. These findings call for a different approach in therapeutic exercise, namely a motor learning exercise protocol. The specific exercise approach has an initial focus on retraining the cocontraction of the deep muscles (ie, the transversus abdominis and lumbar multi-fidus Initial clinical trials point to the effectiveness of the approach in patients with both acute and chronic low back pain in terms of reducing the neuromuscular impairment and in control of pain.

Exercise Therapy↗
PubMed2004

Influence of the load of a rider or of a region with increased stiffness on the equine back: a modelling study.

REASONS FOR PERFORMING STUDY: Knowledge of load effects is crucial for the understanding of the aetiology and pathogenesis of equine back problems. OBJECTIVE: To investigate different load scenarios of the equine back, such as being ridden or increased muscle tone, using biomechanical simulations. METHODS: Kinetic and kinematic data of 15 sound horses and the electromyelograph of their long back muscles were recorded. A biomechanical simulation model was used for simulations under different biomechanical scenarios (ridden/unridden, localised increased stiffness) using ADAMS. RESULTS: The vertical forces acting through a rider were: walk 3.83 N/kg, trot 5.18 N/kg and gallop 5.60 N/kg. No significant changes in transversal forces were found between ridden and unridden horses. Profound changes were seen in the torques at the segment following a region of increased stiffness: in walk, lateral peak torques increased from 342 to 1723 Nm, and in trot from 393 to 1004 Nm, and dorsoventral from 386 to 3705 Nm (walk) and 458 to 4340 Nm (trot). CONCLUSIONS AND POTENTIAL RELEVANCE: The simulation shows that the stress of a rider is lower than that of pathological processes such as partial increased stiffness of the back. Study of revised models with improved anatomical realism might help to raise the plausibility of model results.

Animals↗
PubMed1997

Interrater reliability of six tests of trunk muscle function and endurance.

Some studies have shown a relationship between trunk muscle strength and low back pain. Measures of trunk muscle strength and endurance, which are feasible in the clinical setting, are needed. The purpose of this study was to determine interrater reliability of six tests of abdominal and trunk extensor muscle strength and endurance. The tests included abdominal and extensor dynamic endurance, hand-held dynamometry of isometric flexion and extension, and abdominal and extensor static endurance. Thirty-nine healthy workers were recruited as subjects. Each was tested by three raters on 3 days within 1 week. Intraclass correlation coefficients (ICC) and the standard error of measurement (SEM) were calculated: abdominal dynamic endurance ICC = .89, SEM = 8 repetitions; extensor dynamic endurance ICC = .78, SEM = 9 repetitions; abdominal isometric force ICC = .25, SEM = 60 N; extensor isometric force ICC = .24, SEM = 68 N; abdominal static endurance ICC = .51, SEM = 35 seconds; extensor static endurance ICC = .59, SEM = 20 seconds. The dynamic endurance tests had acceptable interrater reliability. For the others, reliability was poor and the SEMs were large.

Abdominal Muscles↗
PubMedDate not supplied

[A case of stiff-man syndrome with an antineuronal autoantibody against an 80 kDa protein].

A 23-year-old Japanese man had noted intermittent muscle stiffness in his lower limbs and trunk in addition to painful muscle cramps in his back over one year. The muscle stiffness continued and eventually spread to his upper limbs. Neurological examinations revealed saccadic ocular movement and stiffness in the masseter, neck and four limbs and truncal muscles, enhanced by both voluntary and passive movements. Although the mobility of his joints was severely limited, the muscle strength was preserved. Electromyograms showed the continuous firing of normal motor units at rest, which disappeared both during sleep and after the intravenous administration of 10 mg of diazepam. An oral glucose tolerance test showed a normal pattern. Both the adrenal and thyroid functions were normal. No antibody against glutamic acid decarboxylase was detected in either the patient's serum or cerebrospinal fluid (CSF). The serum antibody against the voltage-gated potassium channel was also negative. Western blot analysis revealed the presence of an antibody in his serum and CSF which reacted with an 80kDa protein in the rat cerebrum, cerebellum and human spinal cord, but not in the rat liver. This patient was thus diagnosed as having stiff-man syndrome. Treatment with oral diazepam (50 mg/day), a GABAA agonist, proved to be effective, whereas baclofen (75 mg/day), a GABAB agonist, was not. These results suggest the dysfunction of the GABA neurons in this case, similar to that as previously observed in other cases of stiff-man syndrome while, in addition, the function of the GABAB receptor was also markedly disturbed in this case.

Adult↗
PubMed2005

Trunk muscular activation patterns and responses to transient force perturbation in persons with self-reported low back pain.

Trunk stability requires muscle stiffness associated with appropriate timing and magnitude of activation of muscles. Abnormality of muscle function has been implicated as possible cause or consequence of back pain. This experimental study compared trunk muscle activation and responses to transient force perturbations in persons with and without self-reported history of low back pain. The objective was to determine whether or not history of back pain was associated with (1) altered anticipatory preactivation of trunk muscles or altered likelihood of muscular response to a transient force perturbation and (2) altered muscle activation patterns during a ramped effort. Twenty-one subjects who reported having back pain (LBP group) and twenty-three reporting no recent back pain (NLBP group) were tested while each subject stood in an apparatus with the pelvis immobilized. They performed 'ramped-effort' tests (to a voluntary maximum effort), and force perturbation tests. Resistance was provided by a horizontal cable from the thorax to one of five anchorage points on a wall track to the subject's right at angles of 0 degrees, 45 degrees, 90 degrees, 135 degrees and 180 degrees to the forward direction. In the perturbation tests, subjects first pulled against the cable to generate an effort nominally 15% or 30% of their maximum extension effort. The effort and the EMG activity of five right/left pairs of trunk muscles were recorded, and muscle responses were detected. In the ramped-effort tests the gradient of the EMG-effort relationship provided a measure of each muscle's activation. On average, the LBP group subjects activated their dorsal muscles more than the NLBP group subjects in a maximum effort task when the EMG values were normalized for the maximum EMG, but this finding may have resulted from lesser maximum effort generated by LBP subjects. Greater muscle preactivation was recorded in the LBP group than the NLBP group just prior to the perturbation. The likelihood of muscle responses to perturbations was not significantly different between the two groups. The findings were consistent with the hypothesis that LBP subjects employed muscle activation in a quasi-static task and preactivation prior to a perturbation in an attempt to stiffen and stabilize the trunk. However, interpretation of the findings was complicated by the fact that LBP subjects generated lesser efforts, and it was not known whether this resulted from anatomical differences (e.g., muscle atrophy) or reduced motivation (e.g., pain avoidance).

Adult↗
PubMed2002

Prevalence and site specificity of Sarcocystis greineri sarcocysts in Virginia opossum (Didelphis virginiana) in Florida.

Sarcocysts of Sarcocystis greineri in the Virginia opossum (Didelphis virginiana) were observed for documenting sarcocyst prevalence, seasonal prevalence, and muscle specificity. Characteristics of sarcocysts found in striated muscle were recorded, as were light microscopy measurements. Overall prevalence of sarcocysts in striated muscle was 10.0% (24/240). No statistical difference (P = 0.156) in prevalence was detected between summer (13.1%; 16/122) and fall (6.7%; 8/118). Sarcocysts were found in muscles of the diaphragm, leg, breast, tongue, back, and esophagus. Diaphragm had the highest specificity of 72.7% (8/11), which was significantly different (P = 0.05) when compared with tongue and esophagus at 16.6% (1/6). Breast and leg muscle had a specificity of sarcocysts of 54.5% (6/11), whereas 27.2% (3/11) of back muscles contained sarcocysts.

Animals↗