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PubMed1997

Muscular strength and bone mineral density in haemodialysis patients.

PURPOSE: The objective of this study was to determine the relationship between muscular strength and bone mineral density (BMD) in patients undergoing regular haemodialysis. METHODS: The BMD was measured in the lumbar spine (L2-L4) and in the proximal femur (femoral neck and trochanter) with dual-energy X-ray absorptiometry DEXA (Lunar DPX). Muscular strength of the extensors, flexors and abductors muscles of the femur (proximal muscles) and the extensors muscles of the back was measured with an isometric dynamometer. Thirty patients, 15 women with a mean age of 33.7 years (18-43) and 15 men with a mean age of 45.5 years (18-65) were included in the study. RESULTS: There was a positive and significant correlation between the BMD of the femoral neck and muscular strength of the flexors (r = 0.490, P < 0.005), the extensors (r = 0.658, P < 0.01) and the abductors muscles of the femur (r = 0.671, P < 0.0008), as well as between the muscular strength of the flexors (r = 0.413, P < 0.02) and extensors muscles of the femur (r = 0.433, P < 0.01) with BMD of the trochanter. There was no correlation between the muscular strength of the back extensor muscles and the BMD of the lumbar spine (r = -0.119, P NS). There was no correlation between the BMD and the number of years of haemodialysis therapy (r = -0.032, P NS), the patient's age (r = -159, P NS), or the value of serum PTH (r = 0.369, P NS) respectively. However, there was a significant correlation between the BMD of the femoral neck with muscular strength (r = 0.602, P < 0.05). CONCLUSION: This study reveals the close relationship that exists between muscular strength of the proximal muscles and the BMD of proximal femur in patients undergoing haemodialysis.

Adolescent↗
PubMed2004

Axotomy-dependent and -independent synapse elimination in organ cultures of Wld(s) mutant mouse skeletal muscle.

Progressive "dying back" neurodegenerative diseases are debilitating due to loss of connectivity after nerve terminal and axonal withdrawal, which impairs peripheral nerve function and leads ultimately to neuronal cell death. The mutant mouse (Wallerian degeneration slow; Wld(s)) provides an accessible model system to understand orthograde and retrograde degeneration, because in these mice axotomy induces slow, progressive withdrawal of nerve terminals from motor endplates. Axon degeneration itself is about 10 times slower than in wild-type mice. We describe an organ culture paradigm that permits direct observation of the progressive changes in morphology of neuromuscular junctions in Wld(s) mutant mice. Normal nerve terminal and motor endplate morphology were maintained at most Wld(s) neuromuscular junctions for up to 72 hr in vitro. At others, synaptic boutons were removed from postsynaptic junctional folds in piecemeal fashion, as observed in adults in vivo. By contrast, nerve terminals degenerated rapidly and synchronously in wild-type muscle cultures, resembling Wallerian degeneration in vivo. These observations confirm that in Wld(s) mice, axotomy triggers a mechanism of nerve-terminal withdrawal that seems qualitatively different from that in wild-type animals. The piecemeal dismantling of presynaptic terminals resembles that occurring during neonatal synapse elimination. Organ cultures of neonatal Wld(s) muscle maintained for 1-2 days in vitro also showed no evidence of synaptic terminal degeneration, but elimination of polyneuronal innervation progressed in vitro at approximately the same rate as in vivo. Taken together, the data suggest that both natural and axotomy-induced forms of synapse withdrawal may be accessible to continuous observation and analysis, in organ-cultures of Wld(S) mouse muscles. This offers several advantages over repeated visualization of synaptic remodeling that has thus far been possible only in vivo.

Animals↗
PubMed1994

Return to work following an aquafitness and muscle strengthening program for the low back injured.

Our purpose, in this prospective clinical study, was to identify the best predictors of 2-month return to work or retraining for a group of low back injured subjects (n = 40) who completed at least 8 weeks of a community-based rehabilitation program that combined aerobic and flexibility exercise conducted in the water (aquafitness) with muscle strength and endurance training. Baseline demographic characteristics and changes in physical fitness, pain, disability, and psychological well-being during the course of program participation were compared between two groups of low back injured subjects: those who returned to work (RTW) [n = 24], and those who did not (N-RTW) [n = 16]. Subjects in both groups showed comparable improvement in measures of physical fitness at 8 weeks. However, multivariate analyses showed significant between-group differences in self-report measures. The RTW group showed significant improvement in measures of pain, disability, anxiety, and vigor while self-esteem and affect remained stable. The N-RTW group displayed no change in pain and disability variables and had significant deterioration in mean overall psychological well-being over time. The best predictors of return to work using logistic regression analyses were a first injury rather than a repeat injury to the lower back, and stability in self-esteem. Suggestions are offered for further research to examine the benefits of aquafit exercise for the low back injured, for additional interventions for those with a reinjury, and for maintaining or enhancing self-esteem as a treatment goal.

Adult↗
PubMed2005

Trunk muscle recruitment patterns in specific chronic low back pain populations.

BACKGROUND: It is hypothesized that injury or degeneration of osteoligamentous spinal structures would require compensation by trunk musculature and alterations in motor control to maintain spine stability. While, biomechanical modeling has supported this hypothesis, studies of muscle recruitment patterns in chronic low back pain patients both with and without significant osteoligamentous damage have been limited. This study utilized a non-randomized case-control design to investigate trunk muscle recruitment patterns around the neutral spine position between subgroups of patients with chronic mechanical low back pain and asymptomatic controls. METHODS: Twenty subjects with chronic low back pain attributed to clinical lumbar instability were matched to 20 asymptomatic controls. In addition 12 patients with non-specific chronic low back pain were studied. Surface EMG from five trunk muscles was analyzed to determine activation levels and patterns of recruitment during a standing reach under two different loading conditions. FINDINGS: The chronic low back pain group with symptoms attributed to clinical instability demonstrated significantly higher activation levels of the external oblique and rectus abdominus muscles and lower abdominal synergist ratios than the control group. No significant differences were found between patient subgroups. INTERPRETATION: While these data demonstrate altered muscle recruitment patterns in patients with chronic low back pain, the changes are not consistent with Panjabi's theory suggesting that these alterations are driven by passive subsystem damage. However, the higher activation of global abdominal musculature and altered synergist patterns may represent a motor control pattern that has consequences for continued dysfunction and chronic pain.

Abdominal Muscles↗
PubMed2003

Trunk muscle response to lifting unbalanced loads with and without knowledge of centre of mass.

OBJECTIVE: To examine the effects of lifting a bin with a variable centre of mass on muscle activity, with and without knowledge of the centre of mass. BACKGROUND: Numerous parameters related to lifting have been examined yet the effects of changing the load centre of mass in two dimensions, with or without knowledge, has not been examined. METHODS: Participants lifted a 6 kg industrial tote bin with a 7 and 11 kg mass randomly placed in each of nine compartments, into which the interior of the bin was partitioned. Participants were not restricted in lifting style other than using the handles, which were equipped with force gauges. Two series (9 lifts per series) were completed using the 7 kg load without knowledge of the load placement and one series with knowledge of the load placement. One series was completed using an 11 kg mass without knowledge of load placement. Electromyographic activity of the upper and lower erector spinae, latissimus dorsi and the external obliques were collected bilaterally. RESULTS: Left and right muscle pairs demonstrated mirror images for all muscles with lowest activity levels when the load was placed nearer the lifter in the sagittal plane. Peak electromyographic activity of the upper erector spinae and latissimus dorsi increased with the weight in the compartments nearest the body and/or the ipsilateral handle. Conversely, peak electromyographic activity of the lower erector spinae and the obliques increased when the weight was on the contralateral side. Peak upper erector electromyographic activity reached up to 41% of maximum and the lower erectors reached 50% of maximum, while the obliques and latissimus dorsi were below 5% and 7%, respectively. No electromyographic activity differences were found between the known and unknown load placements. DISCUSSION: A segmental control strategy appears to exist during lifting that works from the upper to lower torso based on peak electromyographic activity activity. When lifting a bin with a varied centre of mass, highest peak electromyographic activity for the upper and lower erector spinae occurred when the load is closest to the body, regardless of load knowledge. Based on our findings with asymmetrical loads, we conclude that the moments acting on the wrist play an important role in spinal loading and must be included in future studies. RELEVANCE: Asymmetrical loads are often encountered in daily life. Regardless of the lifter's knowledge of the balance of the load, the differential and asymmetrical loading of the muscles of the back play a role in the development of low back pain.

Abdominal Muscles↗
PubMed1992

Two myogenic lineages within the developing somite.

It is well known that the muscles of the vertebrate body are derived from the somite. Precursor cells within the somite proper form the back or axial muscles while other precursor cells migrate away from the somite to populate the muscle of the limbs and ventral body wall. Although both types of muscle are generally thought of as arising from a common progenitor population, the myotome, recent evidence points to developmental differences in these two groups of muscles which may reflect different developmental lineages. To test the lineage hypothesis, we used microsurgery and the chick-quail nucleolar marker system to follow the developmental fate of the lateral and medial halves of somites at the wing level. The results showed that the structures of the mature somite (myotome and sclerotome) are derived virtually exclusively from cells residing in the medial half of the newly formed somite. On the other hand, virtually all of the cells residing in the lateral half of the newly formed somite are destined to leave the somite proper and populate the limb muscle and, probably, other somite-derived mesenchymal structures in the limb and ventral body wall. Switch-graft experiments show that the two halves of newly formed somites are largely interchangeable demonstrating that their ultimate developmental fate is position-dependent and that it becomes fixed as a result of extrinsic influences which act during later stages of somitogenesis. We conclude that at least two distinct myogenic lineages exist in the somite; one giving rise to the muscles of the back and the other giving rise to the limb musculature.

Animals↗
PubMed2005

Press stop to start: the role of inhibition for choice and health.

In order to react adequately to any new challenge, it is necessary to stop all ongoing activity. The first phase in the orienting response to a novel stimulus is an arrest of all ongoing activity. Inhibition is also necessary to switch from one behaviour to another, and from one cognitive activity to another. Inhibition was a difficult phenomenon to handle until the role of inhibitory synapses was demonstrated, and that many brain areas have an inhibitory function for overt behaviour and for establishing new responses in learning experiments. The role of these areas for learning and for plasticity of the brain has been well established. Recently, the role of inhibition, or lack of inhibition, for cognitive activities has been discussed for the understanding of somatization and sensitization to afferent somatic impulses. It has been postulated that muscle pain is maintained by positive feed back loops between muscles, the spinal cord, and the brain areas for pain and interpretation of pain. Activity in these loops may lead to sensitisation of the neural circuits, leading to chronic pain states. Similar models have been presented for non-specific gastric and intestinal complaints, and for fatigue and depression. Rumination and perseveration of negative thoughts may maintain the activity in these loops.

Animals↗
PubMed1992

Craniomandibular disorders and masticatory muscle function.

The heading craniomandibular disorders covers a wide range of abnormal and pathologic conditions accompanied by orofacial pain and impaired mandibular function, the masticatory muscles and the temporomandibular joints being the structures most frequently involved. Prevalences of severe craniomandibular disorders accompanied by headache and facial pain urgently in need of treatment are 1-2% in children, about 5% in adolescents, and 5-15% in adults, with higher values in women than in men. With respect to physiology and ergonomics, masticatory muscles are comparable to other human skeletal muscles, e.g. of shoulder, neck and lower back. Therefore these muscles share pathogenesis, symptoms and signs of muscular disorders caused by prolonged, low-level static contractions or intermittent isometric contractions at higher levels. Since the same elements of performance in the masticatory muscles are influenced by occlusal factors, they link the development of muscular fatigue, discomfort and pain to the dental occlusion. Furthermore, changes of the occlusal surfaces, e.g. due to dental treatment, may influence the performance of the masticatory muscles, and consequently interfere with local muscular function.

Adolescent↗
PubMed2004

The value of electromyography of the lumbar paraspinal muscles in discriminating between chronic-low-back-pain sufferers and normal subjects.

The authors studied the surface electromyographic (EMG) spectrum of the paraspinal muscles of 350 subjects. They were classified by their history as normal (n=175), chronic low back pain (n=145), or past history (n=30). They pulled upwards on a floor-mounted load cell at two-thirds of their maximum voluntary contraction for 30 s, while the EMG was measured from the paraspinal muscles at the L4/L5 level. From the EMG signal the root-mean-square (RMS) was calculated. Power spectrum analysis allowed calculation of the median frequency slope, the initial median frequency (IMF), modal frequency, peak amplitude and spectral width at half peak amplitude (half-width). All of the variables of the chronic group were significantly different from the normal group, except the median frequency slope, RMS slope and mode. Half-width, age and maximum voluntary contraction were shown to be independent predictors of back pain classification. Half-width classified the subjects with a sensitivity of 0.65 and a specificity of 0.75.

Chronic Disease↗
PubMed1997

Fibre type characteristics of the lumbar paraspinal muscles in normal healthy subjects and in patients with low back pain.

A knowledge of the alteration in the fibre type profile of paraspinal muscle associated with low back pain is essential for the design of successful rehabilitation programmes. In attempting to compare the muscles of patients with low back pain with those of controls, few previous studies have considered factors such as gender, age, and size of the subjects, each of which can potentially confound interpretation of the results. We obtained samples of lumbar paraspinal muscle during spinal surgery from 21 patients with low back pain and, using the percutaneous biopsy technique, from 21 control volunteers matched for gender, age, and body mass. The samples were subject to routine histochemical analysis to determine characteristics of muscle fibre type. Compared with controls, the muscle of the patients had a significantly higher proportion of type-IIB (fast-twitch glycolytic) fibres than type-I (slow oxidative) fibres. The mean size of a given fibre type did not differ between the patients and the controls. Consequently, the relative area of the muscle occupied by type-IIB fibres was higher and that by type-I fibres was lower in the patients. The patients had a greater number of muscle samples with more than 1% type-IIC fibres, and abnormalities that could be described as pathological were more marked in the patients than in the controls. In conclusion, the paraspinal muscles of patients who have low back pain display a more glycolytic (faster) profile; this can be expected to render them less resistant to fatigue.

Adenosine Triphosphatases↗
PubMed2001

Impaired postural control of the lumbar spine is associated with delayed muscle response times in patients with chronic idiopathic low back pain.

STUDY DESIGN: Balance performance in unstable sitting and trunk muscle response to quick force release were measured in 16 patients with chronic low back pain and 14 matched healthy control subjects. OBJECTIVES: To determine whether patients with low back pain will exhibit poorer postural control, which will be associated with longer average muscle response times. SUMMARY OF BACKGROUND DATA: Larger postural sway during standing and delayed trunk muscle response times for patients with low back pain have been reported in several independent studies. METHODS: Unstable sitting test was accomplished by attaching different sized hemispheres to the bottom of a seat. Subjects performed trials with eyes open and closed while the displacements of the center of pressure were measured with a force plate underneath the seat. Response to a quick force release was recorded from 12 major trunk muscles with surface electromyography. Subjects performed isometric trunk exertions in a semi-seated position when the resisted force was suddenly released with an electromagnet. Average muscle response times and balance performance were correlated using a linear regression analysis. RESULTS: Patients with low back pain demonstrated poorer balance performance than healthy control volunteers, especially at the most difficult levels. Patients also had delayed muscle response times to quick force release. Average muscle onset times together with age and weight correlated significantly with balance performance with closed eyes (R(2) = 0.46), but not with eyes opened (R(2) = 0.18). CONCLUSIONS: Patients with chronic low back pain demonstrated poorer postural control of the lumbar spine and longer trunk muscle response times than healthy control volunteers. Correlation between these two phenomena suggests a common underlying pathology in the lumbar spine.

Adult↗
PubMed2005

Morning warming-up exercise--effects on musculoskeletal fitness in construction workers.

The aim of the present study was to evaluate the effects on muscle stretchability, joint flexibility, muscle strength and endurance in construction workers of a 3-month period of a 10-min morning warming-up exercise (MWU), performed at the building site every working day. Thirty construction workers participated in the program. Seventeen construction workers at other building sites served as controls. Muscle stretchability, joint flexibility, muscle strength and endurance were measured before and after the program. Significant increase of thoracic and lower back mobility, increase of hamstring and thigh muscle stretchability were seen in the MWU group. A significant difference in back muscle endurance was found due to decreased endurance in the controls. Muscular strength was not influenced by the MWU. The results indicate that a short dose of morning warming-up exercise could be beneficial for increasing or maintaining joint and muscle flexibility and muscle endurance for workers exposed to manual material handling and strenuous working positions.

Adult↗
PubMed2000

Optimal sagittal motion axis for trunk extension and flexion tests in chronic low back trouble.

OBJECTIVE: To find the optimal height for sagittal motion axis for trunk strength test in chronic low back trouble. DESIGN: Cross-sectional study. BACKGROUND: The strength of trunk muscles of low back pain patients is decreased. The measured strength depends on the height of the sagittal motion axis but the differences between patients and controls are not known. METHODS: 114 (67 female) patients with chronic low back trouble are classified according to Quebec Task Force, 50 (31 female) patients with rheumatic disorder, but without low back trouble, and 33 (22 female) healthy controls, no appreciable physical differences but clear differences in Oswestry score. Isometric trunk extension-flexion test with different heights for the pelvic fulcrum. RESULTS: Force decreased in extension, increased in flexion, and torque increased both in flexion and extension in every group (P<0.001) as the fulcrum was moved caudally. The male controls were stronger than patients with low back trouble (P<0.01). The female controls were stronger only if the fulcrum was set at the hip joint level (P<0.05). There were no differences between patients with rheumatic disorder and low back trouble, except in extension if the fulcrum was at the hip joint level (P<0.02). CONCLUSIONS: The rotation axis in trunk extension-flexion strength test should be set at the level of the hip joint. RELEVANCE: Trunk muscle weakness is a common sign of different rheumatic disorders. Proper setting of sagittal motion axis and concomitant measurement of trunk and hip extensor or flexor muscles increases the specificity of the strength test for low back trouble.

Abdominal Muscles↗
PubMed2002

Changes in lumbar lordosis in young patients with low back pain during a 10-year period.

Height and muscle strength have reportedly changed among Japanese youth during the past 10 years. Height has increased, and the back muscles have become weaker than 10 years ago. We compared the lumbar lordosis of youth today (113 men and 76 women) and of 10 years ago (85 men and 62 women). Lumbar lordosis and sacral inclination were measured on lateral standing radiographs of the lumbar spine. We also measured the same parameters among adults today (63 men and 63 women) and 10 years ago (56 men and 73 women) to study postural changes in another generation. In both men and women, the lumbar lordosis and the sacral inclination of youth today were approximately 10 degrees larger than they were 10 years ago ( P < 0.0001). However, there was no significant difference between the values among adults today and those of the same generation 10 years ago.

Adolescent↗