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PubMedDate not supplied

Are the changes in postural control associated with low back pain caused by pain interference?

BACKGROUND: Voluntary limb movements are associated with involuntary and automatic postural adjustments of the trunk muscles. These postural adjustments occur prior to movement and prevent unwanted perturbation of the trunk. In low back pain, postural adjustments of the trunk muscles are altered such that the deep trunk muscles are consistently delayed and the superficial trunk muscles are sometimes augmented. This alteration of postural adjustments may reflect disruption of normal postural control imparted by reduced central nervous system resources available during pain, so-called "pain interference," or reflect adoption of an alternate postural adjustment strategy. METHODS: We aimed to clarify this by recording electromyographic activity of the upper (obliquus externus) and lower (transversus abdominis/obliquus internus) abdominal muscles during voluntary arm movements that were coupled with painful cutaneous stimulation at the low back. If the effect of pain on postural adjustments is caused by pain interference, it should be greatest at the onset of the stimulus, should habituate with repeated exposure, and be absent immediately when the threat of pain is removed. Sixteen patients performed 30 forward movements of the right arm in response to a visual cue (control). Seventy trials were then conducted in which arm movement was coupled with pain ("pain trials") and then a further 70 trials were conducted without the pain stimulus ("no pain trials"). RESULTS: There was a gradual and increasing delay of transversus abdominis/obliquus internus electromyograph and augmentation of obliquus externus during the pain trials, both of which gradually returned to control values during the no pain trials. CONCLUSION: The results suggest that altered postural adjustments of the trunk muscles during pain are not caused by pain interference but are likely to reflect development and adoption of an alternate postural adjustment strategy, which may serve to limit the amplitude and velocity of trunk excursion caused by arm movement.

Abdominal Muscles↗
PubMed2003

Short-duration fatigue alters neuromuscular coordination of trunk musculature: implications for injury.

The aim of this investigation was to determine the effect of muscle fatigue, produced by two different fatigue protocols, on the coordination of trunk and thigh muscles during the performance of a manual-handling task (e.g. a weighted stoop lift). The two fatigue protocols were designed to produce either (a) a non-specific widespread fatigue of trunk and limb muscles (e.g. rowing fatigue protocol), or (b) a specific fatigue of the trunk extensor musculature (e.g. back extension fatigue protocol). Specifically, we wished to determine whether the coordination of trunk muscles during a stoop lift was compromised more, or less, by either of these two fatigue protocols. Ten male subjects (20-24 years) were tested utilising an electromyographic technique which collected electromyograms from trunk flexor and extensor muscles, as well as the Hamstring muscle group, during a pre- and a post-fatigue performance of a weighted stoop lift. The results showed that the back extension fatigue protocol, but not the rowing fatigue protocol, produced significant (p<0.05) changes in the timing of trunk muscle activation during a stoop lift. The longer periods of muscle activation seen only after the back extension fatigue protocol, suggested that fatigue of these muscles had required the CNS to alter their periods of activation to a pattern similar to that previously seen in elderly populations. The results also suggested that intense short-duration motor tasks, which may differentially target the back and its musculature, could leave the spine susceptible to increased risk of injury even though worker perceptions of general fatigue are low. Risk assessment guidelines for manual handling should consider not only the weight and frequency of the lift, but lift duration as well to maintain worker safety.

Adult↗
PubMed1979

Ballistic flexion movements of the human thumb.

1. In response to an auditory stimulus normal subjects made ballistic flexion movements of the top joint of the thumb against a lever attached to the spindle of a low-inertia electric motor. 2. Electromyographic (e.m.g.) activity was recorded from pairs of fine wire electrodes inserted into flexor pollicis longus and extensor pollicis longus, respectively the sole flexor and extensor of the joint. 3. Movements of 5 degrees, 10 degrees and 20 degrees were made from initial angles of 10 degrees, 20 degrees and 30 degrees flexion against torques of 0.04, 0.08 and 0.16 Nm. 4. The e.m.g. activity initiating such movements was characterized by a 'triphasic' pattern of sequential bursts of activity in the agonist (flexor pollicis longus), then in the antagonist (extensor pollicis longus), and then in the agonist again. 5. The duration of the first agonist and first antagonist bursts ranged from about 50 to 90 ms and there was no significant change of burst length in the different mechanical conditions. 6. In movements of differing angular distance, the rectified and integrated e.m.g. activity of the first agonist burst could be correlated with the distance moved. The rectified and integrated e.m.g. activity of the first antagonist burst could not be correlated with the distance moved. 7. Responses of the muscles to perturbations either before or during the ballistic movements were studied. Current in the motor could be altered so to extend the thumb ('stretch'), to allow it to accelerate ('release'), or to prevent further movement ('halt'). 8. Suitably timed stretch increased the e.m.g. activity of the first agonist burst while release decreased it. 9. There was a small response of the agonist to stretch or halt timed to act during the interval between the first two agonist bursts; the major response was an augmentation of the second agonist burst. 10. Stretch, timed to act between the first two agonist bursts which released the antagonist, diminished the activity of the first antagonist burst while halt virtually eradicated it in all but one subject. Release, at this time, which stretched the antagonist, increased the activity of the first antagonist burst. 11. It is concluded that the individual components of a ballistic movement are relatively fixed in duration and the amount of e.m.g. activity is altered within this time interval to produce the different forces required for fast movements of different amplitude. 12. Both agonist and antagonist muscles remain under some feed-back control during the entire course of a ballistic movement, but the amount of influence of fedd-back depends on the supraspinal command signal and the changes in the spindle during the course of the movement.

Electromyography↗
PubMed1999

Spinal muscle pathology.

Clinical signs that are easily referred to spinal muscle pathology include atrophy of epaxial muscles, focal swelling and palpable tenderness, as well as enlarged muscles with increased tone. Less easily recognized signs include rigidity of the spine, shortened stride, hindlimb lameness, and indicators of poor performance. Muscle biopsy is one option in evaluating sore backs and is best used when physical examination and imaging procedures do not reveal a likely diagnosis or when conventional treatments are unsuccessful. Rhabdomyolysis of spinal muscles may be due to nutritional myodegeneration (foals), recurrent exertional rhabdomyolysis, and polysaccharide storage myopathy. Atrophy of spinal muscles can be due to severe rhabdomyolysis, immune-related myopathy, or neurogenic atrophy from nerve trauma, EPM, or EMND.

Animals↗
PubMed2002

Injury prevention for the practice of dentistry.

There is an abundance of dental professionals with work-related pain and dysfunction. Dentistry poses a huge challenge because of the ergonomics of dental work. The biggest risk factors are the awkward prolonged seated postures with no back support and the limited range of motion and isometric muscle contraction created by working in a confined area, namely the mouth. The following manuscript offers exercises that constitute a preventive program to target the typical problem areas of the dental professional--the neck, lower back and wrist/hand.

Dentistry↗
PubMed1995

[Changes of masticatory muscle activity after surgical orthodontic treatment for skeletal mandibular protrusion].

The purpose of this study was to analyze the recovery process of masticatory muscle activity after mandibular set-back osteotomy. The subjects were 11 adult patients with skeletal mandibular protrusion. They received surgical orthodontic treatment and attained a stable occlusion. E. M. G. recordings of clenching and habitual jaw movement were taken from the temporalis anterior, posterior, and masseter muscles with surface electrodes before preoperative orthodontic treatment just before surgery, and 6 months, 1 year and over 5 years after surgery. The parameters of E. M. G. analysis were 70% of the maximum voltage, the buildup time from the onset of activity to 70% of the maximum voltage and the time difference of the onset of activity in reference muscles. The results were as follows: 1. The initial level of E. M. G. activity was related to the rate of recovery following surgery. 2. Differences in masticatory muscle activity were reflected in the activity levels of the respective muscles during the recovery period. 3. A fairly complete recovery of E. M. G. activity was attained about ten months after surgery. 4. The time from the onset of activity to attaining 70% of the maximum voltage became progressively shorter. 5. The time difference of the onset of activity in reference to muscles decreased. It was I concluded that masticatory muscle activity could well adapt to the newly surgically-established maxillomandibular skeletal relationship.

Adolescent↗
PubMed2005

Molecular characteristics suggest an effector function of palisade endings in extraocular muscles.

PURPOSE: To analyze palisade endings in cat extraocular muscles (EOMs) and to clarify whether these EOM-specific organs are sensory or motor. METHODS: Twelve cats aged between 1 and 16 years were analyzed. Whole EOM tendons were immunostained using four different combinations of triple fluorescence labeling. Triple labeling included antibodies against choline acetyltransferase (ChAT), neurofilament, synaptophysin, and alpha-bungarotoxin. Preparations were examined by confocal laser scanning microscopy. ChAT-labeled EOMs were also analyzed by immunoelectron microscopy. Three-dimensional reconstructions were made of palisade endings. RESULTS: Palisade endings were found in the distal and proximal myotendinous regions of cat EOMs. These endings arose from thin nerve fibers coming from the muscle and extending into the tendon. There, the nerve fibers turned back 180 degrees to divide into terminal branches around the muscle fiber tips. Terminal branches established numerous contacts with the tendon attached to the muscle fiber tip and only a few contacts with the muscle fiber. Often, nerve fibers forming palisade endings on muscle fiber tips were observed to establish multiple motor contacts on muscle fibers outside palisade endings. Three-dimensional reconstructions depicted the complex morphology of the palisade endings. All nerve fibers supplying palisade endings stained positively for ChAT and neurofilament. All nerve terminals in palisade endings were ChAT and synaptophysin positive. Only neuromuscular contacts in palisade endings were positive for alpha-bungarotoxin, as well. CONCLUSIONS: This study provides evidence that palisade endings in cat EOMs have effector function. The findings may be of significance for strabismus surgery because palisade endings are also found in human EOMs.

Animals↗
PubMed1987

The ventral rib cage muscles in the dog: contractile properties and operating lengths.

To have some insight into the mechanical interplay between the parasternal intercostal and triangularis sterni muscles during breathing, we have examined the isometric contractile properties of these two muscles in the dog. Using piezoelectric crystals, we have also measured the respiratory changes in muscle length in eight spontaneously breathing animals in the supine posture, and we have compared the in situ relaxation length (Lr) of these two muscles to their respective in vitro optimal force-producing length (Lo). The triangularis sterni and parasternal intercostals had similar isometric twitch, force-frequency, and length-tension characteristics. These two muscles, therefore, are intrinsically similar. In supine dogs, however, they operate on quite distinct segments of their length-tension curve. Whereas Lr for the parasternals corresponded to 117% Lo, Lr for the triangularis sterni was only 75% Lo. This suggests that the triangularis sterni in supine dogs operates on a poorly advantageous portion of its length-tension curve. However, shortening of the parasternals during inspiration causes considerable passive distension of the muscle. As a result, the triangularis sterni is much closer to its optimal length when it starts contracting in early expiration.

Animals↗
PubMed2003

Widespread PrPSc accumulation in muscles of hamsters orally infected with scrapie.

Scrapie, bovine spongiform encephalopathy and chronic wasting disease are orally communicable, transmissible spongiform encephalopathies (TSEs). As zoonotic transmissions of TSE agents may pose a risk to human health, the identification of reservoirs for infectivity in animal tissues and their exclusion from human consumption has become a matter of great importance for consumer protection. In this study, a variety of muscles from hamsters that were orally challenged with scrapie was screened for the presence of a molecular marker for TSE infection, PrPSc (the pathological isoform of the prion protein PrP). Sensitive western blotting revealed consistent PrPSc accumulation in skeletal muscles from forelimb and hindlimb, head, back and shoulder, and in tongue. Previously, our animal model has provided substantial baseline information about the peripheral routing of infection in naturally occurring and orally acquired ruminant TSEs. Therefore, the findings described here highlight further the necessity to investigate thoroughly whether muscles of TSE-infected sheep, cattle, elk and deer contain infectious agents.

Animals↗
PubMed1998

Stretch-induced alkalinization of feline papillary muscle: an autocrine-paracrine system.

Myocardial stretch is a well-known stimulus that leads to hypertrophy. Little is known, however, about the intracellular pathways involved in the transmission of myocardial stretch to the cytoplasm and nucleus. Studies in neonatal cardiomyocytes demonstrated stretch-induced release of angiotensin II (Ang II). Because intracellular alkalinization is a signal to cell growth and Ang II stimulates the Na+/H+ exchanger (NHE), we studied the relationship between myocardial stretch and intracellular pH (pHi). Experiments were performed in cat papillary muscles fixed by the ventricular end to a force transducer. Muscles were paced at 0.2 Hz and superfused with HEPES-buffered solution. pHi was measured by epifluorescence with the acetoxymethyl ester form of the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF-AM). Each muscle was progressively stretched to reach maximal developed force (Lmax) and maintained in a length that was approximately 92% Lmax (Li). During the "stretch protocol," muscles were quickly stretched to Lmax for 10 minutes and then released to Li; pHi significantly increased during stretch and came back to the previous value when the muscle was released to Li. The increase in pHi was eliminated by (1) specific inhibition of the NHE (EIPA, 5 micromol/L), (2) AT1-receptor blockade (losartan, 10 micromol/L), (3) inhibition of protein kinase C (PKC) (chelerythrine, 5 micromol/L), (4) blockade of endothelin (ET) receptors with a nonselective (PD 142,893, 50 nmol/L) or a selective ETA antagonist (BQ-123, 300 nmol/L). The increase in pHi by exogenous Ang II (500 nmol/L) was also reduced by both ET-receptor antagonists. Our results indicate that after myocardial stretch, pHi increases because of stimulation of NHE activity. This involves an autocrine-paracrine mechanism in which protein kinase C, Ang II, and ET play crucial roles.

Alkalies↗
PubMed1986

The use of exercise and muscle testing in the rehabilitation of spinal disorders.

The isokinetic evaluation of trunk muscle strength (maximal and fatigue) provides very valuable information for establishing specific exercise programs for patients with low back disorders, and for preventing low back injury in industry by identifying employees with weak trunk muscles and with job-strength mismatches.

Back Pain↗
PubMed2004

Pre-Whitnall levator recession with hang-back sutures in Graves orbitopathy.

PURPOSE: To describe a technique for lengthening the levator palpebrae muscle at the level of the transverse orbital ligament (Whitnall ligament) by using hang-back sutures in cases of upper eyelid retraction in Graves orbitopathy, and to report its results. METHODS: A cohort of consecutive patients undergoing this procedure by a single surgeon was analyzed. The surgical technique involved division of the levator muscle high up, at the level of the transverse orbital ligament, with lengthening of the muscle by a graded amount with the use of nonabsorbable hang-back sutures. The length of the sutures was twice the amount of desired lowering of the eyelid. RESULTS: Surgery was performed on 38 eyelids of 21 patients. The mean preoperative eyelid retraction was 4.7 mm (range, 3 mm to 8 mm). Thirty-two eyelids (84%) were within 1 mm of the desired postoperative position. One patient required reoperation for significant undercorrection (2 eyelids), another 4 had ptosis repairs for overcorrection (5 eyelids, one of which was only 1-mm overcorrected). One eyelid required medial contour repair, but none needed lateral contour correction. CONCLUSIONS: This procedure gives a relatively predictable result in patients with moderate to severe upper eyelid retraction and avoids the postoperative complication of contour deformities, especially lateral flare.

Adult↗
PubMed2006

An MRI investigation into the function of the transversus abdominis muscle during "drawing-in" of the abdominal wall.

STUDY DESIGN: An operator blinded dual modality trial of measurement of the abdominal muscles during "drawing-in" of the abdominal wall. OBJECTIVES: 1) To investigate, using magnetic resonance imaging (MRI), the function of the transversus abdominis muscle bilaterally during a drawing-in of the abdominal wall. 2) To validate the use of real-time ultrasound imaging as a measure of the deep abdominal muscle during a drawing-in of the abdominal wall. SUMMARY OF BACKGROUND DATA: Previous research has implicated the deep abdominal muscle, transversus abdominis, in the support and protection of the spine and provided evidence that training this muscle is important in the rehabilitation of low back pain. One of the most important actions of the transversus abdominis is to "draw-in" the abdominal wall, and this action has been shown to stiffen the sacroiliac joints. It is hypothesized that in response to a draw in, the transversus abdominis muscle forms a deep musculofascial "corset" and that MRI could be used to view this corset and verify its mechanism of action on the lumbopelvic region. METHODS: Thirteen healthy asymptomatic male elite cricket players aged 21.3 +/- 2.1 years were imaged using MRI and ultrasound imaging as they drew in their abdominal walls. Measurements of the thickness of the transversus abdominis and internal oblique muscles and the slide of the anterior abdominal fascia were measured using both MRI and ultrasound. Measurement of the whole abdominal cross-sectional area (CSA) was conducted using MRI. RESULTS: Results of the MRI demonstrated that, as a result of draw-in, there was a significant increase in thickness of the transversus abdominis (P < 0.001) and the internal oblique muscles (P < 0.001). There was a significant decrease in the CSA of the trunk (P < 0.001). The mean slide (+/-SD) of the anterior abdominal fascia was 1.54 +/- 0.38 cm for the left side and 1.48 +/- 0.35 cm for the right side. Ultrasound measurements of muscle thickness of both transversus abdominis and the internal oblique, as well as fascial slide, correlated with measures obtained using MRI (interclass correlations from 0.78 to 0.95). CONCLUSIONS: The MRI results demonstrated that during a drawing-in action, the transversus abdominis contracts bilaterally to form a musculofascial band that appears to tighten (like a corset) and most likely improves the stabilization of the lumbopelvic region. Real-time ultrasound imaging can also be used to measure changes in the transversus abdominis during the draw-in maneuver.

Abdominal Muscles↗
PubMed1999

Low back three-dimensional joint forces, kinematics, and kinetics during walking.

OBJECTIVE: The purpose of this study was to examine the three-dimensional low back loads, spinal motions, and trunk muscular activity during gait. Specific objectives involved assessment of the effects of walking speed, and arm swing on spinal loads, lumbar spine motion, and muscular activation. DESIGN: An in vivo modeling experiment using five male participants. Thirty walking trials were performed by each participant yielding five repeats of each condition (3 walking cadences x 2 arm swing conditions). BACKGROUND: Walking is often prescribed as a rehabilitation task for individuals with low back injuries. However, there are few studies which have examined the joint loading, spinal motions, and muscular activity present when walking. Additionally, the majority of studies examining spine loading during gait have used an inverse dynamics model, commencing at the cranial aspect of the body, approach which does not include the impulsive phases of gait (i.e. heel strikes and toe offs). METHODS: Low back joint forces (bone on bone) and moments were determined using an anatomically complex three-dimensional model (detailing 54 muscles and the passive structures acting at the low back) during three walking cadences and with free arm swing or restricted arm swing. In order to assess the influence of the transient factors such as heel contact on the joint forces a bottom up (from the feet to the lumbar spine) rigid link segment analyses approach was used as one input to the three-dimensional anatomic model. Lumbar spine motion and trunk muscle activation levels were also recorded to assist in partitioning forces amongst the active and passive tissues of the low back. RESULTS: Net joint anterior-posterior shear loading was the only variable significantly affected by walking cadence (fast versus slow P < 0.0003). No variable was significantly affected by the arm swing condition. Trends demonstrated an increase in all variables with increased walking cadence. Similarly, most variables, with the exception of axial twist and lateral bend lumbar spine motion and lateral joint shear, demonstrated increasing trends caused by the restriction of normal arm swing. CONCLUSIONS: Tissue loading during walking appears to be below levels caused by many specific rehabilitation tasks, suggesting that walking is a wise choice for general back exercise and rehabilitation programs. Slow walking with restricted arm swing produced more 'static' lumbar spine loading and motion patterns, which could be detrimental for certain injuries and tissues. Fast walking produced a more cyclic loading pattern.

Adult↗
PubMed2005

Sustained rise in triacylglycerol synthesis and increased epididymal fat mass when rats cease voluntary wheel running.

Four-week-old, Fischer-Brown Norway F1-generation male rats were given access to voluntary running wheels for 21 days, and then the wheels were locked for 5 (WL5), 10 (WL10), 29 (WL29), or 53 (WL53) hours. Two other groups (SED5 and SED10) had no access to voluntary running wheels and were killed at the same time as WL5 and WL10, respectively. Absolute and relative epididymal fat mass, mean cell volume, and amount of lipid per cell increased in WL53 relative to all other groups, with no change in cell number. C/EBPalpha protein levels in epididymal fat were 30% greater in SED5 than in WL5. The rate of triacylglycerol synthesis in epididymal fat was 4.2-fold greater in SED5 than in WL5, increased 14-fold between WLS and WL10, and was 79% lower in SED10 than in WL10. Triacylglycerol synthesis remained at this elevated level (at least 3.5-fold greater than SED5) through WL53. Thus, the rapid increase in epididymal fat mass with the cessation of voluntary wheel running is associated with a prolonged overshoot in epididymal fat triacylglycerol synthesis. Moreover, rats without running wheels had a 9.4% lower body mass after 21 days than those with running wheels. The individual mass of seven different muscles from the hindlimb, upper forelimb, and back were each lower in animals without running wheels, suggesting that physical activity in rapidly growing rats may be requisite for optimal muscle development.

Adipose Tissue↗
PubMed2004

The effects of protease supplementation on skeletal muscle function and DOMS following downhill running.

Protease supplementation has been shown to attenuate soft tissue injury resulting from intense exercise. The aim of this study was to evaluate the effects of protease supplementation on muscle soreness and contractile performance after downhill running. Ten matched pairs of male participants ran at a -10% grade for 30 min at 80% of their predicted maximal heart rate. The participants consumed two protease tablets (325 mg pancreatic enzymes, 75 mg trypsin, 50 mg papain, 50 mg bromelain, 10 mg amylase, 10 mg lipase, 10 mg lysozyme, 2 mg chymotrypisn) or a placebo four times a day beginning 1 day before exercise and lasting a total of 4 days. The participants were evaluated for perceived muscle soreness of the front and back of the dominant leg, pressure pain threshold by dolorimetry of the anterior medial, anterior lateral, posterior medial and posterior lateral quadrants of the thigh, and knee extension/flexion torque and power. The experimental group demonstrated superior recovery of contractile function and diminished effects of delayed-onset muscle soreness after downhill running when compared with the placebo group. Our results indicate that protease supplementation may attenuate muscle soreness after downhill running. Protease supplementation may also facilitate muscle healing and allow for faster restoration of contractile function after intense exercise.

Adolescent↗

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