Trunk strength and lumbar paraspinal muscle activity during isometric exercise in chronic low-back pain patients and controls

The Application of Surface Electromyography Technology in Evaluating Paraspinal Muscle Function

Surface electromyography (sEMG) has emerged as a valuable tool for assessing muscle activity in various clinical and research settings. This review focuses on the application of sEMG specifically in the context of paraspinal muscles. The paraspinal muscles play a critical role in providing stability and facilitating movement of the spine. Dysfunctions or alterations in paraspinal muscle activity can lead to various musculoskeletal disorders and spinal pathologies. Therefore, understanding and quantifying paraspinal muscle activity is crucial for accurate diagnosis, treatment planning, and monitoring therapeutic interventions. This review discusses the clinical applications of sEMG in paraspinal muscles, including the assessment of low back pain, spinal disorders, and rehabilitation interventions. It explores how sEMG can aid in diagnosing the potential causes of low back pain and monitoring the effectiveness of physical therapy, spinal manipulative therapy, and exercise protocols. It also discusses emerging technologies and advancements in sEMG techniques that aim to enhance the accuracy and reliability of paraspinal muscle assessment. In summary, the application of sEMG in paraspinal muscles provides valuable insights into muscle function, dysfunction, and therapeutic interventions. By examining the literature on sEMG in paraspinal muscles, this review offers a comprehensive understanding of the current state of research, identifies knowledge gaps, and suggests future directions for optimizing the use of sEMG in assessing paraspinal muscle activity.

Biofeedback EMG alternative therapy for chronic low back pain: Study protocol of a pilot randomized controlled trial

BACKGROUND

Chronic pain affects about 100 million U.S. adults, with chronic low back pain (CLBP) cited as the most prevalent type. Although there is evidence that non-pharmacological therapies seem to be effective for treating low back pain, there is limited evidence of the effectiveness of EMG biofeedback with non-specific chronic low back pain (NCLBP). The purpose of this study is, therefore, to determine the efficacy of a portable EMG biofeedback device on pain in individuals with CLBP.

METHODS/DESIGN

This study is a prospective, single-center, assessor-blind, two-arm, parallel randomized controlled trial to be conducted at Brigham and Women's Hospital, Boston, MA. Eighty patients with CLBP will be randomized in a 2:1 ratio to receive sEMG-BF (surface EMG biofeedback) or continued care (no intervention). All participants will receive treatment virtually weekly for 8 weeks. The primary outcome will be pain intensity (Brief Pain Inventory). The secondary outcomes will include pain interference (Brief Pain Inventory), disability (The Oswestry Disability Index (ODI)), anxiety and depression (Hospital Anxiety and Depression Scale). All outcomes will be assessed at baseline, immediately post-intervention, and 3 months follow-up.

CONCLUSION

To our knowledge, this study will be the first powered randomized controlled trial to compare the effectiveness of a virtual sEMG-BF protocol specifically designed for CLBP. The outcome of the study may provide evidence for the effectiveness of biofeedback using digital therapeutics to relieve pain in individuals with CLBP.

TRIAL REGISTRATION

Clinical Trials Registry (http://ClinicalTrials.gov Identifier: NCT04607460). Registered on October 29, 2020.

Comparison of two mobilization techniques in management of chronic non-specific low back pain

AIM

The aim of the study was to compare between the effects of Maitland's postero-anterior (PA glide) mobilization and Mulligan's sustained natural apophyseal glide (SNAG) on pain, mobility, muscle activation and functional disability in subjects with chronic, non-specific low back pain.

METHODS

The study was a two arm repeated measure design with random allocation of subjects (n = 33). Subjects in group 1 received Maitland's PA glide mobilization and those in group 2 received Mulligan's SNAG. Along with the respective mobilization technique, individualized exercises were common for subjects in both the groups. Subjects in both groups received treatment for 4 days a week for 4 weeks. The outcome measures were numeric pain rating scale (NPRS) scores, lumbar flexion and extension range of motion, erector spinae muscle activity and Oswestry low back pain disability questionnaire score.

RESULTS

The outcome measure scores showed statistical significance in time effect on NPRS (p = 0.001); lumbar flexion and extension range of motion (p = 0.001); erector spinae muscle activity (0.001); Oswestry low back pain disability questionnaire score (p = 0.001); group effect on lumbar flexion (p = 0.03) and extension range of motion (p = 0.05); and interaction effect (time x group) on lumbar flexion (p = 0.003) and extension range of motion (p = 0.002); and, erector spinae muscle activity (p = 0.05) at the 3rd lumbar vertebral level.

CONCLUSION

The addition of Maitland or Mulligan mobilization techniques of the spine does not show a difference in the improvement of symptoms associated with chronic non-specific low back pain.

Single-motor-unit discharge characteristics in lumbar multifidus muscle of acute low back pain patients

Acute low back pain (ALBP) causes rapid deterioration of paraspinal muscle function. The underlying neurophysiology is poorly understood. We therefore carried out this observational study in patients with ALBP to characterize motor unit (MU) activity in deep lumbar multifidus (LM) muscle and compare with our previous findings from pain-free subjects. Nine subjects (1 woman; age 26-59 yr) with ALBP duration of 1-21 days were recruited from outpatient clinics. Fine wire electromyography (EMG) electrodes were implanted bilaterally at the painful spinal level under computer tomography guidance. EMG was recorded during spontaneous sitting and standing, and during voluntary force production. Linear mixed models were utilized to test or control for the effects of a number of predefined variables. Compared with sitting, standing increased total duration of EMG activity, median MU discharge rate, interspike interval variability, and common drive measured as common drive coefficients (CDC) derived from concurrently active MU pairs. Median discharge rate in 73 MUs was 5.5 and 6.6 pulses per second (pps) during spontaneous sitting and standing, and 7.2 pps during voluntary force production. Interspike interval variability was lower during voluntary tasks than during spontaneous force production. Common drive was less pronounced in bilateral vs. unilateral unit pairs, also in spontaneous standing. This difference was not seen in our previous pain-free subjects, suggesting altered bilateral control of the spine in ALBP. The distribution of CDC values was not a homogeneous continuum but could be seen as two partially overlapping populations of CDC distributions.NEW & NOTEWORTHY We implanted fine-wire electrodes in the deepest part of axial postural muscles in patients with acute low back pain and characterized their motor unit activity. We found less pronounced common drive to the two sides of the spine compared with pain-free subjects, suggesting a different postural control strategy in patients with acute low back pain. An unexpected finding was that common drive coefficient values appeared to consist of two partially overlapping populations of normal distributions.

Changes in Structure and Function of the Back Muscles in Low Back Pain: Different Time Points, Observations, and Mechanisms

Spinal health depends on optimal back muscle performance, and this is determined by muscle structure and function. There has been substantial research evaluating the differences in structure and function of many back muscles, including the multifidus and erector spinae, but with considerable variation in results. Many studies have shown atrophy, fat infiltration, and connective tissue accumulation in back muscles, particularly deep fibers of the multifidus, but the results are not uniform. In terms of function, results are also somewhat inconsistent, often reporting lower multifidus activation and augmented recruitment of more superficial components of the multifidus and erector spinae, but, again, with variation between studies. A major recent observation has been the identification of time-dependent differences in features of back muscle adaptation, from acute to subacute/recurrent to chronic states of the condition. Further, these adaptations have been shown to be explained by different time-dependent mechanisms. This has substantial impact on the rationale for rehabilitation approaches. The aim of this commentary was to review and consolidate the breadth of research investigating adaptation in back muscle structure and function, to consider explanations for some of the variation between studies, and to propose how this model can be used to guide rehabilitation in a manner that is tailored to individual patients and to underlying mechanisms. J Orthop Sports Phys Ther 2019;49(6):464-476. doi:10.2519/jospt.2019.8827.

Verification of Computed Muscle Control and Static Optimization for Isokinetic, Isometric and Isotonic Exercise of Upper Limb

To measure muscle activity during motion is a significant topic in biomechanics. Even though EMG (electromyography) is utilized for this, musculoskeletal simulations are potential alternatives. In this paper, the accuracy of muscle activity calculation of two different algorithms are verified by comparing with EMG during three types of muscle contractions (isokinetic, isotonic and isometric).

Effects of tactile feedback on lumbar multifidus muscle activity in asymptomatic healthy adults and patients with low back pain

BACKGROUND

Reduced lumbar multifidus (LM) muscle contraction has been observed in patients with low back pain (LBP). Clinicians often use various strategies to ensure LM activation, including tactile feedback and verbal instruction. However, the effects of tactile feedback on muscle activation have not been studied previously. Therefore, the purpose of this study was to investigate whether or not tactile feedback would increase LM muscle activity in adults with and without LBP.

METHODS

Twenty asymptomatic adults and 20 patients with existing LBP completed the study. Two electromyographic (EMG) electrodes were applied to both sides of the LM at the L5 segment. EMG activity was collected three times at rest with and without tactile feedback, then five times during contralateral arm lifts with and without tactile feedback. The tactile feedback was applied by direct and continuous hand contact to the bilateral LM over the lumbosacral area. Lastly, two 5-second trials of maximum voluntary isometric contraction (MVIC) during a bilateral arm lift were performed. EMG activity collected at rest and during contralateral arm lifts was normalized to that collected during MVIC. Normalized EMG values of the right side of the asymptomatic group and the painful side of the LBP group were used for data analysis.

RESULTS

Statistical analysis showed significantly decreased LM EMG activity with tactile feedback both at rest and during contralateral arm lifts compared to LM EMG activity without tactile feedback. There was no difference in LM EMG between the asymptomatic and the LBP groups.

CONCLUSIONS

The results of the study showed that adding tactile stimulation to verbal instruction appeared to provide an inhibitory effect on LM activity in both asymptomatic healthy adults and patients with LBP. Contrary to common belief, tactical feedback via direct hand contact may reduce LM muscle recruitment, and may lessen the desired treatment effect.

A Comparison of Isolated Lumbar Extension Strength Between Healthy Asymptomatic Participants and Chronic Low Back Pain Participants Without Previous Lumbar Spine Surgery

STUDY DESIGN

Cross-sectional case-control study.

OBJECTIVE

To compare isolated lumbar extension strength between healthy asymptomatic participants and participants with chronic low back pain (CLBP), while controlling for previous lumbar spine surgery.

SUMMARY OF BACKGROUND DATA

Deconditioning of the lumbar musculature is common in those with previous lumbar surgery, resulting in decreased strength and endurance. Evidence is required to support whether this is the case for participants with CLBP yet no previous surgery compared with asymptomatic participants.

METHODS

Forty-two healthy (25 males and 17 females) asymptomatic participants, and 53 participants with non-specific CLBP (30 males and 23 females) aged between 19 and 76 years were recruited. Maximal isometric isolated lumbar extension (ILEX) strength was examined.

RESULTS

A Mann-Whitney U test indicated that ILEX strength was significantly greater in the asymptomatic group compared with the CLBP group (Z = 1441.00, P = 0.014). Post-hoc effect size was calculated to be d = 0.56, showing a moderate effect.

CONCLUSION

These results indicate that ILEX weakness and lumbar extensor deconditioning is present independent of surgery and may be a factor involved in CLBP. As such, lumbar extensor deconditioning would appear to be a reasonable target for interventions in CLBP.

LEVEL OF EVIDENCE

3.

Does a Better Perfusion of Deconditioned Muscle Tissue Release Chronic Low Back Pain?

Non-specific chronic low back pain (nsCLBP) is a multifactorial condition of unknown etiology and pathogenesis. Physical and genetic factors may influence the predisposition of individuals to CLBP, which in many instances share a musculoskeletal origin. A reduced pain level in low back pain patients that participate in exercise therapy highlights that disuse-related muscle deconditioning may predispose individuals to nsCLBP. In this context, musculoskeletal pain may be the consequence of capillary rarefaction in inactive muscle as this would lower local tissue drainage and washing out of toxic waste. Muscle activity is translated into an angio-adaptative process, which implicates angiogenic-gene expression and individual response differences due to heritable modifications of such genes (gene polymorphisms). The pathophysiologic mechanism underlying nsCLBP is still largely unaddressed. We hypothesize that capillary rarefaction due to a deconditioning of dorsal muscle groups exacerbates nsCLBP by increasing noxious sensation, reducing muscle strength and fatigue resistance by initiating a downward spiral of local deconditioning of back muscles which diminishes their load-bearing capacity. We address the idea that specific factors such as angiotensin-converting enzyme and Tenascin-C might play an important role in altering susceptibility to nsCLBP via their effects on microvascular perfusion and vascular remodeling of skeletal muscle, inflammation, and pain sensation. The genetic profile may help to explain the individual predisposition to nsCLBP, thus identifying subgroups of patients, which could benefit from ad hoc treatment types. Future therapeutic approaches aimed at relieving the pain associated with nsCLBP should be based on the verification of mechanistic processes of activity-induced angio-adaptation and muscle-perfusion.

Descriptive Analysis of Spinal Neuroaxial Injections, Surgical Interventions, and Physical Therapy Utilization for Degenerative Lumbar Spondylolisthesis Within Medicare Beneficiaries from 2000 to 2011

STUDY DESIGN

A retrospective, observational study.

OBJECTIVE

The aim of this study was to determine the utilization of various treatment modalities in the management of degenerative spondylolisthesis within Medicare beneficiaries.

SUMMARY OF BACKGROUND DATA

Degenerative lumbar spondylolisthesis is a condition often identified in symptomatic low back pain. A variety of treatment algorithms including physical therapy and interventional techniques can be used to manage clinically significant degenerative spondylolisthesis.

METHODS

This study utilized the 5% national sample of Medicare carrier claims from 2000 through 2011. A cohort of beneficiaries with a new International Classification of Diseases 9th edition (ICD-9) diagnosis code for degenerative lumbar spondylolisthesis was identified. Current procedural terminology codes were used to identify the number of procedures performed each year by specialty on this cohort.

RESULTS

A total of 95,647 individuals were included in the analysis. Average age at the time of initial diagnosis was 72.8 ± 9.8 years. Within this study cohort, spondylolisthesis was more prevalent in females (69%) than males and in Caucasians (88%) than other racial demographics. Over 50% of beneficiaries underwent at least one injection, approximately one-third (37%) participated in physical therapy, one in five (21%) underwent spinal surgery, and one-third (36%) did not utilize any of these interventions. Greater than half of all procedures (124,280/216,088) occurred within 2 years of diagnosis. The ratio of focal interventions (transforaminal and facet interventions) to less selective (interlaminar) procedures was greater for the specialty of Physical Medicine and Rehabilitation than for the specialties of Anesthesiology, Interventional Radiology, Neurosurgery, and Orthopedic Surgery. The majority of physical therapy was dedicated to passive treatment modalities and range of motion exercises rather than active strengthening modalities within this cohort.

CONCLUSION

Interventional techniques and physical therapy are frequently used treatment modalities for symptomatic degenerative spondylolisthesis. Understanding utilization of these techniques is important to determine relative clinical efficacies and to optimize future health care expenditures.

LEVEL OF EVIDENCE

N/A.

Effect of Superimposed Electromyostimulation on Back Extensor Strengthening: A Pilot Study

Park, JH, Seo, KS, and Lee, S-U. Effect of superimposed electromyostimulation on back extensor strengthening: a pilot study. J Strength Cond Res 30(9): 2470-2475, 2016-Electromyostimulation (EMS) superimposed on voluntary contraction (VC) can increase muscle strength. However, no study has examined the effect of superimposing EMS on back extensor strengthening. The purpose of this study was to determine the effect of superimposed EMS on back extensor strengthening in healthy adults. Twenty healthy men, 20-29 years of age, without low-back pain were recruited. In the EMS group, electrodes were attached to bilateral L2 and L4 paraspinal muscles. Stimulation intensity was set for maximally tolerable intensity. With VC, EMS was superimposed for 10 seconds followed by a 20-second rest period. The same protocol was used in the sham stimulation (SS) group, except that the stimulation intensity was set at the lowest intensity (5 mA). All subjects performed back extension exercise using a Swiss ball, with 10 repetitions per set, 2 sets each day, 5 times a week for 2 weeks. The primary outcome measure was the change in isokinetic strength of the back extensor using an isokinetic dynamometer. Additionally, endurance was measured using the Sorensen test. After 2 weeks of back extension exercise, the peak torque and endurance increased significantly in both groups (p ≤ 0.05). Effect size between the EMS group and the SS group was medium in strength and endurance. However, there was no statistically significant difference between 2 groups. In conclusion, 2 weeks of back extensor strengthening exercise was effective for strength and endurance. Superimposing EMS on back extensor strengthening exercise could provide an additional effect on increasing strength.

Associations between Trunk Extension Endurance and Isolated Lumbar Extension Strength in Both Asymptomatic Participants and Those with Chronic Low Back Pain

BACKGROUND

Strength and endurance tests are important for both clinical practice and research due to the key role they play in musculoskeletal function. In particular, deconditioning of the lumbar extensor musculature has been associated with low back pain (LBP). Due to the relationship between strength and absolute endurance, it is possible that trunk extension (TEX) endurance tests could provide a proxy measure of isolated lumbar extension (ILEX) strength and thus represent a simple, practical alternative to ILEX measurements. Though, the comparability of TEX endurance and ILEX strength is presently unclear and so the aim of the present study was to examine this relationship.

METHODS

Thirty eight healthy participants and nineteen participants with non-specific chronic LBP and no previous lumbar surgery participated in this cross-sectional study design. TEX endurance was measured using the Biering-Sorensen test. A maximal ILEX strength test was performed on the MedX lumbar-extension machine.

RESULTS

A Pearson's correlation revealed no relationship between TEX endurance and ILEX strength in the combined group (r = 0.035, p = 0.793), the chronic LBP group (r = 0.120, p = 0.623) or the asymptomatic group (r = -0.060, p = 0.720).

CONCLUSIONS

The results suggest that TEX is not a good indicator of ILEX and cannot be used to infer results regarding ILEX strength. However, a combination of TEX and ILEX interpreted together likely offers the greatest and most comprehensive information regarding lumbo-pelvic function during extension.

Postural strategy and trunk muscle activation during prolonged standing in chronic low back pain patients

Prolonged standing has been associated with development and aggravation of low back pain (LBP). However, the underlying mechanisms are not well known. The aim of the present study was to investigate postural control and muscle activation during and as a result of prolonged standing in chronic LBP (cLBP) patients compared to healthy controls (HCs). Body weight shifts and trunk and hip muscle activity was measured during 15 min standing. Prior and after the standing trial, strength, postural sway, reposition error (RE), flexion relaxation ratio (FRR), and pain were assessed and after the prolonged standing, ratings of perceived exertion. During prolonged standing, the cLBP patients performed significantly more body weight shifts (p<.01) with more activated back and abdominal muscles (p=.01) and similar temporal variability in muscle activation compared to HCs, while the cLBP patients reported more pain and perceived exertion at the end of prolonged standing. Moreover, both groups had a similar change in strength, postural sway, RE and FRR from before to after prolonged standing, where changes in HC were towards pre-standing values of cLBP patients. Thus, despite a more variable postural strategy, the cLBP patients did not have higher muscle activation variability, but a general increased muscle activation level. This may indicate a reduced ability to individually deactivate trunk muscles. Plausibly, due to the increased variable postural strategy, the cLBP patients could compensate for the relatively high muscle activation level, resulting in normal variation in muscle activation and normal reduction in strength, RE and FRR after prolonged standing.

A reappraisal of the deconditioning hypothesis in low back pain: review of evidence from a triumvirate of research methods on specific lumbar extensor deconditioning

OBJECTIVE

'Disuse' and 'Deconditioning' in relation to low back pain (LBP) are terms often used interchangeably. Discussions of 'disuse' refer to general physical inactivity, which evidence suggests does not differ between symptomatic and asymptomatic persons. 'Deconditioning' refers to a decrease in function, commonly both cardiovascular/aerobic fitness and muscular strength/endurance, again noting little difference. However, examination of decreased function relating specifically to lumbar extensor musculature deconditioning has yet to be examined, corroborating all possible methods. Thus, this review attempts to reappraise the deconditioning hypothesis in LBP, specifically considering lumbar extensor deconditioning.

METHODS

A literature review was conducted examining both cross-sectional and prospective data on specific lumbar extensor deconditioning and LBP. A narrative approach and 'snowballing' style literature search was used involving initial use of PubMed and Google Scholar databases searching up to December 2012. Included were studies utilizing the following three research methods, allowing specific induction of the role of such deconditioning; (1) strength/endurance testing of the isolated lumbar extensor musculature, (2) imaging and histochemical examination of the lumbar extensor musculature, and (3) fatigue testing of the lumbar extensor musculature using electromyography.

RESULTS/FINDINGS

Despite issues interpreting individual studies due to methods, the majority of evidence suggests LBP is associated with decreased strength/endurance, atrophy, and excessive fatigability of the lumbar extensors. Prospective studies also suggest lumbar extensor deconditioning may be a common risk factor predicting acute low back injury and LBP.

CONCLUSIONS

The hypothesis of specific lumbar extensor deconditioning as being a causal factor in LBP is presently well supported. It is by no means the only causative factor and further research should more rigorously test this hypothesis addressing the methodological issues highlighted regarding previous studies. However, its role suggests specific exercise may be a worthwhile preventative and rehabilitative approach.

The effects of muscle length and force output on the EMG power spectrum of the erector spinae

In many skeletal muscles the myoelectric power spectrum median frequency (MF) increases with increasing force output, possibly reflecting the greater size and conduction velocity of the later-recruited (fast twitch) fibres. Muscles, such as the erector spinae, in which fast twitch fibres are smaller than slow twitch, may display an atypical relationship between force output and median frequency. The present study sought to investigate this possibility. Ten healthy men held forces ranging from 20-80% maximal voluntary contraction (MVC) of the back extensors for 4-6 s, at muscle lengths corresponding to 30, 60 and 90% of the lumbar spine's range of flexion (ROF). MF was determined from surface electromyograms recorded from thoracic and lumbar regions of the erector spinae. In each region, MF was significantly higher at 30% ROF (short muscle length) than at 60 or 90% ROF (P < 0.005) and slightly (but not significantly) higher at 60 than 90% ROF. The muscle length effect on MF may reflect a reduction in conduction velocity of the stretched and narrowed muscle fibres. Force output had a significant effect on MF (P < 0.0004), although the shape of the relationship differed between the two levels of the erector spinae: in the thoracic region MF increased with force up to 40-50% MVC and then levelled off, whereas in the lumbar region MF was relatively stable up to 30-40% MVC and then declined with increasing force. The results suggest that the mean fibre size of the later recruited motor units is, in the thoracic region, larger, and in the lumbar region, smaller, than that of the earlier-recruited motor units.

The Relationship between Cross Sectional Area and Strength of Back Muscles in Patients with Chronic Low Back Pain

Objective

To evaluate the relationship between the cross sectional area (CSA) and isokinetic strength of the back muscles in patients with chronic low back pain.

Method

Data of twenty-eight middle-aged patients with chronic back pain were analyzed retrospectively. CSAs of both paraspinal muscles and the disc at the L4-L5 level were measured in MRI axial images and the relative CSAs (rCSA: CSA ratio of muscle and disc) were calculated. The degree of paraspinal muscle atrophy was rated qualitatively. Isokinetic strengths (peak torque, peak torque per body weight) of back flexor and extensor were measured with the isokinetic testing machine. Multiple regression analysis with backward elimination was used to evaluate relations between isokinetic strength and various factors, such as CSA or rCSA and clinical characteristics in all patients. The same analysis was repeated in the female patients.

Results

In analysis with CSA and clinical characteristics, body mass index (BMI) and CSA were significant influencing factors in the peak torque of the back flexor muscles. CSA was a significant influencing factor in the peak torque of total back muscles. In analysis with rCSA and clinical characteristics, BMI was significant in influencing the peak torque of the back flexors. In female patients, rCSA was a significant influencing factor in the peak torque per body weight of the back flexors, and age and BMI were influencing factors in the peak torque of back flexors and total back muscles.

Conclusion

In middle-aged patients with chronic low back pain, CSA and rCSA were influencing factors in the strength of total back muscles and back flexors. Also, gender and BMI were influencing factors.

Needle EMG Response of Lumbar Multifidus to Manipulation in the Presence of Clinical Instability

A proposed mechanism for the persistence of low back pain due to clinical instability is a decrease in control of local spinal musculature, more specifically decreased recruitment of multifidus. Altered segmental mechanoreceptor input has been proposed as a contributing factor responsible for a decrease in local muscle recruitment. In this case report, immediate changes in the recruitment of the deep multifidus following manipulation were examined using needle EMG and isometric testing of trunk rotational force. Trunk rotational force appeared to improve while the multifidus demonstrated a decrease in activity as measured by needle EMG. No specific conclusions can be drawn from this report; however, the results do suggest that immediate multifidus function may be influenced with manipulation, resulting in improved muscular control of the trunk.

Back pain is associated with changes in loading pattern throughout forward and backward bending

STUDY DESIGN

Experimental study to determine the kinetics of the lumbar spine (LS) and hips during forward and backward bending.

OBJECTIVE

To investigate the effects of back pain, with and without a positive straight leg raise (SLR) sign, on the loading patterns in the LS and hip during forward and backward bending.

SUMMARY OF BACKGROUND DATA

Forward and backward bending are important components of many functional activities and are part of routine clinical examination. However, there is a little information about the loading patterns during forward and backward bending in people with back pain with or without a positive SLR sign.

METHODS

Twenty asymptomatic participants, 20 back pain participants, and 20 participants with back pain and a positive SLR sign performed 3 continuous cycles of forward and backward bending. Electromagnetic sensors were attached to body segments to measure their kinematics while 2 nonconductive force plates gathered ground reaction force data. A biomechanical model was used to determine the loading pattern in LS and hips.

RESULTS

Although the loading on the LS at the end of the range decreased significantly, the loading at the early and middle ranges of forward bending actually increased significantly in people with back pain, especially in those with positive SLR sign. This suggests that resistance to movement is significantly increased in people with back pain during this movement.

CONCLUSION

This study suggested that it is not sufficient to study the spine at the end of range only, but a complete description of the loading patterns throughout the range is required. Although the maximum range of motion of the spine is reduced in people with back pain, there is a significant increase in the moment acting through the range, particularly in those with a positive SLR sign.

Ultrasound tissue Doppler imaging reveals no delay in abdominal muscle feed-forward activity during rapid arm movements in patients with chronic low back pain

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

Comparison of the timing of onset of lateral abdominal muscle activity during rapid arm movements in patients with nonspecific chronic low back pain (cLBP) and back-pain-free controls.

SUMMARY OF BACKGROUND DATA

Rapid movements of the arm are normally associated with prior activation of trunk-stabilizing muscles in readiness for the impending postural perturbation. Using invasive intramuscular electromyography techniques, studies have shown that this feed-forward function is delayed in some patients with low back pain (LBP). Ultrasound tissue Doppler imaging (TDI) provides an ultrasound method for quantifying muscle activation in a noninvasive manner, allowing investigation of larger groups of patients and controls.

METHODS

Ninety-six individuals participated (48 patients with cLBP and 48 matched LBP-free controls). During rapid shoulder flexion, abduction, and extension, surface electromyographic signals from the deltoid and motion-mode TDI images from the contralateral lateral abdominal muscles were recorded simultaneously. The onset of muscle activity was given by changes in the tissue velocity of the abdominal muscles, as measured with TDI. Pain and disability in the patients were assessed using standardized questionnaires. Data were analyzed using repeated measures analysis of variance.

RESULTS

In both groups, feed-forward activity of the lateral abdominal muscles was recorded during arm movements in all directions. The main effect of "group membership" revealed no significant difference between the groups for the earliest onset of abdominal muscle activity (P = 0.398). However, a significant "group x body side" interaction (P = 0.015) was observed, and this was the result of earlier onsets in the cLBP group than controls for the abdominal muscles on the right (but not left) body side. No relationship was found between the time of onset of the earliest abdominal muscle activity and pain intensity, pain frequency, pain medication usage, or Roland Morris disability scores.

CONCLUSION

Patients with cLBP did not show a delayed onset of feed-forward activation of the lateral abdominal muscles during rapid arm movements. Earlier activation was observed for one body side compared with the controls. However, the clinical relevance of this finding remains obscure, especially because there was no relationship between the onset of activation and any clinical parameters.

Decrease in postural sway and trunk stiffness during cognitive dual-task in nonspecific chronic low back pain patients, performance compared to healthy control subjects

STUDY DESIGN

A 2-group experimental design.

OBJECTIVE

To investigate the effect of a cognitive dual-task on postural sway of pelvis and trunk during unstable sitting in nonspecific chronic patients with low back pain (CLBP) compared to healthy control subjects.

SUMMARY OF BACKGROUND DATA

Higher cognitive systems as well as sensory processes contribute to postural control. An increase in postural sway due to a cognitive dual task could mean more need of cognitive systems to control balance.

METHODS

A total of 21 CLBP patients and 21 control subjects were included based on detailed clinical criteria. Every subject was submitted to 2 postural control tests in an unstable sitting position (easy test position: 2 feet on the ground and difficult test position: 1 foot lifted). Both tests were performed with and without cognitive dual-task. A 3-dimensional motion analysis system was used measure angular displacement of trunk and pelvis in the 3 cardinal planes.

RESULTS

In the most difficult balance position, postural sway increases in the control group when the cognitive dual-task is added, for 50% of the variables the increase is significant (P between 0.02 and 0.05). On the contrary, postural sway decreases, not significantly, in the CLBP group when the dual-task is added. These findings are the same for trunk as for pelvis deviations. The Pearson correlation coefficient between trunk and pelvis movement from the CLBP group are lower for all 3 movement directions in the dual-task condition (r between 0.441 and 0.988) compared to the single task condition (r between 0.982 and 0.995).

CONCLUSION

In nonspecific CLBP patients, a cognitive dual-task reduces both postural sway and trunk stiffness due to the distracting effect of the dual-task. This effect is only visible when the balance task is difficult.

The association between isoinertial trunk muscle performance and low back pain in male adolescents

The literature reports inconsistent findings regarding the association between low back pain (LBP) and trunk muscle function, in both adults and children. The strength of the relationship appears to be influenced by how LBP is qualified and the means by which muscle function is measured. The aim of this study was to examine the association between isoinertial trunk muscle performance and consequential (non-trivial) low back pain (LBP) in male adolescents. Healthy male adolescents underwent anthropometric measurements, clinical evaluation, and tests of trunk range of motion (ROM), maximum isometric strength (STRENGTH) and peak movement velocity (VEL), using an isoinertial device. They provided information about their regular sporting activities, history and family history of LBP. Predictors of "relevant/consequential LBP" were examined using multivariable logistic regression. LBP status was reassessed after 2 years and the change from baseline was categorised. At baseline, 33/95 (35%) subjects reported having experienced consequential LBP. BMI, a family history of LBP, and regularly playing sport were each significantly associated with a history of consequential LBP (p < 0.05). 85/95 (89%) boys participated in the follow-up: 51 (60%) reported no LBP at either baseline or follow-up (never LBP); 5 (6%) no LBP at baseline, but LBP at follow-up (new LBP); 19 (22%) LBP at baseline, but none at follow-up; and 10 (12%) LBP at both time-points (recurrent/persistent LBP). The only distinguishing features of group membership in these small groups were: fewer sport-active in the "never LBP" group); worse trunk mobility, in the "persistent LBP" group, lower baseline sagittal ROM in the "never LBP" and "new LBP" (p < 0.05). Regular involvement in sport was a consistent predictor of LBP. Isoinertial trunk performance was not associated with LBP in adolescents.

The effect of increasing resistance on trunk muscle activity during extension and flexion exercises on training devices

Although progressive resistance training of trunk muscles on devices is very common, today, the effects of increasing resistance on trunk muscle activity during dynamic extension and flexion movements on training devices have not been reported yet. Thirty healthy subjects participated in maximal isometric and submaximal dynamic (at 30%, 50% and 70% of maximum mean torque (MMT)) extension and flexion exercises on Tergumed lumbar training devices. The normalized (as a percentage of maximal voluntary isometric contractions (MVIC)) electromyographic activity of 16 abdominal and back muscles was investigated. The results of the present study indicated that in general, with increasing resistance from 30% MMT to 50% MMT and 70% MMT, the activity of all back muscles during the extension exercises and the activity of all abdominal muscles during the flexion exercises increased significantly. To train strength (>60% of MVIC), low intensities (30% and 50% MMT) appeared sufficient to affect the back muscles, but for the abdominals higher resistance (70% MMT) was required. In contrast to the other back muscles, the lumbar multifidus demonstrated high activity levels during both the extension and the flexion exercises. As the lumbar multifidus is demonstrated to be an important muscle in segmental stabilization of the lumbar spine, this finding may help in understanding the efficacy of rehabilitation programs using specific training devices.

The effect of muscle relaxant on the paraspinal muscle blood flow: a randomized controlled trial in patients with chronic low back pain

STUDY DESIGN

A randomized controlled trial.

OBJECTIVE

To investigate the effect of muscle relaxant for muscle blood flow at the trunk muscle in patients with chronic low back pain (LBP).

SUMMARY OF BACKGROUND DATA

Paraspinal muscle function is widely believed to play a role and considered to be of etiologic significance in LBP, and intramuscular pressure increases and blood flow decreases in the flexion position. Decrease in oxygenated hemoglobin at the trunk muscle is seen in patients with LBP.

METHODS

A total of 74 male patients with LBP lasting more than 6 months were randomized to 3 treatment groups: (1) physical therapy only (control) (n = 25), (2) administration of eperisone hydrochloride (EMPP) for 4 weeks (n = 24), and (3) McKenzie therapy (n = 25). The primary outcome variables, observed at 2 and 4 weeks, are the Japanese Orthopedic Association LBP score, visual analogue scale (VAS), Faces Pain Scale-Revised, and SF-36. Intramuscular oxygenation was evaluated using near-infrared spectroscopy during lumbar extension and flexion, and oxygenated hemoglobin and deoxygenated hemoglobin were compared.

RESULTS

VAS was significantly lower at 4 weeks in the McKenzie group than in the control group. There were no significant changes at 2 weeks in all parameters, however, the relative change of oxygenated hemoglobin during lumbar extension at 4 weeks was significantly higher in the EMPP group when compared with the other 2 groups. The relative change of deoxygenated hemoglobin during lumbar flexion showed a significant difference at 4 weeks in the EMPP group when compared with the control group.

CONCLUSION

Administration of EMPP for 4 weeks improved the LBP in VAS, though not as effective as McKenzie therapy. Our data demonstrated the effects of eperisone hydrochloride on paraspinal muscle hemodynamics improving intramuscular oxygenation during lumbar extension and flexion in patients with chronic LBP.

Chronic non-specific low back pain - sub-groups or a single mechanism?

BACKGROUND

Low back pain is a substantial health problem and has subsequently attracted a considerable amount of research. Clinical trials evaluating the efficacy of a variety of interventions for chronic non-specific low back pain indicate limited effectiveness for most commonly applied interventions and approaches.

DISCUSSION

Many clinicians challenge the results of clinical trials as they feel that this lack of effectiveness is at odds with their clinical experience of managing patients with back pain. A common explanation for this discrepancy is the perceived heterogeneity of patients with chronic non-specific low back pain. It is felt that the effects of treatment may be diluted by the application of a single intervention to a complex, heterogeneous group with diverse treatment needs. This argument presupposes that current treatment is effective when applied to the correct patient. An alternative perspective is that the clinical trials are correct and current treatments have limited efficacy. Preoccupation with sub-grouping may stifle engagement with this view and it is important that the sub-grouping paradigm is closely examined. This paper argues that there are numerous problems with the sub-grouping approach and that it may not be an important reason for the disappointing results of clinical trials. We propose instead that current treatment may be ineffective because it has been misdirected. Recent evidence that demonstrates changes within the brain in chronic low back pain sufferers raises the possibility that persistent back pain may be a problem of cortical reorganisation and degeneration. This perspective offers interesting insights into the chronic low back pain experience and suggests alternative models of intervention.

SUMMARY

The disappointing results of clinical research are commonly explained by the failure of researchers to adequately attend to sub-grouping of the chronic non-specific low back pain population. Alternatively, current approaches may be ineffective and clinicians and researchers may need to radically rethink the nature of the problem and how it should best be managed.

Evidence-informed management of chronic low back pain with lumbar extensor strengthening exercises

The management of chronic low back pain (CLBP) has proven very challenging in North America, as evidenced by its mounting socioeconomic burden. Choosing among available nonsurgical therapies can be overwhelming for many stakeholders, including patients, health providers, policy makers, and third-party payers. Although all parties share a common goal and wish to use limited health-care resources to support interventions most likely to result in clinically meaningful improvements, there is often uncertainty about the most appropriate intervention for a particular patient. To help understand and evaluate the various commonly used nonsurgical approaches to CLBP, the North American Spine Society has sponsored this special focus issue of to The Spine Journal, titled Evidence-Informed Management of Chronic Low Back Pain Without Surgery. Articles in this supplement were contributed by leading spine practitioners and researchers, who were invited to summarize the best available evidence for a particular intervention and encouraged to make this information accessible to nonexperts. Each of the articles contains five sections (description, theory, evidence of efficacy, harms, and summary) with common subheadings to facilitate comparison across the 24 different interventions profiled in this special focus issue, blending narrative and systematic review methodology as deemed appropriate by the authors. It is hoped that articles in this special focus issue will be informative and aid in decision making for the many stakeholders evaluating nonsurgical interventions for CLBP.

Fatigue-induced changes in phasic muscle activation patterns during dynamic trunk extension exercise

OBJECTIVE

To investigate the influence of fatigue on phasic muscle-activation patterns during dynamic trunk extension exercise.

DESIGN

Fifteen healthy volunteers performed dynamic trunk-extension exercise through a 30-degree range-of-motion (ROM) exercise to task failure at an intensity of 50% of maximum. Electromyography (EMG) signals were recorded unilaterally from the lumbar extensor, gluteus maximus, and biceps femoris muscles, and signal amplitude was analyzed in 10-degree increments during the unfatigued and fatigued states (0-10 degrees from torso horizontal to the ground was considered extension, and 11-20 and 21-30 degrees of flexion relative to this were considered midphase and flexion, respectively).

RESULTS

Lumbar extensor EMG was approximately 75% of maximum EMG, with no differences being observed with respect to ROM or fatigue state. The gluteus maximus demonstrated an altered phasic activation pattern with fatigue, with an increased recruitment during the extension phase (fatigued-state extension-phase EMG: 89.1 +/- 8.3% > flexion phase EMG: 37.8% +/- 9.1%). The biceps femoris demonstrated a similar response during both the fatigued and unfatigued states (fatigued-state extension EMG: 77.8 +/- 5.4% > midphase EMG: 65.8 +/- 5.7% > flexion EMG: 46.8 +/- 4.0%; unfatigued-state extension EMG: 46.1 +/- 3.7% > flexion EMG: 27.1 +/- 2.6%).

CONCLUSIONS

During this exercise, as one moves from flexion to extension, hip extensor muscle activity increases, whereas lumbar extensor activity does not. Additionally, fatigue results in an altered recruitment pattern, with the hip extensors being activated to a greater extent in the extension phase. These findings suggest that when this exercise is performed in the prone position, it can be used to stimulate the lumbar and hip extensor muscles, but the specific exercise protocol in terms of set/repetition number and ROM will influence which muscles are primarily targeted.

Three-dimensional kinetics of the lumbar spine and hips in low back pain patients during sit-to-stand and stand-to-sit

STUDY DESIGN

Experimental, biomechanical study to determine the kinetics of the lumbar spine and hips during sit-to-stand and stand-to-sit.

OBJECTIVE

To investigate the effects of back pain, with and without limitation in straight leg raise, on the joint moment and power of the lumbar and hips during sit-to-stand and stand-to-sit.

SUMMARY OF BACKGROUND DATA

Movements of the lumbar spine and hips, and their coordination have been reported to be affected by the presence of low back pain (LBP), especially in those with a positive straight leg raise. However, the literature has no information concerning moment and power characteristics of the lumbar spine and hips during sit-to-stand and stand-to-sit in such patients.

METHODS

Twenty asymptomatic subjects, 20 LBP patients, and 20 patients with LBP and a positive straight leg raise sign were requested to perform the sit-to-stand and stand-to-sit activities. Electromagnetic sensors were attached to the body segments to measure their kinematics while 2 nonconductive force plates gathered ground reaction force data. Biomechanical models were used to determine the muscle moments and power at the lumbosacral (L5/S1) joint and hips.

RESULTS

Muscle moments acting at the lumbar spine and hip in the sagittal plane were found to decrease in subjects with LBP, but there were significant increases in moments in other planes of motion. The power patterns of the spine and hips were also significantly altered, particularly in subjects with a positive straight leg raise sign.

CONCLUSIONS

Back pain subjects exhibit compensatory movements and altered load sharing strategies during the sit-to-stand and stand-to-sit activities. Exercise therapy should take account of these changes so that the normal kinematic and kinetic characteristics of the spine and hips can be restored.

The association of low back pain, neuromuscular imbalance, and trunk extension strength in athletes

BACKGROUND CONTEXT

Imbalanced patterns of erector spinae activity and reduced trunk extension strength have been observed among patients with low back pain (LBP). The association between LBP and neuromuscular imbalance still remains unclear.

PURPOSE

To examine the relationship between LBP, neuromuscular imbalance, clinical symptoms, and trunk extension strength on two independent occasions, after dynamic neuromuscular changes through a back exercise program.

STUDY DESIGN/SETTING

Experimental longitudinal study of the lower back in a clinical setting.

PATIENT SAMPLE

Eighty-two elite amateur tennis players with and without LBP.

OUTCOME MEASURES

Clinical testing of spinal mobility and muscular flexibility of the lower back. Isometric voluntary maximum trunk extension strength. Surface electromyography (EMG) of lumbar erector spinae.

METHODS

Athletes underwent a standardized clinical examination with common tests for spinal mobility and muscular flexibility, followed by an isometric trunk extension tests in a specially built apparatus with simultaneous surface EMG recording from right and left lumbar erector spinae. Imbalance quotients were calculated using integrated EMG (IEMG) measures. The relationships between LBP, neuromuscular imbalance, trunk extension strength, and clinical findings were investigated before and after a back exercise program using univariate and multivariate logistic regression models.

RESULTS

A significant association between neuromuscular imbalance of erector spinae and the occurrence of LBP was observed, whereas no significant imbalances were found in subjects without LBP. The number of subjects with LBP decreased proportionally with the occurrence of neuromuscular imbalance in the lumbar region after the completion of a back exercise program. However, neuromuscular imbalances were still present during retesting among subjects whose LBP did not resolve; the relationship between neuromuscular imbalance of lumbar erector spinae and LBP was significant again. On the contrary, no significant association between LBP and maximum isometric trunk extension strength or neuromuscular imbalance and maximum isometric trunk extension strength was found before or after the exercise program. No clear relationship between LBP and clinical testing of the lumbar spine or neuromuscular imbalance and clinical testing was found on the two independent testing occasions.

CONCLUSION

A direct relationship between LBP and neuromuscular imbalance was documented in athletes with LBP. Maximum isometric trunk extension strength had no relationship to the presence of LBP or the occurrence of neuromuscular imbalance of erector spinae. Common clinical testing of spinal mobility and muscular flexibility had only limited correlation to LBP and neuromuscular imbalance.

Altered patterns of superficial trunk muscle activation during sitting in nonspecific chronic low back pain patients: importance of subclassification

STUDY DESIGN

A cross-sectional comparative study between healthy controls and two subgroups of nonspecific chronic low back pain (LBP) patients.

OBJECTIVES

To determine differences in trunk muscle activation during usual unsupported sitting.

SUMMARY OF BACKGROUND DATA

Patients with LBP commonly report exacerbation of pain on sitting. Little evidence exists to confirm that subgroups of patients with nonspecific chronic LBP patients use different motor patterns in sitting than pain-free controls.

METHODS

A total of 34 pain-free and 33 nonspecific chronic LBP subjects were recruited. Two blinded clinicians classified nonspecific chronic LBP patients into two subgroups (active extension pattern and flexion pattern). Surface electromyography (sEMG) was recorded from five trunk muscles during subjects' unsupported "usual" and "slumped" sitting.

RESULTS

No differences in trunk muscle activity were observed between healthy controls and nonspecific chronic LBP groups for usual sitting. When the classification system was applied, differences were identified. Compared with no-LBP controls, the active extension pattern group presented with higher levels of cocontraction of superficial fibers of lumbar multifidus (12%), iliocostalis lumborum pars thoracis (36%) and transverse fibers of internal oblique (43%). while the flexion pattern group showed a trend toward lower activation patterns (lumbar multifidus, -7%; iliocostalis lumborum pars thoracis, -6%, and transverse fibers of internal oblique, -5%). The flexion relaxation ratio of the back muscles was lower for nonspecific chronic LBP (superficial lumbar multifidus: t = 4.5; P < 0.001 and iliocostalis lumborum pars thoracis:t = 2.7; P < 0.001), suggesting a lack of flexion relaxation for the nonspecific chronic LBP.

CONCLUSION

Subclassifying nonspecific chronic LBP patients revealed clear differences in sEMG activity during sitting between pain-free subjects and subgroups of nonspecific chronic LBP patients.

The relationship between active and neural measures in patients with nonspecific low back pain

STUDY DESIGN

Cross-sectional study of 50 individuals with nonspecific low back pain (LBP).

OBJECTIVE

To evaluate the relationship between active and neural measurements in individuals with nonspecific LBP.

SUMMARY OF BACKGROUND DATA

The Panjabi model for spinal stability consists of 3 interacting subsystems. Specific musculoskeletal measurements can be identified within the active and neural systems. The relationships among measures within this model have not been identified.

METHODS

A total of 50 individuals with nonspecific LBP were evaluated for measures of the active and neural stability systems, and analyzed using a canonical correlation analysis, which is used to measure the relationship between 2 multidimensional variables.

RESULTS

There were 2 significant relationships identified. The first identified a relationship among fatigue, flexion relation, and the feedforward abdominal response (r = 0.764, P < 0.001). The second relationship was between the Sorenson endurance test and feedforward abdominal response (r = 0.697, P = 0.006).

CONCLUSION

Identification of relationships between back pain measurements may allow discrimination between individuals with different histology and pain levels. This process may assist the specificity of treatment programs prescribed for patients with back pain.

Reliability of the Assessment of Lumbar Range of Motion and Maximal Isometric Strength

OBJECTIVE

To examine the interobserver reliability and intrasubject variability of the assessment of lumbar range of motion (ROM) and maximal isometric strength in asymptomatic subjects by using commercially available equipment.

DESIGN

A cross-sectional repeated-measures design.

SETTING

Ambulatory care in a university hospital.

PARTICIPANTS

Convenience sample of 61 asymptomatic healthy subjects aged 20 to 55 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Six movements of the lumbar spine were assessed with commercially available equipment. Both the ROM and the maximal isometric strength for flexion, extension, lateroflexion, and rotation of the lumbar spine were assessed by 2 investigators who were blinded to the outcome of the assessment performed by their colleague.

RESULTS

The intraclass correlation coefficient (ICC) was above .95 for all the strength measurements. For the assessment of the ROM of the lumbar spine, the ICC varied between .77 and .94. There was a significant intrasubject variability for 8 of 12 measurements.

CONCLUSIONS

The interobserver reliability is excellent for the measurement of the maximal isometric strength and good for the assessment of the ROM of the lumbar spine. There is a significant intrasubject variability, which requires the use of the mean or the best value of different trials.

What predicts outcome in non-operative treatments of chronic low back pain? A systematic review

Systematic reviews have shown that as non-operative treatments exercise, behavioural and multimodal treatment programs are effective for chronic low back pain. There is, however, a lack of knowledge concerning the association between changes in treatment process variables and changes in outcome for the three treatment forms. The objective of this systematic review was to evaluate which changes in treatment process variables predict outcome of exercise, behavioural and multimodal treatment of chronic low back pain. Medline, Embase and PsychInfo were systematically searched. A descriptive analysis was used to summarize the results regarding the outcomes pain, disability and return to work (RTW). 13 studies were identified. The results showed that functional coping mechanisms and pain reduction were associated with a decrease in disability and increase in RTW, and physical performance factors were not. Related to pain reduction decreases in disability, functional coping mechanisms as well as physical performance factors were associated. Strong conclusions cannot be drawn from this review, because of the heterogeneity and the limited number of studies. The results of this review raise the question if changes in behavioural variables and reductions of disability which facilitate an improvement in function, may be more important than physical performance factors for successful treatment of chronic low back pain. This is relevant for the refinement of future treatment programs.

The use of magnetic resonance imaging to evaluate lumbar muscle activity during trunk extension exercise at varying intensities

STUDY DESIGN

Descriptive, repeated measures analysis of exercise-induced changes in lumbar muscle transverse relaxation time (T2).

OBJECTIVES

To use muscle functional magnetic resonance imaging (MRI) to characterize the activity levels and recruitment patterns of the lumbar extensor muscles during trunk extension exercise over 3 intensities.

SUMMARY OF BACKGROUND DATA

Contrast shifts in T2 are indicative of skeletal muscle activity during resistance exercise and are used to characterize the function of a variety of muscles. The use of muscle functional MRI for the lumbar muscles has been limited.

METHODS

In 11 healthy participants, T2 was calculated for the lumbar quadratus lumborum, iliocostalis lumborum, longissimus thoracis, and multifidus at rest and following dynamic trunk extension exercise at 3 exercise intensities (40%, 50%, and 70% peak intensity).

RESULTS

The multifidus displayed the largest T2 increase at each of the 3 exercise intensities, followed by the erector spinae and, finally, the quadratus lumborum. At the lowest intensity, the medial erector spinae (longissimus thoracis) displayed a higher T2 increase than the lateral group (iliocostalis lumborum), while at the higher intensities, this pattern was reversed. In general, the T2 increase was higher during exercise at 50% and 70% intensities than at 40%, while there was no difference in T2 increase between 50% and 70%.

CONCLUSIONS

Muscle functional MRI can be used to characterize lumbar muscle function during trunk extension exercise. The levels and recruitment patterns of the lumbar extensors, as measured by muscle T2 shifts, vary with exercise intensity. Future research is needed to assess the mechanism of the nonlinear relationship between T2 shifts and exercise intensity, and to clarify the effects of fatigue and the order of exercise presentation on the T2 response of the lumbar extensors.

A Meta-Analytic Review of Surface Electromyography Among Persons With Low Back Pain and Normal, Healthy Controls

Significant differences in surface electromyography (SEMG) have been reported between persons with low back pain (LBP) and normal, healthy controls. This manuscript presents a systematic meta-analytic review of studies examining SEMG differences between these groups. Forty-four articles were identified using MEDLINE and a review of reference lists in articles. For static SEMG, the largest effect size was observed for SEMG while standing, with subjects having LBP demonstrating higher SEMG. The effect size for flexion/relaxation measures was found to be very high (d = -1.71). Studies examining SEMG during isometric exercise or muscle recovery following exercise produced inconsistent findings. Sensitivity and specificity of SEMG for dynamic SEMG measures averaged 88.8% and 81.3%. Most classification schemes were statistically determined and utilized a combination of measures. Only one published study prospectively validated a classification scheme. SEMG measures of flexion-relaxation appear to distinguish LBP subjects from controls with good accuracy, and the sensitivity and specificity of SEMG can be increased by using multiple measures. Further research is needed to determine the combination of measures that are cost-effective, reliable, valid and discriminate with a high degree of accuracy between healthy persons and those with LBP.

PERSPECTIVE

SEMG is a simple and noninvasive measure of muscle activity. SEMG measures hold promise as an objective marker of LBP.

Isokinetic muscle strength of the trunk and bilateral knees in young subjects with lumbar disc herniation

STUDY DESIGN

Cross-sectional study comparing normal subjects and patients with lumbar disc herniation.

OBJECTIVE

To evaluate trunk and knee muscle strength in patients with L4-L5 and/or L5-S1 disc herniation.

SUMMARY OF BACKGROUND DATA

Numerous studies have shown that patients with low back pain have weaker trunk muscles. The strength of trunk and knee muscles has not been investigated simultaneously in patients with lumbar disc herniation.

METHODS

Forty-one controls and 2 patients were included. Isokinetic strength of the trunk and bilateral knees was tested on a calibrated isokinetic testing machine (Biodex System 3 Pro) regardless of the laterality of the radiculopathy. The testing was carrying out at two different velocities: 60 degrees and 120 degrees per second.

RESULTS

Total trunk strength and knee strength were significantly lower in these patients (4.34 +/- 1.06 and 4.06 +/- 1.16 vs. 6.21 +/- 1.05 and 5.83 +/- 1.09 Nm/kg at 60 degrees and 120 degrees per second, respectively, P < 0.001). In patients with unilateral sciatica, there was no significant difference (P > 0.05) in unilateral knee strength between sciatica-involved and -uninvolved limbs (1.89 +/- 0.5, 1.08 +/- 0.45, 1.48 +/- 0.58, 0.93 +/- 0.41 vs. 1.68 +/- 0.45, 0.91 +/- 0.38, 1.41 +/- 0.48, 0.79 +/- 0.39 Nm/kg in sciatica-uninvolved vs. sciatica-involved limbs during extension and flexion at 60 degrees and 120 degrees per second, respectively). Total trunk strength was significantly correlated with total knee strength in both groups.

CONCLUSIONS

In the patients with lumbar disc herniation, muscle strength of the trunk and knees was decreased to a similar extent. Weaker knee strength was found on either side of the lower extremity in the patients with unilateral sciatica, regardless of its location.

Effects of home strength training and stretching versus stretching alone after lumbar disk surgery: a randomized study with a 1-year follow-up

OBJECTIVE

To assess the adherence to and effects of a 12-month combined strength and stretching home exercise regimen versus stretching alone, on patient outcome after lumbar disk surgery.

DESIGN

Randomized controlled trial.

SETTING

Departments of physical medicine and rehabilitation and orthopedics at a Finnish hospital.

PARTICIPANTS

Patients (N=126) were randomized into either a combined strength training and stretching group (STG, n=65) or a control group (CG, n=61).

INTERVENTION

The STG was instructed to perform strength training and both the STG and CG were instructed in the same stretching and stabilization exercises for 12 months.

MAIN OUTCOME MEASURES

Pain on the visual analog scale (VAS), the Oswestry and the Million disability indexes, isometric and dynamic trunk muscle strength, mobility in the lumbar spine, and straight-leg raising were measured.

RESULTS

The trial was completed by 71% and 77% of the patients from the STG and the CG, respectively. The mean strength training frequency decreased from 1.5 to 0.6 times a week in the STG during the intervention. The mean stretching frequency decreased from 3.7 to 1.6 times a week in both groups. Median back and leg pain varied between 17 and 23 mm (VAS), and the Million and Oswestry indices varied between 14 and 23 points 2 months postoperatively. No statistically significant changes took place in these outcome measures during the 12-month follow-up in both groups. The changes in isometric trunk extension favored the STG ( P =.016) during the first 2 months. However, during the whole 12-month training period, both dynamic and isometric back extension and flexion strength, as well as mobility of the spine and repetitive squat-test results, improved significantly in both groups, and no differences were found in any of the physical function parameters between the STG and CG.

CONCLUSIONS

At the 12-month follow-up, no statistically significant changes were found in the physical function, pain, or disability measures between the groups. In the STG, training adherence with regard to training frequency and intensity remained too low to lead to specific training-induced adaptations in the neuromuscular system. Progressive loading, supervision of training, and psychosocial support is needed in long-term rehabilitation programs to maintain patient motivation.

Biological risk indicators for recurrent non-specific low back pain in adolescents

OBJECTIVES

A matched case-control study was carried out to evaluate biological risk indicators for recurrent non-specific low back pain in adolescents.

METHODS

Adolescents with recurrent non-specific low back pain (symptomatic; n = 28; mean (SD) age 14.9 (0.7) years) and matched controls (asymptomatic; n = 28; age 14.9 (0.7) years) with no history of non-specific low back pain participated. Measures of stature, mass, sitting height, sexual maturity (Tanner self assessment), lateral flexion of the spine, lumbar sagittal plane mobility (modified Schober), hip range of motion (Leighton flexometer), back and hamstring flexibility (sit and reach), and trunk muscle endurance (number of sit ups) were performed using standardised procedures with established reliability. Backward stepwise logistic regression analysis was performed, with the presence/absence of recurrent low back pain as the dependent variable and the biological measures as the independent variables.

RESULTS

Hip range of motion, trunk muscle endurance, lumbar sagittal plane mobility, and lateral flexion of the spine were identified as significant risk indicators of recurrent low back pain (p<0.05). Follow up analysis indicated that symptomatic subjects had significantly reduced lateral flexion of the spine, lumbar sagittal plane mobility, and trunk muscle endurance (p<0.05).

CONCLUSIONS

Hip range of motion, abdominal muscle endurance, lumbar flexibility, and lateral flexion of the spine were risk indicators for recurrent non-specific low back pain in a group of adolescents. These risk indicators identify the potential for exercise as a primary or secondary prevention method.