Article

Does experimental low back pain change posteroanterior lumbar spinal stiffness and trunk muscle activity? A randomized crossover study

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Abstract

Background: While some patients with low back pain demonstrate increased spinal stiffness that decreases as pain subsides, this observation is inconsistent. Currently, the relation between spinal stiffness and low back pain remains unclear. This study aimed to investigate the effects of experimental low back pain on temporal changes in posteroanterior spinal stiffness and concurrent trunk muscle activity. Method: In separate sessions five days apart, nine asymptomatic participants received equal volume injections of hypertonic or isotonic saline in random order into the L3-L5 interspinous ligaments. Pain intensity, spinal stiffness (global and terminal stiffness) at the L3 level, and the surface electromyographic activity of six trunk muscles were measured before, immediately after, and 25-minute after injections. These outcome measures under different saline conditions were compared by generalized estimating equations. Findings: Compared to isotonic saline injections, hypertonic saline injections evoked significantly higher pain intensity (mean difference: 5.7/10), higher global (mean difference: 0.73N/mm) and terminal stiffness (mean difference: 0.58N/mm), and increased activity of four trunk muscles during indentation (P<0.05). Both spinal stiffness and trunk muscle activity returned to baseline levels as pain subsided. Interpretation: While previous clinical research reported inconsistent findings regarding the association between spinal stiffness and low back pain, our study revealed that experimental pain caused temporary increases in spinal stiffness and concurrent trunk muscle co-contraction during indentation, which helps explain the temporal relation between spinal stiffness and low back pain observed in some clinical studies. Our results substantiate the role of spinal stiffness assessments in monitoring back pain progression.

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... A convenient sample of 20 healthy participants (all males) was recruited from the student population of the Hong Kong Polytechnic University to participate in this study (Table I). Sample exclusion criteria included "high risk" participants with a history of: LBP (using the ten-item Oswestry Disability Index (ODI) > 20 per cent) (Fairbank and Pynsent, 2000;Wong et al., 2016); and/or cardiac or other health problems (e.g. dizziness, chest pain and heart pain) (using a seven-item Physical Activity Readiness Questionnaire (PAR-Q)) (Baecke et al., 1982). ...
... A 20-minute rest was interspersed between the lifting of different weights. Figure 2) (Hermens et al., 1999;Wong et al., 2016). The diameter of the electrode was 15 mm and the inter-electrode distance was 20 mm. ...
... Before performing the lifting task, participants were instructed to perform two trials of back extension MVC against manual resistance. The participants maintained the MVC for 5 seconds with a 2-minute rest between trials (Hu et al., 2009;Wong et al., 2016). The maximum root mean square (RMS) of sEMG signal for each LES muscle was identified using a 1,000 ms moving window passing through the sEMG signals during the two MVCs. ...
Article
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Purpose Work-related low back disorders (LBDs) are prevalent among rebar workers although their causes remain uncertain. The purpose of this study is to examine the self-reported discomfort and spinal biomechanics (muscle activity and spinal kinematics) experienced by rebar workers. Design/methodology/approach In all, 20 healthy male participants performed simulated repetitive rebar lifting tasks with three different lifting weights, using either a stoop ( n = 10) or a squat ( n = 10) lifting posture, until subjective fatigue was reached. During these tasks, trunk muscle activity and spinal kinematics were recorded using surface electromyography and motion sensors, respectively. Findings A mixed-model, repeated measures analysis of variance revealed that an increase in lifting weight significantly increased lower back muscle activity at L3 level but decreased fatigue and time to fatigue (endurance time) ( p < 0.05). Lifting postures had no significant effect on spinal biomechanics ( p < 0.05). Test results revealed that lifting different weights causes disproportional loading upon muscles, which shortens the time to reach working endurance and increases the risk of developing LBDs among rebar workers. Research limitations/implications Future research is required to: broaden the research scope to include other trades; investigate the effects of using assistive lifting devices to reduce manual handling risks posed; and develop automated human condition-based solutions to monitor trunk muscle activity and spinal kinematics. Originality/value This study fulfils an identified need to study laboratory-based simulated task conducted to investigate the risk of developing LBDs among rebar workers primarily caused by repetitive rebar lifting.
... CMRR 100 dB at 60 Hz) and digitized with the Desktop Direct Transmission System (Noraxon Inc., Phoenix, USA). Signals were processed with a Noraxon program, MR 3.10.2, to eliminate electrocardiography signals, notch filter at 50Hz to remove electrical noise, and digitally bandpass between 10Hz and 500Hz [26]. sEMG signals from each muscle were expressed as a percentage of maximum voluntary contraction (%MVC). ...
... Mean + standard deviation; NPRS = 11-point numeric pain rating scale The participant laid in prone with arms placed beside the body, and legs stabilized by a strap on a plinth. The participant performed isometric back extension against a manual resistance applied downward on scapulae [26] 2 ...
... Obliquus externus Midway between the 12th rib and the highest point of iliac crest [26] The participant was positioned in crook lying with pelvis stabilized. With arms crossed the chest, the participant performed diagonal curl-up against manual resistance applied on the rising shoulder and the bent knees [26] 3 Obliquus internus/ transversus abdominis 2 cm inferior to and 2 cm medial to anterior superior iliac spines [26] A maximal expiratory maneuver with abdominal hollowing (i.e. ...
Article
Background Static sitting is thought to be related to low back pain. Of various common seated postures, slouched sitting has been suggested to cause viscoelastic creep. This, in turn, may compromise trunk muscle activity and proprioception, and heightening the risk of low back pain. To date, no research has evaluated immediate and short-term effects of brief exposures to different sitting postures on spinal biomechanics and trunk proprioception. Research question This study aimed to compare the impacts of 20 minutes of static slouched, upright and supported sitting with a backrest on trunk range of motion, muscle activity, and proprioception immediately after and 30 minutes after the sitting tasks. Methods Thirty-seven adults were randomly assigned to the three sitting posture groups. Surface electromyography of six trunk muscles during maximum voluntary contractions were measured at baseline for normalization. Pain intensity, lumbar range of motion, and proprioceptive postural control strategy were assessed at baseline, 20 minutes (immediately post-test) and at 50 minutes (recovery). Trunk muscle activity during sitting was continuously monitored by surface electromyography. Results While the slouched sitting group demonstrated the lowest bilateral obliquus internus/transversus abdominis activity as compared to other sitting postures (F = 4.87, p < 0.05), no significant temporal changes in pain intensity, lumbar range of motion nor proprioceptive strategy were noted in any of the groups. Significance Sitting for 20 minutes of duration appears to have no adverse effects on symptoms or spinal biomechanics regardless of the posture adopted. Future research should determine if there is a point at which does slouched sitting cause significant changes in pain/spinal biomechanics in people both with and without low back pain. https://www.sciencedirect.com/science/article/pii/S0966636218306015?dgcid=author
... Results showed that muscle activity amplitude was not different between both populations, and that muscle activity and spinal stiffness were not significantly correlated. Similar with observations from previous studies evaluating lumbar spinal stiffness in participants with LBP [21,35], most participants with chronic thoracic pain reported pain during the assessment. However, pain intensity was only significantly associated with spinal stiffness at one spinal level. ...
... Interestingly, this result diverges from those reported by Latimer et al. (1996), who showed a concomitant decrease in spinal stiffness and pain intensity during the assessment of this parameter in participants with acute low back pain that reported a 80% of improvement at their second evaluation. [21] Using experimental lumbar pain in healthy participants, Wong et al. (2016) also revealed an Spinal stiffness and chronic thoracic pain association between pain provocation during spinal stiffness assessment, an increase in lumbar muscle activity and an increase in lumbar spinal stiffness. [35] The conflicting results between these studies and the present study highlight the possible distinctive behaviors or adaptions to pain between the lumbar and the thoracic spine or between acute and chronic pain. ...
... [21] Using experimental lumbar pain in healthy participants, Wong et al. (2016) also revealed an Spinal stiffness and chronic thoracic pain association between pain provocation during spinal stiffness assessment, an increase in lumbar muscle activity and an increase in lumbar spinal stiffness. [35] The conflicting results between these studies and the present study highlight the possible distinctive behaviors or adaptions to pain between the lumbar and the thoracic spine or between acute and chronic pain. Until the causes of the increase or decrease in spinal stiffness with chronic back pain are better known, care should be taken when inferring results from studies investigating a spine region to another spine region or from results acquired in healthy participants to participants with chronic back pain. ...
Article
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Objective The objective was to compare thoracic spinal stiffness between healthy participants and participants with chronic thoracic pain and to explore the associations between spinal stiffness, pain and muscle activity. The reliability of spinal stiffness was also evaluated. Material and methods Spinal stiffness was assessed from T5 to T8 using a mechanical device in 25 healthy participants and 50 participants with chronic thoracic pain (symptoms had to be reported within the evaluated region of the back). The spinal levels for which spinal stiffness was measured were standardized (i.e. T5 to T8 for all participants) to minimize between-individual variations due to the evaluation of different spinal levels. The device load and displacement data were used to calculate the global and terminal spinal stiffness coefficients at each spinal level. Immediately after each assessment, participants were asked to rate their pain intensity during the trial, while thoracic muscle activity was recorded during the load application using surface electromyography electrodes (sEMG). Within- and between-day reliability were evaluated using intraclass correlation coefficients (ICC), while the effects of chronic thoracic pain and spinal levels on spinal stiffness and sEMG activity were assessed using mixed model ANOVAs. Correlations between pain intensity, muscle activity and spinal stiffness were also computed. Results ICC values for within- and between-day reliability of spinal stiffness ranged from 0.67 to 0.91 and from 0.60 to 0.94 (except at T5), respectively. A significant decrease in the global (F1,73 = 4.04, p = 0.048) and terminal (F1,73 = 4.93, p = 0.03) spinal stiffness was observed in participants with thoracic pain. sEMG activity was not significantly different between groups and between spinal levels. Pain intensity was only significantly and "moderately" correlated to spinal stiffness coefficients at one spinal level (-0.29≤r≤-0.51), while sEMG activity and spinal stiffness were not significantly correlated. Conclusion The results suggest that spinal stiffness can be reliably assessed using a mechanical device and that this parameter is decreased in participants with chronic thoracic pain. Studies are required to determine the value of instrumented spinal stiffness assessment in the evaluation and management of patients with chronic spine-related pain.
... 6 As a result of these improvements, a number of studies have now been conducted with these devices and demonstrate the responsiveness of spinal stiffness to various interventions or treatment. 7,8 Although the design of spinal stiffness devices varies, the basic principles of instrumented spinal stiffness measurement are similar. A typical spinal stiffness device comprises a motor to control the movement of an indenter that loads the spine of a prone participant, a load cell to measure the loading force, and a displacement sensor to measure the displacement of the indenter (indirect displacement of the spine) in response to the indentation. ...
... This coefficient represents the stiffness of underlying tissues throughout the indentation 6 or the tissue dynamics in response to indentation force. 8 Terminal spinal stiffness is estimated from the final loading force and the overall displacement of the indenter and indicates the overall bulk response. 8 ...
... 8 Terminal spinal stiffness is estimated from the final loading force and the overall displacement of the indenter and indicates the overall bulk response. 8 ...
Article
Objective: Spinal stiffness assessments are commonly used by manual therapists. Although devices have been developed to objectively measure spinal stiffness, individual characteristics (i.e., sex, age, weight, height) may affect the measurement results. Therefore, this study aimed to describe the correlations between individual characteristics and spinal stiffness. Methods: A secondary analysis of three adult datasets using three different devices, in two spinal regions, from a total of five separate cross-sectional studies was conducted. Differences in spinal stiffness between males and females and the strength of correlation between spinal stiffness and age, and anthropometric characteristics were evaluated using either t-test for independent samples, Pearson or Kendall’s Tau rank correlation coefficient. Results: As expected, results varied between datasets, however, few factors displayed consistent correlations. Specifically, spinal stiffness was significantly lower in females than males in all three datasets. Height was positively correlated to spinal stiffness across all datasets. While weight was correlated to thoracic stiffness, it presented varied correlation with lumbar stiffness. Two datasets showed BMI was inversely associated with lumbar spinal stiffness, whereas results from the thoracic spine region showed a positive correlation. The results of one dataset suggest that physiological measurement evaluating body weight distribution may also affect spinal stiffness, however the specific correlation remains unclear. Conclusion: Despite of dataset differences, significant correlations were observed indicating that participant characteristics appear to affect spinal stiffness measurement. Therefore, future studies assessing spinal stiffness should report and control for individual characteristics. Moreover, a standardised testing protocol for spine stiffness measures remains to be developed.
... There is therefore a robust rationale to establish the efficacy of such treatments given their low risk side effects (back pain, trigger of other pain, minor bruises) and potential economic savings. The National Institute for Health and Clinical Excellence (NICE) guidelines have recommended using manual therapy for these reasons (Carnes et al., 2010;Powers et al., 2008;Savigny et al., 2009;Shum et al., 2013;Stamos-Papastamos et al., 2011;Wong et al., 2016). ...
... Previous literature has also shown a large number of studies resulting in a hypoalgesic effect from manual therapy interventions (George et al., 2006;Pentelka et al., 2012;Thomson et al., 2009;Vicenzino et al., 2001;Willett et al., 2010;Yeo & Wright, 2011). Due to the association between stiffness and pain (Fritz et al., 2011;Wong et al., 2016) a reduction in stiffness would be expected to also show a reduction in pain. The VAS was used as it complied well with feasibility and ethical considerations, though it added an element of a subjective pain measure. ...
Thesis
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Background: Multiple Sclerosis (MS) has many disabling symptoms due to weakened signal propagation in the central nervous system. Manual therapeutics are often seen to have a positive effect on these symptoms with limited information as to why. The purpose of this project was to investigate a spinal mobilisation intervention, objectively measuring the changes it may be causing to muscle quality and movement patterns as a contribution to research in MS therapeutics. Methods: A series of 3 studies were designed to investigate the effects of a spinal mobilisation intervention on muscle quality and movement patterns. Study 1 tested people with lower back pain (LBP) as a pilot population (n=40), testing for an immediate effect on muscle quality. Study 2 replicated this with MS patients (n=20) assessing muscle quality, balance, and pain. Study 3 tested the intervention in a longer-term 4 bout study (n=20), assessing muscle quality, balance, pain, and fatigue. Results: Significant muscle stiffness reductions were seen in the LBP population post the intervention (p = 0.01, η2partial = 0.15). Baseline stiffness was found as a significant contributor (p = 0.002, R2 = 0.22). These muscular results were not replicated with the MS population. However, significant improvements in self-reported pain as a result of the intervention were revealed (p = 0.008, η2partial = 0.33). Study 3 findings demonstrated significant improvements from baseline in balance and fatigue measures as a result of the intervention. High variability in the data are seen within the MS population.
... Two pairs of wireless bipolar Ag/AgCl surface electrodes (Noraxon TeleMyo sEMG System, Noraxon USA Inc., USA) were attached bilateral to the left and right muscle of the: biceps brachii (BB); brachioradialis (BR); lumbar erector spinae (LES); rectus femoris (RF) and medial gastrocnemius (MG) [75,76]. The diameter of the electrode was 15 mm and the inter-electrode distance was 20 mm. ...
... Prior to the lifting task, the participant was instructed to perform two trials of maximum voluntary contraction (MVC) against manual resistance of each muscle [75]. The participant maintained the MVC for 5 s with 2-minute rest between trials [76]. The maximum root mean square (RMS) of sEMG signal of each muscle was identified using a 1000 ms moving window passing through the sEMG signals during the two MVCs. ...
... In contrast to the current findings, experimental LBP increased trunk stiffness compared to nonpain conditions. Increased stiffness with experimental pain was also observed by Wong et al (2016) using a device that measures force and displacement of the spine while lying prone (Table 1). Contrasting observations within our cohort imply that adaptation to pain is task specific . ...
... Contrasting observations within our cohort imply that adaptation to pain is task specific . However, in both Hodges et al. (2013) and Wong et al. (2016) stiffness was assessed in quasi-static condition and increasing damping might not be a suitable strategy because velocity of the assessed motions was minimal, and control of displacement via increased stiffness seems to be the only viable option. ...
Article
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Movement adaptations to low back pain (LBP) are believed to protect the painful area. Increased trunk stiffness and decreased trunk damping have been shown in people with recurrent LBP. However, no study has examined these properties using external force perturbations to the trunk during acute LBP when protective adaptations might be expected to have most relevance. Adaptations to an acute painful stimulus via unilateral injection of hypertonic saline into the right longissimus muscle were assessed using a trunk force perturbation paradigm and a mass-spring-damper model to describe effective trunk dynamical properties. Equal weights (15% body weight) were connected to the front and back of the trunk via a cable. Either one was dropped at random to perturb the trunk. Effective trunk dynamical properties were estimated in fourteen males (mean (standard deviation) age 25 (6) years) assuming that trunk movement can be modelled as a second order linear system. Effective trunk dynamical properties were compared before, during and after the experimentally induced painful period. Estimates of effective trunk stiffness (K) decreased and damping (B) increased during pain compared to both before ([mean contrast, 95% CI] K: −403 [−651 to −155] Nm⁻¹, B: 28 [9–50] Nms⁻¹) and after (K: −324 [−58 to −591] Nm⁻¹, B: 20 [4–33] Nms⁻¹) the experimentally induced painful period. We interpret our results to show that, when challenged by a step force perturbation, a healthy system adapts to noxious input by controlling trunk velocity rather than trunk displacement, in contrast to observations during remission from recurrent clinical LBP.
... A decrease in pain intensity and an increase in pressure pain threshold have been reported separately in two themes, but one could consider these potential mechanisms together. Although the work by Wong et al. (2016) shows how experimental pain (increased pain intensity) changes stiffness [36], it is uncertain if this is mediated by direct irritation of the muscles or if this effect is mediated by another system (e.g., nervous system). Interestingly, the result of being able to endure more pain is associated with decreased stiffness [20,37]. ...
... A decrease in pain intensity and an increase in pressure pain threshold have been reported separately in two themes, but one could consider these potential mechanisms together. Although the work by Wong et al. (2016) shows how experimental pain (increased pain intensity) changes stiffness [36], it is uncertain if this is mediated by direct irritation of the muscles or if this effect is mediated by another system (e.g., nervous system). Interestingly, the result of being able to endure more pain is associated with decreased stiffness [20,37]. ...
Article
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Introduction: In individuals having low back pain, the application of spinal manipulative therapy (SMT) has been shown to reduce spinal stiffness in those who report improvements in post-SMT disability. The underlying mechanism for this rapid change in stiffness is not understood presently. As clinicians and patients may benefit from a better understanding of this mechanism in terms of optimizing care delivery, the objective of this scoping review of current literature was to identify if potential mechanisms that explain this clinical response have been previously described or could be elucidated from existing data. Methods: Three literature databases were systematically searched (MEDLINE, CINAHL, and PubMed). Our search terms included subject headings and keywords relevant to SMT, spinal stiffness, lumbar spine, and mechanism. Inclusion criteria for candidate studies were publication in English, quantification of lumbar spinal stiffness before and after SMT, and publication between January 2000 and June 2019. Results: The search identified 1931 articles. Of these studies, 10 were included following the application of the inclusion criteria. From these articles, 7 themes were identified with respect to potential mechanisms described or derived from data: 1) change in muscle activity; 2) increase in mobility; 3) decrease in pain; 4) increase in pressure pain threshold; 5) change in spinal tissue behavior; 6) change in the central nervous system or reflex pathways; and 7) correction of a vertebral dysfunction. Conclusions: This scoping review identified 7 themes put forward by authors to explain changes in spinal stiffness following SMT. Unfortunately, none of the studies provided data which would support the promotion of one theme over another. As a result, this review suggests a need to develop a theoretical framework to explain rapid biomechanical changes following SMT to guide and prioritize future investigations in this important clinical area.
... Diabetes is a recognised comorbidity associated with a worse functional outcome [4] and stiffness [10] after TKA, which supports the findings of the current study. Nonspecific lower lumbar back pain has recently been demonstrated to be directly related to increased lumber stiffness [28], and although there is no link with a fibrotic condition there is an accepted inflammatory element which may be associated with the aetiology of knee stiffness [23]. ...
Article
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Purpose: Symptoms of stiffness after total knee arthroplasty (TKA) cause significant morbidity, but there is limited data to facilitate identification of those most at risk after surgery. Stratifying risk can aid earlier directed treatment options. Methods: A retrospective cohort consisting of 2589 patients undergoing a primary TKA was identified from an established arthroplasty database. Patient demographics, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and short form (SF) 12 scores were collected pre-operatively and 1 year post-operatively. In addition, patient satisfaction was assessed for 1 year. Patients with a worse WOMAC stiffness score in 1 year were defined as the "increased" stiffness group and the other cohort as the non-stiffness group. Results: At 1 year after surgery 129 (5%) patients had a significant increase in their stiffness symptoms (20%, 95% confidence interval (CI) 17.9-22.0, p < 0.001), and had significantly (all p < 0.001) less of an improvement in their pain, function and total WOMAC scores, and SF-12 scores compared to the non-stiffness group (n = 2460). Patient satisfaction was significantly lower (odds ratio (OR) 0.178, CI 0.121 to 0.262, p < 0.001) for the increased stiffness group. Logistic regression analysis identified male gender (OR 1.66, p = 0.02), lung disease (OR 2.06, p = 0.002), diabetes (OR 1.82, p = 0.02), back pain (OR 1.81, p = 0.005), and a pre-operative stiffness score of 44 or more (OR 5.79, p < 0.001) were significantly predictive of increased stiffness. Conclusion: Patients with increased symptoms of stiffness after TKA have a worse functional outcome and a lower rate of patient satisfaction, and patients at risk of being in this group should be informed pre-operatively. Level of evidence: Retrospective prognostic study, Level III.
... However, both studies did not estimate the 295 correlation between absolute segmental spinal stiffness values and the corresponding 296 LBP intensity. Although speculative, increased spinal stiffness may be attributed to spinal 297 degeneration, shrinkage of joint capsules or surrounding ligaments [62], presence of 298 trigger points in trunk muscles [63], or elevated trunk muscle activity [64]. 299 300 ...
Article
Abnormal spinal segmental motion/stiffness is purported to be a cause, or an effect of, low back pain. Therefore, the assessment of posteroanterior segmental spinal stiffness is a common practice in clinical and research settings. In clinical settings, manipulative practitioners routinely assess spinal stiffness manually to guide clinical decision-making. Unfortunately, the reliability of manual segmental spinal stiffness assessment is poor. As a result, various spinal stiffness-testing devices have been developed to improve the reliability and accuracy of spinal stiffness measures. Although previous critical and systematic reviews have summarized the evidence regarding the reliability and confounding factors of manual and/or instrumented spinal stiffness measurements, no available review has summarized the principles of various spinal stiffness measurement methods nor pragmatic recommendations to optimize these measurements. Importantly, although posteroanterior segmental spinal stiffness is hypothesized to be related closely to low back pain or clinical outcomes after treatments, no review has been conducted to summarize evidence related to these premises and to discuss factors that can confound these relations. Against this background, this narrative review revisits the concept of both manual and instrumented spinal stiffness assessments, summarizes the pragmatic recommendations for minimizing measurement errors, reviews the potential relations between segmental spinal stiffness and low back pain, and provides future clinical research directions that can benefit clinicians and researchers alike. Level of evidence: Not applicable.
... Our findings of a heightened protective response in people that report back pain and stiffness raise the possibility that the mechanisms that subserve pain also contribute to the perception of stiffness. Such a possibility would be predicted by several relevant theoretical frameworks, for example: associative learning 46 -pain and stiffness often go together; adaptation to pain model 47 -pain-related muscle activation changes alter trunk stiffness 48,49 to prevent ongoing irritation of sensitive tissues; and the more recent link between motor effort and proprioception 50 -painful movements are predicted to be more effortful [Tabor 2016, unpublished data], which in turn might make them feel stiffer. Together, these suggest that pain and stiffness likely compel similar behavioural responses that limit movement and thus re-injury. ...
Article
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Does feeling back stiffness actually reflect having a stiff back? This research interrogates the long-held question of what informs our subjective experiences of bodily state. We propose a new hypothesis: feelings of back stiffness are a protective perceptual construct, rather than reflecting biomechanical properties of the back. This has far-reaching implications for treatment of pain/stiffness but also for our understanding of bodily feelings. Over three experiments, we challenge the prevailing view by showing that feeling stiff does not relate to objective spinal measures of stiffness and objective back stiffness does not differ between those who report feeling stiff and those who do not. Rather, those who report feeling stiff exhibit self-protective responses: they significantly overestimate force applied to their spine, yet are better at detecting changes in this force than those who do not report feeling stiff. This perceptual error can be manipulated: providing auditory input in synchrony to forces applied to the spine modulates prediction accuracy in both groups, without altering actual stiffness, demonstrating that feeling stiff is a multisensory perceptual inference consistent with protection. Together, this presents a compelling argument against the prevailing view that feeling stiff is an isomorphic marker of the biomechanical characteristics of the back.
... This study demonstrated differential motor behavior (increased trunk muscle activity during drop landing) in adolescents with BP. Thus, it contributes to a substantial existing body of research that has consistently shown that pain is associated with increased trunk muscle activity (Arendt-Nielsen et al., 1996;Graven-Nielsen et al., 1997;Hodges et al., 2009;Wong et al., 2016). However, Mueller et al. (2017) posit that the observed increased trunk muscle activity may be a maladaptive strategy that needs correction without considering that such phenomena may occur as a consequence of an interplay of multidimensional factors, recently reported to be related to BP experience in adolescents . ...
... While the rLBI participants' measures of pain during testing was low and should not modify function, their pain in the recent past could explain alterations in muscle activation patterns according to the motor adaptation to pain model. This model suggests that when individuals experience pain, they modify muscle activation to increase joint stiffness (Hodges et al., 2013;Wong et al., 2016) and it is proposed that in some individuals these muscle activation patterns may persist post pain (Hodges & Tucker, 2010). The present study shows higher antagonist co-activation in rLBI despite the resolution of pain, providing indirect evidence supporting Hodges's model. ...
Article
Theoretical models suggest trunk muscle activation compensates for spinal systems impairments. The purpose of this study was to determine if two populations (older adults and those recovered from a lower back injury (rLBI)) with spinal system impairments have similar muscle activation patterns to each other, but differ from controls. Trunk electromyograms collected from 12 older adults, 16 rLBI, and 19 controls during two dynamic tasks showed that older adults and rLBI had higher activation amplitudes, sustained temporal and more synergistic activation relative to controls. However, differences found between older adults and rLBI suggest that spinal system impairments differed between groups or that recent pain (rLBI) uniquely influenced muscle activation. This sheds light on our understanding of the relationship between spinal system impairments and muscle activation.
... With these motions, we would expect both sides of the multifidus to be active as the right multifidus contribute to left rotation and the left multifidus contribute to left sidebending . However, the degree to which each side is firing may be influenced by pain (Ahern et al., 1988;Danneels et al., 2002;Gagnon et al., 1987;Keir and MacDonell, 2003;Wong et al., 2016). ...
Article
Introduction Healthcare workers are required to engage in repetitive actions when handling patients which leads to widespread low back pain in this population. Many variables are related to low back pain including repetitive motions and abnormal multifidus size and activation. This research sought to observe the relationship between low back pain and three variables in healthcare workers specifically: peak low back force when boosting a patient, multifidus cross-sectional area, and multifidus activation. Materials and methods This cross-sectional, correlational study included 35 healthcare workers who currently work in inpatient hospital, acute hospital, or skilled nursing settings, and engage in patient handling as part of their job. Force and motion data were collected with motion capture and in-ground force plates and processed to estimate low back forces. Multifidus cross-sectional area was measured with ultrasound while activation was measured using surface electromyography. Results There was not a significant difference in peak low back force between pain and nonpain groups. There was a significant difference in multifidus cross-sectional area at 2 of the 3 levels measured (L5 and S1). Lastly, there was not a significant difference in multifidus activation. Conclusions Peak low back force during patient handling and lumbar multifidus activation do not seem to be a factor in pain in healthcare workers. Multifidus cross-sectional area is correlated with pain in this population indicating smaller multifidus may increase the likelihood of experiencing pain. Further work should be done to confirm this finding and offer potential solutions. Relevance to industry Discovering factors in and ways to alleviate low back pain in healthcare workers is essential to the longevity of these professionals in their respective careers.
... Those authors also observed an increase of trunk muscle cocontractions. It has been recently suggested that an increase in trunk stiffness was also present with experimental pain and was correlated with a slight increase of trunk muscle cocontraction (Wong et al. 2016). Since spinal stiffness has been associated with spinal stability (Graham and Brown 2012), it could be suggested that the redistribution of muscle activity is enough to maintain spinal stability under the influence of experimental back pain. ...
Article
Preview Abstract Introduction: In complex anatomical systems, such as the trunk, motor control theories suggest that many motor solutions can be implemented to achieve a similar goal. While reflex mechanisms act as a stabilizer of the spine, how the central nervous system uses the trunk redundancy to adapt the neuromuscular responses under the influence of external perturbations, such as experimental pain or spinal tissue creep is still unclear. The aim of this study was to identify and characterize trunk neuromuscular adaptations in response to unexpected trunk perturbations under the influence of spinal tissue creep and experimental back pain. Methods: Healthy participants experienced a repetition of sudden external trunk perturbations in two protocols: [1] 15 perturbations before and after a spinal tissue creep protocol, [2] 15 perturbations with and without experimental back pain. Trunk neuromuscular adaptations were measured using high-density electromyography to record erector spinae muscle activity recruitment patterns and using a motion analysis system. Results: Muscle activity reflex attenuation was found across unexpected trunk perturbation trials under the influence of creep and pain. A similar area of muscle activity distribution was observed with or without back pain, as well as before and after creep. No change of trunk kinematics was observed. Conclusion: While under normal circumstances muscle activity adaptation occurs throughout the same perturbations, a reset of the adaptation process is present when experiencing a new perturbation such as experimental pain or creep. However, participants are still able to attenuate reflex responses under these conditions using variable recruitment pattern of back muscles.
... First, participants completed three reliable and valid questionnaires to document mean pain intensity during the last 24 h, kinesiophobia and catastrophizing using the numeric pain rating scale (24h-NPRS), the Tampa Scale of Kinesiophobia (TSK) and the Pain Catastrophizing Scale (PCS), respectively (Sullivan, 1995;Vlaeyen et al., 1995;Chapman et al., 2011). Then, after having cleaned the skin with alcohol and shaved it, if necessary, two pairs of electrodes were placed bilaterally parallel to the erector spinae fibers 3 cm lateral to the L3 spinous process (Dupeyron et al., 2013;Wong et al., 2016). Participants then performed one submaximal voluntary contraction in crook lying as described by Dankaerts et al. (2004). ...
Article
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Despite a large body of evidence demonstrating spinal movement alterations in individuals with chronic low back pain (CLBP), there is still a lack of understanding of the role of spinal movement behavior on LBP symptoms development or recovery. One reason for this may be that spinal movement has been studied during various functional tasks without knowing if the tasks are interchangeable, limiting data consolidation steps. The first objective of this cross-sectional study was to analyze the influence of the functional tasks on the information carried by spinal movement measures. To this end, we first analyzed the relationships in spinal movement between various functional tasks in patients with CLBP using Pearson correlations. Second, we compared the performance of spinal movement measures to differentiate patients with CLBP from asymptomatic controls among tasks. The second objective of the study was to develop task-independent measures of spinal movement and determine the construct validity of the approach. Five functional tasks primarily involving sagittal-plane movement were recorded for 52 patients with CLBP and 20 asymptomatic controls. Twelve measures were used to describe the sagittal-plane angular amplitude and velocity at the lower and upper lumbar spine as well as the activity of the erector spinae. Correlations between tasks were statistically significant in 91 out of 99 cases (0.31 ≤ r ≤ 0.96, all p < 0.05). The area under the curve (AUC) to differentiate groups did not differ substantially between tasks in most of the comparisons (82% had a difference in AUC of ≤0.1). The task-independent measures of spinal movement demonstrated equivalent or higher performance to differentiate groups than functional tasks alone. In conclusion, these findings support the existence of an individual spinal movement signature in patients with CLBP, and a limited influence of the tasks on the information carried by the movement measures, at least for the twelve common sagittal-plane measures analysed in this study. Therefore, this work brought critical insight for the interpretation of data in literature reporting differing tasks and for the design of future studies. The results also supported the construct validity of task-independent measures of spinal movement and encouraged its consideration in the future.
... Additionally, the questionnaire also collected data regarding current pain in the thoracic and lumbar region; thoracic and lumbar pain at rest or during activity in the last 7 days, 30 days, 12 months, and lifetime as well as chronic thoracic and lumbar pain that lasted for at least 3 months during the last 12 months. If respondents reported back pain during any of those periods, they rated their pain using a 11-point numeric pain rating scale (NPRS), where 0 means no pain and 10 means the worst imaginable pain [46]. The minimal clinical important difference for the NPRS is 2 [8,10]. ...
Article
Background Adolescent idiopathic scoliosis (AIS) is the most common spine deformity in adolescent patients. Although structural deformity may affect spinal biomechanics of patients with AIS, little is known regarding various period prevalence proportions of back pain and chronic back pain and factors associated with back pain in such patients. Questions/purposes (1) What are the period prevalence rates of back pain among teenagers with AIS? (2) Is back pain in patients with AIS associated with curve severity? Methods A total of 987 patients with AIS who were treated without surgery were recruited from a single center’s scoliosis clinic. Between December 2016 and July 2017, this center treated 1116 patients with suspected AIS. During that time, patients were offered surgery when their Cobb angle was at least 50° and had evidence of curve progression between two visits, and most of the patients who were offered surgery underwent it; other patients with AIS were managed nonsurgically with regular observation, brace prescription, posture training, and reassurance. To be included in this prospective, cross-sectional study, a patient needed to be aged between 10 and 18 years with a Cobb angle > 10°. No followup data were required. A total of 1097 patients with AIS were managed nonsurgically (98.3% of the group seen during the period in question). After obtaining parental consent, patients provided data related to their demographics; physical activity levels; lifetime, 12-month, 30-day, 7-day, and current thoracic pain and low back pain (LBP); chronic back pain (thoracic pain/LBP); brace use; and treatments for scoliosis/back pain. Pain was rated on a 10-point numeric rating scale for pain. The Insomnia Severity Index, Epworth Sleepiness Scale, and Depression Anxiety Stress Scales were also assessed. These features and radiologic study parameters between patients with and without back pain were also compared. Factors associated with current and 12-month back pain as well as chronic back pain were analyzed by multivariate analyses. Results Depending on the types of period prevalence, the prevalence of thoracic pain ranged from 6% (55 of 987) within 12 months to 14% (139 of 987) within 7 days, whereas that of LBP ranged from 6% (54 of 987) to 29% (289 of 987). Specifically, chronic thoracic pain or LBP had the lowest prevalence. Compared with the no pain group, patients with current back pain had more severe insomnia (odds ratio [OR], 1.80; p = 0.02; 95% confidence interval [CI], 1.10-2.93) and daytime sleepiness (OR, 2.41; p < 0.001, 95% CI, 1.43-4.07). Those with chronic back pain had the same problems along with moderate depression (OR, 2.49; p = 0.03; 95% CI, 1.08-5.71). Older age (OR range, 1.17–1.42; all p values ≤ 0.030) and Cobb angle > 40° (OR range, 2.38–3.74; all p values ≤ 0.015), daytime sleepiness (OR range, 2.39-2.41; all p values ≤ 0.011), and insomnia (OR range, 1.76–2.31; all p values ≤ 0.001) were associated with episodic and/or chronic back pain. Females were more likely to experience back pain in the last 12 months than males. Moderate depression (OR, 3.29; 1.45-7.47; p = 0.004) and wearing a brace (OR, 3.00; 1.47-6.15; p = 0.003) were independently associated with chronic back pain. Conclusions Biopsychosocial factors are associated with the presence and severity of back pain in the AIS population. Our results highlight the importance of considering back pain screening/management for patients with AIS with their psychosocial profile in addition to curve magnitude monitoring. In particular, sleep quality should be routinely assessed. Longitudinal changes and effects of psychotherapy should be determined in future studies. Level of Evidence Level II, prognostic study.
... Further, although commonly used in clinical practice to treat musculoskeletal pain, there is limited understanding of the mechanisms responsible for the reported benefits of MT (Goertz et al., 2016;Voogt et al., 2015). The rationale to establish the efficacy of such treatments is supported by the National Institute of Clinical Excellence, given their low risk of minor side effects and potential millions in economic savings (Carnes et al., 2010;National Institute for Health and Care Excellence, 2016;Powers et al., 2008;Stamos-Papastamos et al., 2011;Wong et al., 2016). ...
Article
Background Despite the lack of objective evidence, spinal manual therapies have been common practice for many years, particularly for treatment of lower back pain (LBP). This exploratory study measured and analysed the effect of a spinal mobilisation intervention on muscle tissue quality in LBP sufferers. Methods 40 people with LBP participated in a within-subject repeated measures cross-over study with intervention and control conditions. A myometer was used to assess the change in para-spinal muscle tissue quality before and after the intervention. Analysis considered the magnitude of muscle response together with individual covariates as potential contributors. Results A significant post intervention reduction was observed in muscle stiffness (p = 0.012, η 2 partial = 0.15), tone (p = 0.001, η 2 partial = 0.25) and elasticity (p = 0.001, η 2 partial = 0.24). Significant increases were seen in 2 variables post control: stiffness (p = 0.004, η 2 partial = 0.19), tone (p = 0.006, η 2 partial = 0.18) and a significant decrease in elasticity (p ˂ 0.000, η 2 partial = 0.3). Significant contributing covariates include baseline stiffness, BMI, waist circumference and sex. Baseline stiffness and tone were significantly correlated to their response levels. Conclusions The significant reduction in all muscle tissue qualities following the intervention provide preliminary data for an evidence-based LBP therapeutic. Baseline stiffness, BMI, waist circumference and sex could act as significant contributors to magnitude of response. The results warrant further investigation into spinal mobilisation therapies to further build the objective evidence base.
... Previous studies of the neuromuscular activation pattern found greater co-contraction of the flexor and extensor lumbar muscles [7][8][9] , and greater trunk stiffness coefficient 10 in people with low back pain when performing different tasks, as compared to healthy subjects. One study observed increases in spinal stiffness and trunk muscle activation when low back pain is elicited in healthy subjects and provided empirical evidence about the mediation of muscle activity in the spinal stiffness modification 11 . This adaptive strategy aims to restrict the range of trunk movement to avoid worsening or onset of pain and other injuries 1,9,12 . ...
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OBJECTIVES To compare the activation pattern of the trunk antagonistic muscles and also the myoelectric manifestations of muscle fatigue between subjects with and without recurrent non-specific low back pain, during the fatigue provocation of the erector spinae. METHODS The study involved 19 subjects with recurrent low back pain with a non-specific cause (seven men, 12 women, 38.53 ± 8.12 years, 68.35 ± 18.12 kg, 1.66 ± 0.09 m), and 19 healthy subjects (seven men, 12 women, 40.42 ± 8.63 years, 69.57 ± 12.76 kg, 1.64 ± 0.07 m). The electromyographic signal of the internal oblique, lumbar multifidus, rectus abdominis and lumbar iliocostalis muscles, bilateral, were collected during Biering-Sorensen test execution. RESULTS The group with low back pain showed a lower co-contraction rate of the internal oblique/lumbar multifidus (p = 0.006) and lower activation amplitude of the internal oblique (p = 0.019), both on the right side when compared to the group without low back pain. No differences were observed between the groups for muscle fatigue indicators (p > 0.05). CONCLUSION When the erector spine muscle fatigue occurs - even when the groups were similar as to the ability of extensors muscles to resist fatigue - differences were found between subjects with and without low back pain regarding the recruitment pattern of the task antagonist muscle, because subjects with low back pain showed lesser activation and co-contraction in relation to the healthy group.
Article
Study Design.Controlled clinical trial study.Objective.This study aimed to evaluate the effect of core stabilization exercise program (CSEP) on trunk-pelvis kinematics during gait in non-specific chronic low back pain (NCLBP).Summary of Background Data.NCLBP is a major public burden with variety of dysfunction including gait variability.Methods.Thirty participants (15 NCLBP and 15 healthy) were included in this study via the convenience sampling method. NCLBP group were intervened via the 16 sessions CSEP 3 days for 6 weeks and trunk-pelvis kinematics (angular displacement, waveform pattern [CVp], and offset variability [CVo]) during gait, pain, disability were evaluated before and after the intervention.Results.No significant differences in displacement and CVo in three planes were found between NCLBP and healthy groups. Independent t test was revealed that significant differences in CVp in the sagittal, frontal, and transverse planes were found between healthy and NCLBP in pre intervention. No significant changes in displacement and CVo were found as the result of intervention in NCLBP. Pain and disability decreased significantly after intervention. Paired t test revealed that the CSEP increased the frontal (P = 0.04) and transverse planes (P = 0.02) pattern variability significantly. However, there was a significant difference between groups in the sagittal plane CVp after intervention (sagittal plane CVp in healthy vs. NCLBP in post-CSE: mean difference = 14.1; P = 0.04).Conclusion.Considering the role of the deep trunk muscles in gait, and their common deconditioning in CLBP, a CSEP intervention may increase trunk-pelvis kinematic pattern variability. These results suggest CSEP may specifically increase transverse and frontal plane variability, indicating improved motor pattern replication through this movement planes.Level of Evidence: 2. © 2019 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
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Background The sensation of spinal stiffness is a commonly reported symptom among back pain patients, with the clinical assessment of spinal stiffness usually being part of the decision-making process when deciding on providing manual treatment of low back pain. While any relationship between spinal stiffness and low back pain is likely to be multifactorial, prior exploration of this relationship has been overly simplistic (e.g., univariate regression analyses). The purpose of this study was to address this gap by taking a broader approach to compare instrumented measures of spinal stiffness to demographic characteristics, pain phenotypes, psychometrics, and spine-related disability in a sample of secondary care low back pain patients using multivariate regression analysis. Methods Instrumented spinal stiffness measures from 127 patients in secondary care were used to calculate terminal and global spinal stiffness scores. A best subset analysis was used to find the subsets of 14 independent variables that most accurately predicted stiffness based on the evaluation of the adjusted R-square, Akaike Information Criteria, and the Bayesian Information Criteria. Findings In the resulting multivariate models, sex (p < 0.001) and age (p < 0.001) were the primary determinants of terminal stiffness, while global stiffness was primarily determined by age (p = 0.003) and disability (p = 0.024). Interpretation Instrumented measures of spinal stiffness are multifactorial in nature, and future research into this area should make use of multivariate analyses.
Article
Introduction: Back pain is associated with increased lumbar paraspinal muscle (LPM) stiffness identified by manual palpation and strain elastography. Recently, magnetic resonance elastography (MRE) has allowed the stiffness of muscle to be characterized noninvasively in vivo, providing quantitative 3D stiffness maps (elastograms). The aim of this study was to characterize the stiffness (shear modulus, SM) of the LPM (multifidus and erector spinae) using MRE. Materials and methods: MRE of the lumbar region was performed on seven adults in supine position. MRE was acquired in three muscular states: relaxed with outstretched legs, stretched with passive pelvis flexion, and contracted with outstretched legs and tightened trunk muscles. The mean SM was measured within a region of interest manually defined in the multifidus, erector spinae and the entire paraspinal compartment. The intermuscular difference and the effects of stretching and contraction were assessed by ANOVA and t-tests. Results: At rest, the mean SM of the paraspinal compartment was 1.6±0.2kPa. It increased significantly with stretching to 1.65±0.3kPa, and with contraction to 2.0±0.7kPa. Irrespective of muscular state, the erector spinae was significantly stiffer than the multifidus. The multifidus underwent proportionally higher stiffness changes from rest to contraction and stretching. Conclusions: MRE can be used to measure the stiffness of the LPM in different muscular states. We hypothesize that, irrespective of posture, the erector spinae behaves as semi-rigid beam and ensures permanent stiffness of the spine. The multifidus behaves as an adaptable muscle that provides segmental flexibility to the spine and tunes the spine stiffness. This article is protected by copyright. All rights reserved.
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An exoskeleton system can be an effective ergonomic intervention for mitigating the risks of developing work-related musculoskeletal disorders, yet little attention is given to the effects of its application on physical risk factors and subjective responses. Therefore, the objective of this study was to examine the effects of a passive exoskeleton system on spinal biomechanics and subjective responses during manual repetitive handling tasks among construction workers. Muscle activity of the Thoracic Erector Spinae (TES), Lumbar Erector Spinae (LES) at L3 vertebrae level, Rectus Abdominis (RA), and External Oblique (EO) during the repetitive handling tasks were measured by surface electromyography (sEMG). Additionally, the Borg categorical rating scale (Borg CR 10), local perceived pressure (LPP), and system usability scale (SUS) were used to measure the ratings of perceived discomfort, perceived musculoskeletal pressure, and system usability, respectively. Our results found that: (1) the use of the passive exoskeleton system significantly reduced LES muscle activity (11–33% MVC), with a greater reduction in LES muscle activity (32.71% MVC) for the heaviest lifting load; (2) the use of the passive exoskeleton system significantly reduced perceived discomfort scores (42.40%) of the lower back for the heaviest lifting load; (3) increased lifting load significantly increased LPP scores of the shoulder, lower back, and leg body parts; and (4) majority of the participants rated the passive exoskeleton system as having acceptable usability. The findings of these results indicate that the developed passive exoskeleton system could reduce the internal muscle force, extensor moments, and spinal forces in the lumbar region.
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Introduction Little is known about the underlying biomechanical cause of low back pain (LBP). Recently, technological advances have made it possible to quantify biomechanical and neurophysiological measurements, potentially relevant factors in understanding LBP etiology. However, few studies have explored the relation between these factors. This study aims to quantify the correlation between biomechanical and neurophysiological outcomes in non-specific LBP and examine whether these correlations differ when considered regionally vs. segmentally. Methods This is a secondary cross-sectional analysis of 132 participants with persistent non-specific LBP. Biomechanical data included spinal stiffness (global stiffness) measured by a rolling indenter. Neurophysiological data included pain sensitivity (pressure pain threshold and heat pain threshold) measured by a pressure algometer and a thermode. Correlations were tested using Pearson’s product-moment correlation or Spearman’s rank correlation as appropriate. The association between these outcomes and the segmental level was tested using ANOVA with post-hoc Tukey corrected comparisons. Results A moderate positive correlation was found between spinal stiffness and pressure pain threshold, i.e., high degrees of stiffness were associated with high pressure pain thresholds. The correlation between spinal stiffness and heat pain threshold was poor and not statistically significant. Aside from a statistically significant minor association between the lower and the upper lumbar segments and stiffness, no other segmental relation was shown. Conclusions The moderate correlation between spinal stiffness and mechanical pain sensitivity was the opposite of expected, meaning higher degrees of stiffness was associated with higher pressure pain thresholds. No clinically relevant segmental association existed.
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This commentary explores the importance of considering the biopsychosocial model and contextual factors when prescribing exercise. Diverse exercise programs for patients with chronic low back pain (CLBP) produce similar outcomes, without one specific exercise protocol demonstrating clear superiority. One clear barrier to positive outcomes is poor exercise adherence. We suggest that there are certain common contextual factors present in all exercise prescription scenarios that may impact adherence and health-related outcomes. While challenging common core stability exercise prescription, we present an argument for enhancing and intentionally shaping the following contextual factors: the therapeutic alliance, patient education, expectations and attributions of therapeutic success or failure, and mastery or cognitive control over a problem. Overall, this commentary argues that to improve exercise adherence and outcomes in the CLBP population, the context in which exercise is delivered and the meaning patients embody need to be considered and shaped by clinicians.
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The purpose of this paper is to report on in vivo stiffness measurements of the lower thoracic and lumbar spine. Stiffness was measured with subjects lying supine and spinal force-displacement measurements were recorded from a load cell attached to computer-controlled stepper motors. Stiffness was calculated from the posterior-anterior force-displacement data. Spinal stiffness measurements were made at multiple sites for each subject, from about T9 to L5. We report on the repeatability of stiffness measurements on a single volunteer and investigate the lumbar paraspinal stiffness of 20 subjects without current low back pain (LBP) as well as 47 LBP patients, including 16 having neurological symptoms. We measured the paraspinal tissue stiffness every 10 mm from T9 to L5. The variability of repeated measurements was less than 5% of the average measurement. For subjects without LBP, males had greater average stiffness (3.29 ± 0.47 N/mm) than females (2.87 ± 0.20 N/mm) (p < .01). Thus, male and female subjects were analyzed separately. Subjects with LBP had slightly higher stiffness than those without. Males with LBP had a significantly greater stiffness than those without (3.99 ± 0.83 vs. 3.29 ± 0.47 N/ mm, p < .04). Patients with neurological symptoms had the greatest stiffness; however, the differences were not significant. For all subjects, the stiffness between T9 and L1 was higher than between L1 and L5 (p > .05). Further work is needed to understand spinal stiffness measurements, the differences with gender, and changes associated with back pain.
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Non-randomized controlled studyObjective. To determine if low back pain (LBP) patients who respond to spinal manipulative therapy (SMT) differ biomechanically from non-responders and untreated asymptomatic controls. Some, but not all LBP patients report improvement in function after SMT. When compared to non-responders, studies suggest that SMT-responders demonstrate significant changes in spinal stiffness, muscle contraction and disc diffusion. Unfortunately, the significance of these observations remains uncertain given methodological differences between studies including a lack of controls. LBP participants and asymptomatic controls attended three sessions over 7 days. On sessions 1 and 2, LBP participants received SMT (+LBP/+SMT, n = 32) while asymptomatic controls did not (-LBP/-SMT, n = 57). In these sessions, spinal stiffness and multifidus thickness ratios were obtained before and after SMT and on day 7. Apparent diffusion coefficients (ADC) from lumbar discs were obtained from +LBP/+SMT participants before and after SMT on session 1 and from a LBP control group that did not receive SMT (+LBP/-SMT, n = 16). +LBP/+SMT participants were dichotomized as responders/non-responders based on self-reported disability on day 7. A repeated measures ANCOVA was used to compare ADCs among responders, non-responders and +LBP/SMT, as well as spinal stiffness or multifidus thickness ratio among responders, non-responders and -LBP/-SMT subjects. After the first SMT, SMT-responders displayed statistically significant decreases in spinal stiffness and increases in multifidus thickness ratio sustained over 7 days; these findings were not observed in other groups. Similarly, only SMT-responders displayed significant post-SMT improvement in ADC. Those reporting post-SMT improvement in disability demonstrated simultaneous changes between self-reported and objective measures of spinal function. This coherence did not exist for asymptomatic controls or no-treatment controls. These data imply that SMT impacts biomechanical characteristics within SMT-responders not present in all LBP patients. This work provides a foundation to investigate the heterogeneous nature of LBP, mechanisms underlying differential therapeutic response and the biomechanical and imaging characteristics defining responders at baseline.
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Background: Non-fatal health outcomes from diseases and injuries are a crucial consideration in the promotion and monitoring of individual and population health. The Global Burden of Disease (GBD) studies done in 1990 and 2000 have been the only studies to quantify non-fatal health outcomes across an exhaustive set of disorders at the global and regional level. Neither effort quantified uncertainty in prevalence or years lived with disability (YLDs). Methods: Of the 291 diseases and injuries in the GBD cause list, 289 cause disability. For 1160 sequelae of the 289 diseases and injuries, we undertook a systematic analysis of prevalence, incidence, remission, duration, and excess mortality. Sources included published studies, case notification, population-based cancer registries, other disease registries, antenatal clinic serosurveillance, hospital discharge data, ambulatory care data, household surveys, other surveys, and cohort studies. For most sequelae, we used a Bayesian meta-regression method, DisMod-MR, designed to address key limitations in descriptive epidemiological data, including missing data, inconsistency, and large methodological variation between data sources. For some disorders, we used natural history models, geospatial models, back-calculation models (models calculating incidence from population mortality rates and case fatality), or registration completeness models (models adjusting for incomplete registration with health-system access and other covariates). Disability weights for 220 unique health states were used to capture the severity of health loss. YLDs by cause at age, sex, country, and year levels were adjusted for comorbidity with simulation methods. We included uncertainty estimates at all stages of the analysis. Findings: Global prevalence for all ages combined in 2010 across the 1160 sequelae ranged from fewer than one case per 1 million people to 350 000 cases per 1 million people. Prevalence and severity of health loss were weakly correlated (correlation coefficient -0·37). In 2010, there were 777 million YLDs from all causes, up from 583 million in 1990. The main contributors to global YLDs were mental and behavioural disorders, musculoskeletal disorders, and diabetes or endocrine diseases. The leading specific causes of YLDs were much the same in 2010 as they were in 1990: low back pain, major depressive disorder, iron-deficiency anaemia, neck pain, chronic obstructive pulmonary disease, anxiety disorders, migraine, diabetes, and falls. Age-specific prevalence of YLDs increased with age in all regions and has decreased slightly from 1990 to 2010. Regional patterns of the leading causes of YLDs were more similar compared with years of life lost due to premature mortality. Neglected tropical diseases, HIV/AIDS, tuberculosis, malaria, and anaemia were important causes of YLDs in sub-Saharan Africa. Conclusions: Rates of YLDs per 100 000 people have remained largely constant over time but rise steadily with age. Population growth and ageing have increased YLD numbers and crude rates over the past two decades. Prevalences of the most common causes of YLDs, such as mental and behavioural disorders and musculoskeletal disorders, have not decreased. Health systems will need to address the needs of the rising numbers of individuals with a range of disorders that largely cause disability but not mortality. Quantification of the burden of non-fatal health outcomes will be crucial to understand how well health systems are responding to these challenges. Effective and affordable strategies to deal with this rising burden are an urgent priority for health systems in most parts of the world. Funding: Bill & Melinda Gates Foundation.
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Background Low back pain is often associated with increased spinal stiffness which thought to arise from increased muscle activity. Unfortunately, the association between paraspinal muscle activity and paraspinal stiffness, as well as the spatial distribution of this relation, is unknown. The purpose of this investigation was to employ new technological developments to determine the relation between spinal muscle contraction and spinal stiffness over a large region of the lumbar spine. Methods Thirty-two male subjects performed graded isometric prone right hip extension at four different exertion levels (0%, 10%, 25% and 50% of the maximum voluntary contraction) to induce asymmetric back muscle activity. The corresponding stiffness and muscle activity over bilateral paraspinal lumbar regions was measured by indentation loading and topography surface electromyography, respectively. Paraspinal stiffness and muscle activity were then plotted and their correlation was determined. Findings Data from this study demonstrated the existence of an asymmetrical gradient in muscle activation and paraspinal stiffness in the lumbar spine during isometric prone right hip extension. The magnitude and scale of the gradient increased with the contraction force. A positive correlation between paraspinal stiffness and paraspinal muscle activity existed irrespective of the hip extension effort (Pearson correlation coefficient, range 0.566–0.782 (P<0.001)). Interpretation Our results demonstrate the creation of an asymmetrical gradient of muscle activity and paraspinal stiffness during right hip extension. Future studies will determine if alterations in this gradient may possess diagnostic or prognostic value for patients with low back pain.
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The purpose of this study was to investigate the differentiation in muscle tissue characteristics and recruitment between the deep and superficial multifidus muscle by magnetic resonance imaging. The multifidus is a very complex muscle in which a superficial and deep component can be differentiated from an anatomical, biomechanical, histological and neuromotorial point of view. To date, the histological evidence is limited to low back pain patients undergoing surgery and cadavers. The multifidus muscles of 15 healthy subjects were investigated with muscle functional MRI. Images were taken under three different conditions: (1) rest, (2) activity without pain and (3) activity after experimentally induced low back muscle pain. The T2 relaxation time in rest and the shift in T2 relaxation time after activity were compared for the deep and superficial samples of the multifidus. At rest, the T2 relaxation time of the deep portion was significantly higher compared to the superficial portion. Following exercise, there was no significant difference in shift in T2 relaxation time between the deep and superficial portions, and in the pain or in the non-pain condition. In conclusion, this study demonstrates a higher T2 relaxation time in the deep portion, which supports the current assumption that the deep multifidus has a higher percentage of slow twitch fibers compared to the superficial multifidus. No differential recruitment has been found following trunk extension with and without pain induction. For further research, it would be interesting to investigate a clinical LBP population, using this non-invasive muscle functional MRI approach.
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The purpose of this study was to compare the monopolar electromyographic (EMG) amplitude versus isometric force relationships from three signal processing methods (raw versus notch filtering versus adaptive filtering). Seventeen healthy subjects (mean+/-SD age=24.6+/-4.3 yr) performed incremental isometric muscle actions of the dominant leg extensors in 10% increments from 10% to 100% of the maximum voluntary contraction (MVC). During each muscle action, a monopolar surface EMG signal was recorded from the vastus lateralis and processed with the three signal processing methods. The linear slope coefficients for the EMG amplitude versus isometric force relationships were equivalent for the three signal processing methods and correlated (r=0.997-0.999). However, the mean amplitude values for the notch-filtered signals were less than those for the raw and adaptive-filtered signals. Thus, adaptive filtering may be the best method for removing electromagnetic noise from monopolar surface EMG signals.
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Some patients with low back pain are thought to have increased lumbar posteroanterior (PA) stiffness. Increased activity of the lumbar extensors could contribute to this stiffness. This activity may be seen when a PA force is applied and is thought to represent much less force than occurs with a maximal voluntary contraction (MVC). Although MVCs of the lumbar extensors are known to increase lumbar PA stiffness, the effect of small amounts of voluntary contraction is not known. In this study, the effect of varying amounts of voluntary isometric muscle activity of the lumbar extensors on lumbar PA stiffness was examined. Twenty subjects without low back pain, aged 26 to 45 years (X=34, SD=5.6), participated in the study. Subjects were asked to perform an isometric MVC of their lumbar extensor muscles with their pelvis fixed by exerting a force against a steel plate located over their T4 spinous process. They were then asked to perform contractions generating force equivalent to 0%, 10%, 30%, 50%, and 100% of that obtained with an MVC. Posteroanterior stiffness at L4 was measured during these contractions. A Friedman one-way analysis of variance for repeated measures demonstrated a difference in PA stiffness among all levels of muscle activity. Voluntary contraction of the lumbar extensor muscles will result in an increase in lumbar PA stiffness even at low levels of activity.
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Many studies have identified changes in trunk muscle recruitment in clinical low back pain (LBP). However, due to the heterogeneity of the LBP population these changes have been variable and it has been impossible to identify a cause-effect relationship. Several studies have identified a consistent change in the feedforward postural response of transversus abdominis (TrA), the deepest abdominal muscle, in association with arm movements in chronic LBP. This study aimed to determine whether the feedforward recruitment of the trunk muscles in a postural task could be altered by acute experimentally induced LBP. Electromyographic (EMG) recordings of the abdominal and paraspinal muscles were made during arm movements in a control trial, following the injection of isotonic (non-painful) and hypertonic (painful) saline into the longissimus muscle at L4, and during a 1-h follow-up. Movements included rapid arm flexion in response to a light and repetitive arm flexion-extension. Temporal and spatial EMG parameters were measured. The onset and amplitude of EMG of most muscles was changed in a variable manner during the period of experimentally induced pain. However, across movement trials and subjects the activation of TrA was consistently reduced in amplitude or delayed. Analyses in the time and frequency domain were used to confirm these findings. The results suggest that acute experimentally induced pain may affect feedforward postural activity of the trunk muscles. Although the response was variable, pain produced differential changes in the motor control of the trunk muscles, with consistent impairment of TrA activity.
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Limb movement imparts a perturbation to the body. The impact of that perturbation is limited via anticipatory postural adjustments. The strategy by which the CNS controls anticipatory postural adjustments of the trunk muscles during limb movement is altered during acute back pain and in people with recurrent back pain, even when they are pain free. The altered postural strategy probably serves to protect the spine in the short term, but it is associated with a cost and is thought to predispose spinal structures to injury in the long term. It is not known why this protective strategy might occur even when people are pain free, but one possibility is that it is caused by the anticipation of back pain. In eight healthy subjects, recordings of intramuscular EMG were made from the trunk muscles during single and repetitive arm movements. Anticipation of experimental back pain and anticipation of experimental elbow pain were elicited by the threat of painful cutaneous stimulation. There was no effect of anticipated experimental elbow pain on postural adjustments. During anticipated experimental back pain, for single arm movements there was delayed activation of the deep trunk muscles and augmentation of at least one superficial trunk muscle. For repetitive arm movements, there was decreased activity and a shift from biphasic to monophasic activation of the deep trunk muscles and increased activity of superficial trunk muscles during anticipation of back pain. In both instances, the changes were consistent with adoption of an altered strategy for postural control and were similar to those observed in patients with recurrent back pain. We conclude that anticipation of experimental back pain evokes a protective postural strategy that stiffens the spine. This protective strategy is associated with compressive cost and is thought to predispose to spinal injury if maintained long term.
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A prospective, cohort study of patients with nonradicular low back pain referred to physical therapy. Develop a clinical prediction rule for identifying patients with low back pain who improve with spinal manipulation. Development of clinical prediction rules for classifying patients with low back pain who are likely to respond to a particular intervention, such as manipulation, would improve clinical decision-making and research. Patients with nonradicular low back pain underwent a standardized examination and then underwent a standardized spinal manipulation treatment program. Success with treatment was determined using percent change in disability scores over three sessions and served as the reference standard for determining the accuracy of examination variables. Examination variables were first analyzed for univariate accuracy in predicting success and then combined into a multivariate clinical prediction rule. Seventy-one patients participated. Thirty-two had success with the manipulation intervention. A clinical prediction rule with five variables (symptom duration, fear-avoidance beliefs, lumbar hypomobility, hip internal rotation range of motion, and no symptoms distal to the knee) was identified. The presence of four of five of these variables (positive likelihood ratio = 24.38) increased the probability of success with manipulation from 45% to 95%. It appears that patients with low back pain likely to respond to manipulation can be accurately identified before treatment.
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Literature review, expert panel, and a workshop during the "VIII International Forum on Primary Care Research on Low Back Pain" (Amsterdam, June 2006). To develop practical guidance regarding the minimal important change (MIC) on frequently used measures of pain and functional status for low back pain. Empirical studies have tried to determine meaningful changes for back pain, using different methodologies. This has led to confusion about what change is clinically important for commonly used back pain outcome measures. This study covered the Visual Analogue Scale (0-100) and the Numerical Rating Scale (0-10) for pain and for function, the Roland Disability Questionnaire (0-24), the Oswestry Disability Index (0-100), and the Quebec Back Pain Disability Questionnaire (0-100). The literature was reviewed for empirical evidence. Additionally, experts and participants of the VIII International Forum on Primary Care Research on Low Back Pain were consulted to develop international consensus on clinical interpretation. There was wide variation in study design and the methods used to estimate MICs, and in values found for MIC, where MIC is the improvement in clinical status of an individual patient. However, after discussion among experts and workshop participants a reasonable consensus was achieved. Proposed MIC values are: 15 for the Visual Analogue Scale, 2 for the Numerical Rating Scale, 5 for the Roland Disability Questionnaire, 10 for the Oswestry Disability Index, and 20 for the QBDQ. When the baseline score is taken into account, a 30% improvement was considered a useful threshold for identifying clinically meaningful improvement on each of these measures. For a range of commonly used back pain outcome measures, a 30% change from baseline may be considered clinically meaningful improvement when comparing before and after measures for individual patients. It is hoped that these proposals facilitate the use of these measures in clinical practice and the comparability of future studies. The proposed MIC values are not the final answer but offer a common starting point for future research.
Article
Background: Movement changes in pain. Unlike the somewhat stereotypical response of limb muscles to pain, trunk muscle responses are highly variable when challenged by pain in that region. This has led many to question the existence of a common underlying theory to explain the adaptation. Here, we tested the hypotheses that (1) adaptation in muscle activation in acute pain leads to enhanced spine stability, despite variation in the pattern of muscle activation changes; and (2) individuals would use a similar 'signature' pattern for tasks with different mechanical demands. Methods: In 17 healthy individuals, electromyography recordings were made from a broad array of anterior and posterior trunk muscles while participants moved slowly between trunk flexion and extension with and without experimentally induced back pain. Hypotheses were tested by estimating spine stability (Stability Index) with an electromyography-driven spine model and analysis of individual and overall (net) adaptations in muscle activation. Results: The Stability Index (P < 0.017) and net muscle activity (P < 0.021) increased during pain, although no two individuals used the same pattern of adaptation in muscle activity. For most, the adaptation was similar between movement directions despite opposite movement demands. Conclusions: These data provide the first empirical confirmation that, in most individuals, acute back pain leads to increased spinal stability and that the pattern of muscle activity is not stereotypical, but instead involves an individual-specific response to pain. This adaptation is likely to provide short-term benefit to enhance spinal protection, but could have long-term consequences for spinal health.
Article
Instrumented spinal stiffness measurements have shown high test-retest reliability. However, factors that may affect reliability have yet to be investigated. The objective of this study was to compare the: 1) within- and between-day reliability of a mechanical indentation device (MID) in measuring spinal stiffness, 2) measurement precision of averaging multiple measurements, and 3) reliability of stiffness measurements between individuals with and without LBP. The spinal stiffness of 26 volunteers with and without LBP was measured 3 times by MID in each of two visits 1 to 4 days apart. Two stiffness measures were calculated from the resulting force-displacement data: global stiffness and terminal stiffness. Intraclass correlation coefficients were used to estimate reliability. Measurement precision was measured by minimal detectable changes, bias and 95% limits of agreement. Using the mean of three spinal stiffness measurements, the measurement precision was improved by 33.7% over a single measurement. Averaging three measurements, the within- and between-day reliability point estimates of both global and terminal stiffness were 0.99 and 0.98, respectively. The reliability estimates of spinal stiffness measurement using MID were not significantly altered by the participants’ LBP status across all circumstances (95% confidence intervals overlapped). With our experimental protocol, averaging three spinal stiffness measurements using MID produces reliable stiffness measurements regardless of individuals’ LBP status.
Article
Evidence indicates that previous low back injury (LBI) is a strong predictor for re-injury. The purpose of this study was to examine whether neuromuscular patterns remain altered in a LBI group who were deemed recovered. Surface electromyograms from 12-abdominal and 12-back extensors sites and motion variables were recorded from 33 LBI individuals (sub-acute phase) and 54 asymptomatic controls. Pain-related variables were recorded and a clinical assessment performed for LBI participants. Subjects performed a symmetrical lift and replace task in two reaches. Pattern recognition techniques were applied to normalized activation amplitude patterns to extract key recruitment strategies. Mixed model ANOVAs tested for effects (p<0.05). Despite similar task performance, significantly (p<0.05) different recruitment strategies were observed for the LBI group. There were higher activation amplitudes for LBI subjects in all muscles (except posterior external oblique) and greater co-activation between abdominal and back extensor sites compared to controls. Local abdominal and back extensor sites showed altered responses to increased physical demands in the LBI group. Despite outcomes indicating recovery, the LBI group had altered neuromuscular patterns compared to asymptomatic controls supporting that residual alterations remain following recovery.
Article
It is widely assumed that there is a relationship between pain, stiffness and muscle activity in patients with low back pain. This preliminary study was designed to begin an investigation of the existence of this relationship. Two subjects with low back pain and six normal subjects participated. The postero-anterior mobility of L3 and L4 was measured together with lumbar extensor muscle EMG. All normal subjects showed negligible muscle activity whereas both low back pain subjects demonstrated elevated EMG levels. In addition, both low back pain subjects were found to have relatively low mobility of L3 and L4 as compared to the normal subjects. Further research to investigate the relationship between these variables is indicated.
Article
Prospective case series. To examine spinal stiffness in patients with low back pain (LBP) receiving spinal manipulative therapy (SMT), evaluate associations between stiffness characteristics and clinical outcome, and explore a multivariate model of SMT mechanisms as related to effects on stiffness, lumbar multifidus (LM) recruitment, and status on a clinical prediction rule (CPR) for SMT outcomes. Mechanisms underlying the clinical effects of SMT are poorly understood. Many explanations have been proposed, but few studies have related potential mechanisms to clinical outcomes or considered multiple mechanisms concurrently. Patients with LBP were treated with two SMT sessions over 1 week. CPR status was assessed at baseline. Clinical outcome was based on the Oswestry disability index (ODI). Mechanized indentation measures of spinal stiffness and ultrasonic measures of LM recruitment were taken before and after each SMT, and after 1 week. Global and terminal stiffness were calculated. Multivariate regression was used to evaluate the relationship between stiffness variables and percentage ODI improvement. Zero-order correlations among stiffness variables, LM recruitment changes, CPR status, and clinical outcome were examined. A path analysis was used to evaluate a multivariate model of SMT effects. Forty-eight patients (54% women) had complete stiffness data. Significant immediate decreases in global and terminal stiffness occurred post-SMT regardless of outcome. ODI improvement was related to greater immediate decrease in global stiffness (P = 0.025), and less initial terminal stiffness (P = 0.01). Zero-order correlations and path analysis supported a multivariate model suggesting that clinical outcome of SMT is mediated by improvements in LM recruitment and immediate decrease in global stiffness. Initial terminal stiffness and CPR status may relate to outcome though their relationship with LM recruitment. The underlying mechanisms explaining the benefits of SMT appear to be multifactorial. Both spinal stiffness characteristics and LM recruitment changes appear to play a role.
Article
Acute low back pain (LBP) is associated with differential changes in motor coordination of deep and superficial trunk muscles. Whether this is related to differential changes in excitability of descending corticomotor inputs remains unclear and was investigated in nine healthy individuals. Fine-wire i.m. electrodes were inserted bilaterally into deep (transversus abdominis (TrA)) and superficial abdominal muscles (obliquus externus abdominis (OE)), and surface electrodes were placed bilaterally over obliquus internus abdominis (OI), rectus abdominis (RA) and lumbar erector spinae (LES) muscles. Corticomotor excitability was assessed as amplitude of motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) at a range of stimulator intensities, at rest and during voluntary abdominal contractions. Pain was induced by injection of hypertonic saline into interspinous ligaments of the lumbar spine. Corticomotor excitability was examined before, during and after the induction of LBP. During pain, amplitude of TrA MEPs to contralateral cortical stimulation was reduced, whereas amplitudes of OE and LES MEPs contralateral and ipsilateral to the stimulated cortex were increased. The findings highlight differential changes in excitability of corticomotor inputs to trunk muscles during acute LBP. Further work is required to reveal whether such changes involve spinal and/or supraspinal centres and their consequence for spine control.
Article
People move differently in pain. Although this statement is unquestioned, the underlying mechanisms are surprisingly poorly understood. Existing theories are relatively simplistic, and although their predictions are consistent with a range of experimental and clinical observations, there are many observations that cannot be adequately explained. New theories are required. Here, we seek to consider the motor adaptation to pain from the micro (single motoneuron) to macro (coordination of whole-muscle behaviour) levels and to provide a basis for a new theory to explain the motor changes in pain.
Article
Controlled laboratory study. To clarify whether differences in surface stability influence trunk muscle activity. Lumbar stabilization exercises on unstable surfaces are performed widely. One perceived advantage in performing stabilization exercises on unstable surfaces is the potential for increased muscular demand. However, there is little evidence in the literature to help establish whether this assumption is correct. Nine healthy male subjects performed lumbar stabilization exercises. Pairs of intramuscular fine-wire or surface electrodes were used to record the electromyographic signal amplitude of the rectus abdominis, the external obliques, the transversus abdominis, the erector spinae, and lumbar multifidus. Five exercises were performed on the floor and on an unstable surface: elbow-toe, hand-knee, curl-up, side bridge, and back bridge. The EMG data were normalized as the percentage of the maximum voluntary contraction, and data between doing each exercise on the stable versus unstable surface were compared using a Wilcoxon signed-rank test. With the elbow-toe exercise, the activity level for all muscles was enhanced when performed on the unstable surface. When performing the hand-knee and side bridge exercises, activity level of the more global muscles was enhanced when performed on an unstable surface. Performing the curl-up exercise on an unstable surface, increased the activity of the external obliques but reduced transversus abdominis activation. This study indicates that lumbar stabilization exercises on an unstable surface enhanced the activities of trunk muscles, except for the back bridge exercise.
Article
Injection of hypertonic saline into back muscles or ligaments can induce acute low back pain (LBP). However, no study has systematically investigated pain characteristics from these structures. Further, induced muscle pain can change with stretching and contraction, which is problematic for studies into the effect of pain on sensorimotor control. However, it is unclear whether this occurs with experimental ligament pain. In separate sessions, 10 healthy volunteers received a single bolus injection of hypertonic (0.2ml, 5% NaCl) or isotonic saline (0.3ml, 0.9% NaCl) into L4/5 interspinous ligament, or hypertonic saline into the left paraspinal muscle. Pain intensity, size and duration were recorded, and a body chart was completed for each injection. Changes in pain intensity and size with stretching or back muscle contractions were also assessed during muscle and ligament pain. Injection of hypertonic saline into the interspinous ligament produced central LBP that was longer in duration and greater in intensity and size compared to hypertonic saline injection into lumbar paraspinal muscles. Isotonic saline injection into the interspinous ligament yielded mild pain that was short-lasting (<2min). Intensity and size of muscle pain reduced with stretching and contraction, whereas these tasks did not affect ligament pain. Surprisingly, some participants pointed to a location of pain that was 1-2 segments above or below the injected level. The results highlight that injection into the interspinous ligament elicits consistent pain that is not influenced by trunk movements. These findings support the implementation of this experimental ligament pain model in research.
Article
The sensory and motor systems can reorganise following injury and learning of new motor skills. Recently we observed adaptive changes in motor cortical organisation in patients with recurrent low back pain (LBP), which are linked to altered motor coordination. Although changes in motor coordination can be trained and are associated with improved symptoms and function, it remains unclear whether these training-induced changes are related to reorganisation of the motor cortex. This was investigated using the model of a delay in postural activation of the deep abdominal muscle, transversus abdominis (TrA) in 20 individuals with recurrent LBP. Subjects were allocated to either motor skill training that involved isolated voluntary contractions of TrA, or a control intervention of self-paced walking exercise for 2 weeks. Electromyographic (EMG) activity was recorded from TrA bilaterally using intramuscular fine-wire electrodes. Motor cortical organisation using transcranial magnetic stimulation (TMS) and postural activation associated with single rapid arm movements were investigated before and after training. Motor skill training induced an anterior and medial shift in motor cortical representation of TrA, towards that observed in healthy individuals from our previous study. This shift was associated with earlier postural activation of TrA. Changes were not observed following unskilled walking exercise. This is the first observation that motor training can reverse reorganisation of neuronal networks of the motor cortex in people with recurrent pain. The observed relationship between cortical reorganisation and changes in motor coordination following motor training provides unique insight into potential mechanisms that underlie recovery.
Article
Low back pain is often associated with increased spinal stiffness which thought to arise from increased muscle activity. Unfortunately, the association between paraspinal muscle activity and paraspinal stiffness, as well as the spatial distribution of this relation, is unknown. The purpose of this investigation was to employ new technological developments to determine the relation between spinal muscle contraction and spinal stiffness over a large region of the lumbar spine. Thirty-two male subjects performed graded isometric prone right hip extension at four different exertion levels (0%, 10%, 25% and 50% of the maximum voluntary contraction) to induce asymmetric back muscle activity. The corresponding stiffness and muscle activity over bilateral paraspinal lumbar regions was measured by indentation loading and topography surface electromyography, respectively. Paraspinal stiffness and muscle activity were then plotted and their correlation was determined. Data from this study demonstrated the existence of an asymmetrical gradient in muscle activation and paraspinal stiffness in the lumbar spine during isometric prone right hip extension. The magnitude and scale of the gradient increased with the contraction force. A positive correlation between paraspinal stiffness and paraspinal muscle activity existed irrespective of the hip extension effort (Pearson correlation coefficient, range 0.566-0.782 (P<0.001)). Our results demonstrate the creation of an asymmetrical gradient of muscle activity and paraspinal stiffness during right hip extension. Future studies will determine if alterations in this gradient may possess diagnostic or prognostic value for patients with low back pain.
Article
To investigate the relationship between low back pain (LBP) and lumbar posteroanterior (PA) stiffness. A repeated-measures design was used to measure lumbar posteroanterior stiffness on two occasions in subjects with and without LBP. Twenty-five subjects with acute or subacute LBP and twenty-five pain-free subjects participated. Pain subjects reported pain on the application of a manual PA force to the lumbar spine and had no contraindication to PA stiffness testing. Pain-free subjects reported no history of LBP requiring treatment, and obtained a score of 0 on the McGill Pain Questionnaire. PA stiffness was measured in subjects with LBP when (a) they first presented with pain and (b) when pain had resolved by more than 80%. Pain-free subjects, matched with pain subjects on gender, age, vertebral level to be tested and time between tests, were also measured on two occasions, to control for the effects of repeated stiffness testing and the passing of time. In subjects with low back pain stiffness decreased by 1.21 N/mm between test 1 and test 2. A paired t test found a significant difference between the tests (t = 3.04, df = 24, p = .006). In subjects without pain, there was an increase in stiffness of 0.74 N/mm between test 1 and test 2; a paired t test found no significant difference between the tests (t = -1.673, df = 24, p = .107). Subjects with LBP showed increased PA stiffness compared with when they had little or no pain, whereas pain-free subjects showed unchanged PA stiffness over time.
Article
During muscle contraction, electrical activity necessarily precedes force output, yet models that utilize processed electromyograms sometimes predict force as preceding EMG under rapid ballistic loading conditions. The purpose of this study was to define the frequency response transfer function of the upper and lower erector spinae musculature, at different lengths and tensions, using rectified, low pass filtered EMG. This would enable accurate estimates of force from the processed electromyogram, specifically during impulsive contractions. Abdominal and erector spinae EMG were measured in synchrony with impulsive low back moments in five men. EMG signals were rectified and low pass filtered repeatedly with cut-off frequencies from 1 to 3 Hz at 0.5 Hz increments in order to quantify the frequency response. It was found that EMG signals processed through a simple, Butterworth low pass filter could not produce the measured force output without an additional time shift. These shifts were quantified by cross-correlating EMG and force with increments of 1 ms. In order to define the transfer function of EMG to force, optimal cut-off frequencies were selected two ways: quantitatively by searching for maximum cross correlations coefficients, and qualitatively. Results indicated that the frequency response of both the upper and lower erector spinae can be modelled with a cut-off frequency between 2 and 2.5 Hz and that these values are not significantly modulated by changes in muscle length or tension.
Article
Fear and/or anxiety about pain is a useful construct, in both theoretical and clinical terms. This article describes the development and refinement of the Fear of Pain Questionnaire (FPQ), which exists in its most current form as the FPQ-III. Factor analytic refinement resulted in a 30-item FPQ-III which consists of Severe Pain, Minor Pain, and Medical Pain subscales. Internal consistency and test-retest reliability of the FPQ-III were found to be good. Four studies are presented, including normative data for samples of inpatient chronic pain patients, general medical outpatients, and unselected undergraduates. High fear of pain individuals had greater avoidance/escape from a pain-relevant Behavioral Avoidance Test with Video, relative to their low fear counterparts, suggesting predictive validity. Chronic pain patients reported the greatest fear of severe pain. Directions for future research with the FPQ-III are discussed, along with general comments about the relation of fear and anxiety to pain.
Article
Occurrence and treatment responses associated with the centralization phenomenon were analyzed prospectively in 289 patients with acute neck and back pain with or without referred spinal symptoms. To document symptom changes to mechanical assessment during initial evaluation and during consecutive visits. Using standard operational definitions, patients were categorized reliably into three inclusive and mutually exclusive pain pattern groups: centralization, noncentralization, and partial reduction. It was hypothesized that the occurrence of centralization would be less than previously reported and that the centralization group would have better treatment results. Centralization has been reported to occur with high frequency during mechanical assessments of patients with acute spinal syndromes. When centralization is observed, a favorable treatment result is expected. Because centralization has not been defined consistently in the literature, the true prevalence and treatment responses associated with centralization have not been confirmed. Consecutive patients with neck or back pain syndromes and referred to outpatient physical therapy services were categorized into three pain pattern groups by experienced therapists trained in the McKenzie system. Changes in distal pain location were scored and documented before and after each visit. Maximal pain intensity over 24 hours, perceived functional status, and number of treatment visits were compared between groups. Patients could be categorized reliably according to movement signs and symptoms. The centralization pain pattern group had significantly fewer visits than the other two groups (P < 0.001). Pain intensity rating and perceived function were different between the centralization and noncentralization groups (P < 0.001). There was no difference in treatment response between the centralization and partial-reduction groups (P = 0.306). Prevalence of patients assigned to the three groups was 30.8% in the centralization group, 23.2% in noncentralization, and 46% in the partial-reduction group. Categorization by changes in pain location to mechanical assessment and treatment allowed identification of patients with improved treatment outcomes and facilitated planning of conservative treatment of patients with acute spinal pain syndromes. If a proximal change in pain location is not observed by the seventh treatment visit, the results of this study support additional medical evaluation for physical or nonphysical factors that could be delaying quick resolution of the acute episode.
Article
A quick-release method in four directions of isometric trunk exertions was used to study the muscle response patterns in 17 patients with chronic low back pain and 17 matched control subjects. It was hypothesized that patients with low back pain would react to sudden load release with a delayed muscle response and would exhibit altered muscle recruitment patterns. A delay in erector spinae reaction time after sudden loading has been observed in patients with low back pain. Muscle recruitment and timing pattern play an important role in maintaining lumbar spine stability. Subjects were placed in a semiseated position in an apparatus that provided stable fixation of the pelvis. They exerted isometric contractions in trunk flexion, extension, and lateral bending. Each subject performed three trials at two constant force levels. The resisted force was suddenly released with an electromagnet and electromyogram signals from 12 trunk muscles were recorded. The time delay between the magnet release and the shut-off or switch-on of muscle activity (reaction time) was compared between two groups of subjects using two-factor analysis of variance. The number of reacting muscles and reaction times averaged over all trials and directions showed the following results: For healthy control subjects a shut-off of agonistic muscles (with a reaction time of 53 msec) occurred before the switch-on of antagonistic muscles (with a reaction time of 70 msec). Patients exhibited a pattern of co-contraction, with agonists remaining active (3.4 out of 6 muscles switched off) while antagonists switched on (5.3 out of 6 muscles). Patients also had longer muscle reaction times for muscles shutting off (70 msec) and switching on (83 msec) and furthermore, their individual muscle reaction times showed greater variability. Patients with low back pain, in contrast to healthy control subjects, demonstrated a significantly different muscle response pattern in response to sudden load release. These differences may either constitute a predisposing factor to low back injuries or a compensation mechanism to stabilize the lumbar spine.
Article
Force-displacement properties of spinal tissues assessed by blunt indentation are thought to have clinical relevance; however, numerous variables with respect to spinal indentation have yet to be identified or characterized completely. To identify and quantify, where possible, previously unidentified or incompletely characterized variables with respect to spinal indentation. Multiprotocol design. Four experiments were performed: (1) Twelve asymptomatic subjects were indented with concurrent electromyography during conditions of rest, held inspiration, increased intraabdominal pressure and lumbar extension. (2) Changes in the recumbent position of 12 subjects were measured while a series of movements was performed in restrained and unrestrained conditions. (3) Ten clinicians attempted to locate, and to relocate, a subcutaneous anatomical landmark through visualization/palpation and ultrasonic imaging. (4) Performances of 3 methods of force-displacement curve modeling were compared with respect to stiffness estimation. (1) Spinal stiffness increased significantly in a minority of subjects awaiting indentation and in a majority of subjects during increases in intraabdominal pressure. (2) Changes in subject position were significantly reduced by a restraint system. (3) With respect to interclinician error in locating and relocating an indentation site, there was significant improvement with the use of ultrasonic visualization. (4) The error associated with linear techniques used to model curvilinear force-displacement data plots increased with increasing linear intervals. Several sources of variation in spinal indentation were identified: indentation site relocation, intraabdominal pressure, subject movement, muscular response, and stiffness estimation. These variables, which have been unaccounted for in previous indentation studies, might be responsible for the change or lack of change in force-displacement properties between preintervention and postintervention indentation trials.
Article
In this study, sudden load was applied to the trunk and situations with alternating low levels of intra-abdominal pressure (IAP) realistic to work situations were compared. The aim was to see if IAP and the small increases in co-contraction of back muscles that follow are capable of increasing the stiffness of the lumbar spine. Nine subjects participated in ten sudden load situations during which they were asked to hold a box and conduct a percentage of maximal IAP. The hip was fixed and the load was applied horizontally on the trunk. EMG, IAP, and movement of the trunk were measured. It was found that IAP of a size likely to appear in work situations, and the concomitant increase in muscle co-activation increased the spine stiffness. This increase in stiffness decreased the movement caused by the sudden load. These results show that both abdominal- and back muscles may have an important role in stabilising the spine, and in decreasing movements caused by sudden loads likely to appear in numerous work
Article
The transversus abdominus muscle (TrA) has been demonstrated to be active prior to rapid movements of the upper and lower limbs. This activity is termed feed forward motivation. The lack of feed-forward activation for TrA has been demonstrated in subjects with low back pain. The measures used for investigation of TrA function have been fine-wire needle EMG. This limits the practical application of TrA study due to the cost and level of specialisation required for this technique. The objective of the current study was to investigate the validity and reliability of using a surface EMG site to replicate the findings for the feed-forward activation of TrA prior to rapid limb movement. A population of healthy, young males (n = 20) were studied and it was found that four of the subjects did not meet feed-forward criteria. These results were shown to be highly reliable after a 2-week period for the TrA/IO site only. The validity of the signal was further investigated using several functional tasks to specifically target muscles of the abdominal region. Using a cross-correlation analysis to evaluate crosstalk from adjacent muscles, it was concluded that the signal representing TrA/IO accurately demonstrates the functional activity of the muscle. This study has demonstrated a viable surface EMG method to evaluate the feed-forward activation of TrA/IO prior to rapid limb movement. This may lead to opportunities for the clinical application of this method. It was also a finding of this study that four asymptomatic subjects did not pre-activate, therefore providing a rationale for future prospective investigations on whether the lack of TrA/IO feed-forward activation is a cause or an effect of low back pain.
Article
A quantitative biomechanical comparison of seven different lumbar spine "stabilization exercises." The purpose of this research was to quantify lumbar spine stability resulting from the muscle activation patterns measured when performing selected stabilization exercises. Many exercises are termed "stabilization exercises" for the low back; however, limited attempts have been made to quantify spine stability and the resultant tissue loading. Ranking resultant stability together with spinal load is very helpful for guiding clinical decision-making and therapeutic exercise design. Eight stabilization exercises were quantified in this study. Spine kinematics, external forces, and 14 channels of torso EMG were recorded for each exercise. These data were input into a modified version of a lumbar spine model described by Cholewicki and McGill (1996) to quantify stability and L4-L5 compression. A rank order of the various exercises was produced based on stability, muscle activation levels, and lumbar compression. Quantification of the calibrated muscle activation levels together with low back compression and resultant stability assists clinical decisions regarding the most appropriate exercise for specific patients and specific objectives.
Article
This review aims to explore the research available relating to three commonly used pain rating scales, the Visual Analogue Scale, the Verbal Rating Scale and the Numerical Rating Scale. The review provides information needed to understand the main properties of the scales. Data generated from pain-rating scales can be easily misunderstood. This review can help clinicians to understand the main features of these tools and thus use them effectively. A MedLine review via PubMed was carried out with no restriction of age of papers retrieved. Papers were examined for methodological soundness before being included. The search terms initially included pain rating scales, pain measurement, Visual Analogue Scale, VAS, Verbal Rating Scale, VRS, Numerical/numeric Rating Scale, NRS. The reference lists of retrieved articles were used to generate more papers and search terms. Only English Language papers were examined. All three pain-rating scales are valid, reliable and appropriate for use in clinical practice, although the Visual Analogue Scale has more practical difficulties than the Verbal Rating Scale or the Numerical Rating Scale. For general purposes the Numerical Rating Scale has good sensitivity and generates data that can be statistically analysed for audit purposes. Patients who seek a sensitive pain-rating scale would probably choose this one. For simplicity patients prefer the Verbal Rating Scale, but it lacks sensitivity and the data it produces can be misunderstood. In order to use pain-rating scales well clinicians need to appreciate the potential for error within the tools, and the potential they have to provide the required information. Interpretation of the data from a pain-rating scale is not as straightforward as it might first appear.
Article
Trunk dynamics, including stiffness, mass and damping were quantified during trunk extension exertions with and without voluntary recruitment of antagonistic co-contraction. The objective of this study was to empirically evaluate the influence of co-activation on trunk stiffness. Muscle activity associated with voluntary co-contraction has been shown to increase joint stiffness in the ankle and elbow. Although biomechanical models assume co-active recruitment causes increase trunk stiffness it has never been empirically demonstrated. Small trunk displacements invoked by pseudorandom force disturbances during trunk extension exertions were recorded from 17 subjects at two co-contraction conditions (minimal and maximal voluntary co-contraction recruitment). EMG data were recorded from eight trunk muscles as a baseline measure of co-activation. Increased EMG activity confirms that muscle recruitment patterns were different between the two co-contraction conditions. Trunk stiffness was determined from analyses of impulse response functions (IRFs) of trunk dynamics wherein the kinematics were represented as a second-order behavior. Trunk stiffness increased 37.8% (p < 0.004) from minimal to maximal co-activation. Results support the assumption used in published models of spine biomechanics that recruitment of trunk muscle co-contraction increases trunk stiffness thereby supporting conclusions from those models that co-contraction may contribute to spinal stability.
Article
Randomized clinical trial. Compare outcomes of patients with low back pain receiving treatments matched or unmatched to their subgrouping based on initial clinical presentation. Patients with "nonspecific" low back pain are often viewed as a homogeneous group, equally likely to respond to any particular intervention. Others have proposed methods for subgrouping patients as a means for determining the treatment most likely to benefit patients with particular characteristics. Patients with low back pain of less than 90 days' duration referred to physical therapy were examined before treatment and classified into one of three subgroups based on the type of treatment believed most likely to benefit the patient (manipulation, stabilization exercise, or specific exercise). Patients were randomly assigned to receive manipulation, stabilization exercises, or specific exercise treatment during a 4-week treatment period. Disability was assessed in the short-term (4 weeks) and long-term (1 year) using the Oswestry. Comparisons were made between patients receiving treatment matched to their subgroup, versus those receiving unmatched treatment. A total of 123 patients participated (mean age, 37.7 +/- 10.7 years; 45% female). Patients receiving matched treatments experienced greater short- and long-term reductions in disability than those receiving unmatched treatments. After 4 weeks, the difference favoring the matched treatment group was 6.6 Oswestry points (95% CI, 0.70-12.5), and at long-term follow-up the difference was 8.3 points (95% CI, 2.5-14.1). Compliers-only analysis of long-term outcomes yielded a similar result. Nonspecific low back pain should not be viewed as a homogenous condition. Outcomes can be improved when subgrouping is used to guide treatment decision-making.
Article
A system for measuring posterior-to-anterior spinal stiffness (PAS) was developed for use in clinical trials of manipulation for low back pain (LBP). The current report is an analysis of the baseline PAS data, with particular emphasis on relationships between PAS and clinical and demographic characteristics. Posterior-to-anterior spinal stiffness measurements were recorded over the spinous processes of the lumbar spines from patients who had LBP. The system uses electronic sensors to record displacement and force, whereas a human operator provides the force of indentation. Clinical and outcome measures were compared with spinal stiffness. We recruited 192 patients (89 female and 103 male; average age, 40.0 years; SD, 9.4 years). The average Roland-Morris score was 9.7 (SD, 3.2) on a 24-point scale. The Visual Analog Scale pain scores were 55.7 (SD, 20.9) on a 100-mm scale. Stiffness values ranged from 4.16 to 39.68 N/mm (mean, 10.80 N/mm; SD, 3.72 N/mm). Females' lumbar spines were, on the average, 2 N/mm more compliant than males (P < .001). The PAS system of computer-monitored equipment with human operation performed well in this clinical study of LBP. Spinal stiffness was found to be different between males and females, and age and body mass index were related to PAS. We found no significant relationship between the severity or chronicity of the LBP complaint and spinal stiffness. There was little agreement between the stiff or tender segments identified by the clinicians using palpation and the segment that measured most stiff using the PAS device.
Article
Validity of a clinical test can be defined as the extent to which the test actually assesses what it is intended to assess. In order to investigate the validity of manual physical assessment of the spine, it is therefore essential to establish what physical therapists intend to assess when they are applying these tests. The aims of this study were to (1) establish what manual physical therapists are intending to assess while applying passive intervertebral motion tests; and (2) examine the face validity and content validity for manual physical assessment of the spine. We surveyed 1502 members of the national manual physical therapist organisations of New Zealand and the United States of America using a web-based survey instrument. Sixty-six percent of 466 respondents believed passive accessory intervertebral motion (PAIVM) tests were valid for assessing quantity of segmental motion, and 76% believed passive physiologic intervertebral motion (PPIVM) tests were valid for assessing quantity of segmental motion. Ninety-eight percent of manual physical therapists base treatment decisions at least in part on the results of segmental motion tests. Quality of resistance to passive segmental motion was considered of greater importance than quantity of kinematic motion during PAIVM tests, while the quality of complex kinematic motion was considered of greater importance than quantity of displacement kinematics during PPIVM tests. Manual physical therapists accept the face validity of manual physical assessment of spinal segmental motion to a great extent, however a minority voice scepticism. Content validity is dominated by concepts of segmental kinematics and the force-displacement relationship. Intent of assessment does, however, vary widely between therapists. These data will inform the design of concurrent validity studies. Further work is recommended to increase consistency of intent, methodology and terminology in manual physical assessment of the spine.
Article
Many manual therapists assess and treat spinal stiffness of people with low back pain. The objectives of this study were to investigate: (i) whether spinal stiffness changes after treatment; (ii) the relationship between pre-treatment spinal stiffness and change in stiffness with treatment; (iii) the relationship between spinal stiffness, pain, disability and global perceived effect of treatment; (iv) whether spinal stiffness predicts outcome of treatment or response to treatment in chronic low back pain patients. One hundred and ninety-one subjects with chronic low back pain were randomly allocated to groups that received either spinal manipulative therapy, motor control exercise, or a general exercise program. Spinal stiffness was assessed before and after intervention. All three groups showed a significant decrease in stiffness following treatment (p<0.001). No difference between groups was observed. There was a significant negative correlation between pre-treatment stiffness and change in stiffness (r=-0.61; p<0.001). There was a significant but weak correlation (r=0.18; p=0.02) between change in stiffness and change in global perceived effect of treatment, and a significant but weak correlation between change in stiffness and change in function for subjects in the spinal manipulative therapy group (r=-0.28; p=0.02). No significant association was observed between initial stiffness score and any of the final outcome measures following treatment. Initial stiffness did not predict response to any treatment. In conclusion, spinal stiffness decreases over the course of an episode of treatment, more so in those with the stiffest spines, but the decrease is not dependent on treatment and is not generally related to outcome.
Maitland's Vertebral Manipulation
  • G Maitland
  • E Hengeveld
  • K Banks
  • K English
Maitland G, Hengeveld E, Banks K, English K. Maitland's Vertebral Manipulation. Vol 7 ed. Butterworth-Heinemann, Oxford; 2005.
MVIC, maximum voluntary isometric contraction OE, obliquus externus; OI, obliquus internus
  • Emg Es
  • Erector Spinae
EMG, electromyography; ES, erector spinae; MVIC, maximum voluntary isometric contraction OE, obliquus externus; OI, obliquus internus; TrA, transversus abdominis
  • G Maitland
  • E Hengeveld
  • K Banks
  • K English
  • Maitland
Maitland G, Hengeveld E, Banks K, English K. Maitland's Vertebral Manipulation. Vol 7 ed. Butterworth-Heinemann, Oxford; 2005.