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1.  Contribution of Hamstring Fatigue to Quadriceps Inhibition Following Lumbar Extension Exercise 
The purpose of this study was to determine the contribution of hamstrings and quadriceps fatigue to quadriceps inhibition following lumbar extension exercise. Regression models were calculated consisting of the outcome variable: quadriceps inhibition and predictor variables: change in EMG median frequency in the quadriceps and hamstrings during lumbar fatiguing exercise. Twenty-five subjects with a history of low back pain were matched by gender, height and mass to 25 healthy controls. Subjects performed two sets of fatiguing isometric lumbar extension exercise until mild (set 1) and moderate (set 2) fatigue of the lumbar paraspinals. Quadriceps and hamstring EMG median frequency were measured while subjects performed fatiguing exercise. A burst of electrical stimuli was superimposed while subjects performed an isometric maximal quadriceps contraction to estimate quadriceps inhibition after each exercise set. Results indicate the change in hamstring median frequency explained variance in quadriceps inhibition following the exercise sets in the history of low back pain group only. Change in quadriceps median frequency explained variance in quadriceps inhibition following the first exercise set in the control group only. In conclusion, persons with a history of low back pain whose quadriceps become inhibited following lumbar paraspinal exercise may be adapting to the fatigue by using their hamstring muscles more than controls.
Key PointsA neuromuscular relationship between the lumbar paraspinals and quadriceps while performing lumbar extension exercise may be influenced by hamstring muscle fatigue.QI following lumbar extension exercise in persons with a history of LBP group may involve significant contribution from the hamstring muscle group.More hamstring muscle contribution may be a necessary adaptation in the history of LBP group due to weaker and more fatigable lumbar extensors.
PMCID: PMC3818676  PMID: 24198683
Superimposed burst technique; electromyography; spectral median frequency; correlation and regression; low back pain
2.  Reduced Quadriceps Activation After Lumbar Paraspinal Fatiguing Exercise 
Journal of Athletic Training  2006;41(1):79-86.
Context: Although poor paraspinal muscle endurance has been associated with less quadriceps activation (QA) in persons with a history of low back pain, no authors have addressed the acute neuromuscular response after lumbar paraspinal fatiguing exercise.
Objective: To compare QA after lumbar paraspinal fatiguing exercise in healthy individuals and those with a history of low back pain.
Design: A 2 × 4 repeated-measures, time-series design.
Setting: Exercise and Sport Injury Laboratory.
Patients or Other Participants: Sixteen volunteers participated (9 males, 7 females; 8 controls and 8 with a history of low back pain; age = 24.1 ± 3.1 years, height = 173.4 ± 7.1 cm, mass = 72.4 ± 12.1 kg).
Intervention(s): Subjects performed 3 sets of isometric lumbar paraspinal fatiguing muscle contractions. Exercise sets continued until the desired shift in lumbar paraspinal electromyographic median power frequency was observed. Baseline QA was compared with QA after each exercise set.
Main Outcome Measure(s): An electric burst was superimposed while subjects performed a maximal quadriceps contraction. We used the central activation ratio to calculate QA = (FMVIC/[FMVIC + FBurst])* 100, where F = force and MVIC = maximal voluntary isometric contractions. Quadriceps electromyographic activity was collected at the same time as QA measurements to permit calculation of median frequency during MVIC.
Results: Average QA decreased from baseline (87.4% ± 8.2%) after the first (84.5% ± 10.5%), second (81.4% ± 11.0%), and third (78.2% ± 12.7%) fatiguing exercise sets. On average, the group with a history of low back pain showed significantly more QA than controls. No significant change in quadriceps median frequency was noted during the quadriceps MVICs.
Conclusions: The quadriceps muscle group was inhibited after lumbar paraspinal fatiguing exercise in the absence of quadriceps fatigue. This effect may be different for people with a history of low back pain compared with healthy controls.
PMCID: PMC1421484  PMID: 16619099
superimposed burst technique; quadriceps muscle inhibition; low back pain
3.  Changes in the flexion-relaxation response induced by hip extensor and erector spinae muscle fatigue 
Background
The flexion-relaxation phenomenon (FRP) is defined by reduced lumbar erector spinae (ES) muscle myoelectric activity during full trunk flexion. The objectives of this study were to quantify the effect of hip and back extensor muscle fatigue on FRP parameters and lumbopelvic kinematics.
Methods
Twenty-seven healthy adults performed flexion-extension tasks under 4 different experimental conditions: no fatigue/no load, no fatigue/load, fatigue/no load, and fatigue/load. Total flexion angle corresponding to the onset and cessation of myoelectric silence, hip flexion angle, lumbar flexion angle and maximal trunk flexion angle were compared across different experimental conditions by 2 × 2 (Load × Fatigue) repeated-measures ANOVA.
Results
The angle corresponding to the ES onset of myoelectric silence was reduced after the fatigue task, and loading the spine decreased the lumbar contribution to motion compared to the hip during both flexion and extension. A relative increment of lumbar spine motion compared to pelvic motion was also observed in fatigue conditions.
Conclusions
Previous results suggested that ES muscles, in a state of fatigue, are unable to provide sufficient segmental stabilization. The present findings indicate that, changes in lumbar-stabilizing mechanisms in the presence of muscle fatigue seem to be caused by modulation of lumbopelvic kinematics.
doi:10.1186/1471-2474-11-112
PMCID: PMC2896348  PMID: 20525336
4.  Short term modulation of trunk neuromuscular responses following spinal manipulation: a control group study 
Background
Low back pain (LBP) is one of the most frequent musculoskeletal conditions in industrialized countries and its economic impact is important. Spinal manipulation therapy (SMT) is believed to be a valid approach in the treatment of both acute and chronic LBP. It has also been shown that SMT can modulate the electromyographic (EMG) activity of the paraspinal muscle. The purpose of this study was to investigate, in a group of patients with low back pain, the persistence of changes observed in trunk neuromuscular responses after a spinal manipulation (SMT).
Methods
Sixty adult participants with LBP performed a block of 5 flexion-extension movements. Participants in the experimental group (n=30) received lumbar SMT whereas participants in the control group (n=30) were positioned similarly for the treatment but did not receive SMT. Blocks of flexion-extension movements were repeated immediately after the manipulation as well as 5 and 30 minutes after SMT (or control position). EMG activity of paraspinal muscles was recorded at L2 and L5 level and kinematic data were collected to evaluate the lumbo-pelvic kinematics. Pain intensity was noted after each block. Normalized EMG, pain intensity and lumbo-pelvic kinematics were compared across experimental conditions.
Results
Participants from the control group showed a significant increase in EMG activity during the last block (30 min) of flexion-extension trials in both flexion and full-flexion phases at L2. Increase in VAS scores was also observed in the last 2 blocks (5 min and 30 min) in the control group. No significant group x time interaction was seen at L5. No significant difference was observed in the lumbo-pelvic kinematics.
Conclusion
Changes in trunk neuromuscular control following HVLA spinal manipulation may reduce sensitization or muscle fatigue effects related to repetitive movement. Future studies should investigate short term changes in neuromuscular components, tissue properties and clinical outcomes.
doi:10.1186/1471-2474-14-92
PMCID: PMC3602072  PMID: 23496876
Spinal manipulation; Electromyography; Kinematics; Flexion-relaxation phenomenon
5.  Quadriceps Inhibition After Repetitive Lumbar Extension Exercise in Persons With a History of Low Back Pain 
Journal of Athletic Training  2006;41(3):264-269.
Context: A neuromuscular relationship exists between the lumbar extensor and quadriceps muscles during fatiguing exercise. However, this relationship may be different for persons with low back pain (LBP).
Objective: To compare quadriceps inhibition after isometric, fatiguing lumbar extension exercise between persons with a history of LBP and control subjects.
Design: A 2 × 3 factorial, repeated-measures, time-series design with independent variables of group (persons with a history of LBP, controls) and time (baseline, postexercise set 1, postexercise set 2).
Setting: University research laboratory.
Patients or Other Participants: Twenty-five subjects with a history of LBP were matched by sex, height, and mass to 25 healthy control subjects.
Intervention(s): Electromyography median frequency indexed lumbar paraspinal muscular fatigue while subjects performed 2 sets of isometric lumbar extension exercise. Subjects exercised until a 15% downward shift in median frequency for the first set and a 25% shift for the second set were demonstrated.
Main Outcome Measure(s): Knee extension force was measured while subjects performed an isometric maximal quadriceps contraction. During this maximal effort, a percutaneous electric stimulus was applied to the quadriceps, causing a transient, supramaximal increase in force output. We used the ratio between the 2 forces to estimate quadriceps inhibition. Quadriceps electromyographic activity was recorded during the maximal contractions to compare median frequencies over time.
Results: Both groups exhibited significantly increased quadriceps inhibition after the first (12.6% ± 10.0%, P < .001) and second (15.2% ± 9.7%, P < .001) exercise sets compared with baseline (9.6% ± 9.3%). However, quadriceps inhibition was not different between groups.
Conclusions: Persons with a history of LBP do not appear to be any more or less vulnerable to quadriceps inhibition after fatiguing lumbar extension exercise.
PMCID: PMC1569566  PMID: 17043693
superimposed burst technique; neuromuscular activity; knee
6.  Changes in the flexion relaxation response induced by lumbar muscle fatigue 
Background
The flexion relaxation phenomenon (FRP) is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES) muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task.
Methods
Twenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1), no fatigue/load (2), fatigue/no load(3), and fatigue/load (4). Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG) power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 × 2 repeated-measures ANOVA.
Results
Onset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition.
Conclusion
The results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability.
doi:10.1186/1471-2474-9-10
PMCID: PMC2259346  PMID: 18218087
7.  Influences of trunk muscles on lumbar lordosis and sacral angle 
European Spine Journal  2005;15(4):409-414.
Background: The strength of abdominal muscle and back extensors or their balances are commonly mentioned as major indicators of potential low back pain (LBP). Former studies on anthropometrics in terms of trunk muscle strength seemed to lack precision in methodology. Furthermore, the extension-flexion ratio, which is a good parameter of trunk muscle balance, was not as much studied as simple maximum torques in this area of study. Objectives: To investigate relationship between trunk muscle strength and lumbar lordosis, sacral angle in patients who did not show significant abnormal findings on their simple lateral radiograph. Methods: Thirty-one subjects were participated and their mean age was 35. Lumbar simple lateral radiograph was taken and lordotic angle was obtained by altered Cobb’s method. Sacral angle was also examined on the same film. The relationship between these angles and muscle strength (isometric maximum torques and ratios of them) was investigated by the correlation analysis. Results: None of the isometric maximum torques was related to sacral angle or lordotic angle. However, the ratio of extension to flexion was significantly related to the lordotic angle (Pearson’s correlation coefficient=0.491, p<0.01). Other ratios were not related to any of the angles. Conclusions: An imbalance in trunk muscle strength can influence significantly lordotic curve of lumbar spine and might be one risk factor for potential low back pain.
doi:10.1007/s00586-005-0976-5
PMCID: PMC3489319  PMID: 16151709
Lordosis; Sacral angle; Isometric measurement; Abdominal muscle function
8.  Biological risk indicators for recurrent non-specific low back pain in adolescents 
Objectives: A matched case-control study was carried out to evaluate biological risk indicators for recurrent non-specific low back pain in adolescents.
Methods: Adolescents with recurrent non-specific low back pain (symptomatic; n = 28; mean (SD) age 14.9 (0.7) years) and matched controls (asymptomatic; n = 28; age 14.9 (0.7) years) with no history of non-specific low back pain participated. Measures of stature, mass, sitting height, sexual maturity (Tanner self assessment), lateral flexion of the spine, lumbar sagittal plane mobility (modified Schöber), hip range of motion (Leighton flexometer), back and hamstring flexibility (sit and reach), and trunk muscle endurance (number of sit ups) were performed using standardised procedures with established reliability. Backward stepwise logistic regression analysis was performed, with the presence/absence of recurrent low back pain as the dependent variable and the biological measures as the independent variables.
Results: Hip range of motion, trunk muscle endurance, lumbar sagittal plane mobility, and lateral flexion of the spine were identified as significant risk indicators of recurrent low back pain (p<0.05). Follow up analysis indicated that symptomatic subjects had significantly reduced lateral flexion of the spine, lumbar sagittal plane mobility, and trunk muscle endurance (p<0.05).
Conclusions: Hip range of motion, abdominal muscle endurance, lumbar flexibility, and lateral flexion of the spine were risk indicators for recurrent non-specific low back pain in a group of adolescents. These risk indicators identify the potential for exercise as a primary or secondary prevention method.
doi:10.1136/bjsm.2003.009951
PMCID: PMC1725147  PMID: 15728690
9.  Differences in symmetry of lumbar region passive tissue characteristics between people with and people without low back pain 
Background
Several investigators have suggested that passive tissue characteristics of the lumbar region may be altered in people with low back pain. Passive stiffness of the lumbar region has been examined during physiological movements in healthy individuals and intersegmental spine mobility and stiffness have been examined in people with and people without low back pain. However, no investigators have examined differences in passive tissue characteristics of the lumbar region during a physiological movement between people with and people without low back pain.
Methods
Subjects were moved passively through a trunk lateral bending motion on a passive movement device. Lumbar region kinematics were measured with a motion capture system and force required to move the subject was measured with a force transducer. Lumbar region extensibility was defined as the maximum excursion of the lumbar region. Passive elastic energy was defined as the area under the torque-lumbar region angle curve. Differences in lumbar region extensibility and passive elastic energy between sides were examined in people with and people without low back pain (n = 41).
Findings
People in the Rotation with Extension low back pain subgroup demonstrated greater asymmetry of passive elastic energy than people without low back pain (P = 0.04). There were no differences between groups in symmetry of lumbar region extensibility (P = 0.37).
Interpretation
Asymmetry in passive elastic energy of the lumbar region may be related to the low back pain problem in the Rotation with Extension subgroup. The asymmetry in passive elastic energy may be associated with asymmetry of loading on the spine, which has been reported to be a risk factor for low back pain. Thus, it may be important to consider the asymmetry when planning an intervention strategy for people in the Rotation with Extension subgroup.
doi:10.1016/j.clinbiomech.2008.05.006
PMCID: PMC2577573  PMID: 18590942
low back pain; passive; trunk lateral bending; stiffness
10.  A prospective study of the interrelationship between subjective and objective measures of disability before and 2 months after lumbar decompression surgery for disc herniation 
European Spine Journal  2005;14(5):454-465.
The value of range of motion (ROM) as an indicator of impairment associated with spinal problems, and in monitoring changes in response to treatment, is a controversial issue. The aim of this study was to examine the interrelationship between subjective disability (Roland-Morris scores) and objectively measured impairment (ROM), both before and in response to spinal decompression surgery, in an older group of patients with herniated lumbar disc (DH). Seventy-six individuals took part in the study: 33 patients (mean age 57 years, SD 9 years) presenting with DH and for whom decompression surgery was planned, and 43 controls (mean age 57 years, SD 7 years), with no history of back pain requiring medical treatment. In the patient group, pain intensity (leg and back; visual analog score), self-rated disability (Roland-Morris score), certain psychological attributes, and ROM of the spine (Spinal Mouse) were measured before and 2 months after decompression surgery. In addition, the patients rated the success of surgery on a 1–5 Likert scale. The pain-free control group performed only the tests of spinal mobility. Before surgery, compared with matched controls, significantly lower values were observed in the DH patients for standing lumbar lordosis (p=0.01), and for range of flexion of the lumbar spine (ROFlumbar) (p=0.0006), but not of the hips (ROFhip) (p=0.14). Roland-Morris Disability scores correlated significantly with ROFlumbar (r=0.61, p=0.0002), but less well with ROFhip(r=0.43, p=0.01). Two months after surgery, there were significant reductions in back pain and leg pain (p=0.0001) and in Roland-Morris Disability scores (p=0.019). There was also a significant decrease in the group mean values for lumbar lordosis angle (i.e., a “flatter” spine after surgery, p=0.002) and ROFlumbar (p=0.038). ROFhip showed a (nonsignificant) tendency to increase (p=0.08) towards normal control values. As a result of these two opposing changes, the range of total trunk flexion showed no significant changes from pre-surgery to 2 months post-surgery (p=0.60). On an individual basis, there was a highly significant relationship between the change in self-rated disability scores and the change in ROFlumbar, pre-surgery- to 2 months post-surgery (r= −0.82; p<0.0001). Changes in ROFhip showed no such relationship (r= −0.30, p=0.10). The patients in the “poor” outcome group (“surgery didn’t help”; 9%) had a significantly greater reduction in ROFlumbar post-surgery compared with the “good” outcome group (“surgery helped”; 91%) (p=0.04). In stepwise linear regression, the change in ROFlumbar was the only variable accounting for the change in self-rated disability pre-surgery to post-surgery (variables not included: pain intensity, psychological factors). The pivotal role of lumbar mobility in explaining disability emphasizes the importance of measuring lumbar and hip ranges of motion separately, as opposed to “global trunk motion.” In the patient group examined, the determination of lumbar spinal mobility provides a valid, objective measure of function, that shows differences from normal matched controls, that correlates well with self-rated disability, and the changes in which correlate extremely well with subjective changes in disability following surgery.
doi:10.1007/s00586-004-0787-0
PMCID: PMC3454659  PMID: 15830214
Spinal mobility; Lumbar range of motion; Herniated disc; Spinal decompression surgery; Roland-Morris Disability; Outcome
11.  Effects of Static Flexion-relaxation on Paraspinal Reflex Behavior 
Background.
Static trunk flexion working postures and disturbed trunk muscle reflexes are related to increased risk of low-back pain. Animal studies conclude that these factors may be related; passive tissue strain in spinal ligaments causes subsequent short-term changes in reflex. Although studies have documented changes in the myoelectric onset angle of flexion-relaxation following prolonged static flexion and cyclic flexion we could find no published evidence related to the human reflex response of the trunk extensor muscles following a period of static flexion-relaxation loading.
Methods.
Eighteen subjects maintained static lumbar flexion for 15 min. Paraspinal muscle reflexes were elicited both before and after the flexion-relaxation protocol using pseudorandom stochastic force disturbances while recording EMG. Reflex gain was computed from the peak value of the impulse response function relating input force perturbation to EMG response using time-domain deconvolution analyses.
Findings.
Reflexes showed a trend toward increased gain after the period of flexion-relaxation (P < 0.055) and were increased with trunk extension exertion (P < 0.021). Significant gender differences in reflex gain were observed (P < 0.01).
Interpretations.
Occupational activities requiring extended periods of trunk flexion contribute to changes in reflex behavior of the paraspinal muscles. Results suggest potential mechanisms by which flexed posture work may contribute to low-back pain. Significant gender differences indicate risk analyses should consider personal factors when considering neuromuscular behavior.
doi:10.1016/j.clinbiomech.2004.09.001
PMCID: PMC1630677  PMID: 15567532
Low-back; Reflex; Flexion-relaxation
12.  Kinematic and temporal interactions of the lumbar spine and hip during trunk extension in healthy male subjects  
European Spine Journal  2007;17(1):122-128.
Kinematic properties of trunk extension are considered sensitive differentiators of movement between asymptomatic and low back pain subjects. The aim of this study was to quantify the continuous interaction of the hip and lumbar spine kinematics and temporal characteristics as a function of direction during the task of trunk bending backwards and returning to the upright position in healthy young subjects. The sagittal hip and lumbar spine kinematics during the extension task were examined in 18 healthy male subjects. Five trials of trunk extension were recorded for each subject and paired t-tests were then used to determine significant differences (P < 0.05) between the mean lumbar and the hip time-normalized kinematic and temporal variables. The data from the full cycle of trunk extension was analyzed with respect to movement initiation, time to reach peak velocity and peak angular displacement during the full cycle of trunk extension. Three distinct phases of movements were identified based on the continuous movement trajectories of velocity and angular displacement in the lumbar spine and hip; that of extension, return and, a terminal overcorrection phase. There were significant differences identified in the respective mean peak angular velocities of the lumbar spine (21.7 ± 8.6, 37.0 ± 14.7, 8.3 ± 5.0 deg/s) when compared with those of hip (14.6 ± 6.1, 21.7 ± 8.5, 5.4 ± 3.5 deg/s) in each of these three phases. The lumbar spine initiated the movement of trunk extension when bending backwards and returning to the upright position significantly early than that of the hip. These results highlight that in normal healthy adults there is the tendency for the lumbar spine to dominate over the hip during the task of backward trunk bending in terms of the amount and velocity of movement. At the end of extension the kinematics of the lumbar spine and hip kinematic are characterized by a terminal overcorrection phase marking the completion of the movement.
doi:10.1007/s00586-007-0487-7
PMCID: PMC2365519  PMID: 17786486
Lumbar spine; Hip; Trunk extension; Kinematics; Velocity
13.  Comparative evaluation of a novel measurement tool to assess lumbar spine posture and range of motion 
European Spine Journal  2012;21(11):2170-2180.
Purpose
The diagnosis of low back pain pathology is generally based upon invasive image-based assessment of structural pathology, but is limited in methods to evaluate function. The accurate and robust measurement of dynamic function may assist in the diagnosis and monitoring of therapy success. Epionics SPINE is an advanced strain-gauge measurement technology, based on the two sensor strips SpineDMS system, which allows the non-invasive assessment of lumbar and thoraco-lumbar motion for periods of up to 24 h. The aim of this study was to examine the reliability of Epionics SPINE and to collect and compare normative data for the characterisation of spinal motion in healthy subjects. Furthermore, the identification of parameters that influence lumbar range of motion (RoM) was targeted.
Methods
Spinal shape was measured using Epionics SPINE in 30 asymptomatic volunteers during upright standing, as well as maximum flexion and extension, to check intra-rater reliability. Furthermore, back shape was assessed throughout repeated maximum flexion and extension movements in 429 asymptomatic volunteers in order to collect normative data of the lordosis angle and RoM in different gender and age classes.
Results
The lordosis angle during standing in the healthy collective measured with Epionics SPINE was 32.4° ± 9.7°. Relative to this standing position, the average maximum flexion angle was 50.8° ± 10.9° and the average extension angle 25.0° ± 11.5°. Comparisons with X-ray and Spinal Mouse data demonstrated good agreement in static positions. Age played a larger role than gender in influencing lumbar posture and RoM.
Conclusions
The Epionics SPINE system allows the practical and reliable dynamic assessment of lumbar spine shape and RoM, and may therefore provide a clinical solution for the evaluation of lower back pain as well as therapy monitoring.
doi:10.1007/s00586-012-2312-1
PMCID: PMC3481097  PMID: 22543411
Spine; Back shape; Range of motion; Dynamic functional assessment
14.  Back and hip extensor muscles fatigue in healthy subjects: task-dependency effect of two variants of the Sorensen test 
European Spine Journal  2008;17(12):1721-1726.
Paraspinal muscle fatigability during various trunk extension tests has been widely investigated by electromyography (EMG), and its task-dependency is established recently. Hip extensor muscle fatigability during the Sorensen test has been reported. The aim of the present experiments was to evaluate the task-dependency of back and hip extensor muscle fatigue during two variants of the Sorensen test. We hypothesized that the rate of muscular fatigue of the hip and back extensor muscles varies according to the test position. Twenty healthy young males with no history of low back pain volunteered to participate in this cross-sectional study. They were asked to perform two body weight-dependent isometric back extension tests (S1 = Sorensen test; S2 = modified Sorensen on a 45° Roman chair). Surface EMG activity of the paraspinal muscles (T10 and L5 levels) and hip extensor muscles (gluteus maximus; biceps femoris) was recorded, and muscular fatigue was assessed through power spectral analysis of the EMG data by calculating the rate of median power frequency change. We observed hip extensor muscle fatigue simultaneously with paraspinal muscle fatigue during both Sorensen variants. However, only L5 level EMG fatigue indices showed a task-dependency effect between S1 and S2. Hip extensor muscles appear to contribute to load sharing of the upper body mass during both Sorensen variants, but to a different extent because L5 level fatigue differs between the Sorensen variants. Our findings suggest that task-dependency has to be considered when EMG variables are compared between two types of lumbar muscle-fatiguing tasks.
doi:10.1007/s00586-008-0782-y
PMCID: PMC2587667  PMID: 18813961
Erector spinae; Hip extensors; Sorensen test; Muscle fatigability; Task-dependency
15.  Lumbar Corsets Can Decrease Lumbar Motion in Golf Swing 
Swinging a golf club includes the rotation and extension of the lumbar spine. Golf-related low back pain has been associated with degeneration of the lumbar facet and intervertebral discs, and with spondylolysis. Reflective markers were placed directly onto the skin of 11young male amateur golfers without a previous history of back pain. Using a VICON system (Oxford Metrics, U.K.), full golf swings were monitored without a corset (WOC), with a soft corset (SC), and with a hard corset (HC), with each subject taking 3 swings. Changes in the angle between the pelvis and the thorax (maximum range of motion and angular velocity) in 3 dimensions (lumbar rotation, flexion-extension, and lateral tilt) were analyzed, as was rotation of the hip joint. Peak changes in lumbar extension and rotation occurred just after impact with the ball. The extension angle of the lumbar spine at finish was significantly lower under SC (38°) or HC (28°) than under WOC (44°) conditions (p < 0.05). The maximum angular velocity after impact was significantly smaller under HC (94°/sec) than under SC (177°/sec) and WOC (191° /sec) conditions, as were the lumbar rotation angles at top and finish. In contrast, right hip rotation angles at top showed a compensatory increase under HC conditions. Wearing a lumbar corset while swinging a golf club can effectively decrease lumbar extension and rotation angles from impact until the end of the swing. These effects were significantly enhanced while wearing an HC.
Key pointsRotational and extension forces on the lumbar spine may cause golf-related low back painWearing lumbar corsets during a golf swing can effectively decrease lumbar extension and rotation angles and angular velocity.Wearing lumbar corsets increased the rotational motion of the hip joint while reducing the rotation of the lumbar spine.
PMCID: PMC3761778  PMID: 24149729
Golf; back pain; motion analysis; orthosis; corset
16.  Effect of obesity and low back pain on spinal mobility: a cross sectional study in women 
Background
obesity is nowadays a pandemic condition. Obese subjects are commonly characterized by musculoskeletal disorders and particularly by non-specific chronic low back pain (cLBP). However, the relationship between obesity and cLBP remains to date unsupported by an objective measurement of the mechanical behaviour of the spine and its morphology in obese subjects. Such analysis may provide a deeper understanding of the relationships between function and the onset of clinical symptoms.
Purpose
to objectively assess the posture and function of the spine during standing, flexion and lateral bending in obese subjects with and without cLBP and to investigate the role of obesity in cLBP.
Study design
Cross-sectional study
Patient sample
thirteen obese subjects, thirteen obese subjects with cLBP, and eleven healthy subjects were enrolled in this study.
Outcome measures
we evaluated the outcome in terms of angles at the initial standing position (START) and at maximum forward flexion (MAX). The range of motion (ROM) between START and MAX was also computed.
Methods
we studied forward flexion and lateral bending of the spine using an optoelectronic system and passive retroreflective markers applied on the trunk. A biomechanical model was developed in order to analyse kinematics and define angles of clinical interest.
Results
obesity was characterized by a generally reduced ROM of the spine, due to a reduced mobility at both pelvic and thoracic level; a static postural adaptation with an increased anterior pelvic tilt. Obesity with cLBP is associated with an increased lumbar lordosis.
In lateral bending, obesity with cLBP is associated with a reduced ROM of the lumbar and thoracic spine, whereas obesity on its own appears to affect only the thoracic curve.
Conclusions
obese individuals with cLBP showed higher degree of spinal impairment when compared to those without cLBP. The observed obesity-related thoracic stiffness may characterize this sub-group of patients, even if prospective studies should be carried out to verify this hypothesis.
doi:10.1186/1743-0003-7-3
PMCID: PMC2821381  PMID: 20082692
17.  Load-Relaxation Properties of the Human Trunk in Response to Prolonged Flexion: Measuring and Modeling the Effect of Flexion Angle 
PLoS ONE  2012;7(11):e48625.
Experimental studies suggest that prolonged trunk flexion reduces passive support of the spine. To understand alterations of the synergy between active and passive tissues following such loadings, several studies have assessed the time-dependent behavior of passive tissues including those within spinal motion segments and muscles. Yet, there remain limitations regarding load-relaxation of the lumbar spine in response to flexion exposures and the influence of different flexion angles. Ten healthy participants were exposed for 16 min to each of five magnitudes of lumbar flexion specified relative to individual flexion-relaxation angles (i.e., 30, 40, 60, 80, and 100%), during which lumbar flexion angle and trunk moment were recorded. Outcome measures were initial trunk moment, moment drop, parameters of four viscoelastic models (i.e., Standard Linear Solid model, the Prony Series, Schapery's Theory, and the Modified Superposition Method), and changes in neutral zone and viscoelastic state following exposure. There were significant effects of flexion angle on initial moment, moment drop, changes in normalized neutral zone, and some parameters of the Standard Linear Solid model. Initial moment, moment drop, and changes in normalized neutral zone increased exponentially with flexion angle. Kelvin-solid models produced better predictions of temporal behaviors. Observed responses to trunk flexion suggest nonlinearity in viscoelastic properties, and which likely reflected viscoelastic behaviors of spinal (lumbar) motion segments. Flexion-induced changes in viscous properties and neutral zone imply an increase in internal loads and perhaps increased risk of low back disorders. Kelvin-solid models, especially the Prony Series model appeared to be more effective at modeling load-relaxation of the trunk.
doi:10.1371/journal.pone.0048625
PMCID: PMC3489838  PMID: 23144913
18.  Effects of Exercise Induced Low Back Pain on Intrinsic Trunk Stiffness and Paraspinal Muscle Reflexes 
Journal of biomechanics  2012;46(4):801-805.
The purpose of this study was to 1) compare trunk neuromuscular behavior between individuals with no history of low back pain (LBP) and individuals who experience exercise-induced LBP (eiLBP) when pain free, and 2) investigate changes in trunk neuromuscular behavior with eiLBP. Seventeen young adult males participated including eight reporting recurrent, acute eiLBP and nine control participants reporting no history of LBP. Intrinsic trunk stiffness and paraspinal muscle reflex delay were determined in both groups using sudden trunk flexion position perturbations 1-2 days following exercise when the eiLBP participants were experiencing an episode of LBP (termed post-exercise) and 4-5 days following exercise when eiLBP had subsided (termed post-recovery). Post-recovery, when the eiLBP group was experiencing minimal LBP, trunk stiffness was 26% higher in the eiLBP group compared to the control group (p=0.033) and reflex delay was not different (p=0.969) between groups. Trunk stiffness did not change (p=0.826) within the eiLBP group from post-exercise to post-recovery, but decreased 22% within the control group (p=0.002). Reflex delay decreased 11% within the eiLBP group from post-exercise to post-recovery (p=0.013), and increased 15% within the control group (p=0.006). Although the neuromuscular mechanisms associated with eiLBP and chronic LBP may differ, these results suggest that previously-reported differences in trunk neuromuscular behavior between individuals with chronic LBP and healthy controls reflect a combination of inherent differences in neuromuscular behavior between these individuals as well as changes in neuromuscular behavior elicited by pain.
doi:10.1016/j.jbiomech.2012.11.023
PMCID: PMC3568223  PMID: 23182221
low back pain; exercise; trunk stiffness; reflex
19.  Kinematic analysis of dynamic lumbar motion in patients with lumbar segmental instability using digital videofluoroscopy 
European Spine Journal  2009;18(11):1677-1685.
The study design is a prospective, case–control. The aim of this study was to develop a reliable measurement technique for the assessment of lumbar spine kinematics using digital video fluoroscopy in a group of patients with low back pain (LBP) and a control group. Lumbar segmental instability (LSI) is one subgroup of nonspecific LBP the diagnosis of which has not been clarified. The diagnosis of LSI has traditionally relied on the use of lateral functional (flexion–extension) radiographs but use of this method has proven unsatisfactory. Fifteen patients with chronic low back pain suspected to have LSI and 15 matched healthy subjects were recruited. Pulsed digital videofluoroscopy was used to investigate kinematics of lumbar motion segments during flexion and extension movements in vivo. Intersegmental linear translation and angular displacement, and pathway of instantaneous center of rotation (PICR) were calculated for each lumbar motion segment. Movement pattern of lumbar spine between two groups and during the full sagittal plane range of motion were analyzed using ANOVA with repeated measures design. Intersegmental linear translation was significantly higher in patients during both flexion and extension movements at L5–S1 segment (p < 0.05). Arc length of PICR was significantly higher in patients for L1–L2 and L5–S1 motion segments during extension movement (p < 0.05). This study determined some kinematic differences between two groups during the full range of lumbar spine. Devices, such as digital videofluoroscopy can assist in identifying better criteria for diagnosis of LSI in otherwise nonspecific low back pain patients in hope of providing more specific treatment.
doi:10.1007/s00586-009-1147-x
PMCID: PMC2899390  PMID: 19727854
Videofluoroscopy; Lumbar spine; Segmental instability; Kinematics; Motion
20.  Posterior muscle chain activity during various extension exercises: an observational study 
Background
Back extension exercises are often used in the rehabilitation of low back pain. However, at present it is not clear how the posterior muscles are recruited during different types of extension exercises. Therefore, the present study will evaluate the myoelectric activity of thoracic, lumbar and hip extensor muscles during different extension exercises in healthy persons. Based on these physiological observations we will make recommendations regarding the use of extensions exercises in clinical practice.
Methods
Fourteen healthy subjects performed four standardized extension exercises (dynamic trunk extension, dynamic-static trunk extension, dynamic leg extension, dynamic-static leg extension) in randomized order at an intensity of 60% of 1-RM (one repetition maximum). Surface EMG signals of Latissimus dorsi (LD), Longissimus thoracis pars thoracic (LTT) and lumborum (LTL), Iliocostalis lumborum pars thoracic (ILT) and lumborum (ILL), lumbar Multifidus (LM) and Gluteus Maximus (GM) were measured during the various exercises. Subsequently, EMG root mean square values were calculated and compared between trunk and leg extension exercises, as well as between a dynamic and dynamic-static performance using mixed model analysis. During the dynamic exercises a 2 second concentric contraction was followed by a 2 second eccentric contraction, whereas in the dynamic-static performance, a 5 second isometric interval was added in between the concentric and eccentric contraction phase.
Results
In general, the muscles of the posterior chain were recruited on a higher level during trunk extension (mean ± SD, 56.6 ± 30.8%MVC) compared to leg extension (47.4 ± 30.3%MVC) (p ≤ 0.001). No significant differences were found in mean muscle activity between dynamic and dynamic-static performances (p = 0.053). The thoracic muscles (LTT and ILT) were recruited more during trunk extension (64.9 ± 27.1%MVC) than during leg extension (54.2 ± 22.1%MVC) (p = 0.045) without significant differences in activity between both muscles (p = 0.138). There was no significant differences in thoracic muscle usage between the dynamic or dynamic-static performance of the extension exercises (p = 0.574).
Lumbar muscle activity (LTT, ILL, LM) was higher during trunk extension (70.6 ± 22.2%MVC) compared to leg extension (61.7 ± 27.0%MVC) (p = 0.047). No differences in myoelectric activity between the lumbar muscles could be demonstrated during the extension exercises (p = 0.574). During each exercise the LD (19.2 ± 13.9%MVC) and GM (28.2 ± 14.6%MVC) were recruited significantly less than the thoracic and lumbar muscles.
Conclusion
The recruitment of the posterior muscle chain during different types of extension exercises was influenced by the moving body part, but not by the type of contraction. All muscle groups were activated at a higher degree during trunk extension compared to leg extension. Based on the recruitment level of the different muscles, all exercises can be used to improve the endurance capacity of thoracic muscles, however for improvement of lumbar muscle endurance leg extension exercises seem to be more appropriate. To train the endurance capacity of the LD and GM extension exercises are not appropriate.
doi:10.1186/1471-2474-14-204
PMCID: PMC3716991  PMID: 23834759
Trunk extensor muscles; Multifidus; Posterior muscle chain; Extension exercise; Electromyography; Spine
21.  Altered Spinal Motion in Low Back Pain Associated with Lumbar Strain and Spondylosis 
Study Design We present a patient-specific computer model created to translate two-dimensional (2D) fluoroscopic motion data into three-dimensional (3D) in vivo biomechanical motion data.
Objective The aim of this study is to determine the in vivo biomechanical differences in patients with and without acute low back pain. Current dynamic imaging of the lumbar spine consists of flexion–extension static radiographs, which lack sensitivity to out-of-plane motion and provide incomplete information on the overall spinal motion. Using a novel technique, in-plane and coupled out-of-plane rotational motions are quantified in the lumbar spine.
Methods A total of 30 participants—10 healthy asymptomatic subjects, 10 patients with low back pain without spondylosis radiologically, and 10 patients with low back pain with radiological spondylosis—underwent dynamic fluoroscopy with a 3D-to-2D image registration technique to create a 3D, patient-specific bone model to analyze in vivo kinematics using the maximal absolute rotational magnitude and the path of rotation.
Results Average overall in-plane rotations (L1–L5) in patients with low back pain were less than those asymptomatic, with the dominant loss of motion during extension. Those with low back pain also had significantly greater out-of-plane rotations, with 5.5 degrees (without spondylosis) and 7.1 degrees (with spondylosis) more out-of-plane rotational motion per level compared with asymptomatic subjects.
Conclusions Subjects with low back pain exhibited greater out-of-plane intersegmental motion in their lumbar spine than healthy asymptomatic subjects. Conventional flexion–extension radiographs are inadequate for evaluating motion patterns of lumbar strain, and assessment of 3D in vivo spinal motion may elucidate the association of abnormal vertebral motions and clinically significant low back pain.
doi:10.1055/s-0033-1341640
PMCID: PMC3699246  PMID: 24436694
low back pain; lumbar strain; spondylosis; biomechanics; kinematics
22.  Spinal alignment in low back pain patients and age-related side effects: a multivariate cross-sectional analysis of video rasterstereography back shape reconstruction data 
European Spine Journal  2013;22(9):1979-1985.
Purpose
Spinal form in the sagittal plane and asymmetries of spinal alignment in the frontal plane were identified earlier to be associated with low back pain. This study was aiming at investigating whether age was influencing the significance of these findings.
Methods
Spinal alignment of 155 older and 58 younger low back pain patients was investigated using non-invasive video rasterstereography and compared to 192 pain free controls. Trunk inclination and imbalance, pelvis tilt and torsion, and the thoracic kyphosis and lumbar lordosis angle served as dependent variables, which were analyzed using multivariate procedures.
Results
Frontal plane parameters—trunk imbalance (λ > 0.60) in combination with pelvis tilt (λ > 0.64)—constituted an independent component in a factor analysis model of spine shape parameters in younger and older patients, but not in pain free controls. Trunk imbalance (frontal), trunk inclination (sagittal) and partially thoracic kyphosis angle (sagittal) were extracted to separate patients from controls (discriminant coefficients >0.50). Age could not be excluded as interfering variable for the lumbar lordosis angle. Significant univariate analyses revealed higher effect sizes for trunk imbalance and inclination (η2 > 0.07) than for lordosis, kyphosis or pelvic parameters (η2 < 0.06).
Conclusions
In line with corresponding findings trunk imbalance remained a low back pain-associated parameter not depending on age. Over all, sagittal trunk inclination and the thoracic kyphosis angle could not be established as being completely free from age influences, while the lumbar lordosis angle played a minor role and seemed to be influenced more by age than by low back pain in this rasterstereography study.
doi:10.1007/s00586-013-2787-4
PMCID: PMC3777053  PMID: 23616202
Spine shape; Low back pain; Age; Video rasterstereography; Multivariate analysis
23.  Effects of chronic low back pain on trunk coordination and back muscle activity during walking: changes in motor control 
European Spine Journal  2005;15(1):23-40.
Low back pain (LBP) is often accompanied by changes in gait, such as a decreased (preferred) walking velocity. Previous studies have shown that LBP diminishes the normal velocity-induced transverse counter-rotation between thorax and pelvis, and that it globally affects mean erector spinae (ES) activity. The exact nature and causation of these effects, however, are not well understood. The aim of the present study was to examine in detail the effect of walking velocity on global trunk coordination and ES activity as well as their variability to gain further insights into the effects of non-specific LBP on gait. The study included 19 individuals with non-specific LBP and 14 healthy controls. Gait kinematics and ES activity were recorded during treadmill walking at (1) a self-selected (comfortable) velocity, and (2) sequentially increased velocities from 1.4 up to maximally 7.0 km/h. Pain intensity, fear of movement and disability were measured before the experiment. The angular movements of thorax, lumbar and pelvis were recorded in three dimensions. ES activity was recorded with pairs of surface electrodes. Trunk–pelvis coordination and mean amplitude of ES activity were analyzed. In addition, invariant and variant properties of trunk kinematics and ES activity were studied using principal component analysis (PCA). Comfortable walking velocity was significantly lower in the LBP participants. In the transverse plane, the normal velocity-induced change in pelvis–thorax coordination from more in-phase to more antiphase was diminished in the LBP participants, while lumbar and pelvis rotations were more in-phase compared to the control group. In the frontal plane, intersegmental timing was more variable in the LBP than in the control participants, with additional irregular movements of the thorax. Rotational amplitudes were not significantly different between the LBP and control participants. In the LBP participants, the pattern of ES activity was affected in terms of increased (residual) variability, timing deficits, amplitude modifications and frequency changes. The gait of the LBP participants was characterized by a more rigid and less variable kinematic coordination in the transverse plane, and a less tight and more variable coordination in the frontal plane, accompanied by poorly coordinated activity of the lumbar ES. Pain intensity, fear of movement and disability were all unrelated to the observed changes in coordination, suggesting that the observed changes in trunk coordination and ES activity were a direct consequence of LBP per se. Clinically, the results imply that conservative therapy should consider gait training as well as exercises aimed at improving both intersegmental and muscle coordination.
doi:10.1007/s00586-004-0825-y
PMCID: PMC3454567  PMID: 15864670
Chronic low back pain; Walking; Trunk coordination; Muscle coordination; Variability
24.  A non-randomized clinical control trial of Harrison mirror image methods for correcting trunk list (lateral translations of the thoracic cage) in patients with chronic low back pain 
European Spine Journal  2004;14(2):155-162.
Spinal trunk list is a common occurrence in clinical practice, but few conservative methods of spinal rehabilitation have been reported. This study is a non-randomized clinical control trial of 63 consecutive retrospective subjects undergoing spinal rehabilitation and 23 prospective volunteer controls. All subjects presented with lateral thoracic-cage-translation posture (trunk list) and chronic low back pain. Initial and follow-up numerical pain rating scales (NRS) and AP lumbar radiographs were obtained after a mean of 11.5 weeks of care (average of 36 visits) for the treatment group and after a mean of 37.5 weeks for the control group. The radiographs were digitized and analyzed for a horizontal displacement of T12 from the second sacral tubercle, verticality of the lumbar spine at the sacral base, and any dextro/levo angle at mid-lumbar spine. Treatment subjects received the Harrison mirror image postural correction methods, which included an opposite trunk-list exercise and a new method of opposite trunk-list traction. Control subjects did not receive spinal rehabilitation therapy, but rather self-managed their back pain. For the treatment group, there were statistically significant improvements (approximately 50%) in all radiographic measurements and a decrease in pain intensity (NRS: 3.0 to 0.8). For the control group, no significant radiographic and NRS differences were found, except in trunk-list displacement of T12 to S1, worsened by 2.4 mm. Mirror image (opposite posture) postural corrective exercises and a new method of trunk-list traction resulted in 50% reduction in trunk list and were associated with nearly resolved pain intensity in this patient population. The findings warrant further study in the conservative treatment of chronic low back pain and spinal disorders.
doi:10.1007/s00586-004-0796-z
PMCID: PMC3476700  PMID: 15517424
Exercise; Posture; Rehabilitation; Spine; Traction; Trunk List
25.  Lumbar spine stability can be augmented with an abdominal belt and/or increased intra-abdominal pressure 
European Spine Journal  1999;8(5):388-395.
The increased intra-abdominal pressure (IAP) commonly observed when the spine is loaded during physical activities is hypothsized to increase lumbar spine stability.The mechanical stability of the lumbar spine is an important consideration in low back injury prevention and rehabilitation strategies. This study examined the effects of raised IAP and an abdominal belt on lumbar spine stability. Two hypotheses were tested: (1) An increase in IAP leads to increased lumbar spine stability, (2) Wearing an abdominal belt increases spine stability. Ten volunteers were placed in a semi-seated position in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplished by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexion, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gastric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of the following two factors: belt or no belt and three levels of IAP (0, 40, and 80% of maximum). The belt and raised IAP increased trunk stiffness in all directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IAP levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness depending on the IAP level and the direction of exertion. In all three directions, the EMG activity of all 12 trunk muscles increased significantly due to the elevated IAP. The belt had no effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lumbar erector spinae in flexion, whose activities decreased. The results indicate that both wearing an abdominal belt and raised IAP can each independently, or in combination, increase lumbar spine stability. However, the benefits of the belt must be interpreted with caution in the context of the decreased activation of a few trunk extensor muscles.
doi:10.1007/s005860050192
PMCID: PMC3611203  PMID: 10552322
Key words Lumbar spine; stability; Lumbar spine; intra-abdominal; pressure; Lumbar spine; abdominal belts; Lumbar spine; electromyography

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