Trunk Flexion-extension Research Articles

Repetitive trunk loading leads to faster trunk movement in response to external perturbation

The purpose of the present study was to examine trunk movement pattern responses to mechanical perturbation before and after two different repetitive trunk flexion-extension loading schemes. Spatial and temporal parameters were studied to understand the trunk recovery from an anteriorly directed perturbation. Eighteen male and female subjects (18–27 yrs) participated in active and passive trunk flexion-extension, performed seven days apart. Subjects performed 60 trunk flexion-extension repetitions in each condition. Subjects either volitionally moved their trunks (active condition) or relaxed while a dynamometer controlled the movements (passive condition). Trunk perturbations occurred before and immediately after two 30 repetition sessions. Initial responses included latency measures of trunk displacement and peak trunk velocity (VP). Temporal measures included perturbation onset to initial trunk movement (TD), movement initiation to VP (TMIPV), and perturbation onset to VP (TPPV). Recovery measures included peak recovery velocity (VPR), recovery time (TR), velocity slope (VS), and recovery slope (RS). Differences between loading sessions were present for TPPV (p < .05), TR (p < .05), and RS (p < .05). Overall, the results indicate repetitive loading leads to lower resistance to perturbation, but faster recovery from perturbation although no differences to active or passive repetitive loading was observed.

Effects of pregnancy on lumbar motion patterns and muscle responses

BACKGROUND CONTEXTThe kinematics of the lumbar region and the activation patterns of the erector spinae muscle have been associated with the genesis of low back pain, which is one of the most common complications associated with pregnancy. Despite the high prevalence of pregnancy-related low back pain, the biomechanical adaptations of the lumbar region during pregnancy remain unknown. PURPOSEThis study analyzes lumbar spine motion and the activation pattern of the lumbar erector spinae muscle in healthy pregnant women. STUDY DESIGNA case-control study. PATIENT SAMPLEThe study involved 34 nulliparous women (control group) and 34 pregnant women in the third trimester (week 36 ± 1). OUTCOME MEASURESWe recorded the parameters of angular displacement of the lumbar spine in the sagittal plane during trunk flexion-extension, and the EMG activity of the erector spinae muscles during flexion, extension, eccentric and concentric contractions, and the myolectrical silence. METHODSThe participants performed several series of trunk flexion-extension movements, which were repeated 2 months postpartum. The position of the lumbar spine was recorded using an electromagnetic motion capture system. EMG activity was recorded by a surface EMG system and expressed as a percentage of a submaximal reference contraction. RESULTSAntepartum measurements showed a decrease (relative to control and postpartum measurements) in lumbar maximum flexion (52.5 ± 10.5° vs 57.3 ± 7.7° and 58.7 ± 8.6°; p < .01), the percentage of lumbar flexion during forward bending (56.4 ± 5.6% vs 59.4 ± 6.8% and 59.7 ± 5.6%; p < .01), and the time keeping maximum levels of lumbar flexion (35.7 ± 6.7% vs 43.8 ± 5.3% and 50.1 ± 3.7%; p < .01). Higher levels of erector spinae activation were observed in pregnant women during forward bending (10.1 ± 4.8% vs 6.3 ± 2.4% and 6.6 ± 2.7%; p < .01) and eccentric contraction (12.1 ± 5.2% vs 9.4 ± 3.1% and 9.1 ± 2.9%; p < .01), as well as a shortened erector spinae myoelectric silence during flexion. ConclusionsPregnant women show adaptations in their patterns of lumbar motion and erector spinae activity during trunk flexion-extension. These changes could be associated with the genesis of pregnancy-related low back pain, by means of biomechanical protection mechanisms against the increase on abdominal mass and ligamentous laxity.

Muscle Strength and Neuromuscular Control in Low-Back Pain: Elite Athletes Versus General Population.

The purpose of the study was to investigate the athletic-based specificity of muscle strength and neuromuscular control of spine stability in chronic non-specific low-back pain (LBP). Thirty elite athletes and 29 age-matched non-athletes with (15 athletes and 15 non-athletes) and without LBP (15 athletes and 14 non-athletes) participated in the study. Muscle strength was measured during maximal isometric trunk flexion and trunk extension contractions. The neuromuscular control of spine stability was analyzed by determining trunk stiffness, trunk damping, and onset times of the lumbar and thoracic erector spinae muscles after sudden perturbations (quick release experiments) as well as maximum Lyapunov exponents (local dynamic stability) using non-linear time series analysis of repetitive lifting movements. LBP was assessed using the visual analog scale. We found lower maximal trunk extension moments (p = 0.03), higher trunk damping (p = 0.018) and shorter onset times (p = 0.03) of the investigated trunk muscles in LBP patients in both athletes and non-athletes. Trunk stiffness and the local dynamic stability did not show any differences (p = 0.136 and p = 0.375, respectively) between LBP patients and healthy controls in both groups. It can be concluded that, despite the high-level of training in athletes, both athletes and non-athletes with LBP showed the same deconditioning of the lumbar extensor muscles and developed similar strategies to ensure spine stability after sudden perturbations to protect the spine from pain and damage. The findings highlight that specific training interventions for the trunk muscles are not only crucial for individuals of the general population, but also for well-trained athletes.

Fitts' Law is Applicable to Trunk Coordination Measurements in a Sitting Position

ABSTRACTTrunk coordination is essential for many activities of daily living in wheelchair users. This study investigated whether Fitts' law is applicable to trunk movements in a sitting position. Fourteen healthy adults performed two series of 24 tasks of trunk flexion–extension movements in a sitting position. The results showed significant linear relationships between average group movement time (MT) and index of difficulty (ID) over all tasks (r2 = 0.92) and within target distances (0.94 < r2 < 1.00). Target distance affected intercept and slope (P < 0.001). Hence, Fitts' law is applicable to the studied trunk movements in a sitting position, indicating these trunk movements tasks could serve as a basis for qualitative trunk coordination tests. Transferability of these conclusions to wheelchair users, and optimal test design should be further investigated.

The effect of wearing a lumbar belt on biomechanical and psychological outcomes related to maximal flexion-extension motion and manual material handling

Workers with low back pain (LBP) may benefit from wearing a lumbar belt (LB), but the biomechanical and psychological mechanisms involved are not fully understood. Two types of flexible LB (extensible and non-extensible) were compared to a control condition (no LB) regarding pain-related (pain, fear of pain and catastrophizing) and biomechanical (range of motion – ROM) outcomes related to two tasks: maximal trunk flexion-extension and manual material handling. Healthy controls and participants with LBP were tested. During both tasks, the two LBs reduced the lumbar ROM in participants with LBP in the same way as healthy controls. This was observed even at the beginning of the trunk flexion movement, allowing generalization to many work tasks, that is to say tasks performed with small or deep trunk flexion. The two LBs reduced pain, fear of pain and catastrophizing in subjects with LBP. That may help a gradual re-exposure to physical work activities (disability prevention perspective), or maintaining these activities (secondary prevention perspective), following a LBP episode.

Spasm and flexion-relaxation phenomenon response to large lifting load during the performance of a trunk flexion-extension exercise

BackgroundThe flexion relaxation phenomenon (FRP) has been widely investigated. Nevertheless, no study has been reported on the FRP as well as spasm response to large lifting load. The aim of this study was to evaluate the effect of large lifting load on the FRP response and spasm during execution of a flexion-extension exercise.MethodsTwenty-two healthy male university students without low back pain history participated this study. Subjects randomly performed three trials of trunk flexion-extension cycles of 5 s flexion and 5 s extension in each of 4 conditions (three large lifting loads of 15, 20 and 25 kg and one lifting load of 0 kg for comparison). Surface EMG from bilateral erector spinae was recorded during the performance of a trunk anterior flexion-extension exercise. The relaxation phase was determined through the onset of electromyography (EMG) signals. Spasm was evaluated in the relaxation period. The mean normalized electromyography (NEMG) was derived from the raw EMG.ResultsSpasm was observed in more than 45% of the individuals and the intensity of muscle activation was increased by more than 78% in the relaxation phase.ConclusionsA large lifting load could lead to a high prevalence of spasms as well as a high intensity of muscle activations on erector spinae muscle in the relaxation period, which may be associated with the development of low back disorder during the performance of a flexion-extension exercise.

Validation of the Arm Profile Score in assessing upper limb functional impairments in people with multiple sclerosis

BackgroundAlthough upper limb (UL) impairments are widespread in people with Multiple Sclerosis (pwMS), there is limited quantitative evidence concerning their specific features. The aim of this study is to validate a synthetic measure based on kinematic data to define the degree of deviation from a physiologic pattern during the “hand to mouth” (HTM) task. MethodsTwenty pwMS (mean age 51.2 SD 11.1) years, Expanded Disability Status Scale (EDSS) score in the range 2–6.5, underwent a kinematic analysis of the HTM task using a motion capture system. Spatio-temporal parameters and synthetic indexes (Arm Variable Score, AVS and Arm Profile Score, APS) were calculated and compared with those of age-matched healthy individuals. Kinematic data were correlated with the EDSS score and clinical tests such as the Nine Hole Peg Test (NHPT) and hand-grip strength (HGS). FindingsPwMS exhibit reduced velocity, increased movement duration, sway of adjusting and frequency of direction changes as well as higher APS values (15.4° vs. 8.6°, P<0.001) with respect to controls due to alterations in trunk flexion-extension, shoulder abduction-adduction, flexion-extension and rotation and elbow flexion-extension. Moderate-to-large correlations were found between APS and EDSS (rho=0.609, P<0.001), NHPT (rho=0.468, P=0.03) and HGS (rho=−0.627 P<0.001). InterpretationThe kinematic analysis of HTM provides useful information in quantifying UL impairments in pwMS. The APS index appears suitable to represent UL movement deviations from the physiological pattern in pwMS and to assess disease progression or effectiveness of pharmacologic and rehabilitative treatments effectiveness.

Cross-country skiing movement factorization to explore relationships between skiing economy and athletes' skills.

We investigated the relationships between the biomechanics of the double poling (DP) technique in cross-country skiing, its economy, and athletes' skill. To this aim, skiers' motion has been factorized into components through principal component analysis (PCA). Eight high-level (HL) and eight regional level (RL) male cross-country skiers performed a 5-minute submaximal DP trial while roller skiing on a treadmill at 14kmh-1 and 2° incline. Whole-body kinematics was recorded with a motion capture system. PCA was applied to markers coordinates to extract principal movements (PMk ), which were ranked by their variance. Energy cost (EC) of locomotion was calculated from ergospirometric measurements. Results showed that 96.7%±0.6% of total skiing pattern variance can be described with the first three PMk. (Shoulder and trunk flexion-extension are described PM1 and PM2 and elbow flexion-extension are mainly represented in PM2 and PM3. The variance of further components, consisting of residual movements (eg, slow postural changes or high-frequency vibrations), was greater for the RL than the HL skiers (4.0%±0.5% vs 2.6%±0.3%; P<.001) and was positively correlated with EC (R2 =.646; P<.001). PCA permitted to describe the biomechanics of the DP technique through a limited set of principal movements. Skiing skills and economy appeared to be related to a skier's ability to simplify movement complexity, suggesting that an efficient skier is better able to reduce superfluous movement components during DP.

Axial Sensory Tricks in Chorea-Acanthocytosis: Insights into Phenomenology.

BackgroundTrunk flexion and axial extension are characteristic symptoms of chorea–acanthocytosis (ChAc).Phenomenology ShownA 41-year-old male with ChAc (confirmed by VPS13A mutations) reported that his involuntary axial movements were significantly ameliorated by either folding his arms over his chest or putting his hands behind his head.Educational ValueThese apparent “sensory tricks” suggest a dystonic pathophysiology, and also merit further study to analyze their potential for symptom control in ChAc.

Axial Sensory Tricks in Chorea–Acanthocytosis: Insights into Phenomenology

<strong>Background:</strong> Trunk flexion and axial extension are characteristic symptoms of chorea–acanthocytosis (ChAc). <strong>Phenomenology Shown:</strong> A 41-year-old male with ChAc (confirmed by VPS13A mutations) reported that his involuntary axial movements were significantly ameliorated by either folding his arms over his chest or putting his hands behind his head. <strong>Educational Value:</strong> These apparent ‘‘sensory tricks’’ suggest a dystonic pathophysiology, and also merit further study to analyze their potential for symptom control in ChAc.

Association of lumbar spine stiffness and flexion-relaxation phenomenon with patient-reported outcomes in adults with chronic low back pain \u2013 a single-arm clinical trial investigating the effects of thrust spinal manipulation

BackgroundSpinal manipulation (SM) is used commonly for treating low back pain (LBP). Spinal stiffness is routinely assessed by clinicians performing SM. Flexion-relaxation ratio (FRR) was shown to distinguish between LBP and healthy populations. The primary objective of this study was to examine the association of these two physiological variables with patient-reported pain intensity and disability in adults with chronic LBP (>12 weeks) receiving SM.MethodsA single-arm trial provided 12 sessions of side-lying thrust SM in the lumbosacral region over 6 weeks. Inclusion criteria included 21–65 years old, Roland-Morris Disability Questionnaire (RMDQ) score ≥ 6 and numerical pain rating score ≥ 2. Spinal stiffness and FRR were assessed pre-treatment at baseline, after 2 weeks and after 6 weeks of treatment. Lumbar spine global stiffness (GS) were calculated from the force-displacement curves obtained using i) hand palpation, ii) a hand-held device, and iii) an automated indenter device. Lumbar FRR was assessed during trunk flexion-extension using surface electromyography. The primary outcomes were RMDQ and pain intensity measured by visual analog scale (VAS). Mixed-effects regression models were used to analyze the data.ResultsThe mean age of the 82 participants was 45 years; 48% were female; and 84% reported LBP >1 year. The mean (standard deviation) baseline pain intensity and RMDQ were 46.1 (18.1) and 9.5 (4.3), respectively. The mean reduction (95% confidence interval) after 6 weeks in pain intensity and RMDQ were 20.1 mm (14.1 to 26.1) and 4.8 (3.7 to 5.8). There was a small change over time in the palpatory GS but not in the hand-held or automated GS, nor in FRR. The addition of each physiologic variable did not affect the model-estimated changes in VAS or RMDQ over time. There was no association seen between physiological variables and LBP intensity. Higher levels of hand-held GS at L3 and automated GS were significantly associated with higher levels of RMDQ (p = 0.02 and 0.03, respectively) and lower levels of flexion and extension FRR were significantly associated with higher levels of RMDQ (p = 0.02 and 0.008, respectively) across the 3 assessment time points.ConclusionsImprovement in pain and disability observed in study participants with chronic LBP was not associated with the measured GS or FRR.Trial registrationNCT01670292 on clinicaltrials.gov, August 2, 2012

ACC Research Agenda Conference 2018: Peer Reviewer Acknowledgments and Abstracts of Proceedings

ACC Research Agenda Conference 2018: Peer Reviewer Acknowledgments and Abstracts of Proceedings

Therapy of poor posture in adolescents: Sensorimotor training increases the effectiveness of strength training to reduce increased anterior pelvic tilt

AbstractBackground: Increased anterior pelvic tilt is one important contributor to poor posture in children and adolescents and caused by muscular imbalance. This study aims at identifying the extent to which a sensorimotor training reduces anterior pelvic tilt more effectively than pure strength and stretch training alone. Methods: 54 male adolescents (age 13–17) with an increased pelvic tilt angle >14° were matched to three groups (strength training STR, strength + sensorimotor training STR + SENS, control CON). Maximum isometric torques for knee flexion (HA), trunk flexion (RA), and trunk extension, and pelvic tilt were measured before and after a 12 week physical therapy schedule. Two-way mixed ANOVA were calculated. Results: For STR and STR + SENS the relative torque of HA and RA increased significantly (p < 0.05) between pre- and post-test. Significant improvement of the pelvic tilt angle was identified in both training groups, with STR + SENS exhibiting a significantly larger degree of improvement....

Isokinetic trunk flexion–extension protocol to assess trunk muscle strength and endurance: Reliability, learning effect, and sex differences

PurposeThe purpose of this study was to examine the reliability and the learning effect of an isokinetic trunk flexion–extension protocol designed to simultaneously assess trunk muscle strength and endurance. In addition, the effect of the participants' sex on the reliability data was examined. MethodsFifty-seven healthy and physically active young men (n = 28) and women (n = 29) performed the isokinetic protocol 5 times, separated by a week between each of the first 4 sessions and by a month between the last 2 sessions. The protocol consisted of performing 4 trials of 15 maximum flexion–extension concentric exertions at 120°/s (range of trunk motion = 50°). The absolute and relative peak torque and total work were calculated to assess trunk flexion and extension strength. In addition, endurance ratio, modified endurance ratio, fatigue final ratio, recovery ratio, and modified recovery ratio variables were used for the assessment of trunk muscle endurance in both directions. ResultsRegarding the absolute reliability, no relevant changes were found between paired-comparison sessions for most strength and endurance variables, except for total work and relative total work variables in the flexion movement in both sexes. In addition, the typical error of the isokinetic variables was lower than 10% in both males and females, and minimum detectable changes ranged from 7% to 20%, with a tendency to be higher in females and in endurance variables. The strength variables showed high-to-excellent intraclass correlation coefficients (ICCs; >0.74); however, for the endurance variables only the endurance ratio and the modified endurance ratio obtained moderate-to-high ICC values (0.57 < ICC < 0.82). In addition, the analysis of the variance reported no significant differences between consecutive pairs of sessions for most variables in both sexes. ConclusionOverall, these findings provide clinicians, trainers, and researchers with a 10-min single-session protocol to perform a reliable muscle strength and endurance evaluation of trunk flexor and extensor muscles, all within the same protocol.

Muscular Activation Pattern of Bilateral Extensors Response to Asymmetric Hand Lifting During Trunk Flexion–extension Performance

ABSTRACTThe authors' purpose was to test the effect of asymmetric hand lifting on muscular activation patterns of 3 bilateral extensors. Eighteen male university students without back pain were volunteered. Each performed flexion–extension randomly with conditions of right lifting, left lifting, and nonlifting. Surface electromyography from bilateral thoracic, lumbar erector spinae, and hamstring was recorded. The cross-correlation and relative intensity in paired muscles of bilateral extensors was calculated in flexion as well as extension period. The results showed that the cross-correlation coefficient was decreased and the phase lag as well as the relative intensity of bilateral extensors was increased significantly in thoracic level. The phase lag as well as the relative intensity of bilateral extensors was increased significantly in lumbar level. It was concluded that asymmetric lifting has a significant effect on muscular activation of bilateral extensors in thorax level, which causes the ipsilateral extensor to activate larger and longer. Asymmetric lifting also has some effect on muscular activation of bilateral extensors in lumbar level but with less extent than in thorax level, which causes contralateral extensor to activate larger and longer. Asymmetric lifting seems to have no significant effect on muscular activation of bilateral hamstring.

Diagnostic value of trunk flexion-extension testing in old chronic low back pain patients.

Dynamic trunk flexion-extension testing has been proven to objectively diagnose low back pain in persons under the age of 60years but older persons have difficulty complying with standardized movement velocity. 190 patients and 71 matched healthy volunteers (18-90years of age) performed modified testing by holding static positions at standing, half, and full trunk flexion. Lumbar extensor muscle activity in isometric positions was significantly higher in patients with higher activity in the oldest (60-90years) and the middle-aged (40-59years) but not in the youngest (18-39years) subgroups compared to normal. There were no differences in gross trunk range of motion, half flexion relaxation ratio, proprioception, muscle activity differences between positions, and fear-avoidance behavior. The diagnostic accuracy as expressed by the area under the curve was fair (0.74). Lumbar extensor muscle activity demonstrated moderate to good diagnostic value in old patients.

Identification of Cross-Over in Isokinetic Muscle Strength and PT Ratio by Gravity Correction in Trunk Joint’s ROM

PURPOSE: The aim of this research was to examine the effect of gravity correction and investigate the relationships between trunk flex - ibility and isokinetic strength of trunk. METHODS: To obtain peak torque (PT) used as muscle strength and power index, 41 young men without any orthopedic diseases per- formed isokinetic exercise using HUMAC NORM trunk extension flexion (TEF) modular at 60°/sec, 5 times. Trunk flexibility was mea - sured by trunk forward flexion, sit and reach, and back extension test. RESULTS: During flexion from -15° to 0°, non-gravity corrected (NGC) PT was significantly ( p<.05) lower (4.69%) than gravity cor- rected (GC) PT. Contrastively, NGC PT was significantly ( p<.05) higher (2.52%) than GC PT during extension. Furthermore NGC PT ratio was significantly ( p<.05) lower than GC PT ratio. During flexion 0°to 45°, NGC PT was significantly ( p<.05) higher (27.49%) than GC PT. Contrastively, NGC PT was significantly ( p<.05) lower (15.06%) than GC PT during extension. Furthermore NGC PT ratio was significantly ( p<.05) lower than GC PT ratio. Moreover, only back extension of trunk flexibility was correlated with PT ratio on -15° to 0° regardless of gravity correction.

Relationship between core stability, dynamic balance and jumping performance in soccer players

The purpose of this study was to investigate relationship between core stability, dynamic balance and jumping performance in soccer players. Seventeen male soccer players (mean ± SD: age, 21.06 ± 1.71 years) participated as volunteer in this study. Dynamic balance of the participants were evaluated at directions of anterior (A), posteromedial (PM) and posterolateral (PL) with Star Excursion Balance Test (SEBT). The core stability was evaluated with trunk flexion, side bridge, and trunk extension tests. For jumping performance, squat jump height was measured using a contact mat. There was a negative correlation (r = -0.705) between trunk flexion test and squat jump height ( p 0.05). There was no significant correlation between trunk flexion, side bridge, trunk extension tests and SEBT values ( p > 0.05). The results of this study suggest that trunk flexion is associated with squat jump height in soccer players, but not side bridge and trunk extension tests. The core stability does not contribute significantly on dynamic balance.

Lumbopelvic flexibility modulates neuromuscular responses during trunk flexion–extension

Various stimuli such as the flexibility of lumbopelvic structures influence the neuromuscular responses of the trunk musculature, leading to different load sharing strategies and reflex muscle responses from the afferents of lumbopelvic mechanoreceptors. This link between flexibility and neuromuscular response has been poorly studied.The aim of this study was to investigate the relationship between lumbopelvic flexibility and neuromuscular responses of the erector spinae, hamstring and abdominal muscles during trunk flexion–extension. Lumbopelvic movement patterns were measured in 29 healthy women, who were separated into two groups according to their flexibility during trunk flexion–extension. The electromyographic responses of erector spinae, rectus abdominis and biceps femoris were also recorded.Subjects with greater lumbar flexibility had significantly less pelvic flexibility and vice versa. Subjects with greater pelvic flexibility had a higher rate of relaxation and lower levels of hamstring activation during maximal trunk flexion.The neuromuscular response patterns of the hamstrings seem partially modulated by pelvic flexibility. Not so with the lumbar erector spinae and lumbar flexibility, despite the assertions of some previous studies. The results of this study improve our knowledge of the relationships between trunk joint flexibility and neuromuscular responses, a relationship which may play a role in low back pain.

Age and gender related neuromuscular pattern during trunk flexion-extension in chronic low back pain patients.

BackgroundThe root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from standing has repeatedly been recommended to objectively assess muscle function in chronic low back pain patients. However, literature addressing older patients is sparse. This cross sectional study sought to examine differences in neuromuscular activation between age groups (>60 versus 40-60 versus <40 years) and sexes during a standardized trunk flexion-extension task.MethodsA total of 216 patients (62 older, 84 middle-aged, 70 younger) performed maximum trunk extensions followed by trunk flexion extension testing thereby holding static positions at standing, half, and full trunk flexion. The lumbar extensor muscle activity and 3d-accelerometric signals intended to monitor hip and trunk position angles were recorded from the L5 (multifidus) and T4 (semispinalis thoracis) levels. Permutation ANOVA with bootstrapped confidence intervals were performed to examine for age and gender related differences. Ridge-regressions investigated the impact of physical-functional and psychological variables to the half flexion relaxation ratio (i.e. muscle activity at the half divided by that in maximum flexion position).ResultsMaximum back extension torque was slightly but significantly higher in youngest compared to oldest patients if male and females were pooled. Normalized RMS-SEMG revealed highest lumbar extensor muscle activity at standing in the oldest and the female groups. Patients over 60 years showed lowest activity changes from standing to half (increments) and from half to the maximum flexion position (decrements) leading to a significantly lower half flexion relaxation ratio compared to the youngest patients. These oldest patients demonstrated the highest hip and lowest lumbothoracic changes of position angles. Females had higher regional hip and gross trunk ranges of movement compared to males. Lumbothoracic flexion and the muscle activity at standing had a significant impact on the half flexion relaxation ratio.ConclusionsThe neuromuscular activation pattern and the kinematics in this trunk flexion-extension task involving static half flexion position changed according to age and sex. The test has a good potential to discriminate between impaired and unimpaired neuromuscular regulation of back extensors in cLBP patients, thereby allowing the design of more individualized exercise programs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-016-0121-1) contains supplementary material, which is available to authorized users.