Decreasing the required lumbar extensor moment induces earlier onset of flexion relaxation

Flexion relaxation (FR) is characterized by the lumbar erector spinae (LES) becoming myoelectrically silent near full trunk flexion. This study was designed to: (1) determine if decreasing the lumbar moment during flexion would induce FR to occur earlier; (2) characterize thoracic and abdominal muscle activity during FR. Ten male participants performed four trunk flexion/extension movement conditions; lumbar moment was altered by attaching 0, 5, 10, or 15 lb counterweights to the torso. Electromyography (EMG) was recorded from eight trunk muscles. Lumbar moment, lumbar flexion and trunk inclination angles were calculated at the critical point of LES inactivation (CPLES). Results demonstrated that counterweights decreased the lumbar moment and lumbar flexion angle at CPLES (p < 0.0001 and p = 0.0029, respectively); the hypothesis that FR occurs earlier when lumbar moment is reduced was accepted. The counterweights did not alter trunk inclination at CPLES (p = 0.1987); this is believed to result from an altered hip to spine flexion ratio when counterweights were attached. Lumbar multifidus demonstrated FR, similar to LES, while thoracic muscles remained active throughout flexion. Abdominal muscles activated at the same instant as CPLES, except in the 15 lb condition where abdominal muscles activated before CPLES resulting in a period of increased co-contraction.     

Viscoelastic creep induced by repetitive spine flexion and its relationship to dynamic spine stability

Repetitive trunk flexion elicits passive tissue creep, which has been hypothesized to compromise spine stability. The current investigation determined if increased spine flexion angle at the onset of flexion relaxation (FR) in the lumbar extensor musculature was associated with altered dynamic stability of spine kinematics. Twelve male participants performed 125 consecutive cycles of full forward trunk flexion. Spine kinematics and lumbar erector spinae (LES) electromyographic (EMG) activity were obtained throughout the repetitive trunk flexion trial. Dynamic stability was evaluated with maximum finite-time Lyapunov exponents over five sequential blocks of 25 cycles. Spine flexion angle at FR onset, and peak LES EMG activity were determined at baseline and every 25th cycle. Spine flexion angle at FR increased on average by 1.7° after baseline with significant increases of 1.7° and 2.4° at the 50th and 100th cycles. Maximum finite-time Lyapunov exponents demonstrated a transient, non-statistically significant, increase between cycles 26 and 50 followed by a recovery to baseline over the remainder of the repetitive trunk flexion cycles. Recovery of dynamic stability may be the consequence of increased active spine stiffness demonstrated by the non-significant increase in peak LES EMG that occurred as the repetitive trunk flexion progressed.     

Changes in muscle activation patterns and subjective low back pain ratings during prolonged standing in response to an exercise intervention

BackgroundLow back pain (LBP) development has been associated with occupational standing. Increased hip and trunk muscle co-activation is considered to be predisposing for LBP development during standing in previously asymptomatic individuals. The purpose of this work was to investigate muscle activation and LBP responses to a prescribed exercise program. Pain-developing (PD) individuals were expected to have decreased LBP and muscle co-activation following exercise intervention.MethodsElectromyography (EMG) data were recorded from trunk and hip muscle groups during 2-h of standing. An increase of >10 mm on visual analog scale (VAS) during standing was threshold for PD categorization. Participants were assigned to progressive exercise program with weekly supervision or control (usual activity) for 4 weeks then re-tested.ResultsForty percent were categorized as PD on day 1, VAS = 24.2 (±4.0) mm. PD exercisers (PDEX) had lower VAS scores (8.93 ± 3.66 mm) than PD control (PDCON) (16.5 ± 6.3 mm) on day 2 (p = 0.007). Male PDEX had decreased gluteus medius co-activation levels (p < 0.05) on day 2.DiscussionThe exercise program proved beneficial in reducing LBP during standing. There were changes in muscle activation patterns previously associated with LBP. Predisposing factors for LBP during standing were shown to change positively with appropriate exercise intervention.     

Does prolonged seated deskwork alter the lumbar flexion relaxation phenomenon?

Sustained maximum lumbar spine flexion can increase the angle at which the low back flexion relaxation phenomenon (FRP) is observed. This adaptation has been hypothesized to have implications for the control of lumbar spine stability and increase the potential for low back injury. The objective of this study was to investigate if similar changes in the FRP would occur from sub-maximal spine flexion induced by an extended continuous duration of seated office deskwork. Twenty-three participants (12 male and 11 female) performed three bouts of full forward spine flexion interspersed with two 1-h periods of seated deskwork. Lumbar spine angular kinematics and electromyographic activity from the lumbar erector spinae were obtained throughout all trials. The angles at which myoelectric silence occurred (FRP onset) were documented. Lumbar flexion at FRP onset increased by 1.3 ± 1.5° after 1-h of sitting (p < 0.05) with no further increase after 2-h. However, when the angle at the FRP onset was normalized to the total range of flexion, there was no difference in the FRP onset. These results suggest that the seated posture may induce residual deformation in the viscoelastic passive tissues of the low back; this could increase the challenge of controlling spine motion and reduce the load-bearing capacity of the lumbar spine system during activities performed following extended bouts of sitting.     

Altered trunk muscle coordination during rapid trunk flexion in people in remission of recurrent low back pain

People with a history of low back pain (LBP) are at high risk to encounter additional LBP episodes. During LBP remission, altered trunk muscle control has been suggested to negatively impact spinal health. As sudden LBP onset is commonly reported during trunk flexion, the aim of the current study is to investigate whether dynamic trunk muscle recruitment is altered in LBP remission. Eleven people in remission of recurrent LBP and 14 pain free controls performed cued trunk flexion during a loaded and unloaded condition. Electromyographic activity was recorded from paraspinal (lumbar and thoracic erector spinae, latissimus dorsi, deep and superficial multifidus) and abdominal muscles (obliquus internus, externus and rectus abdominis) with surface and fine-wire electrodes. LBP participants exhibited higher levels of co-contraction of flexor/extensor muscles, lower agonistic abdominal and higher antagonistic paraspinal muscle activity than controls, both when data were analyzed in grouped and individual muscle behavior. A sub-analysis in people with unilateral LBP (n = 6) pointed to opposing changes in deep and superficial multifidus in relation to the pain side. These results suggest that dynamic trunk muscle control is modified during LBP remission, and might possibly increase spinal load and result in earlier muscle fatigue due to intensified muscle usage. These negative consequences for spinal health could possibly contribute to recurrence of LBP.     

Standardized activities of daily living in presence of sub-acute low-back pain: A pilot study

The aim of this pilot study was to investigate how sub-acute low-back pain (LBP) patients differed with respect to control in movements and muscle activation during standardized tasks representing daily living activities, and explore relationships between cognition and measured motor performance. Linear and nonlinear parameters were computed from kinetics, kinematics and muscle activity recorded for 12 sub-acute patients and 12 healthy matched controls during trunk flexion, sit-to-stand from a chair and lifting a box. Cognitive variables were collected to explore relationships with biomechanical parameters. For trunk flexion, left external abdominal oblique muscle activity level was lower for patients compared with controls (p < 0.05), whereas sample entropy (complexity) was higher (p < 0.05). Normalized mutual information was lower for patients compared with controls for left and right erector spinae (p < 0.05). Level of activity of left external abdominal oblique correlated negatively with cognitive ignoring and positively with catastrophizing (p ? 0.05), and catastrophizing also correlated positively with functional connectivity of abdominal muscles (p < 0.05). Signs of reorganization in muscle activation pointed towards different synergistic actions in trunk muscles in sub-acute LBP patients compared with controls. The interplay with maladaptive cognition suggested that in the subacute stage of LBP, both biomechanical and cognitive factors should be taken into account.     

The relationship between flexibility and EMG activity pattern of the erector spinae muscles during trunk flexion–extension

BackgroundMovements in the lumbar spine, including flexion and extension are governed by a complex neuromuscular system involving both active and passive units. Several biomechanical and clinical studies have shown the myoelectric activity reduction of the lumbar extensor muscles (flexion–relaxation phenomenon) during lumbar flexion from the upright standing posture. The relationship between flexibility and EMG activity pattern of the erector spinae during dynamic trunk flexion–extension task has not yet been completely discovered.ObjectiveThe purpose of this study was to investigate the relationship between general and lumbar spine flexibility and EMG activity pattern of the erector spinae during the trunk flexion–extension task.MethodsThirty healthy female college students were recruited in this study. General and lumbar spine flexibilities were measured by toe-touch and modified schober tests, respectively. During trunk flexion–extension, the surface electromyography (EMG) from the lumbar erector spinae muscles as well as flexion angles of the trunk, hip, lumbar spine and lumbar curvature were simultaneously recorded using a digital camera. The angle at which muscle activity diminished during flexion and initiated during extension was determined and subjected to linear regression analysis to detect the relationship between flexibility and EMG activity pattern of the erector spinae during trunk flexion–extension.ResultsDuring flexion, the erector spinae muscles in individuals with higher toe-touch scores were relaxed in larger trunk and hip angles and reactivated earlier during extension according to these angles (P < 0.001) while in individuals with higher modified schober scores this muscle group was relaxed later and reactivated sooner in accordance with lumbar angle and curvature (P < 0.05). Toe-touch test were significantly correlated with trunk and hip angles while modified schober test showed a significant correlation with lumbar angle and curvature variables.ConclusionThe findings of this study indicate that flexibility plays an important role in trunk muscular recruitment pattern and the strategy of the CNS to provide stability. The results reinforce the possible role of flexibility alterations as a contributing factor to the motor control impairments. This study also shows that flexibility changes behavior is not unique among different regions of the body.     

Muscular activation patterns during active prone hip extension exercises

BackgroundChanges in activation patterns of hip extensors and pelvic stabilizing muscles are recognized as factors that cause low back disorders and these disturbances could have an impact on the physiological loading and alter the direction and magnitude of joint reaction forces.ObjectiveTo investigate activation patterns of the gluteus maximus, semitendinosus and erector spinae muscles with healthy young individuals during four different modalities of therapeutic exercise.MethodsThirty-one volunteers were selected: (16 men and 15 women), age (24.5 ± 3.47 years), body mass of 66.89 ± 11.89 kg and a height of 1.70 ± 0.09 m). They performed four modalities of therapeutic exercise while the electromyographic activity of the investigated muscles was recorded to determine muscle pattern activation for each exercise.ResultsRepeated measure ANOVA revealed that muscle activation patterns were similar for the four analyzed exercises, starting with the semitendinosus, followed by the erector spinae, and then, the gluteus maximus. The gluteus maximus was the last activated muscle during hip extension associated with knee flexion (p < 0.0001), knee extension (p < 0.0001), and with lateral rotation and knee flexion (p < 0.05).ConclusionFindings of the present study suggested that despite individual variability, the muscle firing order was similar for the four therapeutic exercises.     

The effect of heel lifts on trunk muscle activation during gait: A study of young healthy females

Heel lifts are a treatment option for low back pain (LBP), whilst high-heeled shoes have been linked to LBP development. This study evaluated the effects of in-shoe 20 mm high bilateral heel lifts on trunk muscle activity. Activity of the erector spinae (ErSp), internal oblique and external oblique muscles was evaluated using surface electromyography in 15 young (20.7 ± 0.9 years) healthy female participants. Measures were taken during overground gait, both immediately and following two days habituation to the heel lifts. Immediately following the addition of the heel lifts, levels of ErSp muscle activity in the 5% epoch following heel strike increased by 19.2% (p < 0.05). Following habituation, levels of ErSp muscle activity in the 5% epoch prior to heel strike increased by 24.1% (p < 0.05), and a 14 ms (p < 0.001) earlier onset of ErSp muscle activity prior to heel strike was observed. These results indicate the heel lifts altered muscle activity reactively around heel strike (i.e. greater activity after heel strike) immediately after application and proactively (i.e. earlier onsets and greater activity prior to heel strike) after short term habituation. When put in context of previous research on trunk muscle activity in LBP populations, these changes may be important considerations for the aetiology, treatment and prevention of LBP.     

Effects of stance width on postural movement pattern and anticipatory postural control associated with unilateral arm abduction

We investigated the effects of stance width on postural movement pattern and activation timing of postural muscles during unilateral arm abduction. Thirty-two healthy subjects abducted the right arm at their own timing. Stance width was 0, 9, 18 or 27 cm. Movement angles of leg lateral inclination and trunk lateral flexion to the leg in the frontal plane were analyzed. Based on movement angles at 0 cm width, subjects were classified into three groups: contralateral whole body leaning (CWBLg); ipsilateral trunk flexion (ITFg); and contralateral trunk flexion (CTFg). A high correlation between the movement angles was obtained at 0 cm width (r = 0.82). With increasing stance width, postural movement pattern in the ITFg shifted to patterns characterized by lateral flexion of the trunk toward the side opposite to arm movement, and movement angle of leg-inclination in ITFg and CWBLg decreased. At 0 cm width, left gluteus medius and tensor fascia latae were activated significantly about 40 ms ahead of the right middle deltoid in CWBLg and CTFg, but not in ITFg. However, preceding activation became prominent (about 20 ms) in ITFg for wide stances. Moreover, bilateral activation of the tensor fascia latae was observed in CTFg for all widths.     

Kinematic chain reactions on trunk and dynamic postural steadiness in subjects with recurrent low back pain

Although subjects with recurrent low back pain (LBP) demonstrate altered trunk control, the kinematic and kinetic responses of the trunk have not been carefully investigated. This study was conducted to compare the standing time, spine range of motion (ROM), and dynamic postural steadiness index (DPSI) based on visual condition between subjects with and without recurrent LBP during upright one leg standing. Sixty-three individuals participated in the study, including 34 control subjects and 29 subjects with recurrent LBP. The DPSI was a composite of the medio-lateral (MLSI), anterior-posterior (APSI), and vertical steadiness indices (VSI) on a force platform. The control group demonstrated longer standing time (s) during the eyes-open condition than the LBP group (26.82 ± 6.03 vs. 19.87 ± 9.36; t = 2.96, p = 0.01). Regarding spine ROM, visual condition was significantly different between groups (F = 7.09, p = 0.01) and demonstrated interactions with spine region and group (F = 5.53, p = 0.02). For the kinetic measures, there was a significant interaction between visual conditions and indices (F = 25.30, p = 0.001). In the LBP group, the DPSI was significantly correlated with the MLSI (r = 0.59, p = 0.002), APSI (r = 0.44, p = 0.03), and VSI (r = 0.98, p = 0.01) in the eyes-closed condition. Overall, the results of this study indicated that the LBP group decreased thorax and lumbar spine rotations during the eyes-closed condition. The LBP group also demonstrated positive correlations with the kinetic indices, enhancing dynamic postural steadiness in the eyes-closed condition in order to possibly avoid pain or further injury. This dynamic postural steadiness strategy is necessary to improve kinetic and kinematic chain reactions in the LBP group. This compensatory pattern supports the development of optimal postural correction strategies to prevent LBP recurrence and might represent a chain reaction to protect trunk control without visual input.     

EMG in rotation–flexion of the torso

The objective of this study was to determine the magnitude and phasic relationship of the torso muscles in rotation–flexion of varying degree of asymmetries of the trunk. Nineteen normal young subjects (7 males and 12 females) were stabilized on a posture stabilizing platform and instructed to assume a flexed and right rotated posture. A combination 20°, 40° and 60° of rotation and 20°, 40° and 60° of flexion resulted in nine postures. These postures were assumed in a random order. The subjects were asked to exert their maximal voluntary isometric contraction (MVC) in the plane of rotation of the posture assumed for a period of 5 s. The surface EMG from the external and internal obliques, rectus abdominis, latissimus dorsi and erector spinae at the 10th thoracic and 3rd lumbar vertebral levels was recorded. The abdominal muscles had the least response at 40° of flexion, the dorsal muscles had the highest magnitude.With increasing right rotation, the left external oblique continued to decrease its activity. The ANOVA revealed that rotation and muscles had a significant main effect on normalized peak EMG (p < 0.02) in both genders. There was a significant interaction between rotation and flexion in both genders (p < 0.02) and rotation and muscle in females. The erector spinae activity was highest at 40° flexion, due to greater mechanical disadvantage and having not reached the state of flexion–relaxation. The abdominal muscle activity declined with increasing asymmetry, due to the decreasing initial muscle length. The EMG activity was significantly affected by rotation than flexion (p < 0.02).     

Pelvic instability and trunk and hip muscle recruitment patterns in patients with total hip arthroplasty

Hip and lumbar spine disorders often coexist in patients with total hip arthroplasty (THA). The current study aimed to reveal pelvic motion pathology and altered trunk and hip muscle recruitment patterns relating to pelvic motion in patients with THA. Twenty-one women who underwent THA and 12 age-matched healthy women were recruited. Pelvic kinematics and muscle recruitment patterns (i.e., amplitude, activity balance, and onset timing) of the gluteus maximus, semitendinosus, multifidus, and erector spinae were collected during prone hip extension. Compared with healthy subjects, the patients showed increased pelvic motion, especially ventral rotation, decreased multifidus muscle activity relative to the hip extensors, and delayed onset of multifidus activity, despite reaction times and speeds of leg motion not being significantly different between the groups. Furthermore, while contributing factors associated with ventral pelvic rotation were not found, delayed onset of multifidus activity was detected as a factor related to the increased anterior tilt of the pelvis (r = 0.47, p < 0.05) in patients with THA. These results suggest that patients with THA have dysfunction of the stabilizer muscles of the lumbopelvic region along with increased pelvic motion.     

A compensation of angular displacements of the hip joints and lumbosacral spine between subjects with and without idiopathic low back pain during squatting

Low back pain (LBP) is one of the most common symptoms reported in adults. However, the contribution of postural control on the lumbar spine and hips during squatting has not been carefully investigated in individuals with LBP. The aim of this study was to compare three-dimensional kinematic changes of the lumbar spine and hips between subjects with and without idiopathic chronic LBP during squatting activities. In total, 30 subjects enrolled in the study (15 control subjects and 15 subjects with idiopathic chronic LBP). All participants were asked to perform squatting activities five times repeatedly while holding a load of 2 kg in a basket. The outcome measures included the Oswestry Disability Index (ODI) and kinematic angular displacement for the hips and lumbar spine. The LBP group demonstrated increased range of motion (ROM) in flexion of the dominant (T = ?2.14, p = 0.03) and non-dominant (T = ?2.11, p = 0.03) hips during squatting. The lumbar spine flexion ROM significantly decreased (T = 2.20, p = 0.03). The kinematic changes demonstrated interactions with region × group (F = 5.56, p = 0.02), plane × group (F = 4.36, p = 0.04), and region × plane (F = 2292.47, p = 0.001). The ODI level demonstrated significant interaction on combined effects of body region and plane (F = 4.91, p = 0.03). Therefore, the LBP group utilized a compensation strategy to increase hip flexion with a stiffened lumbar spine in the sagittal plane during squatting. This compensatory kinematic strategy could apply to clinical management used to enhance lumbar spine flexibility in subjects with idiopathic chronic LBP.     

The role of trunk muscles in sitting balance control in people with low back pain

The purpose of this study was to examine the muscular activities and kinetics of the trunk during unstable sitting in healthy and LBP subjects. Thirty-one healthy subjects and twenty-three LBP subjects were recruited. They were sat on a custom-made chair mounted on a force plate. Each subject was asked to regain balance after the chair was tilted backward at 20°, and then released. The motions of the trunk and trunk muscle activity were examined. The internal muscle moment and power at the hip and lumbar spine joints were calculated using the force plate and motion data. No significant differences were found in muscle moment and power between healthy and LBP subjects (p > 0.05). The duration of contraction of various trunk muscles and co-contraction were significantly longer in the LBP subjects (p < 0.05) when compared to healthy subjects, and the reaction times of the muscles were also significantly reduced in LBP subjects (p < 0.05). LBP subjects altered their muscle strategies to maintain balance during unstable sitting, but these active mechanisms appear to be effective as trunk balance was not compromised and the internal moment pattern remained similar. The changes in muscle strategies may be the causes of LBP or the result of LBP with an attempt to protect the spine.     

Influence of prolonged bed-rest on spectral and temporal electromyographic motor control characteristics of the superficial lumbo-pelvic musculature

Little is known about the motor control of the lumbo-pelvic musculature in microgravity and its simulation (bed-rest). Analysis of spectral and temporal electromyographic variables can provide information on motor control relevant for normal function. This study examined the effect of 56-days of bed-rest with 1-year follow-up in 10 male subjects on the median frequency and the activation timing in surface electromyographic recordings from five superficial lumbo-pelvic muscles during a repetitive knee movement task. Trunk fat mass (from whole body-composition measurements) and movement accuracy as possible explanatory factors were included. Increased median frequency was observed in the lumbar erector spinae starting late in bed-rest, but this was not seen in its synergist, the thoracic erector spinae (p < .0001). These changes persisted up to 1-year after bed-rest and were independent of changes in body-composition or movement accuracy. Analysis suggested decreases of median frequency (p < .0001) in the abdominal and gluteal muscles to result from increased (p < .01) trunk fat levels during and after bed-rest. No changes in lumbo-pelvic muscle activation timing were seen. The results suggest that bed-rest particularly affects the shorter lumbar erector spinae and that the temporal sequencing of superficial lumbo-pelvic muscle activation is relatively robust.     

Decreased fibularis reflex response during inversion perturbations in FAI subjects

Investigate reflex responses in muscles throughout the lower limb and low back during sudden inversion perturbations in individuals with and without Functional Ankle Instability (FAI) while walking. Forty subjects participated in the study. Surface electromyogram recordings were obtained from the fibularis (FIB), gluteus medius (GM), erector spinae (ES), and sternocleidomastoid (SCM) of the injured/matched side as well as the uninjured/matched contralateral side (FIB_CLS, GM_CLS, or ES_CLS). Latency and amplitude data were collected while subjects were walking on a custom-built perturbation walkway. The onset of the short-latency stretch reflex of the FIB was significantly later in the injured side of the FAI individuals when compared to the control group (P = 0.009). Both the short and long latency reflex amplitude was significantly smaller in the FIB muscle in the FAI group than in the control group (P < 0.008). No significant differences in latency or amplitude reflex responses were identified between the two groups in the GM, ES, FIB_CLS, GM_CLS, or ES_CLS (P > .05). Interpretation of these results indicate that during a dynamic perturbation task individuals with FAI demonstrate longer fibularis muscle latencies on the injured side while no significant changes in the proximal muscle groups. Additionally, short and long latency reflex amplitude was significantly decreased in FAI individuals.     

PLAD (personal lift assistive device) stiffness affects the lumbar flexion/extension moment and the posterior chain EMG during symmetrical lifting tasks

The PLAD (personal lift assistive device) was designed to reduce the lumbar moment during lifting and bending tasks via elastic elements. This investigation examined the effects of modulating the elastic stiffness. Thirteen men completed 90 lifts (15 kg) using 6 different PLAD stiffnesses in stoop, squat and freestyle lifting postures. The activity of 8 muscles were recorded (latissimus dorsi, thoracic and lumbar erector spinae, rectus abdominis, external oblique, gluteus maximus, biceps femoris and rectus femoris), 3D electromagnetic sensors tracked the motion of each segment and strain gauges measured the elastic tension. EMG data were rectified, filtered, normalized and integrated as a percentage of the lifting task. The highest PLAD tension elicited the greatest reduction in erector spinae activity (mean of thoracic and lumbar) in comparison to the no-PLAD condition for the stoop (37%), squat (38%), and freestyle (37%) lifts, while prompting comparable reductions in gluteus maximums and biceps femoris activity. The highest PLAD stiffness also elicited the greatest reduction in the integrated L4/L5 flexion moment for the stoop (19.0%), squat (18.4%) and freestyle (17.4%) lifts without changing peak lumbar flexion. Each increase in PLAD stiffness further reduced the muscle activity of the posterior chain and the dynamic lumbar moment.     

Comparison of surface electromyographic activity of erector spinae before and after the application of central posteroanterior mobilisation on the lumbar spine

Lumbar spine accessory movements, used by therapists in the treatment of patients with low back pain, is thought to decrease paravertebral muscular activity; however there is little research to support this suggestion. This study investigated the effects of lumbar spine accessory movements on surface electromyography (sEMG) activity of erector spinae.A condition randomised, placebo controlled, repeated measures design was used. sEMG measurements were recorded from 36 asymptomatic subjects following a control, placebo and central posteroanterior (PA) mobilisation to L3 each for 2 min. The therapist stood on a force platform while applying the PA mobilisation to quantify the force used. The PA mobilisation applied to each subject had a mean maximum force of 103.3 N, mean amplitude of force oscillation of 41.1 N, and a frequency of 1.2 Hz. Surface electromyographic data were recorded from the musculature adjacent to L3, L5 and T10.There were statistically significant reductions of 15.5% (95% CI: 8.0–22.5%) and 17.8% (95% CI: 12.9–22.4%) in mean sEMG values following mobilisation compared with the control and placebo, respectively.This study demonstrates that a central PA mobilisation to L3 results in a statistically significant decrease in the sEMG activity of erector spinae of an asymptomatic population.     

Differences between two subgroups of low back pain patients in lumbopelvic rotation and symmetry in the erector spinae and hamstring muscles during trunk flexion when standing

The present study was performed to examine lumbopelvic rotation and to identify asymmetry of the erector spinae and hamstring muscles in people with and without low back pain (LBP). The control group included 16 healthy subjects, the lumbar-flexion–rotation syndrome LBP group included 17 subjects, and the lumbar-extension–rotation syndrome LBP group included 14 subjects. Kinematic parameters were recorded using a 3D motion-capture system, and electromyography parameters were measured using a Noraxon TeleMyo 2400T. The two LBP subgroups showed significantly more lumbopelvic rotation during trunk flexion in standing than did the control group. The muscle activity and flexion–relaxation ratio asymmetries of the erector spinae muscles in the lumbar-flexion–rotation syndrome LBP group were significantly greater than those in the control group, and the muscle activity and flexion–relaxation ratio asymmetry of the hamstring muscles in the lumbar-extension–rotation syndrome LBP group were significantly greater than those in the control group. Imbalance or asymmetry of passive tissue could lead to asymmetry of muscular activation. Muscle imbalance can cause asymmetrical alignment or movements such as unexpected rotation. The results showed a greater increase in lumbopelvic rotation during trunk flexion in standing among the lumbar-flexion–rotation syndrome and lumbar-extension–rotation syndrome LBP groups compared with the control group. The differences between the two LBP subgroups may be a result of imbalance and asymmetry in erector spinae and hamstring muscle properties.