Electromyographic mapping of the erector spinae muscle with varying load and during sustained contraction

The purpose of the study was to explore changes in the spatial distribution of erector spinae electromyography amplitude during static, sustained contractions and during contractions of increasing load. Surface electromyographic (EMG) signals were detected from nine healthy subjects using a grid of 13 × 5 electrodes placed unilaterally over the lumbar erector spinae musculature. Subjects stood in a 20° forward flexed position and performed: (1) six 20-s long contractions with loads ranging from 2.5 kg to 12.5 kg (2.5 kg increments) and (2) a 6 min sustained contraction with 7.5 kg load. Root mean square (RMS) and mean power spectral frequency (MNF) were computed from the recorded EMG signals. EMG RMS increased (P < 0.0001) and MNF remained constant during contractions of increased load. During the sustained contraction, MNF decreased (P < 0.0001) and RMS did not change over time. The centroid (center of activity) of the RMS map shifted caudally (P < 0.0001) with time during the sustained contraction but did not change with varying load. These results suggest a change in the distribution of erector spinae muscle activity with fatigue and a uniform distribution of muscle activation across loads.     

The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes

In this study, we explore the relationship between moments in the frontal and sagittal planes, generated by a lifting task, vs the electromyographic (EMG) activity of right and left trunk muscle groups. In particular, we postulate that the functional dependence between erector spinae muscle activity and the applied lifting moments about the spine is as follows: the sum of left and right erector spinae processed EMG depends on the sagittal plane moment, and the difference of left and right erector spinae processed EMG depends on the frontal plane moment. A simple out-of-sagittal plane physical model, treating the lumbar spine as a two degree-of-freedom pivot point is discussed to justify these hypotheses. To validate this model, we collected surface EMG and lifting moment data for ten males performing a grid of frontal and sagittal plane lifting tasks. A digital RMS-to-DC algorithm was developed for processing raw EMG. For these tests, we measured EMG for the left and right erector spinae and for the left and right external oblique muscles. The processed EMG signals of the left and right erector spinae muscles are summed and differenced for comparison to the measured sagittal and frontal plane moments. A linear correlation (r2) of 0.96 was obtained for the sum of erector spinae EMG vs the sagittal plane moment; a corresponding value of r2 = 0.95 was obtained for the difference vs the frontal plane moment. No correlations (r2 less than 0.004) was found for the sagittal plane moment and the difference of the left and right erector spinae EMG, and the frontal plane moment and the sum of the left and right erector spinae EMG.     

The influence of age on spinal and lower limb muscle activity during repetitive lifting

This study investigated the effects of age on upper erector spinae (UES), lower erector spinae (LES) and lower body (gluteus maximus; biceps femoris; and vastus lateralis) muscle activity during a repetitive lifting task. Twenty-four participants were assigned to two age groups: ‘younger’ (n = 12; mean age ± SD = 24.6 ± 3.6 yrs) and ‘older’ (n = 12; mean age = 46.5 ± 3.0 yrs). Participants lifted and lowered a box (13 kg) repetitively at a frequency of 10 lifts per minute for a maximum of 20 min. EMG signals were collected every minute and normalised to a maximum voluntary isometric contraction. A submaximal endurance test of UES and LES was used to assess fatigue. Older participants showed higher levels of UES and LES muscle activity (approximately 12–13%) throughout the task, but less fatigue compared to the younger group post-task completion. When lifting, lower-limb muscle activity was generally higher in older adults, although temporal changes were similar. While increased paraspinal muscle activity may increase the risk of back injury in older workers when repetitive lifting, younger workers may be more susceptible to fatigue-related effects. Education and training in manual materials handling should consider age-related differences when developing training programmes.     

Trunk muscle onset and cessation in golfers with and without low back pain

The knowledge of the onset and cessation timing of the paraspinal muscles that surround the lumbar spine is an important area of research for the understanding of low back pain. This study examined the timing of the erector spinae and external oblique muscle activity in a group of golfers with and without low back pain. The study compared the results of surface electromyography measurements for two groups of golfers. Twelve male golfers who had reported a mild or greater level of pain in the lower back that was experienced while playing golf were examined. A further fifteen male golfers who had reported no history of lower back pain in the previous 12 months were recruited as controls. The results showed that the low-back-pain golfers switched on their erector spinae muscle significantly in advance of the start of the backswing. This finding was not evident in the group who did not have low back pain symptoms. Low-back-pain golfers, therefore, may use the erector spinae muscle as a primary spinal stabiliser instead of the stronger deeper muscles such as transversus abdominis and multifidus. These results may have important implications for conditioning programmes for golfers with low back pain.     

Repositioning Suture of the Erector Spinae Muscle for Lumbar Spine Surgery via the Posterior Approach: A Prospective Randomized Study

We prospectively studied the effectiveness of the repositioning suture of the erector spinae muscle for lumbar spine surgery using the posterior approach. 393 patients undergoing lumbar spine surgery were randomized to receive the repositioning or conventional suture of the erector spinae muscle. Time to stitch removal and drainage volume was recorded at 24 and 48 h after operation. Hemoglobin loss rate was determined at 48 h post operation and the rate of malunion (redness, swelling and effusion at stitch removal and would disruption after stitch removal) was recorded. Low back pain was evaluated using the visual analog scale (VAS) preoperatively and 6 and 12 months after operation. Time to stitch removal was comparable in lumbar spine surgery patients receiving the repositioning or conventional suture of the erector spinae muscle (P > 0.05). Compared with the conventional suture, the repositioning suture was associated with significantly reduced drainage volume both at 24 (P < 0.01) and 48 h after operation (P < 0.05). Hemoglobin loss rate at 48 h post operation was also markedly lower in lumbar spine surgery patients receiving the repositioning suture than in those receiving the conventional suture (P < 0.01 or 0.05). Furthermore, the malunion rate in lumbar spine surgery patients using the repositioning suture was markedly lower than that in the conventional group (P < 0.05 or 0.001). There was no difference in preoperative VAS scores in both the groups (P > 0.05). Compared with the conventional suture, the repositioning suture was associated with significantly reduced VAS scores both at 24 and 48 h after operation (P < 0.01 in both). The repositioning suture of the erector spinae muscle is superior to the conventional suture in posterior lumbar spine surgery with marked lessened pain and reduced drainage volume.     

Motor variability during a repetitive lifting task is impaired by wearing a passive back-support exoskeleton

PurposeEvaluate whether wearing a passive back-support exoskeleton during repetitive lifting impairs motor variability of erector spinae muscle and spine movement and whether this association is influenced by lifting style.Scope: Thirty-six healthy males performed ten lifts in four randomized conditions with exoskeleton (without, with) and lifting style (squat, stoop) as dependent variables. One lifting cycle contained four phases: bending/straighten without/with load. Erector spinae muscular activity, thoracic kyphosis and lumbar lordosis were measured with surface electromyography and gravimetric position sensors, respectively. Absolute and relative cycle-to-cycle variability were calculated. The effects of exoskeleton and exoskeleton × lifting style were assessed on outcomes during the complete lifting cycle and its four phases.ResultsFor the complete lifting cycle, muscular variability and thoracic kyphosis variability decreased whereas lumbar lordosis variability increased with exoskeleton. For lifting phases, effects of exoskeleton were mixed. Absolute and relative muscular variability showed a significant interaction effect for the phase straighten with load; variability decreased with exoskeleton during squat lifting.ConclusionUsing the exoskeleton impaired several motor variability parameters during lifting, supporting previous findings that exoskeletons may limit freedom of movement. The impact of this result on longer-term development of muscular fatigue or musculoskeletal disorders cannot yet be estimated.     

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.     

The relation between the flexion relaxation phenomenon onset angle and lumbar spine muscle reflex onset time in response to 30 min of slumped sitting

Viscoelastic creep of spine tissue, induced by submaximal spine flexion in sitting, can delay the onset of the flexion-relaxation phenomenon (FRP) and low back reflexes (LBR). Theoretically, these two outcome measures should be correlated; however, no studies have investigated this. This study aims to determine whether 30 min of near-maximal spine flexion will affect the onset of FRP and LBR in the lumbar erector spinae (LS) and lumbar multifidus (LM), and to examine the relation between these parameters. 15 participants were recruited (9F, 6M). Spine angle (between L1 and S2) was monitored synchronously with bilateral muscle activity in the LS (L1) and the LM (L4). FRP onset and LBR were measured in a randomized order before and after 30 min of slouched sitting. No significant difference was found for any muscle LBR onset time between pre and post-sitting (p > 0.05). A significant increase in FRP onset was found in the RLM (p = 0.016) following sitting. No significant correlation was found between the FRP and the LBR for any muscle. These results suggest that the LBR onset might not be as sensitive as an outcome measure to investigate shorter exposures of sitting as FRP.     

Validation of an OpenSim full-body model with detailed lumbar spine for estimating lower lumbar spine loads during symmetric and asymmetric lifting tasks

There is currently no validated full-body lifting model publicly available on the OpenSim modelling platform to estimate spinal loads during lifting. In this study, the existing full-body-lumbar-spine model was adapted and validated for lifting motions to produce the lifting full-body model. Back muscle activations predicted by the model closely matched the measured erector spinae activation patterns. Model estimates of intradiscal pressures and in vivo measurements were strongly correlated. The same spine loading trends were observed for model estimates and reported vertebral body implant measurements. These results demonstrate the suitability of this model to evaluate changes in lumbar loading during lifting.     

The use of intermittent trunk flexion to alleviate low back pain during prolonged standing

The current study examined of the effect of intermittent, short-term periods of full trunk flexion on the development of low back pain (LBP) during two hours of standing. Sixteen participants completed two 2-h standing protocols, separated by one week. On one day, participants stood statically for 2 h (control day); on the other day participants bent forward to full spine flexion (termed flexion trials) to elicit the flexion relaxation (FR) phenomenon for 5 s every 15 min (experimental day). The order of the control and experimental day was randomized. During both protocols, participants reported LBP using a 100 mm visual analogue scale every 15 min. During the flexion trials, lumbar spine posture, erector spinae and gluteus medius muscle activation was monitored. Ultimately, intermittent trunk flexion reduced LBP by 36% (10 mm) at the end of a 2-h period of standing. Further, erector spinae and gluteus medius muscle quietening during FR was observed in 91% and 65% of the flexion trials respectively, indicating that periods of rest did occurred possibly contributing to the reduction in LBP observed. Since flexion periods do not require any aids, they can be performed in most workplaces thereby increasing applicability.     

Intra-abdominal pressure mechanism for stabilizing the lumbar spine

Currently, intra-abdominal pressure (IAP) is thought to provide stability to the lumbar spine but the exact principles have yet to be specified. A simplified physical model was constructed and theoretical calculations performed to illustrate a possible intra-abdominal pressure mechanism for stabilizing the spine. The model consisted of an inverted pendulum with linear springs representing abdominal and erector spinae muscle groups. The IAP force was simulated with a pneumatic piston activated with compressed air. The critical load of the model was calculated theoretically based on the minimum potential energy principle and obtained experimentally by increasing weight on the model until the point of buckling. Two distinct mechanisms were simulated separately and in combination. One was antagonistic flexor extensor muscle coactivation and the second was abdominal muscle activation along with generation of IAP. Both mechanisms were effective in stabilizing the model of a lumbar spine. The critical load and therefore the stability of the spine model increased with either increased antagonistic muscle coactivation forces or increased IAP along with increased abdominal spring force. Both mechanisms were also effective in providing mechanical stability to the spine model when activated simultaneously. Theoretical calculation of the critical load agreed very well with experimental results (95.5% average error). The IAP mechanism for stabilizing the lumbar spine appears preferable in tasks that demand trunk extensor moment such as lifting or jumping. This mechanism can increase spine stability without the additional coactivation of erector spinae muscles.     

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.     

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.     

Postural taping applied to the low back influences kinematics and EMG activity during patient transfer in physical therapists with chronic low back pain

We examined the influence of the application of postural taping on the kinematics of the lumbo–pelvic–hip complex, electromyographic (EMG) activity of back extensor muscles, and the rating of perceived exertion (RPE) in the low back during patient transfer. In total, 19 male physical therapists with chronic low back pain performed patient transfers with and without the application of postural taping on the low back. The kinematics of the lumbo–pelvic–hip complex and EMG activity of the erector spinae were recorded using a synchronized 3-D motion capture system and surface EMG. RPE was measured using Borg’s CR-10 scale. Differences in kinematic data, EMG activity, and RPE between the two conditions were analyzed using a paired t-test. Peak angle and range of motion (ROM) of lumbar flexion, EMG activity of the erector spinae, and RPE decreased significantly, while peak angle and ROM of pelvic anterior tilt and hip flexion increased significantly during patient transfer under the postural taping condition versus no taping (p < 0.05). These findings suggest that postural taping can change back extensor muscle activity and RPE as well as the kinematics of the lumbo–pelvic–hip complex in physical therapists with chronic low back pain during patient transfer.     

Effect of instruction,surface stability,and load intensity on trunk muscle activity

The aim of this study was to assess the effect of verbal instruction, surface stability, and load intensity on trunk muscle activity levels during the free weight squat exercise. Twelve trained males performed a free weight squat under four conditions: (1) standing on stable ground lifting 50% of their 1-repetition maximum (RM), (2) standing on a BOSU balance trainer lifting 50% of their 1-RM, (3) standing on stable ground lifting 75% of their 1-RM, and (4) receiving verbal instructions to activate the trunk muscles followed by lifting 50% of their 1-RM. Surface EMG activity from muscles rectus abdominis (RA), external oblique (EO), transversus abdominis/internal oblique (TA/IO), and erector spinae (ES) were recorded for each condition and normalized for comparisons. Muscles RA, EO, and TA/IO displayed greater peak activity (39–167%) during squats with instructions compared to the other squat conditions (P = 0.04–0.007). Peak EMG activity of muscle ES was greater for the 75% 1-RM condition than squats with instructions or lifting 50% of 1-RM (P = 0.04–0.02). The results indicate that if the goal is to enhance EMG activity of the abdominal muscles during a multi-joint squat exercise then verbal instructions may be more effective than increasing load intensity or lifting on an unstable surface. However, in light of other research, conscious co-activation of the trunk muscles during the squat exercise may lead to spinal instability and hazardous compression forces in the lumbar spine.     

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.     

Effect of balance taping on trunk stabilizer muscles for back extensor muscle endurance: A randomized controlled study

Objective:The purpose of this study was to investigate the difference in back extensor muscle endurance before and after kinesiology tape application to all back stabilizer muscles and to the erector spinae alone.Methods:We assessed 32 adults (16 men and 16 women), randomly divided into two groups. In the erector spinae taping (EST) group, kinesiology tape was applied only to the erector spinae, and in the total muscle taping (TMT) group, kinesiology tape was applied to the erector spinae, latissimus dorsi, lower trapezius, internal oblique abdominis, and external oblique abdominis.Results:Both groups showed significant difference in terms of back extensor muscle endurance after kinesiology tape application (p<0.05). Between-group comparison revealed that the TMT group had more back extensor muscle endurance than the EST group (p<0.05) after kinesiology tape application.Conclusions:These findings indicate that, to improve back extensor muscle endurance, kinesiology tape should be applied to all back stabilizer muscles, rather than to the erector spinae muscles alone.     

Comparison of erector spinae and hamstring muscle activities and lumbar motion during standing knee flexion in subjects with and without lumbar extension rotation syndrome

The aim of this study was to compare the activity of the erector spinae (ES) and hamstring muscles and the amount and onset of lumbar motion during standing knee flexion between individuals with and without lumbar extension rotation syndrome. Sixteen subjects with lumbar extension rotation syndrome (10 males, 6 females) and 14 healthy subjects (8 males, 6 females) participated in this study. During the standing knee flexion, surface electromyography (EMG) was used to measure muscle activity, and surface EMG electrodes were attached to both the ES and hamstring (medial and lateral) muscles. A three-dimensional motion analysis system was used to measure kinematic data of the lumbar spine. An independent-t test was conducted for the statistical analysis. The group suffering from lumbar extension rotation syndrome exhibited asymmetric muscle activation of the ES and decreased hamstring activity. Additionally, the group with lumbar extension rotation syndrome showed greater and earlier lumbar extension and rotation during standing knee flexion compared to the control group. These data suggest that asymmetric ES muscle activation and a greater amount of and earlier lumbar motion in the sagittal and transverse plane during standing knee flexion may be an important factor contributing to low back pain.     

The effect of backrest inclination, lumbar support and thoracic support on erector spinae muscles when lifting

The effect of backrest inclination, lumbar support and thoracic support on the erector spinae muscle when lifting while sitting has been investigated. It was found that the lowest values of the iEMG of the back muscle were obtained when: (1) the lumbar support was positioned +4 cm forward, the thoracic support inclined to +10 degrees and the backrest inclination at 110 degrees; (2) the lumbar support was positioned +4 cm forward, the thoracic support inclined to +10 degrees and the backrest inclined to 100 degrees; (3) the lumbar support was positioned +1 cm forward, the thoracic support inclined to +10 degrees and the backrest inclination 110 degrees; (4) the backrest was inclined to 100 degrees the thoracic support inclined to 10 degrees and the lumbar support 1 cm forward; (5) the backrest inclination and lumbar support were both increased; (6) the thoracic support and the backrest inclination were both increased.     

Association between abdominal muscle activity and lumbar muscle morphology,and their role in the functional assessment of patients with low back pain: A cross-sectional study

Objectives:The study aims to investigate the relationship between abdominal muscle activity and the cross-sectional area (CSA) of the lumbar muscles and assess their role in the functional assessment of patients with chronic non-specific low back pain (CNSLBP).Methods:142 patients with CNSLBP were included in this study. Disability levels were evaluated with the Roland-Morris Low Back Pain and Disability Questionnaire. The functional assessments of the participants were evaluated with a 6-minute walk test. Abdominal muscle activity was measured using a pressure biofeedback unit. The CSA of the bilateral multifidus, erector spinae, and psoas muscles were measured T2-weighted MRI images at the L2-L5 levels.Results:Significant correlations were found between the abdominal muscle activity during the posterior pelvic tilt movement and the CSA of the erector spinae muscle at the L4 and L5 levels, and the psoas muscle at the L2–L5 levels (correlation coefficient range from 0.32 to 0.48). Abdominal muscle activity yielded a significant additional contribution to the variance on the functional assessment (R² change=0.101).Conclusions:The relationship of abdominal muscle activity with lumbar muscles and the contribution of muscle activities to functional assessment should be considered in the management of patients with CNSLBP.