Lumbar Erector Spinae Muscles Research Articles

Immediate effects of myofascial release on neuromechanical characteristics in female and male patients with low back pain and healthy controls as assessed by tensiomyography. A controlled matched-pair study

BackgroundLow back pain (LBP) is a major health issue in most industrialised countries. Lumbodorsal fascia has been advocated as a potential source of pain in the lumbopelvic region. Myofascial release constitutes a manual therapeutic approach focussing on the restoration of altered soft tissue function. No previous study has focused on quantifying neuromechanical effects of myofascial release on LBP patients through tensiomyography. The purpose of this study was to quantify immediate neuromechanical alterations of myofascial release on patients with LBP and healthy controls through tensiomyography parameters. MethodsThe participants' (n = 30) bilateral lumbar erector spinae muscles were assessed via tensiomyography before and after a 6-min myofascial release treatment of the lumbodorsal fascia to evaluate the muscles' mechanical characteristics. Subjects with LBP (n = 15) were eligible to partake if they reported having had LBP for most days in the past 12 weeks. Muscle displacement (Dm [mm]), velocity of contraction (Vc [mm/s]), and lateral symmetry (Ls [%]) were assessed through tensiomyography testing. FindingsStatistical analyses revealed a significant increase for velocity of contraction in the right (p = .021) and left (p = .041) lumbar erector spinae for the subjects with LBP but not for the healthy controls (both p > .14). InterpretationWe suggested that myofascial release alters neuromechanical characteristics in subjects with LBP. Tensiomyography may be implemented in clinical settings to monitor intervention effects of the myofascial system, especially the tensiomyography parameter velocity of contraction.

Effects of myofascial release on flexibility and electromyographic activity of the lumbar erector spinae muscles in healthy individuals

ObjectiveTo investigate the effects of myofascial release on the flexibility and electromyographic activity of the lumbar erector spinae muscle in healthy individuals. MethodsTen healthy subjects were recruited to an intervention protocol of myofascial release techniques: (1) superficial myofascial release; (2) deep myofascial release apply along 10 sessions, twice a week, with 40 min per sessions. The outcomes evaluated were flexibility (Toe-Touch Test) and electromyography activity (EMG) of the lumbar erector spinae muscle (Iliocostalis and Longissimus bilaterally) during the movement of extension-flexion of the trunk. Paired t-test was used to compare the electromyographic outcomes, while the Wilcoxon test was used to compare the flexibility outcomes. ResultsThe myofascial release techniques increased the flexibility (p = 0.005; r = 0.88) and have no influence over the electromyographic activity of the right iliocostalis (p = 0.179; r = 0.43), right longissimus (p = 0.877; r = 0.05), left iliocostalis (p = 0.386; r = 0.29) and left longissimus (p = 0.418; r = 0.27). ConclusionsThe application of myofascial release techniques increase flexibility and did not influence over the electromyographic activity of the lumbar erector spinae muscles in healthy individuals. Further studies should include a larger sample with a sham group and/or compare EMG activity of the lumbar erector spinae muscles with patients with low back pain during the movement of extension-flexion of the trunk.

Quantification of the Elastic Moduli of Lumbar Erector Spinae and Multifidus Muscles Using Shear-Wave Ultrasound Elastography

Although spinal surgeries with minimal incisions and a minimal amount of X-ray exposure (MIMA) mostly occur in a prone posture on a Wilson table, the prone posture’s effects on spinal muscles have not been investigated. Thus, this study used ultrasound shear-wave elastography (SWE) to compare the material properties of the erector spinae and multifidus muscles when subjects lay on the Wilson table used for spinal surgery and the flat table as a control condition. Thirteen male subjects participated in the study. Using ultrasound SWE, the shear elastic moduli (SEM) of the erector spinae and multifidus muscles were investigated. Significant increases were found in the SEM of erector spinae muscle 1, erector spinae muscle 2, and multifidus muscles on the Wilson table (W) compared to in the flat table (F; W:22.19 ± 7.15 kPa, F:10.40 ± 3.20 kPa, p < 0.001; W:12.10 ± 3.31 kPa, F: 7.17 ± 1.71 kPa, p < 0.001; W: 18.39 ± 4.80 kPa, F: 11.43 ± 2.81 kPa, p < 0.001, respectively). Our results indicate that muscle material properties measured by SWE can be changed due to table posture, which should be considered in biomechanical modeling by guiding surgical planning to develop minimal-incision surgical procedures.

The Effect of Lumbar Erector Spinae Muscle Endurance Exercise on Perceived Low-back Pain in Older Adults

This study investigates changes in lumbar erector spinae (LES) muscle endurance, perceived low-back pain (LBP), and perceived exercise fatigue in older adults, and analyzes the trends of these changes during a 5-week lumbar exercise. Sixteen older adults with LBP were equally and randomly divided into two groups: the experimental group with incline-standing and the control group with the level-standing positions. They were separately treated with lumbar exercise tasks and 10 seconds of muscle endurance tests using surface electromyography (sEMG). There was a trend of changes in both groups. The exercise tasks led to increase LES muscle endurance in the experimental group (53.7%) and the control group (45.4%) and decrease perceived LBP score significantly with the incline-standing position. There was no significant difference between the two groups in perceived exercise fatigue (p>0.05). Trunk flexion and extension with an incline-standing position can be an effective method to increase LES muscle endurance and reduce LBP in older adults.

Effects of standing exercise tasks with a sloped surface intervention on trunk muscle activation and low-back pain intensity in women aged >70 years

This study investigates the effects of standing exercise tasks with an incline-slope surface on the activation of latissimus dorsi (LD) and lumbar erector spinae (LES) muscles, and low-back pain (L...

The Effects of Head Support on Muscle Activity and Pain in a Forward-leaning Posture

Background: Because a forward-leaning posture can cause increased back muscle activity and pain. Therefore, an innovative method to reduce back muscle activity and pain is required. Objects: This study aimed to investigate the effects of a head support on muscle activity and pain in a forward-leaning posture. Methods: A total of 14 male and 16 female students (average age, 21.65 ± 2.37 years; height, 166.15 ± 7.90 cm; and weight, 60.65 ± 9.00 kg) were recruited for the experiment. Two of them were excluded due to musculoskeletal disorders. The muscle activity and pain in the forward-leaning posture were assessed while participants washed dishes for 7 minutes with and without a head support. The condition of using a head support was randomly performed with a 5-minutes break. To confirm a lumbar flexion angle of 30° during the experiment, myoVIDEO was used, and surface electromyography was used to measure muscle activity. Pain was assessed using a 10-point visual analog scale (VAS). The Wilcoxon signed-rank test was used to analyze the data, with p < 0.05 indicating statistical significance. Results: The cervical, thoracic, and lumbar erector spinae muscle activities significantly decreased with the use of the head support, but there was no significant change in the gluteus maximus. There was a significant decrease in the VAS score for the lumbar erector spinae (p < 0.05), but there was no significant change in the VAS score for the cervical region. Conclusion: The use of a head support in a forward-leaning posture reduced cervical, thoracic, and lumbar erector muscle activity and pain. Therefore, it could be recommended during working in a forward-leaning posture, such as during dishwashing, cooking, and working as a factory employee.

Changes in Low Back Muscle Activity and Spine Kinematics in Response to Smartphone Use During Walking.

Within-subject design of an experimental study. The aim of this study was to determine the effects of smartphone use on the activity level of the lumbar erector spinae muscles and spine kinematics during walking. Using a smartphone while walking makes the user hold the phone steady and look downward to interact with the phone. Walking with this non-natural posture of the head and the arms may alter the spine kinematics and increase the muscular load on the low back extensor muscles. Twenty healthy young individuals participated in the laboratory experiment. Each participant walked on a treadmill in five different conditions: normal walking without using a phone, conducting one-handed browsing while walking, two-handed texting while walking, walking with one arm bound, and walking with both arms bound. Spine kinematics variables and the myoelectric activity levels of the lumbar erector spinae muscles were quantified and compared between the five walking conditions. Participants walked with significantly (P < 0.05) more thoracic kyphosis and lumbar lordosis when using a phone compared to when walking without using the phone. The median level of muscle activity was also 16.5% (browsing) to 31.8% (texting) greater for the two smartphone use conditions than for the normal walking condition, and the differences were significant (P < .05). Between the normal walking and the two bound arm walking conditions, no significant difference in the muscle activity was found. Study results show that the concurrent use of a smartphone while walking could pose a larger muscular load to the lumbar erector spinae muscles than that of normal walking. Habitual use of a smartphone while walking could be a risk factor for low back musculoskeletal problems.Level of Evidence: N/A.

Spatial distribution of lumbar erector spinae muscle activity in individuals with and without chronic low back pain during a dynamic isokinetic fatiguing task

BackgroundIndividuals with chronic low back pain (CLBP) commonly present with increased trunk muscle fatigability; typically assessed as reduced time to task failure during non-functional isometric contractions. Less is known about the specific neuromuscular responses of individuals with CLBP during dynamic fatiguing tasks. We investigate the regional alteration in muscle activation and peak torque exertion during a dynamic isokinetic fatiguing task in individuals with and without CLBP. MethodsElectromyography (EMG) was acquired from the lumbar erector spinae unilaterally of 11 asymptomatic controls and 12 individuals with CLBP, using high-density EMG (13 × 5 grid of electrodes). Seated in an isokinetic dynamometer, participants performed continuous cyclic trunk flexion-extension at 60o/s until volitional exhaustion. FindingsSimilar levels of muscle activation and number of repetitions were observed for both groups (p > 0.05). However, the CLBP group exerted lower levels of peak torque for both flexion and extension moments (p < 0.05). The centre of lumbar erector spinae activity was shifted cranially in the CLBP group throughout the task (p < 0.05), while the control participants showed a more homogenous distribution of muscle activity. InterpretationPeople with CLBP displayed altered and potentially less efficient activation of their lumbar erector spinae during a dynamic fatiguing task. Future studies should consider using high-density EMG biofeedback to optimise the spatial activation of the paraspinal musculature in people with low back pain (LBP).

The Effect of Adjusting Screen Height and Keyboard Placement on Neck and Back Discomfort, Posture, and Muscle Activities during Laptop Work

ABSTRACT Laptop work may increase risks of neck and back injuries in the long term due to awkward postures and increased mechanical loads on cervical and lumbar spine. This study was intended to compare the muscle activities and postural changes as well as discomfort of the neck and back resulted from the laptop work in a conventional and adjusted setup. 20 young healthy males performed two 8-min sessions of computer-mouse work and typing in a conventional setup and in an ergonomically adjusted setup during laptop work. In the adjusted setup, the screen height was individually adjusted by a riser and the keyboard was externally connected. The posture of the cervical, thoracic, lumbar spines, and shoulder, as well as electromyographic activity of cervical and lumbar erector spinae, multifidus, upper trapezius and anterior deltoid muscles, were recorded during the first and last 2 min of each computer work session. Having completed the computer work session, furthermore, the participants scored their neck, back, and general discomfort. The very research findings implied that adjusting the screen height and keyboard placement was effective during laptop work in reducing the cervical (−4.53 deg) and thoracic flexion angles (−3.14 deg) as well as the cervical erector spinae (−10.31%) and multifidus (−15.57%) muscle activities, and resulted in lower discomfort. The typing task was associated with higher muscle activity and awkward posture compared with the mouse work. As for workstation setup, simple modifications may reduce risk factors of musculoskeletal complaints.

Do inclined sleeping surfaces impact infants’ muscle activity and movement? A safe sleep product design perspective

The design of inclined sleep products may be associated with an increased risk of suffocation when an infant finds themselves prone in the product. It is important to understand how different inclined sleep surface angles impact infants’ muscle activity when considering a safe sleep environment. The purpose of this study was to assess muscle activity of healthy infants when they lie supine and prone on different inclined crib mattress surfaces (0° vs. 10° vs. 20°). Fifteen healthy infants were recruited for this study. Surface EMG was recorded from cervical paraspinal, abdominal, lumbar erector spinae, and triceps muscles for 60 s during supine and prone positioning. Repeated measures ANOVAs and Bonferroni post-hoc adjustments were performed to test the effect of incline angles. Paired t-tests were performed to test the effect of position (supine vs. prone). During prone lying, abdominal muscle activity increased by 33% and 71% for 10° and 20° compared to 0°, while erector spinae and triceps muscle activity decreased for 20° compared to 0°. Lumbar erector spinae and cervical paraspinal muscle activity increased by 185% and 283% for prone compared to supine lying. During prone positioning, the 20° inclined surface resulted in significantly higher muscle activity of the trunk core muscles (abdominals), which may exacerbate fatigue and contribute to suffocation if an infant cannot self-correct to the supine position. Compared to supine positioning, prone lying requires higher musculoskeletal effort to maintain a safe posture to prevent suffocation, and babies likely fatigue faster when lying prone.

Sex-Based Differences in Tensiomyography as Assessed in the Lower Erector Spinae of Healthy Participants: An Observational Study.

Although there is mounting evidence on sex-linked differences in paraspinal muscle function, it is unknown whether sex-based variations in mechanical and contractile characteristics of the lumbar erector spinae (LES) can be monitored noninvasively in healthy participants at rest using tensiomyography (TMG). Sex-specific effects in muscle displacement (Dm) and velocity of muscle deformation (Vd) will be observed via TMG assessed in the LES. Observational study. Level 3. LES response was measured in a relaxed state in 40 healthy adults (20 females). Possible differences between the conditions were investigated using mixed-model analyses of variance. Two-stage hierarchical linear regression analyses were performed to predict the outcome of TMG Dm and Vd based on participant sex. There were significant main effects of sex with large effect sizes for both TMG parameters, resulting from lower mean values in women compared with men (Dm, P < 0.01; Vd, P < 0.01). In contrast, neither the main effect of side (left vs right LES) nor the interaction between the side and sex reached significance (all P > 0.3). Introducing the sex variable in stage 2 of the regression analyses significantly improved the prediction of the TMG parameters (all ∆R2 ≥ 0.18; all P < 0.01; all f2 ≥ 0.29). Sex-based differences in muscle stiffness and contractile characteristics could be observed by TMG on LES muscles in healthy individuals at rest. The data suggest that these disparities are not exclusively attributable to anthropometric measures but may be linked to intrinsic sex-based differences in skeletal muscle characteristics. We recommend implementing TMG in a clinical setting using the obtained results as a basis to factor for the patient's biological sex when assessing effects of therapeutic/exercise regimens aiming at the optimization of myofascial tissue regeneration and performance.

The determination of the cross-sectional area of the lumbar erector spinae muscles of Olympic style weightlifting athletes by using MRI.

The study aims to measure the cross-sectional area of the lumbar erector spinae muscles from L3-L4 intervertebral disc levels by using magnetic resonance images of Olympic style weightlifting athletes (male n= 15, female n= 15) and sedentary individuals (male n= 15, female n= 15). A 1.5 Tesla device was used for the magnetic resonance imaging process of all participants. The images were then executed in ImageJ software and the cross-sectional area was measured after the required synchronization steps were conducted. On the images taken from L3-L4 intervertebral disc levels, we observed that right-left cross-sectional area measurements of erector spinae muscles of sedentary males and females in the control groups were smaller than those of male and female athletes in Olympic style weightlifting. We also found a symmetry between right-left cross-sectional area measurements of groups of athletes. From the study findings, we might conclude that trainings of Olympic style weightlifting possess a hypertrophic effect on the cross-sectional area of erector spinae muscles of Olympic style weightlifting athletes.

An ergonomic assessment of using laterally-tilting operating room tables and friction reducing devices for patient lateral transfers

Patient lateral transfers between two adjacent surfaces pose high musculoskeletal disorder risks for nurses and patient handlers. The purpose of this research was to examine the ergonomic benefits of utilizing the laterally-tilting function of operating room (OR) tables during such transfers – along with different friction-reducing devices (FRD). This method allows the patient to slide down to the adjacent surface as one nurse guides the transfer and another controls the OR table angle with a remote control. Sixteen nursing students and sixteen college students were recruited to act as nurses and patients, respectively. Two OR table angles were examined: flat and tilted. Three FRD conditions were considered: a standard blanket sheet, a plastic bag, and a slide board. Electromyography (EMG) activities were measured bilaterally from the posterior deltoids, upper trapezii, latissimus dorsi, and lumbar erector spinae muscles. The Borg-CR10 scale was used for participants to rate their perceived physical exertions. The efficiency of each method was measured using a stopwatch. Results showed that the tilted table technique completely replaced the physical efforts that would have been exerted by the pushing-nurse, in that muscle activation did not increase in the pulling-nurse. On the contrary, EMG activities of the pulling-nurse for most of the muscles significantly decreased (p < 0.05). The subjective Borg-ratings also favored the tilted table with significantly lower ratings. However, the tilted table required on average 7.22 s more than the flat table to complete the transfer (p < 0.05). The slide board and plastic bag were associated with significantly lower Borg-ratings and EMG activities for most muscles than blanket sheet, but they both were not significantly different from each other. However, they each required approximately 5 s more than the blanket sheet method to complete the patient transfer (p < 0.05). By switching from flat + blanket sheet to tilted + slide board, EMG activities in all muscles decreased in the range of 18.4–72.3%, and Borg-ratings decreased from about 4 (somewhat difficult) to 1 (very light). The findings of this study propose simple, readily available ergonomic interventions for performing patient lateral transfers that can have significant implications for nurses’ wellbeing and efficiency.

Relationship Between Hamstring Flexibility and Extensor Muscle Activity During a Trunk Flexion Task

ObjectiveThe purpose of this study was to investigate the relationship between hamstring flexibility and electromyography (EMG) muscle parameters in back and lower limb extensor muscles during a trunk flexion task. MethodsThirty healthy women aged 18 to 30 years with normal hip movement were recruited for this study. Hamstring muscle flexibility was measured with the 90-90 active straight leg raise test. Surface EMG activities were simultaneously recorded from the lumbar erector spinae, gluteus maximus, biceps femoris, semitendinosus, lateral gastrocnemius, and medial gastrocnemius muscles during forward bending. Muscle activity onset and offset, amplitude, and duration were calculated with technical computer software (MATLAB, version 1.6.0). Linear regression analysis was used to investigate the relationships between hamstring flexibility test results and EMG parameters during trunk flexion. In addition, the Friedman test was used to determine the recruitment activity pattern in women with low versus normal hamstring flexibility. ResultsDuring flexion, the back extensor muscles in individuals with lower hamstring flexibility test scores were activated and deactivated later, which can lead to delayed flexion-relaxation. Regression analysis did not disclose any significant correlations between hamstring flexibility and other EMG parameters (duration and amplitude) in back extensor muscles. Activation and deactivation recruitment patterns differed between the groups with normal and low hamstring flexibility. ConclusionThe findings of this study suggest that hamstring flexibility plays an important role in the patterns of trunk and lower limb muscle activity onset, offset, and recruitment.

Office Chair Backrest Height Affects Physiological Responses to Sitting

OCCUPATIONAL ABSTRACTProlonged static sitting has been associated with a number of negative health consequences. In prior work investigating office seating designs, the main focus has been on lumbar supports and backrest recline angles. To date, however, there is very limited information on the impact of backrest height on physiologic responses to sitting. Thus, the primary focus of this study was to assess muscular and postural responses to changing backrest height, across various postures, in a standardized office chair. The use of a Tall backrest resulted in significantly more lumbar spine flexion and lumbar erector spinae muscle activation but facilitated a more neutral neck posture. Results from this investigation demonstrate that office chair backrest height influences both posture and muscle activity responses and thus should be a consideration when designing office seating.

Design, Implementation and Preliminary Testing of a Novel Orthosis for Reducing Erector Spinae Muscle Activity, and Improving Balance Control for Hyperkyphotic Elderly Subjects

Background: Aging often results in thoracic kyphosis and adverse postural changes. This may interfere with physiologic activity of paraspinal muscles. Few styles of spinal orthosis have been already used to reduce thoracic kyphosis. This paper describes the development of a novel orthosis, which is designed based on the anatomy of the back muscles. This novel orthosis may potentiate muscle activity and balance control among older hyper kyphotic subjects.Objectives: The object of this study was to design and preliminary testing of a new orthosis to potentiate muscle activity and balance control among older hyper kyphotic subjectsMaterial and Methods: In this quasi-experimental study, a new postural control orthosis with a textile band structure was designed to provide an additional support for spine and muscles of the back. The functional impact of this orthosis was evaluated in six older hyper-kyphotic subjects. According to the results, the paraspinal muscles activity and balance control were significantly improved.Results: The RMS sEMG of the lumbar and thoracic erector spinae muscles reduced significantly (p<0.05), and a significant improvement (p<0.05) was observed in the balance test when patients put on the novel orthosis (p<0.05).Conclusion: The new orthosis can considerably improve the paraspinal muscles activity at both the upper and lower lumbar levels. It can also recover balance control among elderly subjects

Evaluation of the Results of Rehabilitation of Chronic Low Back Pain Syndrome in Physically Active and Inactive Patients During Leisure Time

Introduction: Movement is one of the main, modifiable factors (behaviour-dependent) that affects the health and quality of life of individuals and the entire population. Physical activity, including evidence-based active rehabilitation, is the subject of many studies on the prevention and treatment of spinal disorders, which are some of the most serious health problems. The largest group of people with spinal disorders are patients suffering from Nonspecific Low Back Pain (ang. Nonspecific Low Back Pain – NLBP), with kinesitherapy having the widest application in the chronic pain phase. A significant part of the research is devoted to the problem of movement in patients with chronic non-specific low back pain (CNLBP). One physiotherapy treatment method used in chronic low back pain syndrome is the DBC method. It is based on a detailed functional diagnosis, answers given to a standardized questionnaire, individualized treatment plans and active exercises with spinal resistance using specialized DBC equipment. Aim: The aim of this study was to evaluate the influence of leisure-time physical activity on the results of the DBC functional restoration program in patients with chronic, non-specific, low back pain after outpatient rehabilitation. The researchers tested the hypothesis that patients with regular physical activity attained better results of functional restoration compared to physically inactive participants. M aterials and Methods: The research group was comprised of one-hundred forty-seven participants. All subjects suffered from low back pain syndrome lasting for a period of at least three months without neurological symptoms. All symptoms were non-specific. The subjects were divided into two groups. Group 1 was comprised of participants who undertake regular physical activity for more than 45-minutes per exercise session, at least twice a week. Participants in Group 2 did not undertake any physical activity other than that resulting from everyday activities. The study commenced with an interview and standardized DBC questionnaire to get participants’ subjective assessment of the following parameters: current level of pain, functional limitations and scale of depression. A clinical trial was conducted prior to the measurement of objective parameters in order to exclude radicular pain (Lasegue test). Next, the objective parameters were measured: bioelectric activity of the lumbar erector spinae muscles (ang. surfasce electromyography – sEMG) on the right and left side in two positions: standing upright and leaning forward with straight legs. Also, DBC devices were used to measure the following range of motion of the lumbo-thoracic spine: flexion, extension, rotation and lateral flexion/bending. Upon completing the tests (Test 1) both groups were subject to active DBC therapeutic treatment. The therapy consisted of 12 meetings carried out within a 6 week period. Each session lasted for 1.5 hours. When the treatments ended testing was repeated for each group (Test 2). Results: Mean values of functional parameters of the lumbar spine were calculated for both groups. Statistical significance was determined between the preliminary (Test 1) and final (Test 2) tests. All the objective parameters in Group 1 showed statistically significant improvement post-therapy. Different results were observed in Group 2 for participants who did not perform regular physical activity. Although all parameters improved, only some achieved statistical significance. Significance between the two groups was also studied at the beginning of the experiment (Test 1) and after its completion (Test 2). There results showed no statistically significant difference in values of some objective parameters prior to the treatment, while some parameters differed. The treatment achieved a statistically significant improvement in the “active” group compared to the “inactive” one in almost every tested parameter excluding the extension. Significant differences between the groups were observed in the subjective parameters such as: functional limitations (ADL) (ang. Activity of Daily Living – ADL) and level of depression both in the first and last tests. Conclusions: Patients with chronic non-specific low back pain syndrome who remain physically active in leisure time and participated in the 6-week DBC rehabilitation program achieved a statistically significant improvement in the functional parameters of the spine. Patients with chronic non-specific low back pain syndrome who remain physically active in leisure time and participated in the 6-week DBC rehabilitation program improved more in the objective and subjective functional parameters of the spine in comparison with the inactive participants. Active leisure time contributes to the efficacy of physiotherapy for people with low back disorders.

HDsEMG Activity of the Lumbar Erector Spinae in Violin Players: Comparison of Two Chairs.

This study compared an ergonomic alternative chair (A-chair) with a standard orchestra chair (O-chair) used by a group of 9 violin players. The features of the high-density surface EMG (HDsEMG) of the lumbar erector spinae muscles were used for the comparison. The violinists played the same pieces of music for 2 hrs without interruption on each chair in 2 different days, 1 week apart. HDsEMG was recorded for 20 s every 5 minutes using two electrode arrays of 16 × 8 electrodes each, one on each side of the spine and placed between the T11 and L4 levels. The sEMG was non-stationary and burst-like patterns were observed on 8 out of 9 violinists. The mean root mean square (RMS) and mean spectral frequency (MNF) value over the region of activity (ROA), the centroid of the ROA, the rates of change in time of the spatial mean of the RMS and MNF values, and the burst frequencies associated with the two chairs were compared. Statistically significant reductions of RMS were observed in each violinist between the O-chair and A-chair (range 11.80-78.36%). No significant changes of other spatial or spectral sEMG features were globally observed versus time or between chairs but were demonstrated by some subjects. It is concluded that the A-chair is associated with a decrease of the sEMG amplitude of the ESM without changes of the spatial and temporal patterns of muscle activation.

Effect of different ergonomic supports on muscle activity of dentists during posterior composite restoration.

BackgroundThe aim of this study was to evaluate the effect of different ergonomic supports on the muscle activity of two trunk muscles while a group of dentists performed a common dental procedure on a phantom head, divided into three tasks.MethodsA one-way repeated measures study (ANOVA) was conducted on a group of 36 dentists. The middle trapezius and lumbar erector spinae muscles were measured with and without the use of different ergonomic supports (ergonomic stool, magnification lenses and both) using a portable surface electromyography (sEMG) device. Intraclass correlation coefficients (ICCs) and the absolute standard error of measurement (SEM) were used to establish the reliability of the baseline measures without ergonomic supports.ResultsThe sEMG showed excellent ICCs (ranging from 0.92 to 0.99) and SEM. Bonferroni post hoc tests showed differences between the three ergonomic supports (p < 0.001) in both muscles studied. The lowest muscle activity measurement occurred with the isolated used of magnification lenses. The use of the ergonomic stool increased the muscle activity of the middle trapezius and lumbar erector spinae muscles to a greater extent than the magnification lenses. The combination of the ergonomic stool and the magnification lenses produced a different effect on each muscle.

Evaluation of Trunk-Supporting Exoskeleton

Trunk Supporting Exoskeletons are increasingly being evaluated in workplaces as viable ergonomic interventions for reducing the risk of back injuries. A series of trunk-supporting exoskeletons have been designed and built at the University of California at Berkeley and suitX. These exoskeletons decrease the forces on the wearer’s back at L5/S1 location. This article describes one of these exoskeletons, referred to as backX, and its evaluation method. backX is designed not only to reduce the forces and torques on the wearer’s back at L5/S1 location, but also to allow the wearer to perform all kinds of maneuvers such as walking, squatting, ascending and descending stairs, slopes and ladders, riding bicycles and driving trucks. This study finds that average muscle activities of the thoracic and lumbar erector spinae muscles among equal populations of male and female subjects, wearing backX while maintaining forward bending postures, are reduced by 75% and 56% respectively. The results of this study and extended field evaluations indicate that wearing backX minimizes the risk of back injuries among workers who repeatedly go through stooping, squatting, and bending postures for various tasks, such as lifting objects.