Association of low back pain with muscle stiffness and muscle mass of the lumbar back muscles, and sagittal spinal alignment in young and middle-aged medical workers

Lumbar multifidus layers stiffness at L5-S1 level in prone and sitting posture measured by shear wave elastography

BACKGROUND

Multifidus is an important lumbar muscle with distinct superficial and deep fibers responsible for torque production and stabilization, respectively. Its mechanical properties change when transitioning from lying to sitting positions, necessitating enhanced stability. It holds crucial clinical relevance to assess these layers separately, especially in the sitting posture, which demands increased neuromuscular control compared to the prone position.

OBJECTIVE

To compare lumbar multifidus stiffness in lying versus sitting postures, analyzing both superficial and deep layers.

METHODS

Supersonic Shear Imaging captured elastographic images from 26 asymptomatic volunteers in prone and seated positions.

RESULTS

Left multifidus shear modulus in lying: 5.98 ± 1.80/7.96 ± 1.59 kPa (deep/superficial) and sitting: 12.58 ± 4.22/16.04 ± 6.65 kPa. Right side lying: 6.08 ± 1.97/7.80 ± 1.76 kPa and sitting: 13.25 ± 4.61/17.95 ± 7.12 kPa. No side differences (lying p= 0.99, sitting p= 0.43). However, significant inter-postural differences occurred.

CONCLUSION

Lumbar multifidus exhibits increased stiffness in sitting, both layers affected, with superior stiffness in superficial versus deep fibers. Applying these findings could enhance assessing multifidus stiffness changes, for classifying tension-induced low back pain stages.

Is musculoskeletal pain associated with increased muscle stiffness? Evidence map and critical appraisal of muscle measurements using shear wave elastography

INTRODUCTION AND AIMS

Approximately 21% of the world's population suffers from musculoskeletal conditions, often associated with sensations of stiff muscles. Targeted therapy requires knowing whether typically involved muscles are objectively stiffer compared to asymptomatic individuals. Muscle stiffness is quantified using ultrasound shear wave elastography (SWE). Publications on SWE-based comparisons of muscle stiffness between individuals with and without musculoskeletal pain are increasing rapidly. This work reviewed and mapped the existing evidence regarding objectively measured muscle stiffness in musculoskeletal pain conditions and surveyed current methods of applying SWE to measure muscle stiffness.

METHODS

A systematic search was conducted in PubMed and CINAHL using the keywords "muscle stiffness", "shear wave elastography", "pain", "asymptomatic controls" and synonyms. The search was supplemented by a hand search using Google Scholar. Included articles were critically appraised with the AXIS tool, supplemented by items related to SWE methods. Results were visually mapped and narratively described.

RESULTS

Thirty of 137 identified articles were included. High-quality evidence was missing. The results comprise studies reporting lower stiffness in symptomatic participants, no differences between groups and higher stiffness in symptomatic individuals. Results differed between pain conditions and muscles, and also between studies that examined the same muscle(s) and pathology. The methods of the application of SWE were inconsistent and the reporting was often incomplete.

CONCLUSIONS

Existing evidence regarding the objective stiffness of muscles in musculoskeletal pain conditions is conflicting. Methodological differences may explain most of the inconsistencies between findings. Methodological standards for SWE measurements of muscles are urgently required.

Effects of high-frequency hyperthermia on the elastic modulus of the lumbar muscle in female athletes with low back pain: A randomized crossover trial

OBJECTIVE

To investigate the effects of capacitive and resistive monopolar radiofrequency (CRMF) on the shear elastic modulus of the multifidus and erector spinae muscles in female athletes with low back pain (LBP) and a history of LBP.

DESIGN

Randomized crossover trial.

SETTING

Academic institution.

PARTICIPANTS

Twenty female university athletes with LBP or a history of LBP were included.

INTERVENTIONS

All participants received CRMF, hotpack, and sham (CRMF without power) in a random order on the right side of the lumbar region. More than 2 days were allocated between the experiments to eliminate any residual effects.

MAIN OUTCOME MEASURES

The shear elastic moduli of the right multifidus and erector spinae were evaluated in the prone (rest) position while sitting with 35° trunk flexion (stretched) using shear wave ultrasound imaging equipment. The moduli were measured before, immediately after, and 30 minutes after the intervention.

RESULTS

Repeated-measures 2-way analysis of variance and post hoc analysis showed that the moduli of the CRMF group were significantly lower than those of the sham group in the stretched position immediately after intervention (P = .045). This difference diminished 30 minutes after the intervention (P = .920).

CONCLUSIONS

CRMF can be used to reduce the shear elastic modulus of the multifidus muscle in the short term. Further studies are warranted to determine how to provide longer effects.

TRIAL REGISTRATION

None.

Investigating scapula positioning in individuals with non-specific lower back pain: A preliminary study

INTRODUCTION

Low back pain (LBP) is an economic and physically disabling burden on individuals and society. With 70% of cases classed as non-specific, there is a need for further research into the causes and consequences associated. The involvement of postural balance in musculoskeletal conditions is gaining increasing interest in research and health practice. However, there is a lack of literature surrounding LBP and posture in distal segments of the body.

OBJECTIVE

The current study investigated scapula positioning in those with non-specific LBP.

METHODS

Scapula angle of rotation, scapula protraction, and scapula elevation were assessed in nine participants with chronic non-specific LBP and compared with that of nine asymptomatic controls (aged 18-60 years). The degree of pelvic tilt was assessed across both groups as a secondary outcome measure.

RESULTS

No difference was identified between the two sample groups for scapula angle of rotation (p = 0.707), protraction (p = 0.755), or elevation (p = 0.691). Anterior pelvic tilt was greater in those with LBP (p = 0.046), supporting previous literature.

CONCLUSION

The findings for the scapula position are novel, given that research in this field is limited. It is concluded that there is no change in scapula positioning in those with non-specific LBP, but there is an increased anterior pelvic tilt.

Changes of trunk muscle stiffness in individuals with low back pain: a systematic review with meta-analysis

BACKGROUND

Low back pain (LBP) is one of the most common musculoskeletal conditions. People with LBP often display changes of neuromuscular control and trunk mechanical properties, including trunk stiffness. Although a few individual studies have examined back muscle stiffness in individuals with LBP, a synthesis of the evidence appears to be lacking. Therefore, the aim of this systematic review with meta-analysis was to synthesize and evaluate the available literature investigating back muscle stiffness in association with LBP.

METHODS

We conducted a systematic review of the literature according to the PRISMA guidelines. We searched Pubmed, Scopus, Web of Science and ScienceDirect for studies, that compared back muscle stiffness, measured either by ultrasound-based elastography or myotonometry, between individuals with and without LBP. Pooled data of the included studies were presented descriptively. Additionally, we performed two meta-analyses to calculate the standardized mean difference between the two groups for resting stiffness of the multifidus and erector spinae muscle. For both meta-analyses, the random effect model was used and the weight of individual studies was calculated using the inverse-variance method. The quality of the included studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional studies. Furthermore, the certainty of evidence was evaluated using the GRADE approach.

RESULTS

Nine studies were included in our systematic review. Our results suggest that individuals with LBP have higher stiffness of the multifidus (SMD = 0.48, 95% CI: 0.15 - 0.81, p < 0.01; I2 = 48 %, p = 0.11) and erector spinae at rest (SMD = 0.37, 95% CI: 0.11 - 0.62, p < 0.01; I2 = 39 %, p = 0.14) compared to asymptomatic controls. On the other hand, the evidence regarding muscle stiffness during submaximal contractions is somewhat contradictory.

CONCLUSIONS

Based on the findings of this systematic review we conclude that people with LBP may have higher back muscle stiffness compared to asymptomatic controls. Addressing muscle stiffness might represent an important goal of LBP treatment. Nevertheless, our findings should be interpreted with extreme caution due to a limited quality of evidence, small number of included studies and differences in measurement methodology.

Differential Effects of Classical vs. Sports Massage on Erector Spinae and Upper Trapezius Muscle Stiffness: A Shear-Wave Elastography Study in Young Women

Classical and sports massages are commonly used interventions, but their comparative effects on muscle stiffness remain unclear. Classical massage is more general and uses light to moderate pressure, and its main purpose is relaxation. Sports massage, on the other hand, is more specialized and targets the unique needs of massaged individuals using moderate to firm pressure. This study aimed to evaluate the impacts of classical and sports massages on the stiffness of the erector spinae (ES) and upper trapezius (UT) muscles. Fifteen recreationally active young women, aged 22.9 ± 1.2 years, underwent a randomized cross-over study (with three conditions). Participants received either a five-minute classical or sports massage or a passive rest as a control on distinct days. Muscle stiffness was assessed using shear-wave elastography. The ES shear modulus displayed a significant time effect (p < 0.001; η2 = 0.515) without noticeable differences between the conditions, and the time × massage-type interactions approached statistical significance (F = 2.014; p = 0.073). There was also a large and statistically significant effect of the time on the UT (F = 11.127; p < 0.001; η2 = 0.443). We could not prove that classical and sports massages reduced muscle stiffness. The absence of significant differences might be attributed to the specific intervention parameters (massage duration of 5 min) and the small, only young women sample size. Given some tendencies towards significant effects, larger sample sizes are needed to further investigate this research question.

Comparison of the activation and mechanical properties of scapulothoracic muscles in young tennis players with and without scapular dyskinesis: an observational comparative study

BACKGROUND

In tennis athletes with scapular dyskinesis, the activation of the scapulothoracic muscles during serve is not known. Also, the mechanical properties (tone, elasticity, and stiffness) of the scapulothoracic muscles of the tennis athletes with scapular dyskinesis are likely to change. The study aimed to evaluate the activation of the scapulothoracic muscles while performing tennis serve and to determine the changes in the mechanical properties of the same muscles in young tennis athletes with scapular dyskinesis.

METHODS

Seventeen tennis athletes with scapular dyskinesis aged between 11 and 18 years (the scapular dyskinesis group) and age- and gender-matched 17 asymptomatic tennis athletes (the control group) were included in the study. Activation of scapulothoracic muscles (descending-transverse-ascending trapezius and serratus anterior) in the 3 phases (preparation, acceleration, and follow-through) of the serve was evaluated using surface electromyography, and the mechanical properties of the same muscles were measured at rest by myotonometry.

RESULTS

Ascending trapezius activation in the follow-through phase was lower in the scapular dyskinesis group compared with the control group (mean difference 95% confidence interval: -22.8 [-41.2 to -4.5]) (P = .017). The tone and stiffness of the transverse trapezius (P = .043 and P = .017, respectively) were higher, whereas the same parameters of the ascending trapezius were lower (P = .008 and P = .010, respectively) in the scapular dyskinesis group compared with the control group.

CONCLUSIONS

Activation of the ascending trapezius and the tone and stiffness of the transverse-ascending trapezius were altered in tennis athletes with scapular dyskinesis. Implementations to improve these changes can be included in the rehabilitation or training programs of young tennis athletes with scapular dyskinesis.

Evaluation of the Reproducibility of MR Elastography Measurements of the Lumbar Back Muscles

BACKGROUND

MR elastography (MRE) may provide quantitative imaging biomarkers of lumbar back muscles (LBMs), complementing MRI in spinal diseases by assessing muscle mechanical properties. However, reproducibility analyses for MRE of LBM are lacking.

PURPOSE

To assess technical failure, within-day and inter-day reproducibility, robustness with the excitation source positioning, and inter-observer agreement of MRE of muscles.

STUDY TYPE

Prospective.

SUBJECTS

Seventeen healthy subjects (mean age 28 ± 4 years; 11 females).

FIELD STRENGTH/SEQUENCE

1.5 T, gradient-echo MRE, T1-weighted turbo spin echo.

ASSESSMENT

The pneumatic driver was centered at L3 level. Four MRE were performed during two visits, 2-4 weeks apart, each consisting of two MRE with less than 10 minutes inter-scan interval. At Visit 1, after the first MRE, the coil and driver were removed, then reinstalled. The MRE was repeated. At Visit 2, following the first MRE, only the driver was moved down 5 cm. The MRE was repeated. Two radiologists segmented the multifidus and erector spinae muscles.

STATISTICAL TESTS

Paired t-test, analysis of variance, intraclass correlation coefficients (ICCs). P-values <0.05 were considered statistically significant.

RESULTS

Mean stiffness of LBM ranged from 1.44 to 1.60 kPa. Mean technical failure rate was 2.5%. Inter-observer agreement was excellent (ICC ranging from 0.82 [0.64-0.96] to 0.99 [0.98-0.99] in the multifidus, and from 0.85 [0.69-0.92] to 0.99 [0.97-0.99] in the erector spinae muscles). Within-day reproducibility was fair in the multifidus (ICC: 0.53 [0.47-0.77]) and good in the erector spinae muscles (ICC: 0.74 [0.48-0.88]). Reproducibility after moving the driver was excellent in both multifidus (ICC: 0.85 [0.69-0.93]) and erector spinae muscles (ICC: 0.84 [0.67-0.92]). Inter-day reproducibility was excellent in the multifidus (ICC: 0.76 [0.48-0.89]) and poor in the erector spinae muscles (ICC: 0.23 [-0.61 to 0.63]).

DATA CONCLUSION

MRE of LBM provides measurements of stiffness with fair to excellent reproducibility and excellent inter-observer agreement. However, inter-day reproducibility in the multifidus muscles indicated that the herein used MRE protocol may not be optimal for this muscle.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

The Relationship Between Low Back Pain and Sagittal Spinal Alignment and Back Muscle Mass in Korean Fishery Workers

OBJECTIVE

To investigate the relationship between low back pain (LBP) and sagittal spino-pelvic parameters along with the relationship between LBP and back muscle mass in Korean male and female fishery workers.

METHODS

This retrospective study included a total of 146 subjects who underwent Fishermen's health survey conducted between June 2018 and August 2020. LBP was evaluated through visual analogue scale (VAS) and Oswestry Disability Index (ODI). Sagittal spino-pelvic parameters were measured from whole spine standing X-rays. Back muscle cross-sectional areas were identified through lumbar spine magnetic resonance imaging and body composition was analyzed through bioelectrical impedance analysis.

RESULTS

The study included 75 males and 71 females, with an average age of 58.33 years for males and 56.45 years for females. Female subjects exhibited higher VAS and ODI scores, larger pelvic tilt (PT) and trunk fat mass and smaller trunk muscle mass compared to males. In female, ODI positively correlated with sagittal vertical axis (SVA) and PT. No significant correlations were found between ODI scores and body composition in either sex. The high ODI group showed greater SVA, PT, and pelvic incidence-lumbar lordosis and higher trunk fat/muscle ratio. Psoas muscle mass, total and skeletal muscle mass and trunk muscle mass of that group were smaller than those of low ODI group.

CONCLUSION

Spino-pelvic parameters and back muscle mass were associated with ODI and there were differences between Korean male and female fishery workers.

Correlation between Degenerative Thoracolumbar Kyphosis and Lumbar Posterior Muscle

The relationship between spinal alignment, particularly degenerative thoracolumbar kyphosis (DTLK) combined with lumbar spine stenosis (LSS), and paraspinal muscle content remains underexplored. This study aimed to elucidate the characteristics of paraspinal muscle distribution in DTLK patients and its association with lumbar lordosis (LL) and body mass index (BMI).

METHODS

A case-control study was conducted comparing 126 patients with DTLK and LSS against 87 control patients. The lumbar crossing indentation value (LCIV) was introduced as a novel measurement for paraspinal muscle content, and its relationship with thoracolumbar kyphosis (TLK), BMI, and LL was assessed.

RESULTS

LCIV in DTLK patients was found to be lower than in the control group, with a progressive increase from the upper to lower lumbar spine. In the control group, paraspinal muscle content was observed to increase with age and BMI, and LCIV was higher in males. However, the DTLK group showed no gender difference. LCIV in the DTLK group was more pronounced in patients with increased LL. The degree of TLK was not influenced by BMI but was associated with the content of the paravertebral muscle.

CONCLUSIONS

Paraspinal muscle content, as measured by LCIV, is significantly associated with DTLK and LSS. The study emphasizes the importance of considering paraspinal muscle health in DTLK patients and offers valuable insights for diagnosis and therapeutic interventions.

Effect of Self-Myofascial Release of the Lower Back on Myofascial Gliding, Lumbar Flexibility, and Abdominal Trunk Muscle Strength: A Crossover Study

Roller massage has been recognized as an effective intervention for managing various conditions. However, data on the effects of roller massage on the dynamic mechanisms of the myofascial and soft tissues of the lower back are limited. This study aimed to examine the effect of the self-myofascial release of the lower back on myofascial gliding, lumbar flexibility, and abdominal trunk muscle strength using a roller massager. This crossover study included 24 college athletes who underwent three interventions-roller massage, static stretching, and control (rest). Before and after the intervention, lumbar and fascial gliding were evaluated using ultrasonography. Long-seat anteflexion (lumbar flexibility) and abdominal trunk muscle strength were assessed. The movement velocities of the subcutaneous tissue and the multifidus muscle over time were calculated using echo video analysis software, and gliding was estimated using the cross-correlation coefficient between the velocities. Gliding, lumbar flexibility, and abdominal trunk muscle strength showed significant intervention-by-time interactions. Roller massage significantly improved gliding, lumbar flexibility, and abdominal trunk muscle strength. The self-myofascial release of the lower back using a roller massager improved the lumbar/fascia gliding, lumbar flexibility, and abdominal trunk muscle strength compared to static stretching.

Characteristics of upper limb mass, muscle CSA and stiffness in adolescent baseball players with and without elbow injury

Since elbow injuries are common in adolescent baseball players, this study aimed to determine the relationship between musculoskeletal status and elbow injuries in 47 baseball players aged 12-14 years. Participants answered a questionnaire and had their general body measurements taken. Magnetic resonance imaging was used to evaluate muscle cross sectional areas (CSA) of the upper arm flexor and extensor muscles, and x-ray absorptiometry was used to determine the mass of the upper arm and the total mass of the forearm and hand. Shear wave elastography was used to determine muscle stiffness of the biceps brachii, brachialis, pronator teres, and brachioradialis. An orthopedic surgeon performed a clinical assessment and elbow ultrasonography for each participant to diagnose elbow injuries. The measured values were compared between the elbow injury and control groups using two-sample t-tests. The elbow injury group had significantly higher muscle stiffness in the brachialis (p < 0.001) and brachioradialis (p = 0.004) muscles and greater elbow flexor CSA of the distal upper arm (p = 0.004) than the control group. The total mass of the forearm and hand and the mass ratio of the forearm and hand to the upper arm were significantly greater in the elbow injury group than in the control group (p = 0.002 and p < 0.001). Thus, it may be necessary to increase flexibility of the brachialis and brachioradialis flexible by stretching and massaging in addition to evaluating the mass distal to the elbow and the elbow flexor muscle size of the distal upper arm to manage elbow injury in youth baseball players. Characteristics of Upper Limb Mass, Muscle Cross-Sectional Area and Stiffness in Adolescent Baseball Players with and without Elbow Injury.

Lumbar multifidus muscle morphology is associated with low back-related pain duration, disability, and leg pain: A cross-sectional study in secondary care

BACKGROUND

Systematic reviews and studies exploring associations between morphologic change of paraspinal muscles and low back pain or related outcomes such as disability, radiculopathy, and physical workload, have reported conflicting results. This study explores the associations between lumbar multifidus muscle quality and clinical outcomes relating to low back pain.

METHODS

Cross-sectional study of spinal clinic outpatients presenting with a primary complaint of low back and/or leg symptoms. Univariable and multivariable regression models were used to investigate associations between MRI-based multifidus muscle cross-sectional area at L4 and L5 and clinical outcomes for low back pain, leg pain, disability, restricted motion, and strenuous nature of work. Results were reported with β-coefficients, odds ratios (OR), or incidence rate ratios (IRR) and their corresponding 95% confidence intervals, based on a 10% difference in muscle quality for each clinical variable. Multivariable analyses were adjusted for age, sex, and BMI.

RESULTS

875 patients [487 females; mean (SD) age: 43.6 (10.2) years] were included. In the multivariable analyses, muscle quality was significantly associated with disability (0-23 scale) [β: -0.74, 95% CI: -1.14, -0.34], leg pain intensity (0-10 scale) [β: -0.25, 95% CI: -0.46, -0.03], and current pain duration of more than 12 months [OR: 1.27, 95% CI: 1.03, 1.55]. No associations were found for low back pain intensity, morning stiffness, painful active range of motion, or work nature.

CONCLUSIONS

Patients with higher lumbar multifidus muscle quality reported lower levels of low back pain-related disability and leg pain intensity, indicating that muscle quality may play a role in the etiology of lumbar spine disorders. However, the clinical importance of these associations is uncertain due to the low magnitude of identified associations. Future longitudinal studies are needed to understand the effect of lumbar multifidus muscle quality on lumbar-related pain and disability.

Differences in the elastic modulus of the lumbar muscles between female athletes with and without low back pain

BACKGROUND

Low back pain is the most prevalent musculoskeletal disorder affecting performance and sports participation among athletes and is more prevalent among female athletes. Evaluating the stiffness of the lumbar muscles is important for understanding the pathophysiology of low back pain. Therefore, this study examined the differences in stiffness of the lumbar multifidus and erector spinae muscles between female university athletes with and without low back pain.

METHODS

This was a cross-sectional study. The study was conducted at a single centre, the university research laboratory. Twenty female university athletes with low back pain or a history of low back pain and 20 without low back pain participated in this study. The shear elastic moduli of the multifidus and erector spinae muscles were evaluated in the prone (to relax the muscles) and sitting with 35° of trunk flexion (to stretch the muscles) positions using shear wave ultrasound imaging equipment.

FINDINGS

The low back pain group showed significantly greater shear elastic modulus in the multifidus in both prone and sitting positions than the non-low back pain group. There were no differences in the erector spinae muscle between the two groups at either position.

INTERPRETATION

These results provide new insights into the microscopic characteristics of low back pain pathophysiology in young female athletes. Stiffness assessment using shear wave elastography will help provide a specific treatment strategy for female athletes with low back pain or a history of low back pain.

Cervical and axioscapular muscle stiffness measured with shear wave elastography: A comparison between different levels of work-related neck disability

Assessing muscle mechanical properties in terms of stiffness may provide important insights into mechanisms underlying work-related neck pain. This study compared stiffness of cervical and axioscapular muscles between 92 participants (sonographers) with no (n = 31), mild (n = 43) or moderate/severe (n = 18) neck disability. It was hypothesized that participants with more severe neck pain and disability would present with altered distribution of stiffness in cervical and axioscapular muscles than those with no disability. Using shear wave elastography, the shear modulus (kPa) of five cervical and six axioscapular muscles or muscle segments were measured in a relaxed seated upright or side-lying position. Muscle activity was measured simultaneously using surface electromyography during the elastography measurements and scapular depression was measured using a measurement tape and inclinometer before the elastography measurements to evaluate their potential confounding influences on shear modulus. Increased shear modulus was found in deeper than superficial cervical muscles and more cranial than caudal axioscapular muscles. However, no differences in shear modulus of the cervical or axioscapular muscles were found between sonographers with varying levels of disability. This study suggests no alterations in stiffness of cervical and axioscapular muscles were associated with work-related neck pain and disability.

Foam Rolling Acute Effects on Myofascial Tissue Stiffness and Muscle Strength: A Systematic Review and Meta-Analysis

ABSTRACT

Glänzel, MH, Rodrigues, DR, Petter, GN, Pozzobon, D, Vaz, MA, and Geremia, JM. Foam rolling acute effects on myofascial tissue stiffness and muscle strength: a systematic review and meta-analysis. J Strength Cond Res 37(4): 951-968, 2023-Foam rolling (FR) is widely used in rehabilitation and physical training. However, the effects of FR on myofascial tissue stiffness and muscle strength remain unclear. This study aimed to perform a systematic review with meta-analysis of trials that tested the FR acute effects during warm-up on the myofascial tissue stiffness and muscle strength in healthy adults or athletes. This systematic review (CRD42021227048) was performed according to Cochrane's recommendations, with searches performed in PubMed, Web of Science, Embase, and PEDro databases. Syntheses of included studies' data were performed, and the PEDro scale was used to assess the methodological quality of the studies. Certainty of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluations approach. Twenty included studies assessed trunk and thigh fascial tissue stiffness, and thigh and calf muscle stiffness, whereas muscle strength was assessed in the knee extensors and flexors, and plantar flexors muscles. Qualitative analysis showed decreases in fascial ( n = 2) and muscle ( n = 5) stiffness after FR. However, the meta-analysis showed no effects of FR on myofascial tissue stiffness. Both qualitative and quantitative analyses showed no effects of FR on isometric muscle strength, eccentric torque, and rate of force development. However, the knee extensor concentric torque increased after FR. Foam rolling increases the knee extensor concentric torque, but it does not acutely change the myofascial tissue stiffness and isometric muscle strength. However, evidence of these studies provides low certainty to state that FR does not change these parameters. Therefore, high methodological quality studies should be performed to better ascertain the effects of FR on the myofascial tissue stiffness and muscle strength.

The Utility of Myotonometry in Musculoskeletal Rehabilitation and Human Performance Programming

Myotonometry is a relatively novel method used to quantify the biomechanical and viscoelastic properties (stiffness, compliance, tone, elasticity, creep, and mechanical relaxation) of palpable musculotendinous structures with portable mechanical devices called myotonometers. Myotonometers obtain these measures by recording the magnitude of radial tissue deformation that occurs in response to the amount of force that is perpendicularly applied to the tissue through a device's probe. Myotonometric parameters such as stiffness and compliance have repeatedly demonstrated strong correlations with force production and muscle activation. Paradoxically, individual muscle stiffness measures have been associated with both superior athletic performance and a higher incidence of injury. This indicates optimal stiffness levels may promote athletic performance, whereas too much or too little may lead to an increased risk of injury. Authors of numerous studies suggested that myotonometry may assist practitioners in the development of performance and rehabilitation programs that improve athletic performance, mitigate injury risk, guide therapeutic interventions, and optimize return-to-activity decision-making. Thus, the purpose of our narrative review was to summarize the potential utility of myotonometry as a clinical tool that assists musculoskeletal clinicians with the diagnosis, rehabilitation, and prevention of athletic injuries.

Binary classification of non-specific low back pain condition based on the combination of B-mode ultrasound and shear wave elastography at multiple sites

Introduction: Low back pain (LBP) is a prevalent and complex condition that poses significant medical, social, and economic burdens worldwide. The accurate and timely assessment and diagnosis of LBP, particularly non-specific LBP (NSLBP), are crucial to developing effective interventions and treatments for LBP patients. In this study, we aimed to investigate the potential of combining B-mode ultrasound image features with shear wave elastography (SWE) features to improve the classification of NSLBP patients. Methods: We recruited 52 subjects with NSLBP from the University of Hong Kong-Shenzhen Hospital and collected B-mode ultrasound images and SWE data from multiple sites. The Visual Analogue Scale (VAS) was used as the ground truth to classify NSLBP patients. We extracted and selected features from the data and employed a support vector machine (SVM) model to classify NSLBP patients. The performance of the SVM model was evaluated using five-fold cross-validation and the accuracy, precision, and sensitivity were calculated. Results: We obtained an optimal feature set of 48 features, among which the SWE elasticity feature had the most significant contribution to the classification task. The SVM model achieved an accuracy, precision, and sensitivity of 0.85, 0.89, and 0.86, respectively, which were higher than the previously reported values of MRI. Discussion: In this study, we aimed to investigate the potential of combining B-mode ultrasound image features with shear wave elastography (SWE) features to improve the classification of non-specific low back pain (NSLBP) patients. Our results showed that combining B-mode ultrasound image features with SWE features and employing an SVM model can improve the automatic classification of NSLBP patients. Our findings also suggest that the SWE elasticity feature is a crucial factor in classifying NSLBP patients, and the proposed method can identify the important site and position of the muscle in the NSLBP classification task.

The Effects of Isometric Fatigue on Trunk Muscle Stiffness: Implications for Shear-Wave Elastography Measurements

Muscle stiffness has been implicated as a possible factor in low back pain risk. There are few studies on the effects of isometric fatigue on the shear modulus of trunk muscles. This study aimed to investigate the effects of trunk isometric fatigue on the passive and active (during low and high-level contractions) shear moduli of the erector spinae (ES) and superficial and deep multifidus (MF) muscles. We assessed passive and active shear modulus using shear-wave elastography in healthy young participants (n = 22; 11 males, 11 females), before and after an isometric trunk extension fatigue protocol. Maximal voluntary force decreased from 771.2 ± 249.8 N before fatigue to 707.3 ± 204.1 N after fatigue (-8.64%; p = 0.003). Passive shear modulus was significantly decreased after fatigue in the MF muscle (p = 0.006-0.022; Cohen's d = 0.40-46), but not the ES muscle (p = 0.867). Active shear modulus during low-level contraction was not affected by fatigue (p = 0.697-0.701), while it was decreased during high-level contraction for both muscles (p = 0.011; d = 0.29-0.34). Sex-specific analysis indicated the decrease in ES shear modulus was significant in males (p = 0.015; d = 0.31), but not in females (p = 0.140). Conversely, the shear modulus in superficial MF had a statistically significant decrease in females (p = 0.002; d = 0.74) but not in males (p = 0.368). These results have important implications for further investigations of the mechanistic interaction between physical workloads, sex, muscle stiffness (and other variables affecting trunk stability and neuromuscular control), and the development/persistence of low back pain.

Application of Shear-Wave Elastography in the Evaluation of Hamstring Stiffness in Young Basketball Athletes

Background

Previous literature has postulated a relationship between greater hamstring stiffness and a higher risk of sustaining injury. Shear wave elastography (SWE) presents a relatively new means for non-invasive evaluation of soft tissue elasticity pre- and post- injury or intervention.

Purpose

1. To establish baseline hamstring stiffness measures for young competitive athletes and (2) determine effect of targeted neuromuscular training (TNMT) on shear wave stiffness of the hamstring.

Study Design

Un-blinded, prospective, non-randomized, cohort study.

Methods

Six-hundred forty-two lower extremities from 321 high school and collegiate basketball athletes (177 F: 139 M) were examined for hamstring stiffness prior to the start of their competitive basketball season. Teams were cluster assigned to either the control or intervention (TNMT) group. Subjects in the control group underwent regular season activities as directed, with no influence from the research team. For the TNMT group, the research team introduced a hamstring targeted dynamic warm-up program as an intervention focused on activating the hamstring musculature.

Results

Collegiate status was significant to hamstring stiffness for both sexes (p ≤ 0.02), but hamstring stiffness did not correlate to age or sex (r2 ≤ 0.08). Intervention was a significant factor to hamstring stiffness when the hip was positioned in extension (p ≤ 0.01), but not in deeper flexion (p = 0.12). This effect was sex-specific as TNMT influenced hamstring stiffness in females (p = 0.03), but not in males (p ≥ 0.13). Control athletes suffered three HAM injuries; TNMT athletes suffered 0 hamstring injuries.

Conclusion

Higher SWE measurements correlated with increased risk of injury, male sex, and collegiate athletics. TNMT intervention can lessen muscle stiffness which may reduce relate to injury incidence. Intervention effectiveness may be sex specific.

Level of Evidence

II.

Increased Surgical Experience in Microendoscopic Spinal Surgery Can Reduce Development of Postoperative Spinal Epidural Hematoma and Improve the Clinical Outcomes

No reports have previously evaluated the association between surgical technique and the incidence of postoperative spinal epidural hematoma (PSEH) following microendoscopic decompression surgery (MED). This study aimed to evaluate the association between the development of radiographic PSEH (rPSEH) following MED and microendoscopic surgical experience and postoperative clinical outcomes related to the quality of life (QoL). This retrospective cohort study included 3922 patients who had undergone MED performed by a single surgeon. rPSEH was defined as a hematoma that was identified via routine magnetic resonance images performed 3−4 days postoperatively. Patients were divided into rPSEH and control groups to identify the risk factor of rPSEH and assess clinical outcomes. In the multivariate analysis, age (p = 0.002), surgical experience (p = 0.003), surgical time (p = 0.038), multilevel decompression (p < 0.001), and diagnosis (p = 0.004) were identified as independent variables associated with rPSEH. Moreover, in mixed-effect models, the rPSEH group showed less improvement in Oswestry Disability Index (p = 0.014) than the control group. In conclusion, the surgical experience was identified as a risk factor for rPSEH that could lead to poor QoL. The sharing of microendoscopic surgical techniques among surgeons may reduce rPSEH incidence and improve patients’ QoL.

High elasticity of the flexor carpi ulnaris and pronator teres muscles is associated with medial elbow injuries in youth baseball players

OBJECTIVES

The purpose of the present study was to measure the elasticities of the forearm flexor-pronator muscles in youth baseball players and examine their relationships with medial elbow injuries.

METHODS

We examined the strain ratios (SR) of the flexor digitorum superficialis (FDS), flexor carpi ulnaris (FCU), and pronator teres (PT) in 89 youth baseball players with medial epicondylar fragmentation (injury group) and in 142 healthy baseball players (control group). An index of muscle elasticity was determined using ultrasound strain elastography. The SR of each muscles was compared between the injury and control groups, and the SR of the both side arms was compared within group. Moreover, multivariable logistic regression analyses were conducted to examine the association of forearm muscle elasticity with medial elbow injuries.

RESULTS

The SR of the FCU and PT of the throwing arm were significantly higher in the injury group than in the control group (both P < .001). In the injury group, the SR of the FCU was higher in the throwing arm than in the non-throwing arm (P < .001), but no difference was noted for the PT. Multivariable logistic regression analyses showed that a 0.1 increase of the SR of the FCU of the throwing arm (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.14-1.48) and PT of the throwing arm (OR 1.41, 95% CI 1.19-1.67) and the non-throwing arm (OR 1.31, 95% CI 1.12-1.54) was significantly associated with an increased prevalence of medial elbow injuries.

CONCLUSION

High elasticities of the FCU of the throwing arm and PT of both the arms were observed in individuals with medial elbow injuries, and were associated with increased prevalence of medial elbow injuries. These findings may be characteristic of medial elbow injuries in youth baseball players.

Quantifying the stiffness of lumbar erector spinae during different positions among participants with chronic low back pain

Objective

The purposes of this study were to (1) detect the intra- and inter-reliabilities of the lumbar erector spinae stiffness by MyotonPRO among participants with chronic lower back pain (CLBP); (2) compare the muscle stiffness between pain and non-pain sides during different positions; (3) explore the correlation between intensity of pain and muscle stiffness.

Design

Twenty participants with CLBP were recruited and the stiffness measurements were carried out by two experienced physiotherapists (operators Ⅰ and Ⅱ). Each participant was evaluated by the operatorⅠ in different postures (static prone and sitting). After a 5-day interval, the same participant was reassessed by the operatorⅠ in the static prone posture. For the inter-rater reliability test, each participant was quantified by both operators once, with 30 minutes between the measurements on the same day. The intensity of pain was evaluated using a 0–10 visual analog scale (VAS).

Results

The intra- and inter-rater reliabilities were excellent (ICC = 0.88–0.99). The MDC values ranged from 25.03 to 86.26 N/m. Examples of Bland-Altman plots showed good agreement. The erector spinae stiffness on the painful sides was higher with a marked increase in the sitting position (P < .05) when compared with the non-painful side. However, there was no significant difference in the prone position (P > .05). The intensity of pain among adults with CLBP was not associated with muscle stiffness of the lumbar erector spinae muscle.

Conclusions

Our findings indicated that the MyotonPRO is a feasible device in quantifying the stiffness of the lumbar erector spinae muscle in patients with CLBP. Meanwhile, the erector spinae stiffness on the painful sides was higher in the sitting when compared with the non-painful side.

Biomechanical Properties of Paraspinal Muscles Influence Spinal Loading—A Musculoskeletal Simulation Study

Paraspinal muscles are vital to the functioning of the spine. Changes in muscle physiological cross-sectional area significantly affect spinal loading, but the importance of other muscle biomechanical properties remains unclear. This study explored the changes in spinal loading due to variation in five muscle biomechanical properties: passive stiffness, slack sarcomere length (SSL), in situ sarcomere length, specific tension, and pennation angle. An enhanced version of a musculoskeletal simulation model of the thoracolumbar spine with 210 muscle fascicles was used for this study and its predictions were validated for several tasks and multiple postures. Ranges of physiologically realistic values were selected for all five muscle parameters and their influence on L4-L5 intradiscal pressure (IDP) was investigated in standing and 36° flexion. We observed large changes in IDP due to changes in passive stiffness, SSL, in situ sarcomere length, and specific tension, often with interesting interplays between the parameters. For example, for upright standing, a change in stiffness value from one tenth to 10 times the baseline value increased the IDP only by 91% for the baseline model but by 945% when SSL was 0.4 μm shorter. Shorter SSL values and higher stiffnesses led to the largest increases in IDP. More changes were evident in flexion, as sarcomere lengths were longer in that posture and thus the passive curve is more influential. Our results highlight the importance of the muscle force-length curve and the parameters associated with it and motivate further experimental studies on in vivo measurement of those properties.

[Feeling stiff…but what does it mean objectively? : Can you measure muscle tension?]

Almost everyone is familiar with "tense muscles", but what is muscle tension physiologically behind? Are tense muscles more active; do they have problems relaxing? Are they harder or stiffer than asymptomatic muscles? In this work, current evidence regarding the activity and stiffness of tense neck muscles is presented. Further, measurement methods and their limitations are explained. These limitations reveal the shortcomings of the current knowledge and the need for further research. Finally, a recently funded research project on the measurement of tense muscles is presented.

Asymmetric Biomechanical Properties of the Paravertebral Muscle in Elderly Patients With Unilateral Chronic Low Back Pain: A Preliminary Study

Background: Clinical incidences of chronic low back pain among the elderly are increasing. However, studies have not fully elucidated on changes in biomechanical properties of paravertebral muscles in patients with unilateral chronic low back pain. We evaluated the changes in biomechanical properties of painful and non-painful paravertebral muscles in elderly patients with unilateral chronic low back pain.

Methods: Biomechanical properties of paravertebral muscles, including muscle tone and stiffness, in elderly patients with unilateral chronic low back pain were measured using MyotonPRO. Lumbar Lordosis and Sacral Slope were measured by magnetic resonance imaging. Cross-sectional areas of paravertebral muscles were evaluated using ImageJ software version 1.53. Chronic low back pain severity was assessed by Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores. The correlations between VAS scores, ODI scores, Lumbar Lordosis, Sacral Slope, cross-sectional areas (painful side), disease duration, and biomechanical properties of paravertebral muscles in the painful side were analyzed.

Results: A total of 60 elderly patients with unilateral chronic low back pain were enrolled in this study. The muscle tone and stiffness of paravertebral muscles on the painful side were significantly higher than those on the non-painful side (p &lt; .05). Cross-sectional areas of paravertebral muscles on the painful side at the L3 level were smaller than those of the non-painful side (p &lt; .05). The VAS scores and ODI scores were significantly positively correlated with muscle tone and stiffness of paravertebral muscles on the painful side (p &lt; .05 and p &lt; .01, respectively). There were no significant correlations between disease duration, cross-sectional areas (painful side), Lumbar Lordosis, or Sacral Slope and muscle tone and stiffness of paravertebral muscles on the painful side (p &gt; .05).

Conclusion: In elderly patients with unilateral chronic low back pain, muscle tone and stiffness of paravertebral muscles on the painful side are higher than for those on the non-painful side. The asymmetry of biomechanical properties of paravertebral muscles is associated with severity of chronic low back pain.

In Hamstring Muscles of Patients With Knee Osteoarthritis an Increased Ultrasound Shear Modulus Indicates a Permanently Elevated Muscle Tonus

Background

Some patients with knee osteoarthritis (KOA) show pain, stiffness and limited flexion and extension at the back of the knee, leading to dysfunction and affecting life. This may be related to changes in the biomechanical properties of skeletal muscles. Shear wave elastography (SWE) can detect these changes by measuring muscle shear modulus.

Aims

To investigate hamstring muscle shear modulus of healthy people and patients was studied using SWE method, and the correlation analysis between the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score of patients’ subjective feeling and shear modulus of objective quantification was conducted.

Methods

The hamstring shear modulus was measured by SWE in 50 patients and 50 healthy individuals. Pearson correlation coefficient was used to evaluate the correlation between hamstring stiffness and shear modulus in patients.

Results

The hamstring shear modulus were significantly higher in the KOA group [the semimembranosus (SM) 15.23 ± 7.23, the semitendinosus (ST) 15.94 ± 5.40, the biceps femoris long tendinitis (BFL) 14.21 ± 6.55] than in the control group (the SM 10.95 ± 2.41, the ST 11.25 ± 2.23, the BFL 9.98 ± 2.81) (p = 0.000, p = 0.000, p = 0.001). The hamstring shear modulus in the KOA group was moderately positively correlated with pain, shear modulus, and physical function score.

Conclusion

Preliminary results show that the shear modulus of the hamstring of KOA patients is higher than that of healthy people, the WOMAC score and the shear modulus of patients are moderately correlated. These preliminary results show that ultrasonic shear wave elastography measurement of shear modulus may be enough to sensitive, can detect these effects, more targeted in order to assist the doctor’s diagnosis and treatment.

Influence of Spinal Movements Associated with Physical Evaluation on Muscle Mechanical Properties of the Lumbar Paraspinal in Subjects with Acute Low Back Pain

This research aimed to identify changes in muscle mechanical properties (MMPs) when a standardized sequence of movements is performed and to determine the influence of acute low back pain (LBP) and age on the MMPs. Socio-demographic, clinical variables and MMPs were collected in 33 patients with LBP and 33 healthy controls. A 2 × 2 × 2 (group × age × time) analysis of variance (ANOVA) mixed model was used to determine the effect of the study factors on the different MMPs. There were no significant triple interactions. After the movements, tone and stiffness increased 0.37 Hz and 22.75 N/m, respectively, in subjects <35 years, independent of their clinical status. Relaxation showed differences by age in healthy subjects and creep in LBP subjects. Furthermore, elasticity was higher in <35 years (p < 0.001) without the influence of any other factor. In conclusion, sequenced movements can modify tone and stiffness as a function of age, while age-associated changes in viscoelastic characteristics depends on pain but not on movements. The MMPs should be assessed, not only at the beginning of the physical examination at rest, but also along the patient’s follow-up, depending on their pain and age, in a clinical setting.

Are Morphometric and Biomechanical Characteristics of Lumbar Multifidus Related to Pain Intensity or Disability in People With Chronic Low Back Pain After Considering Psychological Factors or Insomnia?

INTRODUCTION

Lumbar multifidus muscle (LMM) dysfunction is thought to be related to pain and/or disability in people with chronic low back pain (CLBP). Although psychosocial factors play a major role in pain/disability, they are seldom considered as confounders in analyzing the association between LMM and CLBP.

OBJECTIVES

This study aimed to determine: (1) differences in psychological factors, insomnia, and LMM characteristics between people with and without CLBP; (2) associations between psychological factors, insomnia, or LMM characteristics and low back pain (LBP) intensity or LBP-related disability in people with CLBP; and (3) whether LMM characteristics are related to LBP symptoms in people with CLBP after considering confounders.

METHODS

Seventy-eight volunteers with CLBP and 73 without CLBP provided sociodemographic information, filled the 11-point numeric pain rating scale and Roland-Morris disability questionnaire (RMDQ). They completed the Hospital Anxiety and Depression Scale (HADS), Pain Catastrophizing Scale (PCS), Fear Avoidance Belief Questionnaire (FAB), and Insomnia Severity Index Scale (ISI). Resting and contracted thickness of LMM at L4-S1 levels were measured from brightness-mode ultrasound images. Percent thickness changes of LMM at L4-S1 levels during contraction were calculated. Resting LMM stiffness at L4-S1 was measured by shear wave elastography. Associations among LMM, psychosocial or insomnia parameters and clinical outcomes were analyzed by univariate and multivariate analyses.

RESULTS

People with CLBP demonstrated significantly higher LBP-intensity, RMDQ, HADS, FAB, PCS, and ISI scores than asymptomatic controls (p < 0.05). The former also had significantly smaller percent thickness changes of LMM at L4/L5 during contraction. LBP-intensity was positively related to scores of PCS-total, PCS-helplessness, FAB-total, FAB-work, and ISI in people with CLBP (p < 0.05). RMDQ scores were positively associated with the scores of HADS-total, HADS-depression, PCS-total, FAB-total, FAB-physical activity, PCS-helplessness, and ISI in people with CLBP (p < 0.05). FAB-work and ISI scores together explained 24% of LBP-intensity. FAB-total scores alone explained 34% of variance of LBP-related disability in people with CLBP.

CONCLUSION

More fear-avoidance belief or insomnia is related to greater LBP-intensity and/or LBP-related disability in people with CLBP. Although people with CLBP were thought to have aberrant LMM morphometry/function, no LMM characteristics were related to LBP-intensity or LBP-related disability after considering other confounders.

Paravertebral Muscle Mechanical Properties in Patients with Axial Spondyloarthritis or Low Back Pain: A Case-Control Study

Different musculoskeletal disorders are a source of pain in the spinal region; most of them can be divided into mechanical, such as low back pain (LBP), or inflammatory origins, as is the case of axial spondyloarthritis (axSpA). Nevertheless, insufficient information is available about the muscle negative consequences of these conditions. Thus, the objective of this study was to identify whether mechanical muscle properties (MMPs) of cervical and lumbar muscles are different between patients with axSpA, subacute LBP (sLBP), and healthy controls. Furthermore, we aimed identify whether MMPs were related to sociodemographic and clinical variables in various study groups. The MMPs, sociodemographic, and clinical variables were obtained in 43 patients with axSpA, 43 subjects with sLBP, and 43 healthy controls. One-way ANOVAs and ROC curves were applied to identify whether the MMPs could differentiate between the study groups. Intra-group Pearson r coefficients to test the associations between MMPs and the rest of the variables were calculated. The results showed that axSpA subjects have a higher tone and stiffness and a lower relaxation and creep than sLBP and healthy ones (p < 0.05). All lumbar and cervical MMPs, except for decrement, could correctly classify axSpA and healthy subjects and axSpA and sLBP patients (in both cases, Area Under the Curve > 0.8). However, no MMP could differentiate between sLBP and healthy subjects. Each group had a different pattern of bivariate correlations between MMPs and sociodemographic and clinical data, with a worse state and progression of the axSpA group associated with a higher tone and stiffness in both spinal regions. This study supports that MMPs are different and show different patterns of correlations depending on the type of spinal pain.

Effect of Sustained Natural Apophyseal Glides on Stiffness of Lumbar Stabilizer Muscles in Patients With Nonspecific Low Back Pain: Randomized Controlled Trial

OBJECTIVE

The aim of this study was to investigate the immediate effect of Mulligan sustained natural apophyseal glides (SNAGs) on muscular stiffness by using ultrasound shear wave elastography, pain, and function in patients with nonspecific low back pain.

METHODS

In a prospective, randomized, controlled, double-blinded study, 30 participants with nonspecific low back pain were randomly divided into 2 groups: a real SNAG group (aged 21.0 ± 1.7, 5 men, 10 women) and sham SNAG group (aged 20.4 ± 0.5, 4 men, 11 women). Muscular stiffness of the multifidus and erector spinal muscles with ultrasound shear wave elastography, visual analog scale, the sit and reach, flamingo balance, the functional reach, side bridge, and Biering-Sorensen tests were made before and immediately after intervention. The Oswestry Disability Index score was recorded only baseline.

RESULTS

After intervention, the change in visual analog scale, sit and reach, Biering-Sorensen, and side bridge tests scores were significantly different between real SNAG and sham SNAG groups (P < .05), but there was no significant difference in functional reach and flamingo balance test scores between the groups (P > .05). There was no significant difference for all measurements between pre- and post-intervention in sham SNAG group (P > .05). There was a significant reduction in muscular stiffness in the real SNAG group. But there was no change in muscular stiffness between pre- and postintervention in the sham group (P > .05).

CONCLUSIONS

This study demonstrated that the Mulligan SNAG technique had a positive effect on pain severity, flexibility, trunk muscle endurance, and muscle stiffness in patients with nonspecific LBP.

The examination of stress shielding in a finite element lumbar spine inclusive of the thoracolumbar fascia

Despite the prevalence of low back pain (LBP) in society, the pathomechanism of LBP continues to elude researchers. LBP patients have demonstrated morphological and material property changes to their lumbar soft tissues, potentially leading to irregular load sharing within the lumbar spine. This study aims to analyze potential stress shielding consequential of augmented soft tissue properties via the comparison of a healthy and LBP finite element models. The models developed in this study include the vertebrae, intervertebral discs and soft tissues from L1-S1. Soft tissue morphology and material properties for the LBP model were augmented to reflect documented clinical findings. Model validation preceded testing and was confirmed through comparison to the available literature. Relative to the healthy model, the LBP model demonstrated an increase in stress by 15.6%, with 99.8% of this stress increase being distributed towards the thoracolumbar fascia. The majority of stress skewed towards the fascia may indicate a potential stress allocation bias whereby the lumbar muscles are unable to receive regular loading, leading to stress shielding. This load allocation bias and subsequent stress shielding may potentially contribute to the progression and pathomechanism of LBP but prospective studies would be required to make that link.

Repeated standing back extension exercise: Influence on muscle shear modulus change after lumbodorsal muscle fatigue

BACKGROUND

In low back pain, multifidus muscle fibers reportedly exhibit increased stiffness. Low back pain was associated with lumbodorsal muscle fatigue. There is no report of using shear modulus to verify the mechanism of an immediate effect of exercise on low back pain. Here, temporary lumbodorsal muscle fatigue was created, simulating fatigue-related nonspecific low back pain.

OBJECTIVE

To assess the effect of standing back extension exercise on fatigued lumbodorsal muscle based on the results of multifidus muscle elasticity measured using shear wave elastography.

METHODS

Thirty-three healthy subjects were randomly divided into three groups. The subjects performed the Biering-Sorensen test as the fatigue-task of the lumbodorsal muscle before the standing back extension exercise. The fatigue-exercise group exercised five sets after completing the fatigue-task. The fatigue-non-exercise group remained standing for the same duration as the fatigue-exercise group without doing the exercise after the fatigue-task. The non-fatigue-exercise group exercised five sets of without performing the fatigue-task. As intra-group and inter-group factors, the shear modulus of the multifidus muscle was compared before and after the exercise.

RESULTS

The shear modulus of the multifidus muscle after the standing back extension exercise was significantly lower in the fatigue-exercise group, and no significant decrease was observed in the fatigue-non-exercise and non-fatigue-exercise group.

CONCLUSIONS

The standing back extension exercise improved the shear modulus of the fatigued multifidus muscle. Therefore, it was suggested that the change in the elasticity of fatigued muscle might lead to the prevention of low back pain caused by muscle fatigue.

Association between trunk core muscle thickness and functional ability in subacute hemiplegic stroke patients: an exploratory cross-sectional study

BACK GROUND

Balance impairment could occur due to weakness of the core muscles in stroke patients.

OBJECTIVE

To investigate the association between functional ability, including trunk balance and core muscle thickness using ultrasonography in subacute hemiplegic stroke patients.

METHODS

The muscle thickness of the anterior and posterior trunk muscles was measured using ultrasonography. For the evaluation of trunk balance, trunk impairment scale and Berg balance scale (BBS) were used. The functional ambulatory scale (FAS), timed up-and-go test, 10 m gait velocity, functional reach (FR), and functional independence measure were also assessed for functional ability.

RESULTS

Overall, 41 patients with subacute hemiplegic stroke were included. Partial correlation analysis showed that posterior trunk muscle thickness was significantly correlated with BBS, FAS, and FR. As for the paralytic side, the posterior trunk muscle thickness of both paretic and nonparetic sides presented a significant relationship with BBS, FAS, and FR. The quadratus lumborum (QL) thickness of both sides showed a significant relationship with BBS, FAS, and FR.

CONCLUSIONS

The thickness of the posterior trunk muscles, especially the QL, on both the paretic and nonparetic sides, was significantly related with the functional ability after stroke. The exercise program of core posterior trunk muscles closely related with functional ability would be helpful to improve trunk balance and ambulatory function in subacute stroke patients.

Investigation of physiological stress shielding within lumbar spinal tissue as a contributor to unilateral low back pain: A finite element study

INTRODUCTION

The pathomechanism of low back pain (LBP) remains unknown. Unilateral LBP patients have demonstrated ipsilateral morphological and material property changes within the lumbar soft tissues, potentially leading to asymmetric tissue loading. Through the comparison of healthy and unilateral LBP validated finite element models (FEMs), this study investigates potential stress shielding consequential of spinal tissue property augmentation.

METHODS

Two FEMs of the musculoskeletal system - one demonstrating healthy and unilateral LBP conditions - were developed undergoing 30-degree flexion. FEMs included the vertebrae, intervertebral discs, and soft tissues from L1-S1. Material properties selected for the soft tissues were retrieved from published literature. To reflect unilateral LBP, the paraspinal morphology was atrophied, while the tissue moduli were increased. The symptomatic thoracolumbar fascia (TLF) was uniformly increased. Validation of the models preceded testing.

RESULTS

Model validation in spinal flexion was accomplished through comparison to literature. Compared to the healthy model, the unilateral LBP multifidus (MF), longissimus thoracis (LT), and TLF exhibited average tension changes of +7.9, -5.1, and +9.3%, respectively. Likewise, the symptomatic MF, LT, and TLF exhibited tension changes of +19.0, -10.4, and +16.1% respectively, whereas the asymptomatic MF, LT, and TLF exhibited -4.0, -2.0, and +0.4% changes in tension, respectively.

CONCLUSION

Relative to the healthy tissues, the symptomatic LBP soft tissues demonstrated a 19.5 kPa increase in stress, with 99.8% of this increase distributed towards the TLF, suggesting a load allocation bias within the symptomatic unilateral LBP tissues. Consequentially, symptomatic paraspinal muscles may be unable to withstand loading, leading to stress shielding.

The effect of vertebral level on biomechanical properties of the lumbar paraspinal muscles in a rat model

INTRODUCTION

Passive mechanical properties of the paraspinal muscles are important to the biomechanical functioning of the spine. In most computational models, the same biomechanical properties are assumed for each paraspinal muscle group, while cross-sectional area or fatty infiltration in these muscles have been reported to differ between the vertebral levels. Two important properties for musculoskeletal modeling are the slack sarcomere length and the tangent modulus. This study aimed to investigate the effect of vertebral level on these biomechanical properties of paraspinal muscles in a rat model.

METHODS

The left paraspinal muscles of 13 Sprague-Dawley rats were exposed under anesthesia. Six muscle biopsies were collected from each rat: three from multifidus (one per each of the L1, L3, and L5 levels) and similarly three from longissimus. Each biopsy was cut into two halves. From one half, two to three single muscle fibers and two to six muscle fiber bundles (14 ± 7 fibers surrounded in their connective tissue) were extracted and mechanically tested in a passive state. From the resulting stress-strain data, tangent modulus was calculated as the slope of the tangent at 30% strain and slack sarcomere length (beyond which passive force starts to develop) was recorded. The other half of each biopsy, which represented the muscle at the fascicle level, was snap frozen, sectioned, stained for Collagen I and its area fraction was measured. To evaluate the effect of spinal level on these biomechanical properties of multifidus and longissimus, one-way repeated measures ANOVA (p < 0.05) was performed for tangent modulus and slack sarcomere length, while for collagen I content linear mixed-models analysis was adopted.

RESULTS

In total, 192 fibers and 262 fiber bundles were mechanically tested. For both muscle groups, no significant difference in tangent modulus of the single fibers was detected between the three spinal levels (p = 0.9 for multifidus and p = 0.08 for longissimus). Similarly, the tangent modulus values for the fiber bundles were not significantly different between the three spinal levels (p = 0.13 for multifidus and p = 0.49 for longissimus). In both muscle groups, the slack sarcomere lengths were not different among the spinal levels except for multifidus fibers (p = 0.02). Collagen I area fraction in muscle fascicles averaged 6.8% for multifidus and 5.3% for longissimus and was not different between the spinal levels.

DISCUSSION

The results of this study highlighted that the tangent modulus, slack sarcomere length, and collagen I content of the lumbar paraspinal muscles are independent of spinal level. This finding provides the basis for the assumption of similar mechanical properties along a paraspinal muscle group.

Reliability and Validity of Ultrasound Elastography for Evaluating Muscle Stiffness in Neurological Populations: A Systematic Review and Meta-Analysis

OBJECTIVE

Ultrasound elastography is an emerging diagnostic technology used to investigate the biomechanical properties of the musculoskeletal system. The purpose of this study was to systematically review the psychometric properties of ultrasound elastography techniques for evaluating muscle stiffness in people with neurological conditions.

METHODS

A systematic search of MEDLINE, EMBASE, CINAHL, and Cochrane Library databases was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Using software, reviewers independently screened citations for inclusion. Peer-reviewed studies that evaluated in vivo muscle stiffness in people with neurological conditions and reported relevant psychometric properties were considered for inclusion. Twenty-one articles were included for final review. Data relevant to measurement technique, site, and neurological condition were extracted. The Consensus-Based Standards for the Selection of Health Measurement Instruments checklist was used to rate the methodological quality of included studies. The level of evidence for specific measurement outcomes was determined using a best-evidence synthesis approach.

RESULTS

Reliability varied across populations, ultrasound systems, and assessment conditions (ie, joint/body positions, active/passive muscle conditions, probe orientation), with most studies indicating moderate to good reliability (ICC = 0.5-0.9, n = 13). Meta-analysis results showed a good overall correlation across studies (r = 0.78, 95% confidence interval = 0.64-0.86), with no between-group difference based on population (Q1 = 0.00). Convergent validity was demonstrated by strong correlations between stiffness values and measures of spasticity (n = 5), functional motor recovery or impairment (n = 5), and grayscale or color histogram pixel intensities (n = 3). Discriminant or known-groups validity was also established for multiple studies and indicated either significant between-group differences in stiffness values (n = 12) or within-group differences between more and less affected limbs (n = 6). Responsiveness was observed in all intervention studies reporting posttreatment stiffness changes (n = 6).

CONCLUSIONS

Overall, ultrasound elastography techniques showed moderate reliability in evaluating in vivo muscle stiffness, good convergent validity with relevant clinical assessments, and good divergent validity in discriminating tissue changes within and between groups.

IMPACT

Ultrasound elastography has clinical utility in assessing muscle stiffness, monitoring its temporal changes, and measuring the response to intervention in people with neurological conditions.

Effects of a wearable device and functional wear on spinal alignment and jump performance

Background/objective

To elucidate the effects of walking exercise using a wearable device and functional wear on spinal alignment and jump performance.

Methods

In total, 27 female college soccer players were randomly divided into two groups: trunk solution (TS) and compression garments (CGs). Spinal alignment, jump performance, and electromyography activity during the jump performance of the two groups were measured after a 20-min walking exercise. The values for each group were compared t pre- and post-intervention.

Results

The flexibility of the lower thoracic vertebrae in spinal alignment was increased during extension in the TS group. However, the post-value of the abdominal external oblique muscle during a countermovement jump (CMJ) was significantly lower than its pre-value (p < 0.05). In addition, even though spinal alignment was not affected in the CG group, post-values of the jump height during squat jump and CMJ were significantly higher than their pre-values (p < 0.05). Furthermore, the post-value of the biceps femoris during the countermovement jump with arm was significantly lower than its pre-value (p < 0.05).

Conclusion

Our study suggested that walking exercise using TS may increase the range of motion of the lower thoracic vertebrae in athletes and reduce the muscular activity of the vastus lateralis during CMJ. Additionally, although spinal aliment is not affected, the jump height may increase using CGs.

Mapping of Back Muscle Stiffness along Spine during Standing and Lying in Young Adults: A Pilot Study on Spinal Stiffness Quantification with Ultrasound Imaging

Muscle stiffness in the spinal region is essential for maintaining spinal function, and might be related to multiple spinal musculoskeletal disorders. However, information on the distribution of muscle stiffness along the spine in different postures in large subject samples has been lacking, which merits further investigation. This study introduced a new protocol of measuring bilateral back muscle stiffness along the thoracic and lumbar spine (at T3, T7, T11, L1 & L4 levels) with both ultrasound shear-wave elastography (SWE) and tissue ultrasound palpation system (TUPS) in the lying and standing postures of 64 healthy adults. Good inter-/intra-reliability existed in the SWE and TUPS back muscle stiffness measurements (ICC ≥ 0.731, p < 0.05). Back muscle stiffness at the L4 level was found to be the largest in the thoracic and lumbar regions (p < 0.05). The back muscle stiffness of males was significantly larger than that of females in both lying and standing postures (p < 0.03). SWE stiffness was found to be significantly larger in standing posture than lying among subjects (p < 0.001). It is reliable to apply SWE and TUPS to measure back muscle stiffness. The reported data on healthy young adults in this study may also serve as normative reference data for future studies on patients with scoliosis, low back pain, etc.

Shear modulus of multifidus and longissimus muscles measured using shear wave elastography correlates with muscle activity, but depends on image quality

Shear wave elastography (SWE) estimates shear modulus in muscle. This is interpreted as an index of muscle stiffness, but depends on muscle characteristics. This study evaluated relationship between shear modulus and myoelectric activity of lumbar multifidus and longissimus muscles to assess its validity. Intramuscular electromyography (EMG) of multifidus (deep [DM], superficial [SM] fibres) at L4/5, longissimus [LG] at L2, were recorded in nine healthy participants. Participants performed isometric trunk extension in side-lying from 0 to 30% maximal voluntary contraction (MVC) with EMG amplitude feedback. Using SWE, two regions of interest (ROI) were investigated in each muscle. Generally, shear modulus was moderately correlated with root mean squared (RMS) EMG (r = 0.50-0.78). Univariate and multiple regression analyses showed ultrasound/SWE features of 'B-mode quality' (24.5%), '%Void pixels' (17.9%) and 'Connective tissue' (16.2%) explained most variation in the shear modulus/EMG relationship. Regression prediction scores generated using imaging features were correlated with r-coefficients of shear modulus/EMG relationship. When analysis was restricted to high quality data (i.e., regression prediction score above an a priori defined threshold), the shear modulus/EMG relationship increased to r = 0.70-0.96. Although a linear relationship between shear modulus/EMG was confirmed, supporting validity of SWE measures in anatomically distinct back muscles, this depends on image quality.

[Progress on the evaluation method of paraspinal muscle and its correlation with lumbar diseases]

OBJECTIVE

To review the evaluation method of paraspinal muscle and its role in lumbar spine diseases, and offer reference for further research on paraspinal muscles.

METHODS

The related literature of paraspinal muscle measurement and its role in lumbar spine diseases was reviewed. The evaluation methods of paraspinal muscle were analyzed from the advantages and disadvantages and the role of paraspinal muscle in lumbar spine diseases was summarized.

RESULTS

Radiographic methods are often used to evaluate the atrophy of paraspinal muscle, mainly including CT and MRI. The cross-sectional area and fatty infiltration of paraspinal muscle are two key parameters. Radiographic methods are reproducible and widely applied, but CT has the disadvantage of radiation exposure, while the cost of MRI is high. Besides, more and more researchers focus on the functional evaluation of paraspinal muscle, which mainly includes surface electromyogram analysis and back muscle strength test. The surface electromyogram analysis can quantitatively measure neuromuscular function, but the results could be affected by many influencing factors. The back muscle strength test is simple, but it lacks standardized posture. The atrophy of paraspinal muscle is related to many lumbar spine diseases, while the results of different researches are different.

CONCLUSION

There are many methods to evaluate paraspinal muscles, but there is no unified standard. The role of paraspinal muscle in lumbar spine diseases need to be further studied.

The association between pelvic asymmetry and non-specific chronic low back pain as assessed by the global postural system

BACKGROUND

Empirical evidence that demonstrates the relationship between pelvic asymmetry and non-specific chronic low back pain (NCLBP) is currently lacking.

OBJECTIVE

To establish the reliability of the Global Postural System (GPS) in assessing pelvic asymmetry and identify the association between pelvic asymmetry parameters and the occurrence of NCLBP in young adults.

DESIGN

A cross-sectional, regression study.

METHODS

People who were aged between 18 and 30 and were diagnosed with NCLBP were recruited. Healthy individuals who were matched for age, sex, and education level were recruited as controls. Global Postural System (GPS) was employed to assess pelvic asymmetry. Prior to exploring the association, the reliability of GPS was assessed by the ICC (2, k) for interrater reliability, ICC (3, k) for intra-rater reliability, standard error and minimal detectable difference. Bivariate correlation analysis and logistic regression analysis were used to determine the relationship between pelvic asymmetry and the occurrence of NCLBP.

RESULTS

Twenty-eight healthy participants and 28 people with NCLBP were recruited. Moderate to excellent ICCs were observed for the inter-rater and intra-rater reliability of most postural parameters. The bivariate correlation analysis indicated that age, body mass index and pelvic asymmetry parameters were related to the occurrence of NCLBP. Pelvic angle asymmetry (odds ratio = 1.17), and asymmetry of the distance between the posterior superior iliac spine and the floor (odds ratio = 1.21) were associated with NCLBP.

LIMITATIONS

This study did not explore the causal relationship between pelvic asymmetry in the sagittal plane/pelvic asymmetry in the transverse plane and the occurrence of NCLBP. The interpretation of the results may not be generalized beyond the sample population.

CONCLUSIONS

The GPS is a reliable method to assess pelvic asymmetry in a clinical setting. Two pelvic parameters were associated with the presence of NLBP. Measurement of pelvic asymmetry may assist in the early identification of potential occurrence of NCLBP but further work is required.

Static and Dynamic Balance in Adults Undergoing Lumbar Spine Surgery: Screening and Prediction of Postsurgical Outcomes

INTRODUCTION

Balance and fall risk before and after lumbar surgery was assessed to determine whether balance at baseline predicts long-term postsurgical outcomes.

METHODS

Forty-three patients in the United States and Israel performed the single-leg stance (SLS) test, four square step test (FSST), and 8-foot up-and-go (8FUG) test before and 2 to 4 months after lumbar spine surgery. They completed the Oswestry Disability Index (ODI) and pain rating before and 12 months after lumbar surgery.

RESULTS

From baseline to follow-up, the SLS time was 3.74 seconds longer (P = 0.01), the FSST time was 1.94 seconds faster (P < 0.001), and the 8FUG time was 1.55 seconds faster (P = 0.02). Before surgery, 26% of the patients were considered high fall risk according to the FSST and 51% according to the 8FUG. Postsurgery, all patients could complete the physical tests, but 26% remained at high fall risk according to the 8FUG and 7.5% according to the FSST. The three physical measures together explained 30% of the variance in postsurgical ODI scores (P = 0.02). Age was not correlated with performance.

DISCUSSION

Risk of falling is higher than surgeons suspect. Balance tests (ie, SLS, FSST, and 8FUG) are quick and easy to administer. The findings support the importance of screening for balance and fall risk in adults undergoing lumbar spine surgery.

Analysis of Differences in the Degree of Biomechanical Adaptation according to Habituation to Different Heel Heights

This study aims to comprehensively investigate whether there are any differences in the degree of biomechanical adaptation according to habituation to different heel heights. The biomechanical characteristics of 54 subjects in 3 groups habituated to three heel heights (low, medium-high, and high heels) were evaluated by the measurement of surface EMG, myotonometer (e.g., measurement of muscle tension), foot pressure, and lumbosacral angle, and comparative analysis was carried out to find out whether they showed differences in the comfort visual analog scale (comfort VAS). Wearers of high-heeled shoes (6 cm or more in heel height), in foot pressure comparison, showed significantly high peak pressure in the mask of the hallux, high maximum peak EMG in the gastrocnemius medius (GM), and a high percentage of maximum voluntary isometric contraction (%MVIC) in the plantar flexor. Wearers of low-heeled shoes (3 cm and below in heel height) showed the highest plantar peak pressure in the lateral forefoot and midfoot, the highest contact area in midfoot, the highest %MVIC in the plantar flexion and dorsiflexion of the tibialis anterior (TA), and the highest stiffness in the TA, and they showed the lowest static balance ability with eyes open (EO) among the three groups. It was found that there were significant differences between those habituated to high-heeled shoes and those not habituated to high-heeled shoes and that longtime wearing of high-heeled shoes brings about biomechanical adaptive changes in the human body.

Role of Ultrasound in Low Back Pain: A Review

Low back pain is one of most common musculoskeletal disorders around the world. One major problem clinicians face is the lack of objective assessment modalities. Computed tomography and magnetic resonance imaging are commonly utilized but are unable to clearly distinguish patients with low back pain from healthy patients with respect to abnormalities. The reason may be the anisotropic nature of muscles, which is altered in function, and the scans provide only structural assessment. In view of this, ultrasound may be helpful in understanding the disease as it is performed in real-time and comprises different modes that measure thickness, blood flow and stiffness. By the use of ultrasound, patients with low back pain have been found to differ from healthy patients with respect to the thickness and stiffness of the transversus abdominis, thoracolumbar fascia and multifidus. The study results are currently still not conclusive, and further study is necessary to validate. Future work should focus on quantitative assessment of these tissues to provide textural, structural, hemodynamic and mechanical studies of low back pain. This review highlights the current understanding of how medical ultrasound has been used for diagnosis and study of low back pain and discusses potential new applications.

Analysis of Biomechanical Properties of the Lumbar Extensor Myofascia in Elderly Patients with Chronic Low Back Pain and That in Healthy People

There is limited research on the changes of biomechanical characteristics of the lumbar extensor myofascia in elderly patients with chronic low back pain. This study aimed to compare the biomechanical properties of the lumbar extensor myofascia in elderly patients with chronic low back pain and healthy people when resting and to analyze the relationship between the Japanese Orthopedic Association (JOA) score, visual analog scale (VAS) score, Cobb angle, and disease course and the biomechanical characteristics of the lumbar extensor myofascia. This case-control study included 40 elderly patients with chronic low back pain and 40 healthy volunteers. MyotonPRO was used to measure the biomechanical properties of the bilateral lumbar extensor myofascia (at L3/L4 level) in all participants, and the reliability of the MyotonPRO test was measured. Cobb angle was measured from lumbar computed tomography or magnetic resonance imaging data. JOA and VAS scores were used to evaluate lumbar function and pain. We found that muscle tone, stiffness, and elasticity of the left and right lumbar extensor myofascia in patients with chronic low back pain were very reliable among different operators. The average lumbar extensor muscle tone and stiffness were significantly higher in patients with chronic low back pain than those in healthy controls. The average elasticity of the lumbar extensor myofascia of patients with chronic low back pain was significantly lower than that of the healthy controls. The JOA score was negatively correlated, while the VAS score was positively correlated with the mean values of tone, stiffness, and elasticity of the bilateral lumbar extensor myofascia (logarithmic decrement). Disease course had no significant correlation with muscle tone, stiffness, and elasticity of the lumbar extensor myofascia. No significant correlation was found between Cobb angle and muscle tone, stiffness, and elasticity of the lumbar extensor myofascia in either group.

Lumbar muscle stiffness is different in individuals with low back pain than asymptomatic controls and is associated with pain and disability, but not common physical examination findings

BACKGROUND

Lumbar muscle dysfunction is commonly implicated in low back pain (LBP). Shear-wave elastography (SWE) uses ultrasound technology to quantify absolute soft tissue stiffness (shear modulus), thereby allowing for estimation of individual muscle contraction and function.

OBJECTIVES

To compare resting and contracted stiffness of lumbar spine musculature in individuals with and without LBP using SWE. A secondary aim was to explore for relationships between common self-report and physical examination measures and resting and contracted muscle stiffness in individuals with LBP.

DESIGN

Cross-sectional.

METHODS

Shear modulus of the lumbar musculature was measured in 60 participants with LBP and 60 asymptomatic controls (120 total) using SWE. The lumbar erector spinae were imaged at rest only, while the lumbar multifidus was imaged at rest and during contraction. Before imaging, participants with LBP underwent a standardized clinical examination including a brief history, self-report questionnaires, and a physical examination. Lumbar muscle shear modulus was compared between participants with LBP and asymptomatic controls using ANCOVA. Potential associations between shear modulus and selected self-report and physical examination measures were assessed using correlation analysis.

RESULTS

Stiffness of the erector spinae and lumbar multifidus at rest (but not during contraction) was greater in participants with LBP than in asymptomatic controls (p < 0.05). Many of the self-report measures, but none of the physical examination findings were associated with muscle stiffness.

CONCLUSION

Resting lumbar muscle stiffness is greater in individuals with LBP than asymptomatic controls and is associated with self-reported pain and disability, but not physical exam findings.

Sedentary behaviour at work increases muscle stiffness of the back: Why roller massage has potential as an active break intervention

There is increasing evidence that subjects who are exposed to long sitting periods suffer from musculoskeletal discomfort and back pain. The underlying mechanism and effective prevention strategies are still largely unknown. In this study, muscle stiffness of the back was measured in 59 office workers who followed their usual desk work regime for 4.5 h in a sitting posture. The sitting period was either followed by an 8-min roller massage intervention or a controlled standing task. Results showed that muscle stiffness increased significantly after the 4.5 h sitting period. When the sitting period was followed by roller massage, the stiffness values dropped slightly below baseline stiffness. In contrast, the stiffness values remained increased when the sitting period was followed by controlled standing. This study indicates that short-duration tissue manipulation can be an effective active break between prolonged sitting periods to prevent musculoskeletal issues, such as musculoskeletal discomfort and back pain.