The effect of exercise training on lower trunk muscle morphology

Aquatic exercise versus standard care on paraspinal muscle morphology and function in chronic low back pain patients: a randomized controlled trial

Low back pain (LBP) is a disabling disease and a public health concern. Aquatic exercise is an alternative form of exercise with less spinal loading and difficulty performing movements, benefiting those with pain-related fear. This study aimed to investigate the effect of an aquatic exercise program (SwimEx) versus standard care (SC) on lumbar paraspinal muscle volume and composition, strength and patient outcomes in individuals with chronic LBP. This randomized controlled trial included 34 participants with chronic LBP. Participants were randomly allocated to each group (SwimEx, n = 18; SC, n = 16) and underwent a 10-week supervised intervention program twice per week. Magnetic resonance imaging was performed at baseline and 10-weeks to examine the impact of each intervention on multifidus (MF) and erector spinae (ES) muscle volume (cm3) and fatty infiltration (% FI) at L1-L2, L2-L3, L3-L4, L4-L5, and L5-S1. Mixed model repeated measures ANCOVA revealed no significant time*group interactions for MF and ES volume and %FI. SwimEX had significant increases in MF volume at L2-L3 and L3-L4, and ES volume at L1-L2. Furthermore, SwimEX also had a significant increase in MF %FI at L2-L3. Both groups displayed significant increases in lumbar strength. Correlations between muscle morphology and patient outcomes showed improvements in MF volume were moderately correlated with an increase in physical quality of life and decrease in anxiety/depression. Interestingly, improvements in MF volume, MF %FI, and ES %FI, were each moderately correlated with a decrease in sleep disturbance. In conclusion, aquatic therapy may help increase lumbar paraspinal muscle volume and strength in participants with chronic LBP. Our findings support the notion that improvements in paraspinal muscle health are related to improvements in patient-reported outcomes. More imaging studies are required to examine the impact of exercise on overall paraspinal muscle health in chronic LBP and investigate these associations.

The effects of exercise therapy on lumbar muscle structure in low back pain: A systematic review and meta-analysis

BACKGROUND

Changes in muscle structure are observed in people with low back pain (LBP). Although exercise therapy is arguably one of the most commonly used methods to treat LBP, evidence regarding its effects on muscle structure is still lacking.

OBJECTIVES

To answer the following questions: (1) What are the effects of exercise therapy on lumbar muscle structure in people with LBP and (2) which type of exercise intervention has the greatest effects?

METHODS

Six electronic databases were systematically searched. The RoB 2 tool and the ROBINS-I tool were used to blindly assess the Risk of bias (RoB), and the RevMan 5 tool was used for the meta-analysis. Due to heterogeneity, the various exercise interventions were classified into 4 groups. Interventions that could not be classified into 1 of these 4 groups were not included in the meta-analyses and were qualitatively analysed.

RESULTS

In total, 984 records were retrieved, of which 34 articles were included. The meta-analyses showed that when considering the overall effect size per muscle structural outcome in chronic LBP (cLBP), exercise therapy showed significant positive effects on Lumbar Multifidus (LM) muscle thickness (MT) and LM cross-sectional area (CSA), but not on Lumbar Erector Spinae (LES) CSA and Quadratus Lumborum CSA. Considering the different intervention groups, significant positive effects were observed for: (1) "Motor control + stabilization" with small effect on LM MT, (2) "Stabilization" with medium effect on LM MT, and large effect on LM CSA, and (3) "Motor control + Stabilization + Lumbar strengthening" with large effect on LM MT and LES CSA. There were no significant effects observed for "Lumbar strengthening".

CONCLUSIONS

Overall, exercise therapy has a positive effect on lumbar muscle structural properties in a cLBP population, with a combination of Motor control + Stabilization + Lumbar strengthening giving the best results.

DATABASE REGISTRATION

This systematic review was registered on PROSPERO (CRD42021232583).

Comparison of Combined Motor Control Training and Isolated Extensor Strengthening Versus General Exercise on Lumbar Paraspinal Muscle Health and Associations With Patient-Reported Outcome Measures in Chronic Low Back Pain Patients: A Randomized Controlled Trial

Study DesignProspective Randomized Controlled Trial.ObjectivesTo investigate the effect of combined motor control and isolated lumbar strengthening exercise (MC + ILEX) vs general exercise (GE) on upper lumbar paraspinal muscle volume and composition, strength and patient outcomes in individuals with chronic low back pain (LBP).Methods50 participants with nonspecific chronic LBP were randomly allocated (1:1) to each group (MC + ILEX or GE) and underwent a 12-week supervised intervention program 2 times per week. Magnetic resonance imaging was performed at baseline, 6-weeks and 12-weeks to examine the impact of each intervention on multifidus (MF) and erector spinae (ES) muscle volume (cm3) and fatty infiltration (%FI) at L1-L2, L2-L3 and L3-L4.ResultsOur results revealed no significant between-groups findings for MF and ES %FI and volume, and patient-reported psychosocial measures. However, both groups had significant within-groups decreases in MF %FI at L1-L2, L2-L3 and L3-L4, with concomitant decreases in MF volume at L1-L2 and L2-L3, and at L3-L4 in the GE group. Each group displayed significant improvements in Kinesiophobia, while only MC + ILEX had significant improvements in pain catastrophizing, anxiety, depression and sleep. Lastly, significant correlations were found between change in Kinesiophobia and upper lumbar MF %FI, and between change in strength and lower lumbar MF and ES size.ConclusionsBoth exercise interventions may help reduce upper lumbar MF %FI in individuals with chronic LBP, while MC + ILEX could significantly improve important patient outcomes. Our results support the idea that improvements in paraspinal muscle health associate with better patient outcomes. Further high-quality imaging studies are needed to explore these relationships.

The effects of a 12-week combined motor control exercise and isolated lumbar extension intervention on lumbar multifidus muscle stiffness in individuals with chronic low back pain

Introduction

Exercise therapy is the primary endorsed form of conservative treatment for chronic low back pain (LBP). However, there is still conflicting evidence on which exercise intervention is best. While motor control exercise can lead to morphological and functional improvements of lumbar multifidus muscle in individuals with chronic LBP, the effects of exercise prescription on multifidus stiffness assessed via shear wave elastography are still unknown. The primary aim of this study is to determine the effects of a combined motor control and isolated lumbar extension (MC + ILEX) intervention on lumbar multifidus muscle stiffness.

Methods

A total of 25 participants aged 18 to 65 were recruited from local orthopedic clinics and the university community with moderate to severe non-specific chronic LBP. Participants performed a 12-week MC + ILEX intervention program. Stiffness of the lumbar multifidus muscle (primary outcome) at L4 and L5 was obtained at baseline, 6-week, and 12-week using shear wave elastography. Changes in stiffness ratio (e.g., ratio of lumbar multifidus muscle stiffness from rest to contracted) were also assessed at both time points. Pre to post-intervention changes in lumbar multifidus muscle stiffness were assessed using a one-way repeated measure ANOVA.

Results

Following the 12-week intervention, there were no statistically significant changes in lumbar multifidus muscle stiffness at rest on the right side at L4 (p = 0.628) and the left side at L4 and L5 (p = 0.093, p = 0.203), but a statistically significant decrease was observed on the right side at L5 (p = 0.036). There was no change in lumbar multifidus muscle stiffness ratio.

Conclusion

This study provides preliminary evidence to suggest that a 12-week MC + ILEX intervention had minimal effect on lumbar multifidus muscle stiffness in individuals with chronic LBP. Further investigations are needed to confirm our findings and clarify the relationship between muscle stiffness and functional outcomes.

Fatty infiltration of the erector spinae at the upper lumbar spine could be a landmark for low back pain

PURPOSE

Intervertebral disc degeneration (IVDD), Modic changes, and fatty infiltration in the paraspinal muscles are possible causes of low back pain (LBP). Multifidus has been the most commonly blamed paraspinal muscle in the etiology of LBP. However, it contributes to 20% of the extensor moment on the lumbar spine. In the present study, we aimed to identify whether patients with LBP and asymptomatic subjects differed in terms of intervertebral discs, end-plates, and fatty infiltration in their paraspinal muscles.

METHODS

Consecutive women and men, who visited the spine outpatient clinics with chronic LBP and had lumbar spine MRI for their LBP without leg pain were included. Asymptomatic subjects without LBP/leg pain for the last year were recruited. Modic changes, IVDD, and fatty infiltration in the paraspinal muscles were evaluated on lumbar spine magnetic resonance imagings of the patients with LBP and age-, gender- and BMI-matched asymptomatic controls.

RESULTS

Low back pain was closely associated with fatty infiltration in the paraspinal muscles at all lumbar levels whereas it had association with severe IVDD and Modic changes at lower lumbar levels. Multifidus at the lower lumbar levels was the fattiest paraspinal muscle in both asymptomatic subjects and patients with LBP. Patients with LBP had severe fatty infiltration in the erector spinae at the upper lumbar levels.

CONCLUSION

Severe IVDD and Modic changes were more common at lower lumbar levels in patients with LBP. Both asymptomatic subjects and those with LBP had fatty multifidus at lower lumbar levels, whereas those with LBP had fatty infiltration in the erector spinae at upper lumbar levels. We suggest that fatty infiltration could have started in the multifidus. The erector spinae had greater contribution to the lumbar extension compared to the multifidus. Thus, LBP could develop when the quality of the erector spinae at the upper lumbar levels impairs due to fatty infiltration.

Effect of aquatic exercise versus standard care on paraspinal and gluteal muscles morphology in individuals with chronic low back pain: a randomized controlled trial protocol

BACKGROUND

Low back pain (LBP) is one of the most disabling diseases and a major health issue. Despite the evidence of a link between paraspinal and gluteal muscle dysfunction and LBP, it is unknown whether aquatic exercises can lead to improvements in paraspinal and gluteal muscle morphology and function, and whether improvements in overall muscle health are associated with improvements in patients' outcomes. The unique properties of water allow a water-based exercise program to be tailored to the needs of those suffering from LBP. This study uses magnetic resonance imaging (MRI) to investigate the effect of an aquatic exercise program versus standard exercise on 1) paraspinal and gluteal muscle size, quality and strength and 2) pain, disability, and psychological factors (pain related fear, depression, anxiety, sleep quality) in chronic LBP.

METHODS

This study will include 34 participants with chronic non-specific LBP and moderate to severe disability, aged between 18 and 65, who will be randomly assigned (1:1) to the aquatic exercise group or land-based standard care exercise group. Both groups will receive 20 supervised sessions, twice per week over 10 weeks. MRIs will be obtained along the lumbosacral spine (L1-L5) and pelvis at the start and end of the intervention to assess the effect of each exercise intervention on paraspinal and gluteal muscle size and quality. Pre- to post-intervention changes in all outcomes between each group will be assessed, and the association between the changes in back muscle quality and clinical outcomes will be examined. Between-subjects repeated measure analysis of variance will be used to examine the changes in paraspinal muscle morphology over the different time points. Linear mixed models will be used to assess whether baseline scores can modify the response to the exercise therapy treatment.

DISCUSSION

This study will determine if water-based exercises targeting the lower back and gluteal muscles can lead to important changes in muscle quality and function, and their possible relation with patients' pain and functional improvements. Our findings will have strong clinical implications and provide preliminary data to design a community program to better support individuals with chronic LBP.

TRIAL REGISTRATION

NCT05823857, registered prospectively on April 27th, 2023.

The Role of Back Muscle Dysfunctions in Chronic Low Back Pain: State-of-the-Art and Clinical Implications

Changes in back muscle function and structure are highly prevalent in patients with chronic low back pain (CLBP). Since large heterogeneity in clinical presentation and back muscle dysfunctions exists within this population, the potential role of back muscle dysfunctions in the persistence of low back pain differs between individuals. Consequently, interventions should be tailored to the individual patient and be based on a thorough clinical examination taking into account the multidimensional nature of CLBP. Considering the complexity of this process, we will provide a state-of-the-art update on back muscle dysfunctions in patients with CLBP and their implications for treatment. To this end, we will first give an overview of (1) dysfunctions in back muscle structure and function, (2) the potential of exercise therapy to address these dysfunctions, and (3) the relationship between changes in back muscle dysfunctions and clinical parameters. In a second part, we will describe a framework for an individualised approach for back muscle training in patients with CLBP.

Is fatty infiltration in paraspinal muscles reversible with exercise in people with low back pain? A systematic review

PURPOSE

Increased fatty infiltration in paraspinal muscles has been recognized as a feature of muscle quality loss in people with Low Back Pain (LBP) and is highly associated with the severity of LBP and dysfunction. Reducing fatty infiltration has been recognized as a rehabilitation aim. An earlier systematic review published in 2014 revealed conflicting evidence for the reversibility of paraspinal muscle quality by means of exercise and no updates have been published since. A new systematic literature search is warranted.

METHOD

Pubmed, CINAHL and Embase were searched from inception to July 2022. Randomized, non-randomized controlled trials (RCT and non-RCT) and single-arm trials were included if they reported the effect of exercise on paraspinal fatty infiltration in people with LBP. Effect sizes and statistical power were calculated for (1) exercise versus control, and (2) pre-post exercise changes. Available data from the RCTs were pooled via meta-analysis when appropriate. Otherwise, data were synthesized qualitatively.

RESULTS

Two RCTs, one non-RCT and three single-arm trials met the selection criteria. Data were not pooled due to substantial clinical heterogeneity. Effect sizes from the RCTs revealed no significant difference for exercise versus control. One single-arm trial with high risk of bias demonstrated a significant pre-post difference with moderate effect size, but only at one (T12-L1) of the investigated levels.

CONCLUSION

Moderate quality evidence is available that paraspinal fatty infiltration is not reversible with exercise in people with LBP. More larger RCT's are needed to draw firmer conclusions.

Factors impacting adherence to an exercise-based physical therapy program for individuals with low back pain

Background/Objective

Exercise-based rehabilitation is a conservative management approach for individuals with low back pain. However, adherence rates for conservative management are often low and the reasons for this are not well described. The objective of this study was to evaluate predictors of adherence and patient-reported reasons for non-adherence after ceasing a supervised exercise-based rehabilitation program in individuals with low back pain.

Design

Retrospective observational study.

Methods

Data was retrospectively analyzed from 5 rehabilitation clinics utilizing a standardized exercise-based rehabilitation program. Baseline demographics, diagnosis and symptom specific features, visit number, and discontinuation profiles were quantified for 2,243 patients who underwent the program.

Results

Forty-three percent (43%) of participants were adherent to the program, with the majority (31.7%) discontinuing treatment prior to completion due to logistic and accessibility issues. Another 13.2% discontinued prior to the prescribed duration due to clinically significant improvements in pain and/or disability without formal discharge evaluation, whereas 8.3% did not continue due to lack of improvement. Finally, 6.0% were discharged for related and unrelated medical reasons including surgery. Individuals diagnosed with disc pathology were most likely to be adherent to the program.

Limitations

This study was a retrospective chart review with missing data for some variables. Future studies with a prospective design would increase quality of evidence.

Conclusions

The majority of individuals prescribed an in-clinic exercise-based rehabilitation program are non-adherent. Patient diagnosis was the most important predictor of adherence. For those who were not adherent, important barriers include personal issues, insufficient insurance authorization and lack of geographic accessibility.

Effectiveness of resisted training through translation of the pelvis in chronic low back pain

BACKGROUND

Resisted training of the trunk muscles improves outcomes in chronic low back pain (CLBP). The Itensic b-effect machine was designed to provide resisted training through posterior translation of the pelvis in a seated, forward-tilted position, in contrast with traditional machines that involve extension of the trunk.

OBJECTIVE

To study the effectiveness of lumbopelvic training on the Itensic b-effect machine in individuals with CLBP.

METHODS

Participants were allocated to 4 weeks of either progressive Itensic (I) training in addition to an education/exercise (EE) program (I+EE group, n= 23) or the education/exercise program alone (EE group, n= 22).

PRIMARY OUTCOME

Roland Morris Disability Questionnaire (RMDQ).

SECONDARY OUTCOMES

pain (0-10 numeric rating scale), trunk extensor endurance (Sorensen test), motor control (thoraco-lumbar dissociation test) and mobility (finger-to-floor test).

RESULTS

RMDQ score improved more in the I+EE group than in the EE group (with a between-group difference at the pos-test). Pain and mobility improved in the I+EE group only, motor control improved in both groups with no between-group difference and the Sorensen test did not improve significantly in either group.

CONCLUSIONS

Resisted posterior pelvic translation using the Itensic machine in addition to an education/exercise program improved disability, pain and mobility more than the education/exercise program alone.

The relationships between physical activity, lumbar multifidus muscle morphology, and low back pain from childhood to early adulthood: a 12-year longitudinal study

We investigated the longitudinal associations between physical activity (PA), lumbar multifidus morphology, and impactful low back pain (LBP) in young people. Nine-year-old children were recruited from 25 primary schools and followed up at age 13, 16, and 21 years. We measured PA with accelerometers at age 9, 13, and 16; quantified patterns of lumbar multifidus intramuscular adipose tissue (IMAT) change from 13 to 16 years using magnetic resonance imaging; and recorded LBP and its impact with standardised questionnaires and interviews. Associations were examined with crude and adjusted logistic or multinomial models and reported with odds ratios (OR) or relative risk ratios (RRR). We included data from 364 children (mean[SD] age = 9.7[.4] years). PA behaviour was not associated with LBP. Having persistently high IMAT levels at age 13 and 16 was associated with greater odds of LBP (OR[95% CI] = 2.98[1.17 to 7.58]). Increased time in moderate and vigorous intensity PA was associated with a lower risk of higher IMAT patterns (RRR[95% CI] = .67[.46 to .96] to .74[.55 to 1.00]). All associations became non-significant after adjusting for sex and body mass index (BMI). Future studies investigating the relationships between PA behaviour, lumbar multifidus IMAT, and impactful LBP should account for potential confounding by sex and BMI.

Strength and Power-Related Measures in Assessing Core Muscle Performance in Sport and Rehabilitation

While force-velocity-power characteristics of resistance exercises, such as bench presses and squats, have been well documented, little attention has been paid to load, force, and power-velocity relationships in exercises engaging core muscles. Given that power produced during lifting tasks or trunk rotations plays an important role in most sport-specific and daily life activities, its measurement should represent an important part of the test battery in both athletes and the general population. The aim of this scoping review was 1) to map the literature related to testing methods assessing core muscle strength and stability in sport and rehabilitation, chiefly studies with particular focus on force-velocity-power characteristics of exercises involving the use of core muscles, 2) and to identify gaps in existing studies and suggest further research in this field. The literature search was conducted on Cochrane Library databases, Scopus, Web of Science, PubMed and MEDLINE, which was completed by SpringerLink, Google Scholar and Elsevier. The inclusion criteria were met in 37 articles. Results revealed that among a variety of studies investigating the core stability and core strength in sport and rehabilitation, only few of them analyzed force-velocity-power characteristics of exercises involving the use of core muscles. Most of them evaluated maximal isometric strength of the core and its endurance. However, there are some studies that assessed muscle power during lifting tasks at different loads performed either with free weights or using the Smith machine. Similarly, power and velocity were assessed during trunk rotations performed with different weights when standing or sitting. Nevertheless, there is still scant research investigating the power-velocity and force-velocity relationship during exercises engaging core muscles in able-bodied and para athletes with different demands on stability and strength of the core. Therefore, more research is needed to address this gap in the literature and aim research at assessing strength and power-related measures within cross-sectional and intervention studies. A better understanding of the power-force-velocity profiles during exercises with high demands on the core musculature has implications for designing sport training and rehabilitation programs for enhancement of athletes' performance and/or decrease their risk of back pain.

Paraspinal muscle imaging measurements for common spinal disorders: review and consensus-based recommendations from the ISSLS degenerative spinal phenotypes group

PURPOSE

Paraspinal muscle imaging is of growing interest related to improved phenotyping, prognosis, and treatment of common spinal disorders. We reviewed issues related to paraspinal muscle imaging measurement that contribute to inconsistent findings between studies and impede understanding.

METHODS

Three key contributors to inconsistencies among studies of paraspinal muscle imaging measurements were reviewed: failure to consider possible mechanisms underlying changes in paraspinal muscles, lack of control of confounding factors, and variations in spinal muscle imaging modalities and measurement protocols. Recommendations are provided to address these issues to improve the quality and coherence of future research.

RESULTS

Possible pathophysiological responses of paraspinal muscle to various common spinal disorders in acute or chronic phases are often overlooked, yet have important implications for the timing, distribution, and nature of changes in paraspinal muscle. These considerations, as well as adjustment for possible confounding factors, such as sex, age, and physical activity must be considered when planning and interpreting paraspinal muscle measurements in studies of spinal conditions. Adoption of standardised imaging measurement protocols for paraspinal muscle morphology and composition, considering the strengths and limitations of various imaging modalities, is critically important to interpretation and synthesis of research.

CONCLUSION

Study designs that consider physiological and pathophysiological responses of muscle, adjust for possible confounding factors, and use common, standardised measures are needed to advance knowledge of the determinants of variations or changes in paraspinal muscle and their influence on spinal health.

The effects of combined motor control and isolated extensor strengthening versus general exercise on paraspinal muscle morphology and function in patients with chronic low back pain: a randomised controlled trial protocol

BACKGROUND

Exercise is a common approach for the management of patients with chronic non-specific low back pain (LBP). However, there is no clear mechanistic evidence or consensus on what type of exercise is more effective than others. While considerable evidence suggests a link between lumbar muscle health (e.g., atrophy and fatty infiltration) with functional deficits, it is unknown whether exercises targeting the lumbar spine can lead to noticeable improvements in muscle health and functional outcomes. The primary aim of this study is to compare the effect of combined motor control and isolated strengthening lumbar exercises (MC + ILEX) versus a general exercise group (GE) on multifidus muscle morphology (size and composition). Secondary aims include assessing the effect of the interventions on overall paraspinal muscle health, pain and disability, as well as psychological factors as possible effect modifiers.

METHODS

A total of 50 participants with chronic non-specific LBP and moderate to severe disability, aged between 18 and 60, will be recruited from the local orthopaedic clinics and university community. Participants will be randomised (1:1) to either the MC + ILEX or GE group. Participants will undergo 24 individually supervised exercise sessions over a 12-week period. The primary outcome will be multifidus morphology (atrophy) and composition (fatty infiltration). Secondary outcomes will be muscle function (e.g., % thickness change during contraction), morphology, lumbar extension strength, pain intensity and disability. Potential treatment effect modifiers including maladaptive cognitions (fear of movement, catastrophizing), anxiety, depression, physical activity, and sleep quality will also be assessed. All measurements will be obtained at baseline, 6-week and 12-week; self-reported outcomes will also be collected at 24-week. Between-subjects repeated measure analysis of variance will be used to examine the changes in paraspinal muscle morphology over the different time points. Linear mixed models will be used to assess whether baseline scores can modify the response to the exercise therapy treatment.

DISCUSSION

The results of this study will help clarify which of these two common interventions promote better results in terms of overall paraspinal muscle heath, back pain, disability and psychological factors in adults with chronic LBP.

TRIAL REGISTRATION

NTCT04257253 , registered prospectively on February 5, 2020.

Back Problems: Pros and Cons of Core Strengthening Exercises as a Part of Athlete Training

While competitive training is usually associated with the prevalence of back pain and injuries in athletes, little attention is being paid to the positive effects of sport-specific exercises on core musculature in the prevention of back problems. This scoping review aims (i) to map the literature that addresses the effects on reduction of back problems following athlete training with differing demands on the core musculature and (ii) to identify gaps in the existing literature and propose future research on this topic. The main literature search was conducted on the MEDLINE, PubMed, Web of Science, Scopus, and Cochrane Library databases and was completed on Elsevier, SpringerLink, and Google Scholar. A total of 21 research articles met the inclusion criteria. The findings of 17 studies identified that core strengthening and core stabilization exercises, alone or in combination with athlete training, contribute to the reduction of back pain in athletes, whereas only four studies revealed no significant association of core muscle strength and/or endurance with back problems. Nevertheless, more research is warranted to elucidate the pros and cons of purely sport-specific training with differing demands on the core musculature on back health in athletes. This could help us to design prevention strategies specifically tailored to individual athletes.

Intervertebral disc degeneration and regeneration: a motion segment perspective

Back and neck pain have become primary reasons for disability and healthcare spending globally. While the causes of back pain are multifactorial, intervertebral disc degeneration is frequently cited as a primary source of pain. The annulus fibrosus (AF) and nucleus pulposus (NP) subcomponents of the disc are common targets for regenerative therapeutics. However, disc degeneration is also associated with degenerative changes to adjacent spinal tissues, and successful regenerative therapies will likely need to consider and address the pathology of adjacent spinal structures beyond solely the disc subcomponents. This review summarises the current state of knowledge in the field regarding associations between back pain, disc degeneration, and degeneration of the cartilaginous and bony endplates, the AF-vertebral body interface, the facet joints and spinal muscles, in addition to a discussion of regenerative strategies for treating pain and degeneration from a whole motion segment perspective.

Cell populations and muscle fiber morphology associated with acute and chronic muscle degeneration in lumbar spine pathology

Many chronic musculoskeletal conditions are associated with loss of muscle volume and quality, resulting in functional decline. While atrophy has long been implicated as the mechanism of muscle loss in these conditions, recent evidence has emerged demonstrating a degenerative phenotype of muscle loss consisting of disrupted muscle fiber membranes, infiltration of cells into muscle fibers, and as previously describer, possible replacement of muscle fibers by adipose tissue. Here, we use human lumbar spine pathology as a model system to provide a more comprehensive analysis of the morphological features of this mode of muscle loss between early and late stages of disease, including an analysis of the cell populations found in paraspinal muscle biopsies from humans with acute vs chronic lumbar spine pathology. Using longitudinal sections, we show that degeneration of muscle fibers is localized within a fiber (ie, focal), and is characterized by discontinuous or ragged membrane disruption, cellular infiltration, and apparently vacant space containing limited numbers of nuclei and hyper-contractile cell debris. Samples from patients with acute and chronic pathology demonstrate similar magnitudes of muscle degeneration, however, larger proportions of PDGFRβ-positive progenitor cells and leukocytes were observed in the acute group, with no differences in myogenic cells, macrophages, or T-cells. By better understanding the cell population behaviors over the course of disease, therapies can be optimized to address the appropriate targets and timing of administration to minimize the functional consequences of muscle degeneration in lumbar spine pathology.

Intervertebral disc herniation effects on multifidus muscle composition and resident stem cell populations

BACKGROUND

Paraspinal muscles are crucial for vertebral stabilization and movement. These muscles are prone to develop fatty infiltration (FI), fibrosis, and atrophy in many spine conditions. Fibro-adipogenic progenitors (FAPs), a resident muscle stem cell population, are the main contributors of muscle fibrosis and FI. FAPs are involved in a complex interplay with satellite cells (SCs), the primary myogenic progenitor cells within muscle. Little is known about the stem cell composition of the multifidus. The aim of this study is to examine FAPs and SCs in the multifidus in disc herniation patients. Multifidus muscle samples were collected from 10 patients undergoing decompressive spine surgery for lumbar disc herniation. Hamstring muscle was collected from four patients undergoing hamstring autograft ACL reconstruction as an appendicular control. Multifidus tissue was analyzed for FI and fibrosis using Oil-Red-O and Masson's trichrome staining. FAPs and SCs were visualized using immunostaining and quantified with fluorescence-activated cell sorting (FACS) sorting. Gene expression of these cells from the multifidus were analyzed with reverse transcription-polymerase chain reaction and compared to those from hamstring muscle. FI and fibrosis accounted for 14.2%± 7.4% and 14.8%±4.2% of multifidus muscle, respectively. The multifidus contained more FAPs (11.7%±1.9% vs 1.4%±0.2%; P<.001) and more SCs (3.4%±1.6% vs 0.08%±0.02%; P=.002) than the hamstring. FAPs had greater α Smooth Muscle Actin (αSMA) and adipogenic gene expression than FAPs from the hamstring. SCs from the multifidus displayed upregulated expression of stem, proliferation, and differentiation genes.

CONCLUSION

The multifidus in patients with disc herniation contains large percentages of FAPs and SCs with different gene expression profiles compared to those in the hamstring. These results may help explain the tendency for the multifidus to atrophy and form FI and fibrosis as well as elucidate potential approaches for mitigating these degenerative changes by leveraging these muscle stem cell populations.

Multiparametric MRI characterization of level dependent differences in lumbar muscle size, quality, and microstructure

Magnetic resonance imaging (MRI) is a diagnostic tool that can be used to noninvasively assess lumbar muscle size and fatty infiltration, important biomarkers of muscle health. Diffusion tensor imaging (DTI) is an MRI technique that is sensitive to muscle microstructural features such as fiber size (an important biomarker of muscle health), which is typically only assessed using invasive biopsy techniques. The goal of this study was to establish normative values of level-dependent lumbar muscle size, fat signal fraction, and restricted diffusion assessed by MRI in a highly active population. Forty-two active-duty Marines were imaged using a (a) high-resolution anatomical, (b) fat-water separation, and (c) DT-MRI scan. The multifidus and erector spinae muscles were compared at each level using two-way repeated measures ANOVA. Secondary analysis included Three dimensional (3D) reconstructions to qualitatively assess lumbar muscle size, fatty infiltration, and fiber orientation via tractography. The erector spinae was found to be larger than the multifidus above L5, with lower fat signal fraction above L3, and a less restricted diffusion profile than the multifidus above L4, with this pattern reversed in the lower lumbar spine. 3D reconstructions demonstrated accumulations of epimuscular fat in the anterior and posterior regions of the lumbar musculature, with minimal intramuscular fatty infiltration. Tractography images demonstrated different orientations of adjacent lumbar musculature, which cannot be visualized with standard MRI pulse sequences. The level dependent differences found in this study provide a normative baseline, for which to better understand whole muscle and microstructural changes associated with aging, low back pain, and pathology.

The effect of high-intensity resistance exercise on lumbar musculature in patients with low back pain: a preliminary study

Background

Muscle atrophy and fatty infiltration of the lumbar extensors is associated with LBP. Exercise-based rehabilitation targets strengthening these muscles, but few studies show consistent changes in muscle quality with standard-of-care rehabilitation. The goal of this study was to assess the effect of high-intensity resistance exercise on lumbar extensor muscle size (cross sectional area) and quality (fat fraction) in individuals with low back pain (LBP).

Methods

Fourteen patients with LBP were recruited from a local rehabilitation clinic. Patients underwent MRI scanning before and after a standardized 10-week high-intensity machine-based, resistance exercise program. Patient pain, disability, anxiety/depression, satisfaction, strength, and range of motion was compared pre- and post-rehabilitation using analysis of covariance (covariates: age, gender). Exercise-induced changes in MRI, and patient functional outcome measures were correlated using Pearson’s correlation test.

Results

No significant differences were found in muscle size or fatty infiltration of the lumbar extensors over the course of rehabilitation (p > 0.31). However, patients reported reduced pain (p = 0.002) and were stronger (p = 0.03) at the conclusion of the program. Improvements in muscle size and quality for both multifidus and erector spinae correlated with improvements in disability, anxiety/depression, and strength.

Conclusion

While average muscle size and fatty infiltration levels did not change with high-intensity exercise, the results suggest that a subgroup of patients who demonstrate improvements in muscle health demonstrate the largest functional improvements. Future research is needed to identify which patients are most likely to respond to this type of treatment.

Changes in Structure and Function of the Back Muscles in Low Back Pain: Different Time Points, Observations, and Mechanisms

Spinal health depends on optimal back muscle performance, and this is determined by muscle structure and function. There has been substantial research evaluating the differences in structure and function of many back muscles, including the multifidus and erector spinae, but with considerable variation in results. Many studies have shown atrophy, fat infiltration, and connective tissue accumulation in back muscles, particularly deep fibers of the multifidus, but the results are not uniform. In terms of function, results are also somewhat inconsistent, often reporting lower multifidus activation and augmented recruitment of more superficial components of the multifidus and erector spinae, but, again, with variation between studies. A major recent observation has been the identification of time-dependent differences in features of back muscle adaptation, from acute to subacute/recurrent to chronic states of the condition. Further, these adaptations have been shown to be explained by different time-dependent mechanisms. This has substantial impact on the rationale for rehabilitation approaches. The aim of this commentary was to review and consolidate the breadth of research investigating adaptation in back muscle structure and function, to consider explanations for some of the variation between studies, and to propose how this model can be used to guide rehabilitation in a manner that is tailored to individual patients and to underlying mechanisms. J Orthop Sports Phys Ther 2019;49(6):464-476. doi:10.2519/jospt.2019.8827.

Trunk exercise training improves muscle size, strength, and function in older adults: A randomized controlled trial

The aim of this study was to assess the effectiveness of a multimodal exercise program to increase trunk muscle morphology and strength in older individuals, and their associated changes in functional ability. Using a single-blinded parallel-group randomized controlled trial design, 64 older adults (≥60 years) were randomly allocated to a 12-week exercise program comprising walking and balance exercises with or without trunk strengthening/motor control exercises; followed by a 6-week walking-only program (detraining; 32 per group). Trunk muscle morphology (ultrasound imaging), strength (isokinetic dynamometer), and functional ability and balance (6-Minute Walk Test; 30 second Chair Stand Test; Sitting and Rising Test; Berg Balance Scale, Multi-Directional Reach Test; Timed Up and Go; Four Step Square Test) were the primary outcome measures. Sixty-four older adults (mean [SD]; age: 69.8 [7.5] years; 59.4% female) were randomized into two exercise groups. Trunk training relative to walking-balance training increased (mean difference [95% CI]) the size of the rectus abdominis (2.08 [1.29, 2.89] cm² ), lumbar multifidus (L4/L5:0.39 [0.16, 0.61] cm; L5/S1:0.31 [0.07, 0.55] cm), and the lateral abdominal musculature (0.63 [0.40, 0.85] cm); and increased trunk flexion (29.8 [4.40, 55.31] N), extension (37.71 [15.17, 60.25] N), and lateral flexion (52.30 [36.57, 68.02] N) strength. Trunk training relative to walking-balance training improved 30-second Chair Stand Test (5.90 [3.39, 8.42] repetitions), Sitting and Rising Test (1.23 [0.24, 2.23] points), Forward Reach Test (4.20 [1.89, 6.51] cm), Backward Reach Test (2.42 [0.33, 4.52] cm), and Timed Up and Go Test (-0.76 [-1.40, -0.13] seconds). Detraining led to some declines but all outcomes remained significantly improved when compared to pre-training. These findings support the inclusion of trunk strengthening/motor control exercises as part of a multimodal exercise program for older adults.

Predictors of clinical success with stabilization exercise are associated with lower levels of lumbar multifidus intramuscular adipose tissue in patients with low back pain

Purpose: Investigate the construct validity of prognostic factors purported to predict clinical success with stabilization exercise for low back pain by exploring their associations with lumbar multifidus composition.Methods: Patients with low back pain were recruited from a hospital imaging department. The presence of fivepredictors (age <40 years, positive prone instability test, aberrant trunk flexion movements, straight leg raise range of motion >91°, spinal hypermobility) were identified by standardized physical examination. Predictors were grouped by total positive findings and status on a clinical prediction rule. The proportion of lower lumbar multifidus intramuscular adipose tissue was measured with 3.0 T magnetic resonance imaging. Univariate and multivariate associations were examined with linear regression and reported with standardized beta coefficients (β) and 95% confidence intervals.Results: Data from 62 patients (11 female) with mean (SD) age of 45.2 (11.8) years were included. Total number of predictors (β[95% CI] = -0.37[-0.61,-0.12]; R² = 0.12), positive prediction rule status (β[95% CI] = -0.57[-0.79,-0.35]; R² = 0.30), and age <40 years were associated with lower intramuscular adipose tissue (β[95% CI] = -0.55[-0.77,-0.33]; R² = 0.27). No other individual factors were associated with lumbar multifidus intramuscular adipose tissue.Conclusions: These findings support the construct validity of the grouped prognostic criteria. Future research should examine the clinical utility of these criteria. Implications for RehabilitationLow back pain is the single largest cause of disability worldwide and exercise therapy is recommended by international low back pain treatment guidelines.Lower levels of lumbar multifidus intramuscular adipose tissue were associated with predictors of clinical success with stabilization exercise.Higher proportions of lumbar multifidus intramuscular adipose tissue may help identify patients who require longer duration exercise training, or those who are unlikely to respond to stabilization exercise.

The use of electromyography and magnetic resonance imaging to evaluate a core strengthening exercise programme

BACKGROUND

The question that was asked in the study was whether a training routine based on curl-up exercises with a load provided by body mass of the person increases local muscle strength or local muscle endurance.

OBJECTIVE

The aim of this study was to evaluate the effect of 4 weeks training based on a small load and low movement velocity on electrical activity (EMG), cross-sectional area (CSA) of core stabilisers.

METHODS

The EMG activity was measured in the rectus abdominis (RA), obliquus abdominis externus and erector spinae (ES) muscles. CSA of the muscles: RA, anterolateral abdominal, psoas major, quadratus lumborum, ES, and multifidus at the level of L3-L4 were measured too.

RESULTS

The training increased the CSA and thickness in most of the muscles studied. Statistically significant correlation was found only for the ES circumference (left side) and EMG activity for the right side (r= 0.627, p= 0.022) and left side (r= 0.624, p= 0.023).

CONCLUSIONS

The training programme resulted in a increase in the number of curl-up repetitions revealing an endurance increase in abdominal muscles. Furthermore, there was a increase in the EMG activity of the RA. An increase of the CSA of all tested muscles showed an increase of muscle active force.

Associations between trunk muscle morphology, strength and function in older adults

Skeletal muscle plays an important role in performing activities of daily living. While the importance of limb musculature in performing these tasks is well established, less research has focused on the muscles of the trunk. The purpose of the current study therefore, was to examine the associations between functional ability and trunk musculature in sixty-four community living males and females aged 60 years and older. Univariate and multivariate analyses of the a priori hypotheses were performed and reported with correlation coefficients and unstandardized beta coefficients (β) respectively. The univariate analysis revealed significant correlations between trunk muscle size and functional ability (rectus abdominis: six-minute walk performance, chair stand test, sitting and rising test; lumbar multifidus: timed up and go) as well as trunk muscle strength and functional ability (trunk composite strength: six-minute walk performance, chair stand test, Berg balance performance, sitting and rising test). After controlling for covariates (age and BMI) in the multivariate analysis, higher composite trunk strength (β = 0.34) and rectus abdominis size (β = 0.33) were associated with better performance in the sitting and rising test. The importance of incorporating trunk muscle training into programs aimed at improving balance and mobility in older adults merits further exploration.

Self-Managed Exercises, Fitness and Strength Training, and Multifidus Muscle Size in Elite Footballers

CONTEXT

  Low back pain (LBP) and lower limb injuries are common among Australian Football League (AFL) players. Smaller size of 1 key trunk muscle, the lumbar multifidus (MF), has been associated with LBP and injuries in footballers. The size of the MF muscle has been shown to be modifiable with supervised motor-control training programs. Among AFL players, supervised motor-control training has also been shown to reduce the incidence of lower limb injuries and was associated with increased player availability for games. However, the effectiveness of a self-managed MF exercise program is unknown.

OBJECTIVE

  To investigate the effect of self-managed exercises and fitness and strength training on MF muscle size in AFL players with or without current LBP.

DESIGN

  Cross-sectional study.

SETTING

  Professional AFL context.

PATIENTS OR OTHER PARTICIPANTS

  Complete data were available for 242 players from 6 elite AFL clubs.

INTERVENTION(S)

  Information related to the presence of LBP and history of injury was collected at the start of the preseason. At the end of the preseason, data were collected regarding performance of MF exercises as well as fitness and strength training. Ultrasound imaging of the MF muscle was conducted at the start and end of the preseason.

MAIN OUTCOME MEASURE(S)

  Size of the MF muscles.

RESULTS

  An interaction effect was found between performance of MF exercises and time (F = 13.89, P ≤ .001). Retention of MF muscle size was greatest in players who practiced the MF exercises during the preseason (F = 4.77, P = .03). Increased adherence to fitness and strength training was associated with retained MF muscle size over the preseason (F = 5.35, P = .02).

CONCLUSIONS

  Increased adherence to a self-administered MF exercise program and to fitness and strength training was effective in maintaining the size of the MF muscle in the preseason.

Increased strength of the scapular stabilizer and lumbar muscles after twelve weeks of Pilates training using the Reformer machine: A pilot study

OBJECTIVE

The aim of this work was to analyze muscle strength in Pilates novices who used the Reformer equipment during twelve training sessions.

METHODS

Twenty-four healthy young female volunteers, who were non-smokers and did not exercise regularly, were split into a control group (mean age 28 ± 4 years and BMI 24.55 ± 3.21 kg/m²) and a training group (mean age 29 ± 4 years and BMI 22.69 ± 2.87 kgm²). The data were checked for normality using the Kolmogorov-Smirnov test, and were then analyzed using the t-test (p < 0.05).

RESULTS

After the training sessions, there were statistically significant differences between the groups for the scapular stabilizer muscles (p = 0.0263) and the lumbar muscles (p = 0.0001). For the scapular stabilizers, the initial/final values were 14.69 ± 2.80/14.79 ± 2.89 (control group) and 15.99 ± 3.54/17.44 ± 2.88 (Pilates group). The corresponding values for the lumbar muscles were 53.83 ± 11.66/53.28 ± 11.14 (control group) and 54.75 ± 10.27/64.80 ± 10.20 (Pilates group).

CONCLUSION

After twelve sessions of Pilates with the Reformer equipment, there were improvements in lumbar extensor and scapular stabilizer strength. Several benefits are reported by practitioners of Pilates, but until now, there has been limited scientific evidence of the improvement of strength in the trunk and limbs after application of the technique.

Do Muscle Characteristics on Lumbar Spine Magnetic Resonance Imaging or Computed Tomography Predict Future Low Back Pain, Physical Function, or Performance? A Systematic Review

OBJECTIVE

To determine whether lumbar muscle characteristics on magnetic resonance imaging (MRI) or computed tomography (CT) can inform clinicians as to the course of future low back pain (LBP), functional limitations, or physical performance, in adults with or without LBP. TYPE: Systematic review.

LITERATURE REVIEW

We searched PubMed, Embase, and CINAHL through October 2014 for articles published in English in which authors assessed lumbar muscle characteristics on conventional MRI/CT as predictors of future LBP, functional limitations, or physical performance in adults. Studies with only postsurgical subjects were excluded. Our search identified 3554 articles, of which 6 observational cohort studies were included in the final review.

METHODOLOGY

We used the Newcastle Ottawa Scale to evaluate potential bias. Data were extracted on study design, study population, sample size, participant characteristics, details of MRI/CT assessments, interventions, study outcomes, analysis methods, and study results. Because of heterogeneity between studies, we conducted a qualitative evidence synthesis.

SYNTHESIS

Among high-quality studies, there was limited evidence that, for individuals with or without LBP, greater MRI-detected multifidus cross-sectional area at L5-S1 predicted greater LBP intensity at 1-year follow-up, lesser erector spinae fat infiltration (FI) at L5-S1 predicted greater LBP intensity at 15-year follow-up, and greater erector spinae side-to-side FI asymmetry at L3-L4 predicted lower LBP frequency at 15-year follow-up; however, there was also limited evidence that all other MRI-detected paraspinal muscle characteristics examined were not predictive of LBP incidence, prevalence, frequency, or intensity at follow-up durations ranging from 1 to 15 years. There was limited evidence that greater CT-detected trunk muscle FI predicted worse physical performance in older adults at 3-year follow-up, but that trunk muscle cross-sectional area did not.

CONCLUSION

Few lumbar muscle characteristics have limited evidence for an association with future LBP and physical performance outcomes, and the vast majority have limited evidence for having no association with such outcomes.