Magnitude of spinal muscle damage is not statistically associated with exercise-induced low back pain intensity

The difference in multifidus muscle morphology and motor control in non-specific low back pain with clinical lumbar instability and healthy subjects: A case-control study

BACKGROUND

Low back pain (LBP) with clinical lumbar instability (CLI) is considered a subgroup of back pain. Poor core stability function and/or lack of motor controls are thought to play a role in inappropriate inter-segmental movements and pain. There is no study investigating the changes in the lumbar multifidus muscle (LMM) morphology and motor control in this subgroup of patients.

OBJECTIVE

To assess motor control components and morphological changes of LMM in the patients suffering from chronic nonspecific low back pain (CNSLBP) with CLI.

DESIGN

Observational case-control study.

METHODS

Thirty-two patients suffering from (CNSLBP) with CLI and 32 healthy individuals were included. The muscle force element of lumbar motor control was assessed by using (the active straight-leg raise test, leg lowering test, and Trendelenburg test). Ultrasonography was used to assess changes in the LMM morphology.

RESULTS

There was a significant decrease in motor control (p = 0.0001), an increase in LMM fatty infiltration (p = 0.002), and a decrease in the thickness of LMM in patients suffering from CNSLBP during contraction (p = 0.006), during rest (p = 0.018). The cross-section area of the LMM showed no statistically significant differences during rest on the right and left sides (p = 0.827, 0.220 respectively) and contraction (p = 0.160, 0.278 respectively) between patients and healthy subjects.

CONCLUSION

Motor control and the morphology of LMM in patients with CNSLBP with CLI may provide insight into the mechanisms of underlying pain and their effect on muscle function and structure.

Pain and Disability Following Exercise-Induced Injury in Prognostic and Intervention Studies: The Why May Be More Important Than the How

OBJECTIVES

In preclinical prognostic studies, the description of expected outcomes during an informed consent process indicates that the extent of pain and disability experienced and recovery time is unknown. In intervention studies, the consent process suggests that pain and disability will definitely occur and a treatment provided. Our objective was to determine whether study design (prognosis or intervention) was associated with the severity of pain intensity and disability reports from a preclinical model.

MATERIALS AND METHODS

We pooled pain and disability outcomes from prognostic and intervention studies using an exercise-induced muscle injury model of pain. Pain intensity, disability, and fear of pain were collected by validated self-report measures. Pain and disability data were z-transformed for pooled analyses and compared across the study design.

RESULTS

Data from 310 people were included. The primary findings were that self-reported pain intensity and disability were: (1) higher in prognostic studies than in the intervention studies and (2) associated with fear of pain. A secondary finding was that fear of pain was lower in the intervention compared with the prognostic studies.

DISCUSSION

Although there are other possible explanations, we speculate that these results could be related to the uncertainty inherent to providing informed consent for a prognostic study. In light of these findings, we recommend that informed consent language be more carefully considered when pain is induced in a controlled manner. Incorporating informed consent language commonly used in prognostic studies could result in higher pain intensity and disability ratings in studies that use preclinical models to test the efficacy of pain interventions.

Comparison of brain structure between pain-susceptible and asymptomatic individuals following experimental induction of low back pain

BACKGROUND CONTEXT

Peripheral differences often do not adequately account for variation in reports of pain intensity in people with musculoskeletal pain.

PURPOSE

Here we sought to determine the extent to which structural differences in the brain (grey matter density) of pain free individuals might relate to subsequent pain (or lack thereof) after standardized peripheral muscle injury (ie, micro trauma from high intensity exercise).

STUDY DESIGN

This was an observational laboratory-based study that was a secondary analysis from a larger trial.

METHODS

Participants completed baseline testing (functional MRI and quantitative pain testing) followed by high intensity trunk exercise to induce delayed onset muscle soreness in the erector spinae. Forty-eight hours later, back pain intensity ratings were collected and all participants were re-imaged. Grey matter density was determined using voxel-based morphometry. The "asymptomatic" group (no reports of any pain within 48 hours after induction) to a 'pain' group (rating of pain at rest and movement pf>20 on a 101-point numeric rating scale).

RESULTS

Our results revealed several large clusters where, compared to participants with pain, asymptomatic participants had significant greater grey matter density. These brain regions included left medial frontal gyrus, left middle occipital gyrus, left middle temporal gyrus, left inferior frontal gyrus, and right superior frontal gyrus.

CONCLUSIONS

Lower grey matter density in brain regions previously linked to discriminative, emotional, and cognitive aspects of cortical processing are associated with reporting musculoskeletal pain after a standardized peripheral muscle injury.

CLINICAL SIGNIFICANCE

Cortical gray matter density of people without any pain may influence response to a standardized high intensity exercise protocol. This finding adds further support to the relevance of central factors in explaining the tremendous individual variability in pain report following acute musculoskeletal injury.

The association between occupational loading and spine degeneration on imaging - a systematic review and meta-analysis

Background

There are inconsistencies in findings regarding the relationship of occupational loading with spinal degeneration or structural damage. Thus, a systematic review was conducted to determine the current state of knowledge on the association of occupational loading and spine degeneration on imaging.

Methods

We performed electronic searches on MEDLINE, CINAHL and EMBASE. We included cross-sectional, case control and cohort studies evaluating occupational loading as the exposure and lumbar spine structural findings on imaging as the outcomes. When possible, results were pooled.

Results

Seventeen studies were included in the review. Ten studies evaluated the association of occupational loading with disc degeneration (signal intensity), four of which were pooled into a meta-analysis. Of the 10 studies, only two did not identify a relationship between occupation loading and disc degeneration. A meta-analysis including four of the studies demonstrated an association between higher loading and degeneration for all spinal levels, with odds ratios between 1.6 and 3.3. Seven studies evaluated disc height narrowing and seven evaluate disc bulge, with six and five identifying an association of loading and with imaging findings respectively. Three studies evaluated modic changes and one identified and association with occupational load.

Conclusions

There was moderate evidence suggesting a modest association between occupational loading and disc degeneration (signal intensity), and low-quality evidence of an association between occupational loading and disc narrowing and bulging.

Paraspinal muscle function and pain sensitivity following exercise-induced delayed-onset muscle soreness

PURPOSE

The aim of this study was to evaluate the effectiveness of an exercise protocol designed to induce delayed-onset muscle soreness (DOMS) in paraspinal muscles and its effects on low back functional capacities.

METHODS

Twenty-four healthy participants were asked to perform four series of 25 trunk flexion-extension in a prone position (45° inclined Roman chair). The protocol was performed using loads corresponding to participant's trunk weight plus 10% of their trunk extension maximal voluntary contraction. Perceived soreness and pain were assessed using an 11-point numerical analogue scale three times a day during 5 day post-DOMS protocol. Pressure-pain thresholds (PPT) in paraspinal muscles (L2 and L4 bilaterally) and the vastus medialis (control site), and trunk extension maximal voluntary contraction were assessed 24-36 h post-protocol and compared to baseline (t tests).

RESULTS

Muscle soreness (3.8/10) and pain (2.1/10) peak scores were observed 24-36 h post-protocol (mean of 28 h). A significant reduction in trunk extension maximal voluntary contraction was observed post-protocol (p = 0.005). Significant reductions in PPT were observed post-protocol for all trunk extensor sites (ps < 0.01), but not for the control site (p = 0.40).

CONCLUSIONS

The exercise protocol efficiently led to low back muscle DOMS, reduced functional capacities, and increased pain sensitivity locally. Such protocol could be used as an efficient and safe experimental low back pain model.

Low back pain

Low back pain affects individuals of all ages and is a leading contributor to disease burden worldwide. Despite advancements in assessment and treatment methods, the management of low back pain remains a challenge for researchers and clinicians alike. One reason for the limited success in identifying effective treatments is the large variation in the manifestations, possible causes, precipitating and maintaining factors, course, prognosis and consequences in terms of activity interference and quality of life. However, despite these challenges, steady progress has been achieved in the understanding of back pain, and important steps in the understanding of the psychological and social risk factors, genetics and brain mechanisms of low back pain have been made. These new findings have given impetus to the development of new diagnostic procedures, evidence-based screening methods and more targeted interventions, which underscore the need for a multidisciplinary approach to the management of low back pain that integrates biological, psychological and social aspects.

Functional and Morphological Changes in the Deep Lumbar Multifidus Using Electromyography and Ultrasound

Surface electromyography (sEMG) studies have indicated that chronic low back pain (cLBP) involves altered electromyographic activity and morphological structure of the lumbar multifidus (LM) beyond pain perception; however, most studies have evaluated the superficial lumbar multifidus. It is difficult to record electromyography (EMG) signals from the deep multifidus (DM) to determine the neuromuscular activation patterns, making it difficult to determine the relationship between functional and structural changes in cLBP. We developed a novel method to record intramuscular EMG signals in the DM based on the sEMG system and fine-wire electrodes. We measured EMG signals of the DM in 24 cLBP patients and 26 pain-free healthy controls to identify changes in neuromuscular activation. We also used ultrasound to measure DM muscle thickness, cross-sectional area, and contraction activity to identify potential relationships between EMG activity and structural damage. cLBP patients had decreased average EMG and root mean square, but increased median frequency and mean power frequency. Average EMG was positively correlated with contractile activity, but not statistically correlated with noncontractile anatomical abnormalities. Our results suggest that cLBP alters the neuromuscular activation patterns and morphological structure of the contractile activity of the DM, providing insights into the mechanisms underlying pain perception.

Effects of the Inertia Barbell Training on Lumbar Muscle T2 Relaxation Time

Sun, M-Y, Lu, J-Q, Ma, Z-C, Lü, J-J, Huang, Q, Sun, Y-N, and Liü, Y. Effects of the inertia barbell training on lumbar muscle T2 relaxation time. J Strength Cond Res 34(12): 3454-3462, 2020-The purpose of this study was to investigate variations in T2 relaxation time in normal human lumbar muscles caused by inertia barbell training. Thirty undergraduate healthy men (mean age = 19 ± 1.2 years, body mass = 72 ± 10.0 kg, and height = 1.78 ± 0.1 m) were recruited to participate in this study. Subjects were randomly assigned into 2 groups: an inertia barbell training group (IBTG) (n = 15) and a normal barbell-training group (NBTG) (n = 15). All subjects participated in lumbar flexion and extension muscle strength training for 1 hour per time, 3 times per week for a total of 8 weeks. The lumbar area of each subject was scanned before and after the experiment using a 3.0T superconductive magnetic resonance imaging system. The T2 values measured after intervention were significantly different compared with the T2 values measured before the experiment in both the IBTG and NBTG groups (p < 0.001). After intervention, there was no significant difference in T2 values between the IBTG and NBTG groups (p = 0.17). The ([INCREMENT]T2)/T2 percentage was significantly different in the IBTG group (p < 0.01). This study demonstrated that 8 weeks of strength training led to significant improvements in the values for T2 relaxation time of the lumbar muscles. Furthermore, the ([INCREMENT]T2)/T2 percentage for IBTG was higher than that for NBTG, which suggested that lumbar muscle activity increased more with inertial barbell training.

Does lumbar paraspinal muscle fatty degeneration correlate with aerobic index and Oswestry disability index?

BACKGROUND

We sought to analyze whether the amount of paraspinal fatty degeneration correlates with a patient's physical fitness, and to determine if these findings on lumbar magnetic resonance imaging (MRI) scans can help predict functional outcomes.

METHODS

A retrospective review was performed on 172 patients. Inclusion criteria involved being seen by a spine surgeon for low back pain, having aerobic index (AI), body mass index (BMI), Oswestry disability index (ODI), and body fat percentage measured recently, and having had a recent lumbar MRI scan. The percentage of fatty muscle degeneration was graded by three reviewers using T2-weighted axial images at L3 and L5 using a newly proposed system that was validated independently. The system is graded as follows: Grade 1: 0-24%, Grade 2: 25-49%, Grade 3: 50-74%, and Grade 4: 75-100%. An independent t-test was used for comparisons.

RESULTS

The average AI was 34.87, and the cohort was divided into two groups: above-average AI (89 patients) and below-average AI (83 patients). For all paraspinal fat measurements and body fat percentage, the difference between the above- and below-average AI groups was statistically significant (P < 0.05), with the least amount of paraspinal fatty degeneration and body fat in the greater AI group. Weight alone and BMI were not found to be significantly different between those with above-average AI when compared to those with below-average AI (P = 0.491 and P = 0.122, respectively). There was a trend for lower ODI scores in the above-average AI group (41.9 vs 46.1), but this did not reach statistical significance between the two groups (P = 0.075). For all patients it was shown that there was significantly less paraspinal fat at the L3 level as compared to L5 (P < 0.001).

CONCLUSIONS

We were able to show that patients with a higher AI have lower body fat percentages and lower amounts of fatty degeneration in their lumbar paraspinal musculature. The amount of paraspinal fatty degeneration, therefore, correlates with physical fitness. Patients with higher AI also showed a trend toward having a lower ODI score.

Statin-induced rhabdomyolysis: a comprehensive review of case reports

PURPOSE

To identify case reports of statin-induced rhabdomyolysis and summarize common predisposing factors, symptoms, diagnostic findings, functional outcomes, characteristics, treatment, and rehabilitation.

METHOD

MEDLINE, CINAHL, SCOPUS, and PEDro databases were searched (1990-2013) for relevant case reports using the search terms "Statins," "Rhabdomyolysis," "Myalgia," "Muscle damage," "Muscle injury," and "Myopathy." Relevance (based on title and abstract) was assessed by one investigator; two investigators independently reviewed the relevant articles to determine inclusion in the review.

RESULTS

A total of 112 cases met the inclusion criteria. The majority were in men (70%) and people over 45 years of age (mean 64 [SD 14] years). Simvastatin was the most commonly reported statin (n=55); the majority of cases reported the use of concomitant medications such as fibrates (n=25). Weakness (n=65) and muscle pain (n=64) were the most common symptoms. In 19 cases, the patient was referred to rehabilitation, but the case reports do not include descriptions of the treatment.

CONCLUSION

Statin-induced rhabdomyolysis was more commonly reported when statins were used in conjunction with other drugs, which potentiated its effect. Research is needed to identify the role of exercise and rehabilitation following statin-induced rhabdomyoloysis since muscle damage may be severe and may have long-term effects on muscle function.

Dynamic, but not static, pain sensitivity predicts exercise-induced muscle pain: covariation of temporal sensory summation and pain intensity

Cross-section studies suggest that measures of pain sensitivity, derived from quantitative sensory testing (QST), are elevated in persons with chronic pain conditions. However, little is known about whether development of chronic pain is preceded by elevated pain sensitivity or pain sensitivity increases as a result of prolonged experience of pain. Here we used QST to test static (single suprathreshold stimuli) and dynamic (temporal sensory summation) pain processing of thermal stimuli. Muscle pain was induced using high-intensity exercise (DOMS). Multi-level modeling approaches determined the daily covariation among static and dynamic QST measures and pain intensity. Variation in responses to static pain sensitivity was not associated with pain intensity from DOMS while, in contrast, variation in dynamic pain sensitivity was positively associated with variation in pain intensity from DOMS. This finding supports the use of TSS as a marker of the central pain state and potentially as an appropriate measure for treatment monitoring.