The influence of fatigue and chronic low back pain on muscle recruitment patterns following an unexpected external perturbation

Comparison of psoas major activation during standing hip flexion between chronic low back pain and healthy populations

BACKGROUND

The psoas major (PM) has been identified as a potential contributor to chronic low back pain (LBP). However, few studies have investigated the effects of upright functional movement on PM activation in cLBP individuals.

OBJECTIVE

This cross-sectional study aims to compare PM muscle activation characteristics in chronic LBP (cLBP) and healthy subjects during the transition from quiet double-leg standing to standing hip flexion.

METHODS

Ultrasound Imaging was used to assess PM thickness at the lumbar vertebral level of L4-5 in 12 healthy and 12 cLBP participants. The changes in thickness between the test positions were utilized as a proxy for PM activation.

RESULTS

The cLBP group exhibited greater thickness changes on the non-dominant side PM during contralateral hip flexion but not ipsilateral hip flexion (p= 0.369) compared to their healthy counterparts (p= 0.011; cLBP: resting 27.85 mm, activated 34.63 mm; healthy: resting 29.51 mm, activated 29.00 mm). There were no significant differences in dominant side PM thickness changes between the two groups during either contralateral or ipsilateral hip flexion (p= 0.306 and p= 0.077).

CONCLUSION

Our findings suggest a potential overactivation of the PM in the cLBP population. This insight may aid in the development of tailored rehabilitation programs.

Electromyography-driven musculoskeletal models with time-varying fatigue dynamics improve lumbosacral joint moments during lifting

Muscle fatigue is prevalent across different aspects of daily life. Tracking muscle fatigue is useful to understand muscle overuse and possible risk of injury leading to musculoskeletal disorders. Current fatigue models are not suitable for real-world settings as they are either validated using simulations or non-functional tasks. Moreover, models that capture the changes to muscle activity due to fatigue either assume a linear relationship between muscle activity and muscle force or utilize a simple muscle model. Personalised electromygraphy (EMG)-driven musculoskeletal models (pEMS) offer person-specific approaches to model muscle and joint kinetics during a wide repertoire of daily life tasks. These models utilize EMG, thus capturing central fatigue-dependent changes in multi-muscle bio-electrical activity. However, the peripheral muscle force decay is missing in these models. Thus, we studied the influence of fatigue on a large scale pEMS of the trunk. Eleven healthy participants performed functional asymmetric lifting task. Average peak body-weight normalized lumbosacral moments (BW-LM) were estimated to be 2.55 ± 0.26 Nm/kg by reference inverse dynamics. After complete exhaustion of the lower back, the pEMS overestimated the peak BW-LM by 0.64 ± 0.37 Nm/kg. Then, we developed a time-varying muscle force decay model resulting in a time-varying pEMS (t-pEMS). This reduced the difference between BW-LM estimated by the t-pEMS and reference to 0.49 ± 0.14 Nm/kg. We also showed that five fatiguing contractions are sufficient to calibrate the t-pEMS. Thus, this study presents a person and muscle specific model to track fatigue during functional tasks.

Understanding the Biering-Sørensen test: Contributors to extensor endurance in young adults with and without a history of low back pain

The Biering-Sørensen test is commonly used to assess paraspinal muscle endurance. Research using a single repetition of the test has provided conflicting evidence for the contribution of impaired paraspinal muscle endurance to low back pain (LBP). This study investigated how Sørensen test duration, muscle activation, and muscle fatigability are affected by multiple repetitions of the test and determined predictors of Sørensen test duration in young adults with and without a history of LBP. Sixty-four young individuals performed three repetitions of the Sørensen test. Amplitude of activation and median frequency slope (fatigability) were calculated for the lumbar and thoracic paraspinals and hamstrings. Duration of the test was significantly less for the 3rd repetition in individuals with LBP. In individuals without LBP, test duration was predicted by fatigability of the lumbar paraspinals. In individuals with LBP, Sørensen test duration was predicted by fatigability of the hamstrings and amplitude of activation of the thoracic and lumbar paraspinals. Our findings demonstrate that it is necessary to amplify the difficulty of the Sørensen test to reveal impairments in young, active adults with LBP. Training programs aiming to improve lumbar paraspinal performance should monitor performance of other synergist muscles during endurance exercise.

Relationship between Fear-Avoidance Beliefs and Reaction Time Changes Prior to and following Exercise-Induced Muscle Fatigue in Chronic Low Back Pain

Background

Reaction time is a reliable indicator of the velocity and efficiency of neuromuscular control and may be associated with fear-avoidance beliefs. However, the effect of exercise-induced muscle fatigue on reaction time in chronic low back pain (cLBP) and its relationship with fear-avoidance beliefs remains poorly understood.

Objectives

This study aimed to reveal the relationship between fear-avoidance beliefs and reaction time changes before and after exercise-induced muscle fatigue in cLBP.

Methods

Twenty-five patients with cLBP were tested by the Biering-Sorensen test (BST) to induce exhaustive muscle fatigue. Total reaction time (TRT), premotor time (PMT), and electromechanical delay (EMD) of dominated deltoid muscle were recorded by surface electromyography during the arm-raising task with visual cues before and after muscle fatigue. The mean difference (MD) of TRT (MDTRT), PMT (MDPMT), and EMD (MDEMD) was calculated from the changes before and after muscle fatigue. Fear-avoidance beliefs questionnaire (FABQ) was applied to evaluate fear-avoidance beliefs before muscle fatigue. In addition, the duration time of BST was recorded for each subject.

Results

TRT and PMT of dominated deltoid muscle were prolonged after exercise-induced muscle fatigue (Z = 3.511, p < 0.001; t = 3.431, p = 0.001), while there was no statistical difference in EMD (Z = 1.029, p = 0.304). Correlation analysis showed that both the MDTRT and MDPMT were positively correlated with FABQ (r = 0.418, p = 0.042; r = 0.422, p = 0.040).

Conclusions

These findings suggested that we should pay attention to both muscle fatigue-induced reaction time delay in cLBP management and the possible psychological mechanism involved in it. Furthermore, this study implied that FABQ-based psychotherapy might serve as a potential approach for cLBP treatment by improving reaction time delay. This trial is registered with ChiCTR2300074348.

Ankle reaction times with tray usage following a slip perturbation between subjects with and without chronic low back pain

BACKGROUND

Abnormal stepping strategies have been associated with handheld tasks in subjects with chronic low back pain (LBP). However, the dominant ankle reactions of subjects with LBP remain unclear following a perturbation during handheld tasks.

RESEARCH QUESTION

Are there differences in the reaction times of the ankle muscles during handheld tasks between subjects with and without LBP following a treadmill-induced slip perturbation?

METHODS

Thirty-seven right limb dominant subjects with LBP and 37 subjects without LBP participated in the study. Each subject was introduced to a slip perturbation (1.37 m/sec velocity for 8.22 cm) with and without a handheld tray in random order. Subjects were allowed to recover by stepping forward for a 0.12 s duration while bilateral tibialis anterior (TA) and gastrocnemius (GA) muscle reaction times were measured by electromyography (EMG).

RESULTS

The EMG results indicated that the groups demonstrated significant interactions on the limb sides and muscles (F = 4.86, p = 0.03). The dominant TA reaction time was significantly faster in the LBP group (t = 2.14, p = 0.03) while holding a tray.

SIGNIFICANCE

The LBP group demonstrated faster reaction times on the dominant TA muscles during perturbations. Clinicians need to consider dominance-dependent compensatory ankle dorsiflexion strategies in LBP patients to help enhance dynamic balance and control.

Impaired static postural control correlates to the contraction ability of trunk muscle in young adults with chronic non-specific low back pain: A cross-sectional study

INTRODUCTION

Patients with chronic non-specific low back pain (CNSLBP) were found with impaired postural control in previous studies. Since the trunk muscle take important efforts on core stability, the study aimed to examine the relationships of postural control during stance tasks and the contractility of trunk muscle in young adults with CNSLBP and without.

METHODS

Healthy individuals (n = 25) and individuals with CNSLBP (n = 30) were included. The thickness of the bilateral transversus abdominis (TrA) and lumbar multifidus (MF) was measured during rest and maximal voluntary contraction, and the change percentages (TrA%, MF%) were calculated. Regarding postural control, COP path length and sway area during the stance tasks were measured thrice in each group.

RESULTS

The bilateral TrA% of the CNSLBP group was less than that of the HC group (p < 0.05). The bilateral TrA% of the CNSLBP group was less than that of the HC group (p < 0.05). The bilateral MF% showed no significantly different(p > 0.05) between the two groups. Compared with healthy controls, CNSLBP patients resulted larger path length and sway area of COP during most of static stance tasks. During the EO task in the CNSLBP group, TrA% was found correlate to COP path length (p < 0.05); the right MF% was correlated with COP sway area (p < 0.05). No significant correlations appeared in the healthy controls (p > 0.05).

CONCLUSIONS

Compared with healthy individuals, impaired postural control during static stance with eyes open in patients with CNSLBP was likely to be related to the poor contraction ability of bilateral transversus abdominis and correlated to the normal contraction ability of right lumbar multifidus.

Influence of Anterior-Posterior External Surface Perturbation on Trunk Stability During Abdominal Stabilization Strategies While Sitting

Background

Spinal and pelvic injuries during an unexpected perturbation are closely related to spinal stability, which is known to be controlled by abdominal stabilization maneuvers. This study aimed to evaluate the effects of unexpected perturbations on trunk stability and abdominal stabilization strategies in 42 sedentary adults while sitting.

Material/Methods

Abdominal stabilization strategies consisted of bracing and hollowing maneuvers. Abdominal bracing maneuvers (ABM) were focused on the abdominal wall muscles [inferior oblique (IO), exterior oblique (EO)], and abdominal hollowing maneuvers (AHM) were focused on deep muscle (TrA) activation. The subjects were instructed in abdominal stabilization maneuvers. Afterward, subjects were seated in a chair that could be moved forward or backward suddenly with the support surface.

Results

Angular displacements of the upper thorax, lower thorax, and lumbopelvic during unexpected perturbation, with different abdominal stabilization maneuvers, were measured. During forward perturbation (d=0.71, F=10.324, P=0.001) and backward perturbation in high speed (d=0.62, F=9.265, P=0.011), there were significant differences in angular displacements of the upper thorax between hollowing and bracing maneuvers. Additionally, significant differences were found in the lumbopelvic angular displacement between the hollowing and bracing maneuvers (d=0.62, F=4.071, P=0.044).

Conclusions

Our findings indicate that the ABM is a better stabilizing technique for the upper thorax, and the AHM is a better stabilizing technique for the lumbopelvic region during unexpected perturbations at high speed in the seated position.

The association of reactive balance control and spinal curvature under lumbar muscle fatigue

Background

Although low back fatigue is an important intervening factor for physical functioning among sedentary people, little is known about its possible significance in relation to the spinal posture and compensatory postural responses to unpredictable stimuli. This study investigates the effect of lumbar muscle fatigue on spinal curvature and reactive balance control in response to externally induced perturbations.

Methods

A group of 38 young sedentary individuals underwent a perturbation-based balance test by applying a 2 kg load release. Sagittal spinal curvature and pelvic tilt was measured in both a normal and Matthiass standing posture both with and without a hand-held 2 kg load, and before and after the Sørensen fatigue test.

Results

Both the peak anterior and peak posterior center of pressure (CoP) displacements and the corresponding time to peak anterior and peak posterior CoP displacements significantly increased after the Sørensen fatigue test (all at p < 0.001). A lumbar muscle fatigue led to a decrease of the lumbar lordosis in the Matthiass posture while holding a 2 kg load in front of the body when compared to pre-fatigue conditions both without a load (p = 0.011, d = 0.35) and with a 2 kg load (p = 0.000, d = 0.51). Also the sacral inclination in the Matthiass posture with a 2 kg additional load significantly decreased under fatigue when compared to all postures in pre-fatigue conditions (p = 0.01, d = 0.48). Contrary to pre-fatigue conditions, variables of the perturbation-based balance test were closely associated with those of lumbar curvature while standing in the Matthiass posture with a 2 kg additional load after the Sørensen fatigue test (r values in range from −0.520 to −0.631, all at p < 0.05).

Conclusion

These findings indicate that lumbar muscle fatigue causes changes in the lumbar spinal curvature and this is functionally relevant in explaining the impaired ability to maintain balance after externally induced perturbations. This emphasizes the importance for assessing both spinal posture and reactive balance control under fatigue in order to reveal their interrelations in young sedentary adults and predict any significant deterioration in later years.

Effects of Vertical Lifting Distance on Upper-Body Muscle Fatigue

Manual material handling (MMH) is commonly demanded in the manufacturing industry. Occupational muscle fatigue of the arm, shoulder, and back, which arise from MMH tasks, can cause work absences and low efficiency. The available literature presents the lack of the fatigue comparison between targeted muscles, on the same part or on different parts. The main aim of the present study was to evaluate and compare the fatigue of upper-body muscles during repetitive bending tasks, an experiment involving 12 male subjects has been conducted to simulate material handling during furniture board drilling. The vertical lifting distance was chosen to be the single independent variable, and the three levels were 0, 250, and 500 mm. Surface electromyography (sEMG) was used to measure the muscle fatigue of the biceps brachii, upper trapezius, and multifidus, while the sEMG parameters, including the normalized electromyographic amplitude (Normalized EA) and mean power frequency (MPF), of the target muscles were analyzed. The experimental results reveal that during the manual handling tasks, the biceps brachii was the most relaxed muscle, contributing the least muscle tension, while the multifidus was the most easily fatigued muscle. Furthermore, the EMG MPF fatigue threshold (MPFFT) of multifidus muscle tension was tested to estimate its maximum workload in the long-term muscle contraction. In conclusion, bending angle should be maintained to a small range or bending should even be avoided during material-handling tasks.

Back Pain Related with Age, Anthropometric Variables, Sagittal Spinal Curvatures, Hamstring Extensibility, Physical Activity and Health Related Quality of Life in Male and Female High School Students

Spinal pain (SP) is widely extended among adolescents. The origin of SP can be multifactorial; thus, the present study aimed to estimate the prevalence and risk of SP in high school students and to determine the differences in sagittal spinal curvatures and pelvic tilt, hamstring extensibility, age, anthropometric variables and healthy lifestyle habits dependent on SP between sexes. Two hundred seventy-three teenagers took part in this cross-sectional study. Age, sagittal spinal curvatures, hamstring extensibility, physical activity, sedentary lifestyle, anthropometric variables and health related quality of life (HRQL) were recorded. SP was reported by 16.12% of adolescents. Differences were observed in the HRQL according to SP (p < 0.05). Participants without SP were less sedentary (22.12%) and younger (13.10 years old) than participants with SP (40.91% and 13.66, respectively) (p < 0.05). A logistic regression model showed that both variables were significantly collinear (VIF = 1.01; Durbin-Watson = 2.10). Subjects with low back pain (LBP) had a higher weight, body max index, and hip girth than subjects without pain (p < 0.05). A misalignment in the lumbar spine was associated with LBP for males (Cramer’s V = 0.204, p = 0.022). In conclusion, adolescents with SP were older and had a lower HRQL in all dimensions. SP could be predicted according to age and sedentary habits.

Clinical reasoning framework for thoracic spine exercise prescription in sport: a systematic review and narrative synthesis

BACKGROUND

The thoracic spine is critical for athletic kinetic chain functioning yet widely overlooked in terms of specific evidenced-based exercise prescription. Thoracic mobility, motor control and strength are required to optimise performance in sport and minimise excessive load/stress on other components of the kinetic chain.

OBJECTIVE

To identify and evaluate mobility, motor control, work capacity and strength thoracic exercises for use in athletes.

DESIGN

Systematic review involving expert reviewers at key stages: searches and screening (n=1), eligibility, evaluation, data extraction and evaluation (n=3). Key databases and social media sources were searched to 16 August 2019. Eligible exercises were thoracic exercises to promote mobility, motor control, work capacity and strength. A narrative synthesis enabled an outcome-based classification of exercises, with level of evidence of individual sources informing overall level of evidence for each outcome (Oxford Centre for Evidence-based Medicine).

RESULTS

From 2348 sources (social media, database searches and other sources), 38 exercises were included. Sources included images, video clips and written descriptions of exercises. Exercises targeting all planes of motion were evaluated and classified according to outcome. Exercises comprised functional and non-functional exercises for mobility (n=9), work capacity (n=15), motor control (n=7) and strength (n=7). Overall level of evidence for each outcome was level 5.

CONCLUSION

This synthesis and evaluation of exercises has captured the scope of thoracic exercises used in 'practice'. Evaluation against an expert-derived outcome-based classification provides practitioners with a framework to facilitate exercise prescription. Evaluation of validity and effectiveness of exercises on outcomes is now required.

Compensatory spinopelvic motions with and without a handheld task following a perturbation in standing between subjects with and without chronic low back pain

BACKGROUND

A handheld task-related compensation strategy could be used to avoid injuries in subjects with chronic low back pain (LBP). Those who suffer with LBP demonstrate reduced spinopelvic motion; however, there is a lack of understanding on dynamic mobility with a handheld task.

RESEARCH QUESTION

Are there differences in three-dimensional spinopelvic motions following a treadmill-induced perturbation in subjects with LBP while considering a handheld task?

METHODS

Twenty-five subjects (11 female and 14 male) with LBP and 38 control subjects (15 female and 23 male) participated in the study. Each group was introduced to walking perturbations (0.86 m/sec, velocity in 0.1 sec) with and without a handheld tray in a standing position. The induced trip allowed subjects to recover by walking forward for a 5 second duration while the spinopelvic angles were measured during the trip and the subsequent recovery period.

RESULTS

There was no significant group difference in the three-dimensional (3D) spinopelvic motions while holding or not holding a tray. However, the groups demonstrated a significant interaction on tray usage with 3D motions in the spinopelvic regions (F = 13.46, p = 0.001). The sagittal plane motion was significantly minimized with a handheld task for both the lumbar spine and pelvis in the LBP group.

SIGNIFICANCE

The LBP group demonstrated minimized lumbar and pelvic motions in the sagittal plane, which underpins their concern to reduce motion while holding a tray. The significant interaction between groups on tray usage for spinopelvic compensation represents a strategy for avoiding injuries. Further studies are required to determine strategies to enhance lumbopelvic integration with handheld tasks in individuals with LBP.

The effect of chronic, non-specific low back pain on superficial lumbar muscle activity: a protocol for a systematic review and meta-analysis

INTRODUCTION

Chronic, non-specific low back pain is a major global cause of disability. One factor which might potentially contribute to ongoing pain is maladaptive variation in the level of activity in the lumbar musculature. Several studies have investigated this activity using surface electromyography, in varied muscles and during a number of functional activities. Due to differences in the applied methodology, the results have been difficult to compare, and previous reviews have been limited in scope. In this protocol, we aim to perform a comprehensive review of the effect of chronic low back pain on lumbar muscle activity.

METHODS AND ANALYSIS

This protocol was informed by the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols (PRISMA-P) and results will be reported in line with the PRISMA. Searches will be conducted on the Web of Science, PubMed, MEDLINE, EMBASE, ZETOC and CINAHL databases, along with a comprehensive review of grey literature and key journals. One reviewer will conduct the searches, but two independent reviewers will screen potential studies and assess the risk of bias within studies which meet the inclusion criteria. The Newcastle-Ottawa risk of bias tool, and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) guidelines will be used to assess the quality of the data. Meta-analysis will be conducted where appropriate on groups of studies with homogenous methodology. Where studies are too heterogeneous to allow for meta-analysis, meta-synthesis will instead be completed, comparing results in terms of net increases or decreases of activity.

ETHICS AND DISSEMINATION

This review aims to identify common adaptations of muscle activity in people with low back pain and it is expected that the results will influence future research directions and future rehabilitation approaches. The results will be submitted for publication in a peer-reviewed journal and presented at conferences.

PROSPERO REGISTRATION NUMBER

CRD42019125156.

Assessing aberrant muscle activity patterns via the analysis of surface EMG data collected during a functional evaluation

BACKGROUND

Surface electromyographic (EMG) recordings collected during the performance of functional evaluations allow clinicians to assess aberrant patterns of muscle activity associated with musculoskeletal disorders. This assessment is typically achieved via visual inspection of the surface EMG data. This approach is time-consuming and leads to accurate results only when the assessment is carried out by an EMG expert.

METHODS

A set of algorithms was developed to automatically evaluate aberrant patterns of muscle activity. EMG recordings collected during the performance of functional evaluations in 62 subjects (22 to 61 years old) were used to develop and characterize the algorithms. Clinical scores were generated via visual inspection by an EMG expert using an ordinal scale capturing the severity of aberrant patterns of muscle activity. The algorithms were used in a case study (i.e. the evaluation of a subject with persistent back pain following instrumented lumbar fusion who underwent lumbar hardware removal) to assess the clinical suitability of the proposed technique.

RESULTS

The EMG-based algorithms produced accurate estimates of the clinical scores. Results were primarily obtained using a linear regression approach. However, when the results were not satisfactory, a regression implementation of a Random Forest was utilized, and the results compared with those obtained using a linear regression approach. The root-mean-square error of the clinical score estimates produced by the algorithms was a small fraction of the ordinal scale used to rate the severity of the aberrant patterns of muscle activity. Regression coefficients and associated 95% confidence intervals showed that the EMG-based estimates fit well the clinical scores generated by the EMG expert. When applied to the clinical case study, the algorithms appeared to capture the characteristics of the muscle activity patterns associated with persistent back pain following instrumented lumbar fusion.

CONCLUSIONS

The proposed approach relies on EMG-based measures to generate accurate estimates of the severity of aberrant patterns of muscle activity. The results obtained in the case study suggest that the proposed technique is suitable to derive clinically-relevant information from EMG data collected during functional evaluations.