The effects of abdominal muscle coactivation on lumbar spine stability

Influence of muscle activation on lumbar injury under a specific +Gz load

PURPOSE

The present study aimed to analyze the influence of muscle activation on lumbar injury under a specific +Gz load.

METHODS

A hybrid finite element human body model with detailed lumbar anatomy and lumbar muscle activation capabilities was developed. Using the specific +Gz loading acceleration as input, the kinematic and biomechanical responses of the occupant's lower back were studied for both activated and deactivated states of the lumbar muscles.

RESULTS

The results indicated that activating the major lumbar muscles enhanced the stability of the occupant's torso, which delayed the contact between the occupant's head and the headrest. Lumbar muscle activation led to higher strain and stress output in the lumbar spine under +Gz load, such as the maximum Von Mises stress of the vertebrae and intervertebral discs increased by 177.9% and 161.8%, respectively, and the damage response index increased by 84.5%.

CONCLUSION

In both simulations, the occupant's risk of lumbar injury does not exceed 10% probability. Therefore, the activation of muscles could provide good protection for maintaining the lumbar spine and reduce the effect of acceleration in vehicle travel direction.

Muscle Strength Identification Based on Isokinetic Testing and Spine Musculoskeletal Modeling

Subject-specific spinal musculoskeletal modeling can help understand the spinal loading mechanism during human locomotion. However, existing literature lacks methods to identify the maximum isometric strength of individual spinal muscles. In this study, a muscle strength identification method combining isokinetic testing and musculoskeletal simulations was proposed, and the influence of muscle synergy and intra-abdominal pressure (IAP) on identified spinal muscle strength was further discussed. A multibody dynamic model of the spinal musculoskeletal system was established and controlled by a feedback controller. Muscle strength parameters were adjusted based on the measured isokinetic moments, and muscle synergy vectors and the IAP piston model were further introduced. The results of five healthy subjects showed that the proposed method successfully identified the subject-specific spinal flexor/extensor strength. Considering the synergistic activations of antagonist muscles improved the correlation between the simulated and measured spinal moments, and the introduction of IAP slightly increased the identified spinal extensor strength. The established method is beneficial for understanding spinal loading distributions for athletes and patients with sarcopenia.

Evaluation of trunk muscle coactivation predictions in multi-body models

Musculoskeletal simulations with muscle optimization aim to minimize muscle effort, hence are considered unable to predict the activation of antagonistic muscles. However, activation of antagonistic muscles might be necessary to satisfy the dynamic equilibrium. This study aims to elucidate under which conditions coactivation can be predicted, to evaluate factors modulating it, and to compare the antagonistic activations predicted by the lumbar spine model with literature data. Simple 2D and 3D models, comprising of 2 or 3 rigid bodies, with simple or multi-joint muscles, were created to study conditions under which muscle coactivity is predicted. An existing musculoskeletal model of the lumbar spine developed in AnyBody was used to investigate the effects of modeling intra-abdominal pressure (IAP), linear/cubic and load/activity-based muscle recruitment criterion on predicted coactivation during forward flexion and lateral bending. The predicted antagonist activations were compared to reported EMG data. Muscle coactivity was predicted with simplified models when multi-joint muscles were present or the model was three-dimensional. During forward flexion and lateral bending, the coactivation ratio predicted by the model showed good agreement with experimental values. Predicted coactivation was negligibly influenced by IAP but substantially reduced with a force-based recruitment criterion. The conditions needed in multi-body models to predict coactivity are: three-dimensionality or multi-joint muscles, unless perfect antagonists. The antagonist activations are required to balance 3D moments but do not reflect other physiological phenomena, which might explain the discrepancies between model predictions and experimental data. Nevertheless, the findings confirm the ability of the multi-body trunk models to predict muscle coactivity and suggest their overall validity.

Clinical significance of diastasis recti: Literature review and awareness amongst health care professionals

BACKGROUND

A variety of physical complaints have been related to chronic diastasis recti (DR), including back pain, pelvic pain, and urinary incontinence. However, its clinical significance is still subject of debate, leaving many patients to feel unheard when experiencing symptoms. This study aims to assess current knowledge on DR, its potential treatments, and the awareness of this condition amongst involved health care professionals.

METHODS

A literature review was performed to analyze current available knowledge on DR and its treatment. Then, a survey was conducted to investigate the awareness on DR amongst general practitioners, midwives, gynecologists, general surgeons, and plastic surgeons.

RESULTS

Over 500 health care professionals completed our survey, including 46 general practitioners, 39 midwives, 249 gynecologists, 33 general surgeons, and 74 plastic surgeons. Although the majority of respondents (>78% in all groups) reported to encounter DR in daily practice, opinions differed markedly on most significant symptoms, associated physical complaints, best first referral for treatment, and best treatment modality.

CONCLUSION

Current literature is not unanimous on the relation between DR and physical complaints and on its most suitable treatment. This incongruity is corroborated by the variety of responses from involved health care professionals in our survey. More clinical data are needed to provide clarity on this issue.

Evaluating Overall Performance in High-Level Dressage Horse-Rider Combinations by Comparing Measurements from Inertial Sensors with General Impression Scores Awarded by Judges

In the sport of dressage, one or more judges score the combined performance of a horse and rider with an emphasis on the technical correctness of the movements performed. At the end of the test, a single score is awarded for the 'general impression', which considers the overall performance of the horse and rider as a team. This study explored original measures that contributed to the general impression score in a group of 20 horse-rider combinations. Horses and riders were equipped with inertial measurement units (200 Hz) to represent the angular motion of a horse's back and the motions of a rider's pelvis and trunk. Each combination performed a standard dressage test that was recorded to video. Sections of the video were identified for straight-line movements. The videos were analyzed by two or three judges. Four components were scored separately: gaits of the horse, rider posture, effectiveness of aids, and harmony with the horse. The main contributor to the score for gaits was stride frequency (R = -0.252, p = 0.015), with a slower frequency being preferred. Higher rider component scores were associated with more symmetrical transverse-plane trunk motion, indicating that this original measure is the most useful predictor of rider performance.

Significance of Lower Body Postures in Chair Design

OBJECTIVE

This study examined a system-level perspective to investigate the changes in the whole trunk and head postures while sitting with various lower extremity postures.

BACKGROUND

Sitting biomechanics has focused mainly on the lumbar region only, whereas the anatomy literature has suggested various links from the head and lower extremity.

METHOD

Seventeen male participants were seated in six lower extremity postures, and the trunk kinematics and muscle activity measures were captured for 5 s.

RESULTS

Changes in the trunk-thigh angle and the knee angle affected the trunk and head postures and muscle recruitment patterns significantly, indicating significant interactions between the lower extremity and trunk while sitting. Specifically, the larger trunk-thigh angle (T135°) showed more neutral lumbar lordosis (4.0° on average), smaller pelvic flexion (1.8°), smaller head flexion (3.3°), and a less rounded shoulder (1.7°) than the smaller one (T90°). The smaller knee angle (K45°) revealed a more neutral lumbar lordosis (6.9°), smaller pelvic flexion (9.2°), smaller head flexion (2.6°), and less rounded shoulder (2.4°) than the larger condition (K180°). The more neutral posture suggested by the kinematic measures confirmed significantly less muscular recruitment in the trunk extensors, except for a significant antagonistic co-contraction.

CONCLUSION

The lower and upper back postures were more neutral, and back muscle recruitment was lower with a larger trunk-thigh angle and a smaller knee angle, but at the cost of antagonistic co-contraction.

APPLICATION

The costs and benefits of each lower extremity posture can be used to design an ergonomic chair and develop an improved sitting strategy.

Recovering from Laboratory-Induced slips and trips causes high levels of lumbar muscle activity and spine loading

Slips, trips, and falls are some of the most substantial and prevalent causes of occupational injuries and fatalities, and these events may contribute to low-back problems. We quantified lumbar kinematics (i.e., lumbar angles relative to pelvis) and kinetics during unexpected slip and trip perturbations, and during normal walking, among 12 participants (6F, 6 M). Individual anthropometry, lumbar muscle geometry, and lumbar angles, along with electromyography from 14 lumbar muscles were used as input to a 3D, dynamic, EMG-based model of the lumbar spine. Results indicated that, in comparison with values during normal walking, lumbar range of motion, lumbosacral (L5/S1) loads, and lumbar muscle activations were all significantly higher during the slip and trip events. Maximum L5/S1 compression forces exceeded 2700 N during slip and trip events, compared with ∼ 1100 N during normal walking. Mean values of L5/S1 anteroposterior (930 N), and lateral (800 N) shear forces were also substantially larger than the shear force during the normal walking (230 N). These observed levels of L5/S1 reaction forces, along with high levels of bilateral lumbar muscle activities, suggest the potential for overexertion injuries and tissue damage during unexpected slip and trip events, which could contribute to low back injuries. Outcomes of this study may facilitate the identification and control of specific mechanisms involved with low back disorders consequent to slips or trips.

Effectiveness of Spinal Stabilization Exercises on Movement Performance in Adults with Chronic Low Back Pain

Introduction

Low back pain (LBP) is a musculoskeletal disorder that affects more than 80% of people in the United States at least once in their lifetime. LBP is one of the most common complaints prompting individuals to seek medical care. The purpose of this study was to determine the effects of spinal stabilization exercises (SSEs) on movement performance, pain intensity, and disability level in adults with chronic low back pain (CLBP).

Methods

Forty participants, 20 in each group, with CLBP were recruited and randomly allocated into one of two interventions: SSEs and general exercises (GEs). All participants received their assigned intervention under supervision one to two times per week for the first four weeks and then were asked to continue their program at home for another four weeks. Outcome measures were collected at baseline, two weeks, four weeks, and eight weeks, including the Functional Movement ScreenTM (FMSTM), Numeric Pain Rating Scale (NPRS), and Modified Oswestry Low Back Pain Disability Questionnaire (OSW) scores.

Results

There was a significant interaction for the FMSTM scores (p = 0.016), but not for the NPRS and OSW scores. Post hoc analysis showed significant between-group differences between baseline and four weeks (p = 0.005) and between baseline and eight weeks (p = 0.026) favor SSEs over GEs. Further, the results demonstrated that all participants, regardless of group, had significant improvements in movement performance, pain intensity, and disability level over time.

Conclusion

The results of the study favor SSEs over GEs in improving movement performance for individuals with CLBP, specifically after four weeks of the supervised SSE program.

Passive exoskeletons alter low back load transfer mechanism

Previous studies that tested passive back-support exoskeletons focused only on active low-back tissue. Therefore, this study examines the effect from a passive back-support exoskeleton by investigating changes in the load transfer mechanism between active and passive tissue in the low back. Twelve healthy male participants performed a full range of trunk flexion-extension movements under three conditions-FREE (no exoskeleton), the backX, or the CoreBot exoskeleton-while holding 0 kg, 4 kg, and 8 kg loads. Body kinematics and electromyography were recorded. Results showed that the average muscle activity of the lumbar erector spinae (LES) was significantly reduced while wearing the exoskeletons, with a 5.9%MVC reduction with the backX and a 3.3%MVC reduction with the CoreBot. Earlier occurrence of the flexion-relaxation phenomenon induced by the trunk extension moment of exoskeletons played an important role in reducing LES muscle activity because the LES returned to a relaxed state earlier (EMG-Off: a 3.1° reduction with the backX, and a 1.8° reduction with the CoreBot; EMG-On: a 2.3° reduction with the backX, and a 1.4° reduction with the CoreBot). In addition, the maximum lumbar flexion angle (a 2.2° reduction with the backX and a 1.5° reduction with the CoreBot) showed significant decreases compared to the FREE condition, indicating that exoskeleton use can prevent low-back passive tissue from being fully activated. These results suggested the overall effects of passive back-support exoskeletons in reducing loads on both active and passive tissue in the low back.

The relationship between core muscle endurance and functional movement screen scores in females with lumbar hyperlordosis: a cross-sectional study

Background

Core muscle endurance is essential for proper movement and lower extremity injury prevention. In addition, the Functional Movement Screen (FMS) score is a tool to assess body movement patterns to predict the risk of injury. Although various researches have investigated the relationship between the core muscle endurance and the FMS score, no study has ever assessed the effect of postural deformity on the FMS score. This study investigates the relationship between core muscle endurance and FMS scores in females with lumbar hyperlordosis.

Methods

42 healthy females aged 24.03 ± 4.4 years with hyperlordosis ( > = 45/66 degrees) participated in this study. Core muscle endurance was assessed by the McGill stability test. Correlations were evaluated between the FMS score, McGill test, and lordosis angle using spearman correlation coefficients (p ≤ 0.05).

Results

Most individual FMS scores were not correlated with the McGill test except stability trunk push up. Also, lordosis angle was not correlated with the FMS composite score (r=-0.077; p = 0.631), while it was negatively correlated with the McGill test (r=-0.650; p = 0.000).

Conclusion

The lack of correlation between the FMS score and the McGill test implies that one’s level of core endurance may not influence their functional movement patterns. In contrast, the lumbar lordosis angle might impact one’s core muscle endurance but not their functional movement patterns.

Surface Electromyographic Activity of the Rectus Abdominis and External Oblique during Isometric and Dynamic Exercises

Exercises for the abdominal muscles are widely used in athletic activities for strength training and prevention of low back disorders. The timing and volume of muscle activation for various movements have not yet been clarified. The purpose of this research was to evaluate the surface electromyographic activity from the upper (RAU) and lower part (RAL) of the rectus abdominis and the external oblique (EO) muscles during eleven abdominal muscle strength training exercises. Thirty-five healthy male university students with a subspecialty in soccer participated in the study. They performed exercises involving isometric, concentric, and eccentric muscle contractions. The electromyographic recordings were amplified by a factor of 1000, rectified, and integrated. Mean integrated values were calculated by dividing the elapsed time for the five repetitions, to provide the mean integrated electromyographic values for each exercise. Leg movements from a long lying position showed higher activity of the rectus abdominis, compared to the EO (p < 0.001). The dynamic sit-ups showed an obvious dominant activity of the EO, compared to the rectus abdominis (p < 0.001). During eccentric exercise, higher activity was found in the RAU, compared to the RAL (p < 0.001). The results could serve as a basis for improving the design and specification of training exercises. Pre-exercises should be performed before testing abdominal muscle strength.

Comparison of core stabilization techniques on ultrasound imaging of the diaphragm, and core muscle thickness and external abdominal oblique muscle electromyography activity

BACKGROUND

To restore core stability, abdominal drawing-in maneuver (ADIM), abdominal bracing (AB), and dynamic neuromuscular stabilization (DNS) have been employed but outcome measures varied and one intervention was not superior over another.

OBJECTIVE

The purpose of this study was to compare the differential effects of ADIM, AB, and DNS on diaphragm movement, abdominal muscle thickness difference, and external abdominal oblique (EO) electromyography (EMG) amplitude.

METHODS

Forty-one participants with core instability participated in this study. The subjects performed ADIM, AB, and DNS in random order. A Simi Aktisys and Pressure Biofeedback Unit (PBU) were utilized to measure core stability, an ultrasound was utilized to measure diaphragm movement and measure abdominal muscles thickness and EMG was utilized to measure EO amplitude. Analysis of variance (ANOVA) was conducted at P< 0.05.

RESULTS

Diaphragm descending movement and transverse abdominis (TrA) and internal abdominal oblique (IO) thickness differences were significantly increased in DNS compared to ADIM and AB (P< 0.05). EO amplitude was significantly increased in AB compared to ADIM, and DNS.

CONCLUSIONS

DNS was the best technique to provide balanced co-activation of the diaphragm and TrA with relatively less contraction of EO and subsequently producing motor control for efficient core stabilization.

Validation and comparison of trunk muscle activities in male participants during exercise using an innovative device and abdominal bracing maneuvers

BACKGROUND

Abdominal bracing is effective in strengthening the trunk muscles; however, assessing performance can be challenging. We created a device for performing abdominal trunk muscle exercises. The effectiveness of this device has not yet been evaluated or comparedOBJECTIVE: We aimed to quantify muscle activity levels during exercise using our innovative device and to compare them with muscle activation during abdominal bracing maneuvers.

METHODS

This study included 10 men who performed abdominal bracing exercises and exercises using our device. We measured surface electromyogram (EMG) activities of the rectus abdominis (RA), external oblique, internal oblique (IO), and erector spinae (ES) muscles in each of the exercises. The EMG data were normalized to those recorded during maximal voluntary contraction (%EMGmax).

RESULTS

During the bracing exercise, the %EMGmax of IO was significantly higher than that of RA and ES (p< 0.05), whereas during the exercises using the device, the %EMGmax of IO was significantly higher than that of ES (p< 0.05). No significant difference was observed in the %EMGmax of any muscle between bracing exercises and the exercises using the device (p= 0.13-0.95).

CONCLUSIONS

The use of our innovative device results in comparable activation to that observed during abdominal bracing.

Coordination Between Trunk Muscles, Thoracolumbar Fascia, and Intra-Abdominal Pressure Toward Static Spine Stability

STUDY DESIGN

Numerical in-silico human spine stability finite element analysis.

OBJECTIVE

The purpose of this study was to investigate the contribution of major torso tissues toward static spine stability, mainly the thoracolumbar fascia (TLF), abdominal wall with its intra-abdominal pressure (IAP), and spinal muscles inclusive of their intramuscular pressure.

SUMMARY OF BACKGROUND DATA

Given the numerous redundancies involved in the spine, current methodologies for assessing static spinal stability are limited to specific tissues and could lead to inconclusive results. A three-dimensional finite element model of the spine, with structured analysis of major torso tissues, allows for objective investigation of static spine stability.

METHODS

A novel previously fully validated spine model was employed. Major torso tissues, mainly the muscles, TLF, and IAP were individually, and in combinations, activated under a 350N external spine perturbation. The stability contribution exerted by these tissues, or their ability to restore the spine to the unperturbed position, was assessed in different case-scenarios.

RESULTS

Individual activations recorded significantly different stability contributions, with the highest being the TLF at 75%. Combined or synergistic activations showed an increase of up to 93% stability contribution when all tissues were simultaneously activated with a corresponding decrease in the tensile load exerted by the tissues themselves.

CONCLUSION

This investigation demonstrated torso tissues exhibiting different roles toward static spine stability. The TLF appeared able to dissipate and absorb excessive loads, the muscles acted as antagonistic to external perturbations, and the IAP played a role limiting movement. Furthermore, the different combinations explored suggested an optimized engagement and coordination between different tissues to achieve a specific task, while minimizing individual work.Level of Evidence: N/A.

A Lower-Back Exoskeleton with a Four-bar Linkage Structure for Providing Extensor Moment and Lumbar Traction Force

Lower back pain and related injuries are prevalent and serious problems in various industries, and high compression force to the lumbosacral (L5/S1) region has been known as one of the key factors. Previous research on passive lower back exoskeletons focused on reducing lumbar muscle activation by providing an extensor moment. Additionally, lumbar traction forces can reduce the compression force, and is a common treatment method for lower back pain in clinics. In this paper, we propose a novel passive lower back exoskeleton that provides both extensor moment and lumbar traction force. The working principle of the exoskeleton, extending the coil springs during lumbar flexion, and its design criteria regarding the amount of each force element were provided. The kinematic model explained its operation, and the dynamic simulation estimated its performance and validated its satisfaction with the design criteria. The biomechanical model provided a brief insight into the expected exoskeleton's effect on the reduced lower back compression force. Ten subjects performed static holding and dynamic lifting tasks, and the generated force elements in two directions, parallel and perpendicular to the trunk, were evaluated using a force sensor and electromyography sensors, respectively. The experiment demonstrated a pulling force opposite to the direction of intradiscal pressure and reduced erector spinae activation. This implies the effect of wearing the exoskeleton to decrease the intervertebral pressure during static back bending or heavy lifting tasks.

Internal and External Oblique Muscle Asymmetry in Sprint Hurdlers and Sprinters: A Cross-Sectional Study

The abdominal muscles are vital in providing core stability for functional movements during most activities. There is a correlation between side asymmetry of these muscles and dysfunction. Thus, the purpose of this study was to evaluate and compare trunk muscle morphology and trunk rotational strength between sprint hurdlers, an asymmetrical sport, and sprinters, a symmetrical sport. Twenty-one trained collegiate sprint hurdlers and sprinters were recruited for the study (Hurdlers: 4M, 7F; Sprinters: 8M, 2F), average age (years) hurdlers: 20 ± 1.2; sprinters: 20.4 ± 1.9, height (cm) hurdlers: 172.6 ± 10.2; sprinters: 181.7 ± 4.5, and weight (kg) hurdlers: 67.6 ± 12.0; sprinters: 73.9 ± 5.6. Using real-time ultrasound, panoramic images of the internal oblique (IO) and external oblique (EO) were obtained at rest and contracted (flexion and rotation) in a seated position for both right and left sides of the trunk. While wearing a specially crafted shoulder harness, participants performed three maximal voluntary trunk rotational contractions (MVC). The three attempts were then averaged to obtain an overall MVC score for trunk rotation strength. Average MVC trunk rotational strength to the right was greater among all participants, p < 0.001. The IO showed greater and significant thickness changes from resting to contracted state than the EO, this was observed in all participants. The IO side asymmetry was significantly different between groups p < 0.01. Hurdlers, involved in a unilaterally demanding sport, exhibited the expected asymmetry in muscle morphology and in trunk rotational strength. Interestingly, sprinters, although involved in a seemingly symmetrical sport, also exhibited asymmetrical trunk morphology and trunk rotational strength.

A passive back exoskeleton supporting symmetric and asymmetric lifting in stoop and squat posture reduces trunk and hip extensor muscle activity and adjusts body posture - A laboratory study

The influence of a passive exoskeleton was assessed during repetitive lifting with different lifting styles (squat, stoop) and orientations (frontal/symmetric, lateral/asymmetric) on trunk and hip extensor muscle activity (primary outcomes), abdominal, leg, and shoulder muscle activity, joint kinematics, and heart rate (secondary outcomes). Using the exoskeleton significantly and partially clinically relevant reduced median/peak activity of the erector spinae (≤6%), biceps femoris (≤28%), rectus abdominis (≤6%) and increased median/peak activity of the vastus lateralis (≤69%), trapezius descendens (≤19%), and median knee (≤6%) and hip flexion angles (≤11%). Using the exoskeleton had only limited influence on muscular responses. The findings imply the exoskeleton particularly supports hip extension and requires an adjusted body posture during lifting with different styles and orientations. The potential of using exoskeletons for primary/secondary prevention of musculoskeletal disorders should be investigated in future research including a greater diversity of users in terms of age, gender, health status.

The reliability of rehabilitative ultrasound to measure lateral abdominal muscle thickness: A systematic review and meta-analysis

BACKGROUND

Variations in rehabilitative ultrasound imaging (RUSI) protocols may alter lateral abdominal muscle (LAM) thickness measurements. A standardised protocol is required for clinicians to accurately compare LAM thickness changes.

OBJECTIVE

In healthy and lower back pain (LBP) populations, to assess the 1) overall reliability of RUSI to diagnose LAM thickness via meta-analysis, 2) reliability of ultrasound variables to diagnose LAM thickness via systematic review, and 3) propose a RUSI protocol for the LAM using variables associated with excellent reliability (intraclass correlation coefficient [ICC] >0.9).

DESIGN

Systematic review and meta-analysis.

METHOD

Databases were searched from January 2000 for studies reporting the reliability of RUSI on the LAM at rest. Title, abstract and full-text screening were performed. Reference lists of reviews and included full-text articles were scanned for further articles. Study characteristic, ultrasound procedure and reliability data were extracted, and article quality assessed. Data was synthesised using meta-analysis to determine the overall reliability for RUSI in different subgroups; calculation of the mean ICCs and standard error of measurements of protocol variables; and narrative synthesis of protocols to contrast those of differing reliability.

RESULTS

Twenty-seven articles, involving 884 participants were included. Reliability ranged from good-to-excellent (ICC 0.859-0.958) in all subgroups. Protocols ranged in subject selection and position, examiner experience, transducer position with the comprehensiveness of protocol description the main limitation of the reviewed literature. Based on the findings an ultrasound protocol was proposed.

CONCLUSIONS

RUSI variables for the LAM at rest show moderate-to-excellent reliability; future research should explore reliability following the proposed protocol.

Age-Related Changes in Concentric and Eccentric Isokinetic Peak Torque of the Trunk Muscles in Healthy Older Versus Younger Men

This study investigated age-related changes in trunk muscle function in healthy men and the moderating effect of physical activity. Twelve older (67.3 ± 6.0 years) and 12 younger (24.7 ± 3.1 years) men performed isokinetic trunk flexion and extension tests across a range of angular velocities (15°/s-180°/s) and contractile modes (concentric and eccentric). For concentric trunk extension, mixed-effects analysis of covariance revealed a significant interaction between Angular velocity × Age group (p = .026) controlling for physical activity. Follow-up univariate analysis of covariance revealed that the younger group produced significantly greater peak torque for all concentric extension conditions. Eccentric trunk strength was somewhat preserved in the older group. Age-related changes in trunk strength were independent of physical activity. The normal loss of trunk muscle strength in older age is muscle- and contractile-mode specific. These findings provide guidance for effective intervention strategies to offset adverse health outcomes related to trunk strength loss in older adults.

Coordination of Axial Trunk Rotations During Gait in Low Back Pain. A Narrative Review

Chronic low back pain patients have been observed to show a reduced shift of thorax-pelvis relative phase towards out-of-phase movement with increasing speed compared to healthy controls. Here, we review the literature on this phase shift in patients with low back pain and we analyze the results presented in literature in view of the theoretical motivations to assess this phenomenon. Initially, based on the dynamical systems approach to movement coordination, the shift in thorax-pelvis relative phase with speed was studied as a self-organizing transition. However, the phase shift is gradual, which does not match a self-organizing transition. Subsequent emphasis in the literature therefore shifted to a motivation based on biomechanics. The change in relative phase with low back pain was specifically linked to expected changes in trunk stiffness due to 'guarded behavior'. We found that thorax-pelvis relative phase is affected by several interacting factors, including active drive of thorax rotation through trunk muscle activity, stride frequency and the magnitude of pelvis rotations. Large pelvis rotations and high stride frequency observed in low back pain patients may contribute to the difference between patients and controls. This makes thorax-pelvis relative phase a poor proxy of trunk stiffness. In conclusion, thorax-pelvis relative phase cannot be considered as a collective variable reflecting the orderly behaviour of a complex underlying system, nor is it a marker of specific changes in trunk biomechanics. The fact that it is affected by multiple factors may explain the considerable between-subject variance of this measure in low back pain patients and healthy controls alike.

Trunk stiffness decreases and trunk damping increases with experimental low back pain

Movement adaptations to low back pain (LBP) are believed to protect the painful area. Increased trunk stiffness and decreased trunk damping have been shown in people with recurrent LBP. However, no study has examined these properties using external force perturbations to the trunk during acute LBP when protective adaptations might be expected to have most relevance. Adaptations to an acute painful stimulus via unilateral injection of hypertonic saline into the right longissimus muscle were assessed using a trunk force perturbation paradigm and a mass-spring-damper model to describe effective trunk dynamical properties. Equal weights (15% body weight) were connected to the front and back of the trunk via a cable. Either one was dropped at random to perturb the trunk. Effective trunk dynamical properties were estimated in fourteen males (mean (standard deviation) age 25 (6) years) assuming that trunk movement can be modelled as a second order linear system. Effective trunk dynamical properties were compared before, during and after the experimentally induced painful period. Estimates of effective trunk stiffness (K) decreased and damping (B) increased during pain compared to both before ([mean contrast, 95% CI] K: -403 [-651 to -155] Nm^-1, B: 28 [9-50] Nms^-1) and after (K: -324 [-58 to -591] Nm^-1, B: 20 [4-33] Nms^-1) the experimentally induced painful period. We interpret our results to show that, when challenged by a step force perturbation, a healthy system adapts to noxious input by controlling trunk velocity rather than trunk displacement, in contrast to observations during remission from recurrent clinical LBP.

Development of a multiscale model of the human lumbar spine for investigation of tissue loads in people with and without a transtibial amputation during sit-to-stand

Quantification of lumbar spine load transfer is important for understanding low back pain, especially among persons with a lower limb amputation. Computational modeling provides a helpful solution for obtaining estimates of in vivo loads. A multiscale model was constructed by combining musculoskeletal and finite element (FE) models of the lumbar spine to determine tissue loading during daily activities. Three-dimensional kinematic and ground reaction force data were collected from participants with ([Formula: see text]) and without ([Formula: see text]) a unilateral transtibial amputation (TTA) during 5 sit-to-stand trials. We estimated tissue-level load transfer from the multiscale model by controlling the FE model with intervertebral kinematics and muscle forces predicted by the musculoskeletal model. Annulus fibrosis stress, intradiscal pressure (IDP), and facet contact forces were calculated using the FE model. Differences in whole-body kinematics, muscle forces, and tissue-level loads were found between participant groups. Notably, participants with TTA had greater axial rotation toward their intact limb ([Formula: see text]), greater abdominal muscle activity ([Formula: see text]), and greater overall tissue loading throughout sit-to-stand ([Formula: see text]) compared to able-bodied participants. Both normalized (to upright standing) and absolute estimates of L4-L5 IDP were close to in vivo values reported in the literature. The multiscale model can be used to estimate the distribution of loads within different lumbar spine tissue structures and can be adapted for use with different activities, populations, and spinal geometries.

BIOMECHANICAL EFFECTS OF HYPERPRONATION ON MULTIDIRECTIONAL ANKLE ANGULAR DISPLACEMENT AND STIFFNESS

Hyperpronation of the foot is believed to contribute to ankle hypermobility and associated stiffness reduction, but the underlying biomechanical mechanisms remain unknown. This study aimsed to investigate multidirectional ankle displacement and associated stiffness when a posterior–anterior impact force was applied to the posterior knee compartment. Forty healthy adults with and without foot hyperpronation were recruited. A three-dimensional motion capture system and force plates were used to acquire angular displacement and ankle joint moment data. The independent [Formula: see text]-test and Mann–Whitney [Formula: see text] test were used to compare the group differences in ankle angular displacement, moment, and stiffness. Spearman’s rho test was performed to determine the relationship between ankle angular displacement and stiffness. The hyperpronation group demonstrated significantly greater sagittal ([Formula: see text]) and frontal plane ([Formula: see text]) angular displacements and reduced sagittal plane ankle stiffness ([Formula: see text]) than the neutral group. The Spearman’s correlation analysis showed a close inverse relationship between the ankle angular displacement and stiffness, ranging from [Formula: see text] to [Formula: see text]. The biomechanical data in our study suggest that individuals with foot hyperpronation present with multidirectional hypermobility and a reduction in ankle stiffness. These factors contribute to an increased risk of ankle-foot injury in individuals with foot hyperpronation.

Core muscles thickness is not associated with knee frontal plane projection angle during single-leg squat in healthy people

BACKGROUND

Core muscles play an important role in lower limb stability and alignment, with their weakness being associated with poor alignment and, consequently, with injuries. Despite muscle structure being critical to muscle strength production, we did not find studies associating the morphology of the core muscles and lower limb alignment during functional tasks.

RESEARCH QUESTION

Is there association between thickness of core muscles (external oblique - EO, internal oblique - IO, transversus abdominis - TrA and gluteus medius - GMed) and lower limb alignment during the single-leg squat in healthy subjects?

METHODS

Forty-six healthy participants (27 male and 19 female) performed the following evaluations: (i) measurements of muscle thickness of the EO, IO, TrA and GMed using ultrasound and (ii) measurements of lower limb alignment using the knee frontal plane projection angle (FPPA) during the single-leg squat. A Spearman rank correlation coefficient (r_s) was performed between the thickness of selected core muscles (OE, OI, TrA and GMed) and the knee FPPA. In addition, a partial correlation (r) was performed, using sex, physical activity level and body mass index as control variables.

RESULTS

We did not observe significant correlations between the knee FPPA and the thickness of the EO (r_s = 0.194; p = 0.197), IO (r_s = 0.182; p = 0.225), TrA (r_s = 0.073; p = 0.627) and GMed (r_s = -0.092; p = 0.542). When controlling for sex, physical activity level and body mass index, similar results were observed [EO (r = 0.157; p = 0.316), IO (r = 0.261; p = 0.092), TrA (r = 0.030; p = 0.850) and GMed (r = -0.144; p = 0.356)] SIGNIFICANCE: Our results demonstrated that core muscles' thickness is not associated with lower limb alignment during the single-leg squat in healthy people.

Assessing sensorimotor control of the lumbopelvic-hip region using task-based functional MRI

Recent brain imaging studies have suggested that cortical remodeling within sensorimotor regions are associated with persistent low back pain and may be a driving mechanism for the impaired neuromuscular control associated with this condition. This paper outlines a new approach for investigating cortical sensorimotor integration during the performance of small-amplitude lumbopelvic movements with functional MRI. Fourteen healthy right-handed participants were instructed in the lumbopelvic movement tasks performed during fMRI acquisition. Surface electromyography (EMG) collected on 8 lumbopelvic and thigh muscles captured organized patterns of muscle activation during the movement tasks. fMRI data were collected on 10 of 14 participants. Sensorimotor cortical activation across the tasks was identified using a whole brain analysis and further explored with regional analyses of key components of the cortical sensorimotor network. Head motion had low correlation to the tasks (r = -0.101 to 0.004) and head translation averaged 0.98 (0.59 mm) before motion correction. Patterns of activation of the key lumbopelvic and thigh musculature (average amplitude normalized 2-17%) were significantly different across tasks (P > 0.001). Neuroimaging demonstrated activation in key sensorimotor cortical regions that were consistent with motor planning and sensory feedback needed for performing the different tasks. This approach captures the specificity of lumbopelvic sensorimotor control using goal-based tasks (e.g., "lift your hip" vs. "contract your lumbar multifidus to 20% of maximum") performed within the confines of the scanner. Specific patterns of sensorimotor cortex activation appear to capture differences between bilateral and unilateral tasks during voluntary control of multisegmental movement in the lumbopelvic region.NEW & NOTEWORTHY We demonstrated the feasibility of using task-based functional magnetic resonance imaging (fMRI) protocols for acquiring the blood oxygen level-dependent (BOLD) response of key sensorimotor cortex regions during voluntary lumbopelvic movements. Our approach activated lumbopelvic muscles during small-amplitude movements while participants were lying supine in the scanner. Our data supports these tasks can be done with limited head motion and low correlation of head motion to the task. The approach provides opportunities for assessing the role of brain changes in persistent low back pain.

Effect of abdominal drawing-in maneuver with prone hip extension on muscle activation of posterior oblique sling in normal adults

[Purpose] There have been many studies on ipsilateral erector spinae in regard of prone hip extension (PHE). However, mediating methods have been focusing on the reinforcement of gluteus. Hereupon, this study is intended to identify how an increase of abdominal drawing-in maneuver influences on posterior oblique sling (POS) and suggest a mediating method to effectively reinforce them. [Participants and Methods] This study has been conducted on normal male (10) and female (10), and participants were asked to prove PHE exercise and abdominal drawing-in maneuver prone hip extension exercise (ADIM PHE). Surface electromyography (EMG) was recorded from the contralateral latissimus dorsi, ipsilateral erector spinae, ipsilateral gluteus maximus, and ipsilateral biceps femoris. A pared t-test was used to compare muscle activity POS. [Results] EMG activity of the contralateral latissimus dorsi, ipsilateral gluteus maximus was significantly greater performed ADIM PHE than PHE. As for ipsilateral erector spinae muscle, ipsilateral biceps femoris activation was lower in ADIM PHE than PHE. [Conclusion] According to the results of this study, abdominal drawing-in maneuver seems to be an important factor that influences on muscular activation of POS.

Fatty infiltration of paraspinal muscles is associated with bone mineral density of the lumbar spine

A total of 88 subjects were enrolled to investigate the relationship between paraspinal muscle fatty infiltration and lumbar bone mineral density (BMD) using chemical shift encoding-based water-fat MRI and quantitative computed tomography (QCT), respectively. A moderate inverse correlation between paraspinal muscle proton density fat fraction and lumbar QCT-BMD was found with age, sex, and BMI controlled.

PURPOSE

To investigate the relationship between paraspinal muscle fatty infiltration and lumbar bone mineral density (BMD).

METHODS

A total of 88 subjects were enrolled in this study (52 females, 36 males; age, 46.6 ± 14.2 years old; BMI, 23.2 ± 3.49 kg/m²). Proton density fat fractions (PDFF) of paraspinal muscles (erector spinae, multifidus, and psoas) were measured at L2/3, L3/4, and L4/5 levels using chemical shift encoding-based water-fat MRI. Quantitative computed tomography (QCT) was used to assess BMD of L1, L2, and L3. The differences in paraspinal muscle PDFF among subjects with normal bone density, osteopenia, and osteoporosis were tested using one-way ANOVA. The relationship between paraspinal muscle PDFF and QCT-BMD was analyzed using linear regression with age, sex, and BMI variables.

RESULTS

PDFF of the erector spinae, multifidus, and psoas of subjects with normal bone density were all significantly less than those with osteopenia and those with osteoporosis (all p < 0.001). There was an inverse correlation between paraspinal muscle PDFF and BMD after controlling for age, sex, and BMI (standardized beta coefficient, - 0.21~- 0.29; all p < 0.05).

CONCLUSIONS

Paraspinal muscle fatty infiltration increased while lumbar BMD decreased after adjusting for age, sex, and BMI. Paraspinal muscles and vertebrae are interacting tissues. Paraspinal muscle fatty infiltration may be a marker of low lumbar BMD. Chemical shift imaging is an efficient and fast quantitative method and can be easily added to the clinical protocol to measure paraspinal muscle PDFF when the patient underwent the routine lumbar MRI with low-back pain.

Sensitivity to Physical Activity Predicts Daily Activity Among Pain-Free Older Adults

Objective

Prior research indicates that older adults with knee osteoarthritis have increased sensitivity to physical activity (SPA) and respond to physical activities of stable intensity with increases in pain. Whether SPA is present in healthy older adults without chronic pain and predicts functional outcomes remains relatively unexplored. The purpose of this study was to determine the degree of SPA in healthy older adults in response to a standardized walking task, and whether SPA was associated with temporal summation of pain, pain-related fear of movement, and functional outcomes.

Methods

Fifty-two older adults without chronic pain completed self-reported measures of activity-related pain and physical function, completed the Six-Minute Walk Test (6MWT), underwent quantitative sensory testing to measure temporal summation of heat pain, and wore an accelerometer for one week to measure physical activity behavior. Subjects rated overall bodily discomfort (0-100 scale) prior to and during each minute of the 6MWT. An SPA index was created by subtracting the initial bodily discomfort ratings from the peak ratings.

Results

Repeated-measures analysis of variance indicated that bodily discomfort significantly increased across the walking task, with approximately 60% of the sample experiencing SPA. Hierarchical regressions indicated that greater SPA was associated with fewer average steps per day and greater activity-related pain. Additionally, analyses revealed that temporal summation of pain and pain-related fear of movement significantly predicted the degree of SPA on the walking task.

Conclusions

These findings shed light on potential mechanisms underlying SPA in older adults and suggest that SPA might be a risk factor for reduced physical activity.

The effect of extensible and non-extensible lumbar belts on trunk muscle activity and lumbar stiffness in subjects with and without low-back pain

BACKGROUND

Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this is associated with trunk muscle co-contraction, which would increase the compression on the spine. It has been hypothesized that lumbar belts increase lumbar stiffness by increasing intra-abdominal pressure, which would increase spinal stability without increasing the compressive load on the spine.

METHODS

Trunk muscle activity and lumbar stiffness and damping were measured in healthy and low-back pain subjects during three conditions: no lumbar belt; wearing an extensible lumbar belt; wearing a non-extensible lumbar belt. Muscle activity was measured while subjects performed controlled forward and backward 20° trunk sways. Lumbar stiffness and damping were measured by applying random continuous perturbation to the chest.

FINDINGS

External oblique activity was decreased when wearing either lumbar belt during all phases of movement, while rectus abdominis and iliocostalis activity were decreased during the phase of movement where the muscles were maximally active while wearing either belt. Trunk stiffness was greatly increased by wearing either belt. There were no consistent differences in either lumbar stiffness or muscle activity between the two belts. Wearing a lumbar belt had little to no effect on damping. There were no group differences in any of the measures between healthy and low-back pain populations.

INTERPRETATION

The findings are consistent with the hypothesis that lumbar belts can increase spinal stability by increasing intra-abdominal pressure, without any increase in the compressive load on the spine. The findings can also be generalized, for the first time, to subjects with low-back pain.

Characterizing trunk muscle activations during simulated low-speed rear impact collisions

Objective: The purpose of this study was to evaluate the activation profiles of muscles surrounding the lumbar spine during unanticipated and braced simulated rear-end collisions. Methods: Twenty-two low-speed sled tests were performed on 11 human volunteers ( △ V = 4 km/h). Each volunteer was exposed to one unanticipated impact and one braced impact. Accelerometers were mounted on the test sled and participants' low back. Six bilateral channels of surface electromyography (EMG) were collected from the trunk during impact trials. Peak lumbar accelerations, peak muscle activation delay, muscle onset time, and peak EMG magnitudes, normalized to maximum voluntary contractions (MVCs), were examined across test conditions. Results: Though not statistically significant, bracing for impact tended to reduce peak lumbar acceleration in the initial rearward impact phase of the occupant's motion by approximately 15%. The only trunk muscles with peak activations exceeding 10% MVC during the unanticipated impact were the thoracic erector spinae. Time of peak muscle activation was slightly longer for the unanticipated condition (unanticipated = 296 ms; braced = 241 ms). Conclusions: Results from this investigation demonstrate that during an unanticipated low-speed rear-end collision, the peak activation of muscles in the lumbar spine are low in magnitude. As such, muscle activation likely has minimal contribution to the internal joint loads that are experienced in the lumbar intervertebral joints during low-speed rear impact collisions. These findings justify the use of simplified joint models in estimating the joint loads in the lumbar spine during low-speed rear impact collisions and support the application of cadaveric and anthropomorphic test device (ATD) testing in understanding the resultant joint loads in the lumbar spine associated with rear-end collisions.

The influence of external load configuration on trunk biomechanics and spinal loading during sudden loading

Sudden loading is a major risk factor for work-related lower back injuries among occupations involving manual material handling (MMH). The current study explored the effects of external weight configuration on trunk biomechanics and trunk rotational stiffness in the sagittal plane during sudden loading. Fifteen asymptomatic volunteers experienced sudden loadings using the same magnitude of weight (9 kg) with two different configurations (medially- or laterally-distributed) at three levels of height (low, middle and high). Results of this study showed that the medially distributed weight resulted in a significantly higher peak L5/S1 joint compression force (2861 N vs. 2694 N) and trunk rotational stiffness (2413 Nm/rad vs. 1785 Nm/rad) compared to the laterally distributed weight. It was concluded that when experiencing sudden loading, a more laterally distributed weight could increase the load's resistance to physical perturbations and alleviate spinal loading during sudden loading events. Practitioner summary: Increased trunk rotational stiffness and peak L5/S1 joint compression force were observed when undergoing a sudden load release of a medially distributed load compared to a laterally distributed load revealing a less stable hand load condition due to the reduced moment of inertia. The laterally distributed load could increase the load's resistance to physical perturbations and mitigate spinal loading during sudden loading events.

Wheels-in-wheels: Use of gravity in human locomotion

Although a wheel is an ideal method for transportation and the invention of the spoke wheel made a wheel lighter and swifter, a wheel cannot function well on slanted or rough surfaces; these are common in the natural environment. Further, the load support of the wheel is limited to a point of the whole wheel in contact with the ground. Then, we humans may be using the legs as a part of spoke wheel and place our legs and feet on the ground alternatively to support the body weight while the gravitational torque makes the center of mass (COM) rotate around the hip joint when proper stiffness and balance is made. Through a pulley-like action involving the hamstrings and a lever-like action of back muscles via the psoas muscle, the energy expenditure for locomotion can be reduced to the energy for lifting the swing leg to maintain the proper position of the COM. Further, the stabilizing action of the psoas muscle to the spinal column can be achieved between the stance leg and the swing leg by the weight of the lifted swing leg during the forward movement. This lifting action during swing phase can assist an energy-efficient eccentric contraction of the stance leg. The passive tension generated by gravity (own weight and the carried load) can be the reason for the energy efficiency of both head-carrying and the Nepalese porter method. Using this passive gravitational force via actively synchronized neuromuscular action may be universal for animal locomotion.

Effects of unstable shoes on trunk muscle activity in patients with chronic low back pain

INTRODUCTION

Unstable shoes were developed as a walking device to strengthen the lower extremity muscles and reduce joint loading. Many studies have reported increased muscle activity throughout the gait cycle in most of the lower limb muscles in healthy adults using these shoes. However, no previous studies have explored the effects of wearing unstable shoes on trunk muscle activity in patients with chronic low back pain (CLBP). Therefore, the aim of the present study was to compare the activity of selected trunk muscles in patients with CLBP during a gait test while walking wearing unstable shoes or conventional flat shoes (control).

METHODS

Thirty-five CLBP patients (51.1 ± 12.4 y; 26 ± 3.8 kg/m2; 9.3 ± 5.2 Roland Morris Disability Questionnaire score) were recruited from the Orthopedic Surgery Service at the Hospital to participate in this cross-sectional study. All the participants underwent gait analysis by simultaneously collecting surface electromyography (EMG) data from erector spinae (ES), rectus abdominis (RA), obliquus internus (OI), and obliquus externus (OE) muscles, while walking on a treadmill with flat control shoes or experimental unstable shoes.

RESULTS

The results showed significantly higher %EMG activity in the ES (mean difference: 1.8%; 95% CI: 1.3-2.2), RA (mean difference: 1.5%; 95% CI: 0.3-2.7), and OI (mean difference: 1.5%; 95% CI: 0.2-2.8) in the unstable versus the flat-shoe condition, with a large effect size for the ES (Cohen's d = 1.27).

CONCLUSIONS

Based on these findings, the use of unstable shoes may be implicated in promoting spine stability, particularly in improving neuromuscular control of the trunk muscles in CLBP treatment.

Comparison of rider stability in a flapless saddle versus a conventional saddle

The purpose of a saddle is to improve the rider’s safety, security, and comfort, while distributing the forces exerted by the rider and saddle over a large area of the horse’s back without focal pressure points. This study investigates the effects on rider stability of an innovative saddle design that differs from a conventional saddle in having no flaps. Five horses were ridden by their regular rider in their usual saddle and in a flapless saddle. A pressure mat (60 Hz) placed between the saddle and the horse’s back was used to determine the position of the center of pressure, which represents the centroid of pressure distribution on the horse’s back. Data were recorded as five horses were ridden at collected and extended walk, trot and canter in a straight line. Data strings were split into strides with 5 strides analysed per horse/gait/type. For each stride the path of the rider’s center of pressure was plotted, maximal and minimal values in the anteroposterior and mediolateral directions were extracted, and ranges of motion in anteroposterior and mediolateral directions were calculated. Differences between the conventional and flapless saddles were analysed using mixed models ANOVA. Speed and stride length of each gait did not differ between saddles. Compared with the conventional saddle, the flapless saddle was associated with significant reductions in range of motion of the rider’s center of pressure in the mediolateral direction in all gaits and in the anteroposterior direction in collected trot, extended trot and extended canter. The improved stability was thought to result from the absence of saddle flaps allowing the rider’s thighs to lie in more adducted positions, which facilitated the action of the lumbopelvic-hip musculature in stabilizing and controlling translations and rotations of the pelvis and trunk. The closer contact between rider and horse may also have augmented the transfer of haptic information.

Development of a pressure sensor system for unobtrusive monitoring of abdominal muscle activities

Surface electromyogram (sEMG) is often used by to objectively measure muscular activity during rehabilitation exercises. sEMG is accurate, but it is unsuitable for uses outside the clinic, and patients can benefit from an unobtrusive device which can be readily used to ubiquitously measure abdominal muscle activation. In this study, we present a pressure sensor system which can be latched onto a belt to measure abdominal muscle activation. sEMG and pressure sensor output were measured in 15 healthy young males during isometric trunk flexion exercise (public trials registration number, KCT0002351), and the results were highly correlated (median R > 0.939). As initial contact force can change the pressure sensor sensitivity, the experiment was performed at two different levels of belt tightness, but the correlations did not significantly improve after tightening the belt, suggesting that the system can be used to ubiquitously and unobtrusively monitor abdominal muscle activity with minimal discomfort.

Pilates training improves 5-km run performance by changing metabolic cost and muscle activity in trained runners

Purpose

Strength training improves distance running economy and performance. This finding is based predominantly on maximal and explosive strength programmes applied to locomotor muscles, particularly on the lower limbs. It is not certain whether a minimization of metabolic cost (C_met) and an improvement in running performance is feasible with strength training of the postural and trunk muscles.

Methods

Using kinematic, neuromuscular and metabolic measurements of running at two different speeds before and after a 12-week Pilates training programme, we tested the hypothesis that core training might improve the running C_met and performance of trained runners. Thirty-two individuals were randomly assigned to the control group (CG, n = 16) or the Pilates group (PG, n = 16).

Results

Confirming our hypothesis, a significant improvement (p<0.05) was observed for running performance in the PG (pre: 25.65±0.4 min; post: 23.23±0.4 min) compared to the CG (pre: 25.33±0.58 min; post: 24.61±0.52 min). Similarly, the PG (4.33±0.07 J.kg^-1.m^-1) had better responses than the CG (4.71±0.11 J.kg^-1.m^-1) during post-training for C_met. These findings were accompanied by decreased electromyographic activity of the postural muscles at submaximal running intensities in the PG.

Conclusions

Overall, these results provide a rationale for selecting strength training strategies that target adaptations on specific postural and locomotor muscles for trained distance runners.

Asymmetry of activation of lateral abdominal muscles during the neurodevelopmental traction technique

OBJECTIVE

The aim of the study was to evaluate the symmetry and pattern of activation of lateral abdominal muscles (LAM) in response to neurodevelopmental traction technique.

DESIGN AND PARTICIPANTS

Measurements of LAM thickness were performed in four experimental conditions: during traction with the force of 5% body weight (5% traction): 1) in neutral position, 2) in 20° posterior trunk inclination; during traction with the force of 15% body weight (15% traction): 3) in neutral position, 4) in 20° posterior trunk inclination. Thirty-seven healthy children participated in the study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

To evaluate LAM activation level ultrasound technology was employed (two Mindray DP660 devices (Mindray, Shenzhen, China) with 75L38EA linear probes). An experiment with repeated measurements of the dependent variables was conducted.

RESULTS

Side-to-side LAM activation asymmetry showed relatively high magnitude, however, significant difference was found only in case of the obliquus externus (OE) during stronger traction (P < 0.05). The magnitude of LAM thickness change formed a gradient, with the most profound transversus abdominis (TrA) showing the smallest change, and the most superficial OE - the greatest. The inter-muscle differences were most pronounced between the OE and TrA (P < 0.001).

CONCLUSIONS

During the neurodevelopmental traction technique there is a difference in individual LAM activation level, with deeper muscles showing less intense activation. In statistical terms, the only signs of side-to-side asymmetry of LAM activation are visible in case of the OE, however, the magnitude of asymmetry is relatively high. The results allow to identify patterns of activation of LAM in children showing typical development that will serve as a reference in future studies in children with neurological disorder.

Comparative effectiveness of two stabilization exercise positions on pain and functional disability of patients with low back pain

The study investigated the effects of two stabilization exercise positions (prone and supine) on pain intensity (PI) and functional disability (FD) of patients with nonspecific chronic low back pain (NSCLBP). The 56 subjects that completed the study were randomly assigned into stabilization in prone (SIP) (n=19), stabilization in supine (SIS) (n=20), and prone and supine (SIPS) position (n=17) groups. Subjects in all the groups received infrared radiation for 15 min and kneading massage at the low back region. Subjects in SIP, SIS, and SIPS groups received stabilization exercise in prone lying, supine lying and combination of both positions respectively. Treatment was applied twice weekly for eight weeks. PI and FD level of each subject were measured at baseline, 4th and 8th week of the treatment sessions. Data were analyzed using descriptive and inferential statistics. The alpha level was set at P<0.05. Within-group comparison indicated that PI and FD at the 4th and 8th week were significantly reduced (P<0.001) when compared with baseline in all the three groups. However, the result showed that there was no significant difference in the PI and FD at the 8th week (P>0.05) of the treatment sessions across the three groups when compared. It can be concluded that stabilization exercises carried out in prone, supine and combination of the two positions were equally effective in managing pain and disability of patients with NSCLBP. However, no position was superior to the other.

The effect of bridge exercise method on the strength of rectus abdominis muscle and the muscle activity of paraspinal muscles while doing treadmill walking with high heels

[Purpose] The purpose of this research is to investigate the effect of the method of bridge exercise on the change of rectus abdominis muscle and the muscle activity of paraspinal muscles while doing treadmill walking with high heels. [Subjects and Methods] The subjects of this research are healthy female students consisting of 10 persons performing bridge exercises in a supine group, 10 persons performing bridge exercises in a prone group, and 10 persons in a control group while in S university in Busan. Bridge exercise in supine position is performed in hook lying position. Bridge exercise in prone position is plank exercise in prostrate position. To measure the strength of rectus abdominis muscle, maintaining times of the posture was used. To measure the muscle activity of paraspinal muscles, EMG (4D-MT & EMD-11, Relive, Korea) was used. [Results] The strength of rectus abdominis muscle of both bridge exercises in the supine group and bridge exercises in the prone group increases significantly after exercise. The muscle activity of paraspinal muscle such as thoracic parts and lumbar parts in bridge exercises in the prone group decreases statistically while walking on a treadmill with high heels. Muscle activity of thoracic parts paraspinal muscle and bridge exercises in the supine group decreased significantly. [Conclusion] According to this study, we noticed that bridge exercise in a prone position is desirable for women who prefer wearing high heels as a back pain prevention exercise method.

Estimation of lumbar spinal loading and trunk muscle forces during asymmetric lifting tasks: application of whole-body musculoskeletal modelling in OpenSim

Large spinal compressive force combined with axial torsional shear force during asymmetric lifting tasks is highly associated with lower back injury (LBI). The aim of this study was to estimate lumbar spinal loading and muscle forces during symmetric lifting (SL) and asymmetric lifting (AL) tasks using a whole-body musculoskeletal modelling approach. Thirteen healthy males lifted loads of 7 and 12 kg under two lifting conditions (SL and AL). Kinematic data and ground reaction force data were collected and then processed by a whole-body musculoskeletal model. The results show AL produced a significantly higher peak lateral shear force as well as greater peak force of psoas major, quadratus lumborum, multifidus, iliocostalis lumborum pars lumborum, longissimus thoracis pars lumborum and external oblique than SL. The greater lateral shear forces combined with higher muscle force and asymmetrical muscle contractions may have the biomechanical mechanism responsible for the increased risk of LBI during AL. Practitioner Summary: Estimating lumbar spinal loading and muscle forces during free-dynamic asymmetric lifting tasks with a whole-body musculoskeletal modelling in OpenSim is the core value of this research. The results show that certain muscle groups are fundamentally responsible for asymmetric movement, thereby producing high lumbar spinal loading and muscle forces, which may increase risks of LBI during asymmetric lifting tasks.

The effect of short-term isometric training on core/torso stiffness

"Core" exercise is a basic part of many physical training regimens with goals ranging from rehabilitation of spine and knee injuries to improving athletic performance. Core stiffness has been proposed to perform several functions including reducing pain by minimising joint micro-movements, and enhancing strength and speed performance. This study probes the links between a training approach and immediate but temporary changes in stiffness. Passive and active stiffness was measured on 24 participants; 12 having little to no experience in core training (inexperienced), and the other 12 being athletes experienced to core training methods; before and after a 15 min bout of isometric core exercises. Passive stiffness was assessed on a "frictionless" bending apparatus and active stiffness assessed via a quick release mechanism. Short-term isometric core training increased passive and active stiffness in most directions for both inexperienced and experienced participants, passive left lateral bend among experienced participants being the exception (P < 0.05). There was no difference between the inexperienced and experienced groups. The results confirm that the specific isometric training exercise approach tested here can induce immediate changes in core stiffness, in this case following a single session. This may influence performance and injury resilience for a brief period.

The effects of Pilates breathing trainings on trunk muscle activation in healthy female subjects: a prospective study

[Purpose] To investigate the effects of Pilates breathing on trunk muscle activation. [Subjects and Methods] Twenty-eight healthy female adults were selected for this study. Participants’ trunk muscle activations were measured while they performed curl-ups, chest-head lifts, and lifting tasks. Pilates breathing trainings were performed for 60 minutes per each session, 3 times per week for 2 weeks. Post-training muscle activations were measured by the same methods used for the pre-training muscle activations. [Results] All trunk muscles measured in this study had increased activities after Pilates breathing trainings. All activities of the transversus abdominis/internal abdominal oblique, and multifidus significantly increased. [Conclusion] Pilates breathing increased activities of the trunk stabilizer muscles. Activation of the trunk muscle indicates that practicing Pilates breathing while performing lifting tasks will reduce the risk of trunk injuries.

Three-dimensional trajectories affect the epaxial muscle activity of arboreal snakes crossing gaps

The need for long-axis support is widespread among non-aquatic vertebrates and may be particularly acute for arboreal snakes when many vertebrae span sizable gaps between branches with diverse orientations. Hence, we used brown tree snakes (Boiga irregularis) bridging gaps to test how three-dimensional trajectories affected muscle activity and whether these motor patterns differed from those for the locomotion of terrestrial snakes and movements of other vertebrates. We used five trajectories: pitch angles of 90, 0 and -90 deg (downward) when yaw=0, and 90 deg yaw angles to the left and right when pitch=0 deg. We recorded movement and EMGs from the three largest epaxial muscles, which from dorsal to ventral are the semispinalis-spinalis (SSP), longissimus dorsi (LD), and iliocostalis (IL). Overall, the SSP had extensive bilateral activity, which resembled the motor pattern during the dorsiflexion of sidewinding snakes. Unlike any previously described terrestrial snake locomotion, bilateral activity of the LD and IL was also common during gap bridging. The largest amounts of muscle activity usually occurred for horizontal gaps, and muscle activity decreased markedly as soon as the snake's head touched the far edge of the gap. Snakes had the least amount of muscle activity for pitch=-90 deg. While turning sideways, muscles on the convex side had less activity when turning compared to the concave side. Hence, the orientation relative to gravity profoundly affected muscle activity during gap bridging, and these complex three-dimensional movements involved several previously undescribed variants of axial motor pattern.

Goal equivalent manifold analysis of task performance in non-specific LBP and healthy subjects during repetitive trunk movement: Effect of load, velocity, symmetry

Motor abundance allows reliability of motor performance despite its variability. The nature of this variability provides important information on the flexibility of control strategies. This feature of control may be affected by low back pain (LPB) and trunk flexion/extension conditions. Goal equivalent manifold (GEM) analysis was used to quantify the ability to exploit motor abundance during repeated trunk flexion/extension in healthy individuals and people with chronic non-specific LBP (CNSLBP). Kinematic data were collected from 22 healthy volunteers and 22 CNSLBP patients during metronomically timed, repeated trunk flexion/extension in three conditions of symmetry, velocity, and loading; each at two levels. A goal function for the task was defined as maintaining a constant movement time at each cycle. Given the GEM, flexibility index and performance index were calculated respectively as amounts of goal-equivalent variability and the ratio of goal-equivalent to non-goal-equivalent variability. CNSLBP group was as similar as healthy individuals in both flexibility index (p=0.41) and performance index (p=0.24). Performance index was higher in asymmetric (p<0.001), high velocity (p<0.001), and loaded (p=0.006) conditions. Performance and flexibility in using motor abundance were influenced by repeated trunk flexion/extension conditions. However, these measures were not significantly affected by CNSLBP.

Measurement of superficial and deep abdominal muscle thickness: an ultrasonography study

Background

Real-time ultrasound imaging is a valid method in the field of rehabilitation. The ultrasound imaging allows direct visualization for real-time study of the muscles as they contract over the time. Measuring of the size of each abdominal muscle in relation to the others provides useful information about the differences in structure, as well as data on trunk muscle activation patterns. The purpose of this study was to assess the size and symmetry of the abdominal muscles at rest in healthy adults and to provide a reference range of absolute abdominal muscle size in a relatively large population.

Method

A total 156 healthy subjects with the age range of 18–44 years were randomly recruited. The thickness of internal oblique, external oblique, transverse abdominis, and rectus abdominis muscles was measured at rest on both right and left sides using ultrasound. Independent t test was used to compare the mean thickness of each abdominal muscle between males and females. Differences on side-to-side thicknesses were assessed using paired t test. The association between abdominal muscle thicknesses with gender and anthropometric variables was examined using the Pearson correlation coefficient.

Results

A normal pattern of increasing order of mean abdominal muscle thickness was found in both genders at both right and left sides: transverse abdominis < external oblique < internal oblique < rectus abdominis. There was a significant difference on the size of transverse abdominis, internal oblique, and external oblique muscles between right and left sides in both genders. Males had significantly thicker abdominal muscles than females. Age was significantly correlated with the thickness of internal oblique, external oblique, and rectus abdominis muscles. Body mass index was also positively correlated with muscle thickness of rectus abdominis and external oblique.

Conclusions

The results provide a normal reference range for the abdominal muscles in healthy subjects and may be used as an index to find out abnormalities and also to evaluate the effectiveness of different interventions.

Incorporating Six Degree-of-Freedom Intervertebral Joint Stiffness in a Lumbar Spine Musculoskeletal Model-Method and Performance in Flexed Postures

Intervertebral translations and rotations are likely dependent on intervertebral stiffness properties. The objective of this study was to incorporate realistic intervertebral stiffnesses in a musculoskeletal model of the lumbar spine using a novel force-dependent kinematics approach, and examine the effects on vertebral compressive loading and intervertebral motions. Predicted vertebral loading and intervertebral motions were compared to previously reported in vivo measurements. Intervertebral joint reaction forces and motions were strongly affected by flexion stiffness, as well as force-motion coupling of the intervertebral stiffness. Better understanding of intervertebral stiffness and force-motion coupling could improve musculoskeletal modeling, implant design, and surgical planning.