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Most of the studies evaluating core muscle activity during exercises have been conducted with healthy participants. The objective of this study was to compare core muscle activity and tolerability of a variety of dynamic and isometric exercises in patients with non-specific low back pain (NSLBP). 13 outpatients (average age 52 years; all with standing or walking work in their current or latest job) performed 3 consecutive repetitions at 15-repetition maximum during different exercises in random order. Surface electromyography was recorded for the rectus abdominis; external oblique and lumbar erector spinae. Patients rated tolerability of each exercise on a 5-point scale. The front plank with brace; front plank and modified curl-up can be considered the most effective exercises in activating the rectus abdominis; with a median normalized EMG (nEMG) value of 48% (34-61%), 46% (26-61%) and 50% (28-65%), respectively. The front plank with brace can be considered the most effective exercise in activating the external oblique; with a nEMG of 77% (60-97%). The squat and bird-dog exercises are especially effective in activing the lumbar erector spinae; with nEMG of 40% (24-87%) and 29% (27-46%), respectively. All the exercises were well tolerated; except for the lateral plank that was mostly non-tolerated. In conclusion; the present study provides a variety of dynamic and isometric exercises; where muscle activity values and tolerability can be used as guide to design evidence-based exercise programs for outpatients with NSCLBP., Competing Interests: The authors declare no conflict of interest.

The VT-Lowe's exoskeleton is a novel passive lift-assistive device designed to offload the back muscles during repetitive lifting. In this study, the effect of the exoskeleton on electromyographic (EMG) signals was investigated in four different lifting types (stoop, squat, freestyle and asymmetric) and two box weights (0% and 20% of body weight). Twelve young healthy adults ages 18-31 years (mean = 22.75, SD = 4.35) were participants. The EMG signals for twelve muscles (iliocostalis erector spinae (IL), longissimus erector spinae (LT), multifidus (MF), bicep femoris (BF), vastus lateralis (VL) and abdominal external oblique (AEO) muscles) were measured. The exoskeleton significantly decreased the peak and mean activity of back muscles (IL and LT) by 31.5% and 29.3%, respectively, for symmetric lifts and by 28.2% and 29.5%, respectively, for asymmetric lifts. The peak and mean EMG of leg muscles were significantly reduced by 19.1% and 14.1% during symmetric lifts, and 17.4% and 14.6% during asymmetric lifts. Although the exoskeleton reduced the activation of back and leg muscles, it slightly increased the activity of external oblique muscles, although this was not statistically significant. In conclusion, the exoskeleton is promising as a lift-assist device for manual material handlers and workers performing repetitive lifting., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Due to anecdotal reports of back pain during a 12-minute rotational bridge test by uniformed services, the level of fatigue leading to possible back pain and or injury was investigated. We hypothesised a high level of fatigue due to diminishing core muscle activation. Nineteen highly trained uniformed service members were measured by surface electromyography of the rectus abdominis, external oblique, internal oblique, lumbar erector spinae, thoracic erector spinae and latissimus dorsi. Average rectified electromyography amplitude (AEMG) and median power frequency were analysed to determine activation and fatigue. All AEMG were normalised and expressed as a percentage of maximal voluntary isometric contraction (%MVIC). Significant increases in AEMG were observed over the test duration for the rectus abdominis (+19.5%MVIC), external oblique (+18.0%MVIC) and internal oblique (+23.2%MVIC) during the prone position; and for the external oblique (+21.8%MVIC) when bracing on the measurement side (all, p  < 0.05). No significant changes in median power frequency were observed (all, p  > 0.05). Combining prone and side bridge positions is a reasonable measure of anterior, posterior and lateral trunk musculature. Muscular fatigue remained low throughout making this a safe assessment in trained individuals.

Background and Objective: The objective of this study was to investigate the effect of incorporating various passive elements, which could represent combined or individual effects of intervertebral disc, facet articulation and ligaments, on the prediction of lumbar muscle activation and L4-L5 intradiscal pressure., Methods: The passive elements representing the intervertebral disc, facet articulations, and ligaments were added to the existed lumbar musculoskeletal model with nonlinear rotational stiffness or force-strain relationships. The model was fed with kinematics of trunk flexion, extension, axial rotation and lateral bending to calculate muscle activation and L4-L5 intradiscal pressure., Results: In the trunk axial rotation, the intradiscal pressure values predicted by the models with elements representing facet articulation were much higher than that predicated by models removing these elements. In the trunk flexion, the models with passive elements showed lower muscle activation of extensors than model with no passive elements. At the end of trunk flexion, extension, axial rotation and lateral bending, the intradiscal pressure values predicted by model with intact passive elements were 120.6%, 92.5%, 334.8% and 74.9% of the values predicted by model with no passive elements, respectively., Conclusions: Caution must be taken while modeling facet articulation as elements with rotational stiffness, as they may lead to overestimation of intradiscal pressure in trunk axial rotation. The inclusion of ligaments as spring-like elements may improve the simulation of flexion-relaxation phenomenon in trunk flexion. Future models considering detailed properties of passive elements are needed to allow more access to understanding the mechanics of the lumbar spine., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Context: Previous studies highlighted that exercises executed on unstable surfaces can yield important benefits to the function of the core musculature in rehabilitation settings, general conditioning settings, and athletic training when properly introduced within a periodized training schedule. No previous study has analyzed core-stability exercises executed in lying, quadruped, plank, and bridge positions on a whole-body wobble board (WWB) specifically designed to accommodate the exerciser's entire body and promote whole-body instability. We have designed a WWB allowed to roll in a plane perpendicular to its longitudinal axis to promote proactive and reactive activation of the core muscles with a transverse or diagonal line of action, which provides trunk and pelvic stability with low spine compression forces., Purpose: To determine the effect of the use of this newly designed WWB by assessing differences in core-muscle activity during core-stability exercises performed on the ground, in a stable condition, and on the WWB., Design: Controlled laboratory study., Setting: Research laboratory., Patients or Other Participants: Eighteen participants recruited from fitness centers., Intervention(s): The electromyographic (EMG) activity of lumbopelvic and scapular muscles has been recorded during core-stability exercises executed on the WWB (unstable condition) and on ground (stable condition)., Main Outcome Measure(s): Mean and peak EMG activity were compared between stable and unstable condition with paired t tests or Wilcoxon signed-rank tests., Results: Overall, exercises performed on the WWB yielded significantly higher EMG activity in the serratus anterior and anterolateral abdominal muscles compared with the same exercises executed on the ground. Conversely, for the bird dog exercise, lower-back muscle activity was significantly higher on the ground., Conclusions: Compared with the ground, core-stability exercises executed on WWB constitute a simple and effective strategy to increase the activity level of the core muscles that control transverse-plane lumbopelvic and trunk stability, avoiding the use of external overload.

The cutaneus trunci muscle (CTM) reflex produces a skin "shrug" in response to pinch on a rat's back through a three-part neural circuit: 1 ) A-fiber and C-fiber afferents in segmental dorsal cutaneous nerves (DCNs) from lumbar to cervical levels, 2 ) ascending propriospinal interneurons, and 3 ) the CTM motoneuron pool located at the cervicothoracic junction. We recorded neurograms from a CTM nerve branch in response to electrical stimulation. The pulse trains were delivered at multiple DCNs (T 6 -L 1 ), on both sides of the midline, at two stimulus strengths (0.5 or 5 mA, to activate Aδ fibers or Aδ and C fibers, respectively) and four stimulation frequencies (1, 2, 5, or 10 Hz) for 20 s. We quantified both the temporal dynamics (i.e., latency, sensitization, habituation, and frequency dependence) and the spatial dynamics (spinal level) of the reflex. The evoked responses were time-windowed into Early, Mid, Late, and Ongoing phases, of which the Mid phase, between the Early (Aδ fiber mediated) and Late (C fiber mediated) phases, has not been previously identified. All phases of the response varied with stimulus strength, frequency, history, and DCN level/side stimulated. In addition, we observed nociceptive characteristics like C fiber-mediated sensitization (wind-up) and habituation. Finally, the range of latencies in the ipsilateral responses were not very large rostrocaudally, suggesting a myelinated neural path within the ipsilateral spinal cord for at least the A fiber-mediated Early-phase response. Overall, these results demonstrate that the CTM reflex shares the temporal dynamics in other nociceptive reflexes and exhibits spatial (segmental and lateral) dynamics not seen in those reflexes. NEW & NOTEWORTHY We have physiologically studied an intersegmental reflex exploring detailed temporal, stimulus strength-based, stimulation history-dependent, lateral and segmental quantification of the reflex responses to cutaneous nociceptive stimulations. We found several physiological features in this reflex pathway, e.g., wind-up, latency changes, and somatotopic differences. These physiological observations allow us to understand how the anatomy of this reflex may be organized. We have also identified a new phase of this reflex, termed the "mid" response.

Background: The chair influences the position of the user in relation to his or her devices. Prolonged static sitting is a frequently mentioned risk factor for low back pain. Seat design, thus, plays an important role in the study of human sitting. Quantitative information is needed on what happens to body when one sits in chairs with different seat depth., Objective: To determine the myoelectric activity (EMG) of individual lumbar erector spinae muscles after sitting in chairs with different seat pan depth., Methods: EMG recordings were taken using surface electrodes placed on the lumbar erector spine muscles of 25 normal, volunteer subjects. EMG recordings for muscle activity were made while the study participants were in a comfortable position and performed the required tasks. The experiments investigated with 3 seat depths according to the 5 th , 50 th and 95 th percentiles of the buttock popliteal length. The recorded EMG data were normalized to the maximal voluntary contraction. The mean EMG recording was calculated for each of the 3 chairs tested. A mixed model was used to assess the differences among the situations., Results: A significant (p<0.05) difference was observed between the mean EMG recordings for the 3 tested seat pan depths. EMG activity was higher in seats with the 5 th and 95 th percentiles compared with that for the seat with 50 th percentile of buttock popliteal length depth., Conclusion: The seat pan depth used during a comfortable position has a significant effect on the level of myoelectric activity in the lumbar erector spinal muscles. The finding of this study may contribute to our understanding of the biomechanics of sitting.

Objectives: To investigate whether peripheral electrical stimulation (PES) of back extensor muscles changes excitability of the corticospinal pathway of the stimulated muscle and synergist trunk muscles., Methods: In 12 volunteers with no history of low back pain (LBP), intramuscular fine-wire electrodes recorded electromyography (EMG) from the deep multifidus (DM) and longissimus muscles. Surface electrodes recorded general EMG from the erector spinae and abdominal muscles. Single- and paired-pulse transcranial magnetic stimulation (TMS) paradigms tested corticospinal excitability, short-interval intracortical inhibition (SICI-2 and 3 ms), and intracortical facilitation (ICF) optimized for recordings of DM. Active motor threshold (aMT) to evoke a motor-evoked potential (MEP) in DM was determined and stimulation was applied at 120% of this intensity. PES was provided via electrodes placed over the right multifidus. The effect of 20-min PES (ramped motor activation) was studied., Results: Mean aMT for DM was 42.7 ± 10% of the maximal stimulator output. No effects of PES were found on MEP amplitude (single-pulse TMS) for any trunk muscles examined. There was no evidence for changes in SICI or ICF; that is, conditioned MEP amplitude was not different between trials after PES., Conclusion: Results indicate that, unlike previous reports that show increased corticospinal excitability of limb muscles, PES of back muscles does not modify the corticospinal excitability. This difference in response of the motor pathway of back muscles to PES might be explained by the lesser importance of voluntary cortical drive to these muscles and the greater role of postural networks. Whether PES influences back muscle training remains unclear, yet the present results suggest that potential effects are unlikely to be explained by the effects of PES at corticospinal level with the parameters used in this study., (© 2019 International Neuromodulation Society.)

Various donor muscles have been identified for restoring facial function due to longstanding facial paralysis. Donor muscles such as the gracilis and latissimus dorsi are frequently used and often produce one or two reliable vectors of force. However, there are drawbacks of using these muscles, including the instability of separating multivector functioning muscle units and limited amount of muscle contraction. Serratus anterior muscle transfer has the advantages of multiple independently functioning motor units that can be created with a single neurovascular pedicle. This article describes multivector muscle transfer using two or three superficial subslips of the serratus anterior muscle on a single neurovascular pedicle to produce an esthetic smile that is customized to imitate the function of the contralateral mimetic muscles. Twelve patients who had longstanding unilateral facial paralysis underwent muscle transfer consisting of multivector superficial subslips of the serratus anterior muscle innervated by the ipsilateral masseteric nerve. The procedure had an uneventful postoperative course, and patients obtained excellent results, with sufficient upper lip excursion, mouth angle, and lower lip working simultaneously. Functioning muscle transfer using multivector superficial subslips of the serratus anterior muscle is effective for treating longstanding facial paralysis. This technique avoids postoperative bulkiness of the cheek muscle and achieves a more natural and symmetrical smile., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The Hybrid Assistive Limb Lumbar Type (HAL) is an active exoskeleton that provides motion according to the wearer's voluntary drive. It was developed to support back muscles during repetitive lifting tasks. The purpose of this paper was to determine if the myoelectric activity of the back muscles is reduced or altered when using the HAL and to investigate a possible influence of its use on the cardiovascular system. Fourteen healthy young men without lower back pain underwent a freestyle, symmetrical-lifting protocol. Participants lifted a 17.05 kg handled-box for 10 min. with and without HAL support. Surface electromyography (sEMG) signals were recorded at thoracic (TES) and lumbar erector spinae (LES) and quadriceps femoris (QF). Heart rate was recorded from electrocardiogram. The subjects rated their level of physical exertion using the Borg Rating of Perceived Exertion (BORG) scale. Additionally they commented on sites of discomfort, perceptions of force, and loss of range of motion. The root mean square and integrated sEMG value was significantly reduced at the LES and TES. Heart rate variability output variables did not show any significant difference. The BORG-Scale showed no difference, with a mean score of 2.5. The HAL decreased the magnitude and onset of muscle activity and force in the lower back in a repetitive lifting task. Reduction of the muscle force and activity required during the lifting process is meaningful regarding lower back pain prevention, and the HAL may contribute to reducing the incidence of lower back pain in the working population., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Footwear devices that shift foot center of pressure (COP), thereby impacting lower-limb biomechanics to produce clinical benefit, have been studied regarding degenerative diseases of knee and hip joints, exhibiting evidence of clinical success. Ability to purposefully affect trunk biomechanics has not been investigated for this type of footwear. Fifteen healthy young male subjects underwent gait and electromyography analysis using a biomechanical device that shifts COP via moveable convex elements attached to the shoe sole. Analyses were performed in three COP configurations for pairwise comparison: (1) neutral (control) (2) laterally deviated, and (3) medially deviated. Sagittal and frontal-plane pelvis and spine kinematics, external oblique activity, and frontal and transverse-plane lumbar moments were affected by medio-lateral COP shift. Transverse-plane trunk kinematics, activity of the lumbar longissimus, latissimus dorsi, rectus abdominus, and quadratus lumborum, and sagittal-plane lumbar moment, were not significantly impacted. Two linear mixed effects models assessed predictive impact of (I) COP location, and (II) trunk kinematics and neuromuscular activity, on the significant lumbar moment parameters. The COP was a significant predictor of all modeled frontal and transverse-plane lumbar moment parameters, while pelvic and spine rotation, and lumbar longissimus activity were significant predictors of one frontal-plane lumbar moment parameter. Model results suggest that, although trunk biomechanics and muscle activity were altered by COP shift, COP offset influences lumbar kinetics directly, or via lower-limb changes not assessed in this study, but not by means of alteration of trunk kinematics or muscle activity. Further study may reveal implications in treatment of low back pain., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Introduction: Gait termination is a transitory task that requires the lower body to produce braking forces and inhibit forward propulsion. However, it is still unknown whether the upper body plays an active role in braking of gait and whether this mechanism is impaired with ageing., Research Question: Do older women exhibit an impaired control of upper body segments during gait termination with respect to young women?, Methods: Ten young and 10 older women performed three gait termination trials at comfortable speed while fixing the gaze on a visual target. A 3D motion analysis system was used to measure head, trunk and pelvis angular displacement and velocity, and estimate neck, waist and hip moments through Plug-in Gait modeling. Cross-correlation analysis of kinematic waveforms between paired adjacent segments (head-trunk and trunk-pelvis) was performed to investigate upper body coordination. Surface EMG activity of erector spinae (L3), sternocleidomastoid and neck extensor muscles was recorded. Statistics was carried out by MANOVA., Results: Older participants exhibited delayed peak extensor torques of neck, waist and hip compared to young participants, along with lower progression speed. Both groups showed a slight flexion of the trunk counteracted by a backward tilt of head and pelvis during braking. In addition, older women displayed a peculiar upper body coordination pattern, with the head coupling with trunk motion, as shown by cross-correlation. Older women displayed shorter lumbar erector spinae onset latency relative to last heel contact than young (16 ± 68 ms vs 92 ± 37 ms)., Significance: The upper body plays an active role in the braking of gait and this mechanism is impaired in older women. Moreover, the age-related coupling of head and trunk motion may produce an unbalancing effect on whole-body stability during the braking mechanism, thus leading to a higher risk of falls., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: The purpose of this study was to examine the relationship between hip extensor strength and back extensor length in patients with low back pain (LBP) and healthy controls., Methods: In 266 patients with LBP and 215 matched controls, back extensor length and hip extensor strength were measured and compared in the 2 groups using an independent t test. The Pearson correlation coefficient was used to determine correlation between these 2 variables. Multivariate logistic regression was used to test the risk of sustaining LBP with having these muscle insufficiencies., Results: A significant difference in hip extensor strength was found between patients with LBP and controls (P < .001). Back extensor length was different in healthy men compared with the patients with LBP (P < .001) but was not significant between women with and without LBP (P = .34). The results showed a significant relationship between back extensor length and hip extensor strength in men with LBP (r = 0.6, P = .01). Multivariate logistic regression revealed that having a weak hip extensor (P = .001) or shortened back extensor (P = .01) could increase the risk of LBP occurrence., Conclusion: The findings support the assumptions of the presence of muscle imbalance of hip extensor weakness and back extensor tightness in male patients with LBP and that each muscle impairment may contribute to LBP., (Copyright © 2019. Published by Elsevier Inc.)

With mechanical loading as the main risk factor for LBP in mind, exoskeletons are designed to reduce the load on the back by taking over a part of the required moment. The present study assessed the effect of a passive exoskeleton on back and abdominal muscle activation, hip and lumbar flexion and on the contribution of both the human and the exoskeleton to the L5/S1 net moment, during static bending at five different hand heights. Two configurations of the exoskeleton (LOW & HIGH) differing in angle-torque characteristics were tested. L5/S1 moments generated by the subjects were significantly reduced (15-20% for the most effective type) at all hand heights. LOW generated 4-11 Nm more support than HIGH at 50%, 25% and 0% upright stance hand height and HIGH generated 4-5 Nm more support than LOW at 100% and 75%. Significant reductions (11-57%) in back muscle activity were found compared to WITHOUT for both exoskeletons for some conditions. However, EMG reductions compared to WITHOUT were highly variable across subjects and not always significant. The device allowed for substantial lumbar bending (up to 70°) so that a number of participants showed the flexion-relaxation phenomenon, which prevented further reduction of back EMG by the device and even an increase from 2% to 6% MVC in abdominal activity at 25% hand height. These results indicate that flexion relaxation and its interindividual variation should be considered in future exoskeleton developments., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Trunk prevention training, which provides the basis of several conditioning training programs, is used in sports at professional and amateur levels, taking the specifications of the given sport and the age-related characteristics of the athletes into consideration., Objective: Our aim was to examine the strength and flexibility of muscles responsible for correct posture, the lumbar motor control ability and the posture of recruitment kayak-canoe athletes., Methods: Controlled, randomized examination with 103 persons (age: 15.1 ± 3.5 years), who were divided into two groups. Fifty were in the intervention group, who took part in the 6-month trunk prevention training program (height: 162.30 cm, body weight: 49.70 ± 10.32 kg), 53 in the control group (not performing trunk prevention training) (height: 158.24 cm, body weight: 51.45 ± 11.71 kg). The strength of core muscles was measured with Kraus-Weber test, muscle flexibility with Kempf-test, lumbar motor control ability with Sitting Forward Lean and Leg Lowering test and posture with photogrammetry test before and after the program., Results: Static strength of abdominal muscles (p< 0.001), superficial and deep dorsal muscles (p< 0.001), flexibility of knee extensors (p< 0.001), chest muscles (p< 0.001), the lumbar motor control ability (p< 0.001) and habitual posture (p< 0.001) significantly improved in the intervention group. The post-measurements in the intervention group were significantly (p< 0.001) better than in the control group., Conclusions: As a result of the trunk prevention training the strength of core stabilization muscles, the lumbar motor control ability and the posture also improved in case of recruitment athletes.

This study investigates the relationship between peak force and rate of force development (RFD) obtained from maximal voluntary isometric contraction (MVC) of the back muscles and the power produced during a loaded lifting task. A group of 27 resistance-trained and 41 recreationally physically active men performed a maximal isometric strength test of the back muscles and a deadlift to high pull while lifting progressively increasing weights. Peak RFD correlated significantly with the peak and mean power produced during a deadlift to high pull with lower weights (from 20 to 40 kg), with r values ranging from .941 to .673 and from .922 to .633. The r 2 values ranged from .89 to .45 and from .85 to .40, explaining 89%-45% and 85%-40% of total variance. There were also significant relationships between MVC peak force and peak and mean values of power produced during a deadlift to high pull with weights ≥60 kg ( r in range from .764 to .888 and from .735 to .896). Based on r 2 , a moderate-to-high proportion of variance was explained (58%-79% and 54%-80%). These findings indicate that peak RFD obtained from MVC of the back muscles may be predictive of power performance during a lifting task at light loads. In addition to MVC peak force produced by back muscles, the ability of subjects to develop a high force in a short time should be evaluated in order to gain deeper insight into a loaded lifting performance, namely, in those prone to low back pain.

Background and Objective: No reports exist regarding skeletal muscle involvement in patients with Mycobacterium avium complex lung disease (MAC-LD). The cross-sectional area of the erector spinae muscles (ESM CSA ) reflects physical activity and can be assessed by computed tomography (CT). We investigated the relationship between ESM CSA and physiological parameters and prognosis in MAC-LD patients., Material and Methods: In this prospective observational study, the ESM CSA was measured on single-slice axial CT images. MAC-LD patients and sex- and age-matched controls (non-MAC-LD participants) were evaluated. We evaluated the relationship between the ESM CSA and physiological parameters and prognosis., Results: A total of 260 patients (209 female; median age, 69 years; 190 with nodular/bronchiectatic disease; 74 with cavitary lesions) were enrolled. The ESM CSA was not different between MAC-LD patients and controls. In MAC-LD patients, the ESM CSA was significantly associated with age, body mass index (BMI), pulmonary function, CT severity, and health-related quality of life (HRQL). Multivariate Cox proportional hazards analyses revealed that an ESM CSA  < -1 standard derivation (hazards ratio [HR], 2.76; P = 0.047) was significantly associated with all-cause mortality, along with BMI < 18.5 kg/m 2 (HR, 3.67; P = 0.02) and presence of cavitary lesions (HR, 5.84; P = 0.001). However, the ESM CSA was not significantly associated with all-cause mortality when current treatment status, % predicted functional vital capacity, and forced expiratory volume in 1 s were added to the analyses., Conclusions: Although the prognostic impact was limited, ESM CSA was significantly associated with HRQL and prognostic physiological parameters, such as BMI and pulmonary function., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

- Paralumbar muscle performance and fatigue were evaluated by measuring electromagnetic activity during entire body vibration (EBV) in 44 healthy subjects. Physical fitness of subjects was estimated on a 5-degree scale. Electric activity was recorded in 200 seconds with 1 kHz sampling on the Biopac Student Lab during EBV. Data were used to produce time series for two vectors of the phase space and spatial axis: X (left-right), Y (up-down) and Z (ventral-dorsal). Time series were evaluated by calculating fractal dimension by the R/S algorithm. Movement of the electric field along the Y-axis showed changes (up-down) extracted in the first and second quarter of the measurement (p=0.02 and p=0.03, respectively). These changes were not specific for gender but showed dependence on subject age and fitness. The fractal dimension values by the R/S algorithm were larger in female subjects. Results suggested the electric field changes during EBV in the up-down direction to contain information on muscular performance and fatigue, not dependent on gender, but on the age and degree of overall physical fitness.

Axial compressive loads whose direction changes along the spinal curvature (so called compressive follower loads (CFLs)) was postulated as a normal physiological load in the lumbar spine in the literature. Computational analyses were conducted in this study using finite element and optimization models of the spinal system incorporating 244 fascicles of back muscles. It was feasible to find optimum solutions for spinal muscle forces generating CFLs in the lumbar spine in 3-D postures of neutral standing, flexion 40°, extension 10°, axial rotation 10°, or lateral bending 30°. FE analyses demonstrated that the lumbar spine can be in a stable condition not under all CFL generating muscle forces but under those producing CFLs along a curve parallel to the spinal curvature located in the vicinity of the base spinal curve constructed by connecting the geometrical centers of the vertebral bodies. It was also possible to estimate the stable range of the relative location of such CFL curve to the base spinal curve. These results suggest that the lumbar spine in various 3-D postures can be stabilized by spinal muscles that generate CFLs in the spine, which at least in part supports the hypothesis of CFLs as a physiological load in the lumbar spine. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3004-3012, 2018., (© 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

This work investigates the effect of different seats on violin and viola players sitting postures using High-Density-surface-Electromyography techniques (HDsEMG), biomechanical and comfort indices. Five types of chairs were assessed on 18 violin and three viola players by comparing: (a) pelvic tilt and kyphosis and lordosis angles, (b) subjective comfort indices, and (c) EMG amplitude of erector spinae and trapezius. Sitting "as you like" on a standard orchestra chair is the condition with the highest subjective comfort (but not significantly different from other chairs). A saddle chair with low back support is associated to the lowest EMG of the erector spinae (p < 0.05) and a saddle stool is associated to the spinal angles closest to those of the standing posture. In 12 out of 21 (57%) musicians, the erector spinae was activated in an intermittent manner, regardless of the chair used. These findings justify further research on the selected chairs, on muscle fatigue and on the intermittent postural control strategy., (Copyright © 2018. Published by Elsevier Ltd.)

Aging has been associated with decreases in muscle strength and bone quality. In older patients, paravertebral muscle atrophy tends to coincide with vertebral osteoporosis. The purpose of this study was to investigate the effects of a paravertebral injection of botulinum toxin-A (BTX) on paravertebral muscle atrophy and lumbar vertebral bone quality. Forty 16-week-old female SD rats were randomly divided into four groups: (1) a control group (CNT); (2) a resection of erector spinae muscles group (RESM); (3) a botulinum toxin-A group (BTX), treated with 5U BTX by local injection into the paravertebral muscles bilaterally; and (4) a positive control group (OVX), treated by bilateral ovariectomy. Rats were sacrificed at 12 weeks post-surgery, and the lumbar vertebrae (L3-L6) were collected. Micro-CT scans showed that rats in the three experimental groups-particularly the OVX rats-had fewer trabeculae and trabecular connections than rats in the CNT group. BMD was significantly lower in rats in the OVX, RESM, and BTX groups than in the CNT group (p < 0.01). Vertebral compression testing revealed significantly lower maximum load, energy absorption, maximum stress, and elastic modulus values in the three experimental groups compared with the CNT group (p < 0.01); these parameters were lowest in the OVX group (p < 0.05). Our results demonstrate that local BTX injection causes sufficient muscle atrophy and dysfunction to result in local lumbar vertebral bone loss and quality deterioration in a model of paravertebral muscle atrophy. Clinical Significance: The muscular tissues surrounding the lumbar vertebrae should be preserved during clinical surgery to avoid loss of bone quality and mass in the adjacent bone. Maintaining paravertebral muscle strength is an important consideration for patients with early osteoporosis. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2664-2670, 2018., (© 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

Background: The aim of this cluster-randomised, controlled study was to examine whether a teacher-led multifactorial back education programme could improve back pain in pupils, motor skills, back behaviour, and back knowledge over a 10-month period., Methods: There were 176 children from two schools, who were cluster-randomised into intervention and control groups. The intervention programme consisted of 3 parts: 1) knowledge improvement, 2) posture awareness training, and 3) reducing imbalance of core muscles through mandatory back and abdominal muscle exercises at the beginning of each physical education lesson. Outcome measures included a clinical orthopaedic examination, a health questionnaire, a motor test, a back-behaviour trial, and a knowledge test., Results: Clinical examination showed a reduction of orthopaedic abnormalities in both groups, from 90.5 to 42%, with a posture test showing an improvement in both groups at the post-test. However, the rate of children reporting back pain at least once a month could not be reduced below 30%. Long lasting physical activity, carrying heavy schoolbags, and long periods of sitting were the top three causes for back pain. Push-up number and balancing skills improved significantly in both groups from pre- to post-test. In the water crate carrying task and knowledge test, only the intervention group (IG) showed a statistically significant improvement from pre- to post-test., Conclusions: The results show that back pain rate could not be decreased. However, back care knowledge and parts of back-friendly behaviour could be significantly improved. On the other hand, the problem of prolonged sitting and using heavy schoolbags persists., Trial Registration: Deutsches Register Klinische Studien DRKS00013794 ; Date of Registration: 15.1.2018; Retrospectively registered.

This study examined characteristics of trunk muscles electrical activity in young adults performed in the course of static and dynamic trunk muscles strengthening exercises using different lumbar spine stabilization manoeuvres. Twenty young adults (Mage = 25.5 SD = 2.91) participated in this study. Of the 20, 11 subjects (5 males and 6 females) reported no history of pain, 9 subjects (5 males and 4 females) reported lower back pain (LBP) within the last three months. Subjects performed lumbar spine stabilization manoeuvres (abdominal bracing (AB) and abdominal hollowing (AH)) with static and dynamic abdominal muscles strengthening exercises (i.e., plank, side-bridges, and curl-ups). Noraxon Telemyo twelve channel electromyography device (Noraxon USA, Inc.) was used to record EMG data from rectus abdominal muscle (RA), external oblique muscles (EO), internal oblique muscles (IO), and erector spine muscles (ES). In static exercises such as side-bridge exercise, significantly higher RA muscle electrical activity was recorded with AB manoeuvre compared to AH manoeuvre both on the right side and left side respectively (Z = -2.17; p = 0.03; Z = 3.40; p = 0.001). In dynamic exercises such as curl-up exercise, during the lifting phase, median value of RA muscle activity with AB was significantly higher than with AH (Z = -2.315; p = 0.021). Median value of IO muscles activity with AH was significantly higher than with AB (Z = -3.230; p = 0.001). Our findings indicated that although surface muscles are more activated with AB manoeuvre exercises, deep abdominal muscles are more activated in exercises with AH manoeuvre. These findings can help practitioners design interventions to integrate AH manoeuvre for benefiting persons with lumbar instability., Competing Interests: The authors have declared that no competing interests exist.

Purpose: Low back pain is a major public health issue. Identifying factors associated with better intervertebral disc (IVD) characteristics gives insight into IVD metabolism and highlights intervention targets for improvement of IVD health. This cross-sectional study investigates whether IVD T2-relaxation time on magnetic resonance imaging (MRI) is associated with vertebral fat fraction (VFF; to quantify marrow adipose tissue), trunk muscle cross-sectional area (CSA), muscle function and physical activity (PA)., Methods: Seventy-nine healthy subjects (35 males, 44 females) without history of spinal disease were included. Lumbar IVDs T2-relaxation time, lumbar VFF and CSA of multifidus, erector spinae, quadratus lumborum, and psoas muscles were quantified via MRI. Isometric trunk flexion and extension endurance times as well as habitual PA levels and exposure to occupational spine risk factors were documented. Pearson-partial correlations adjusted for anthropometric differences by controlling for vertebral body height., Results: Higher IVD T2-time correlated with: (a) lower VFF (r = - 0.27, p < 0.05), (b) greater trunk extensor muscle endurance (r = 0.37, p < 0.01), and (c) greater trunk flexor muscle endurance (r = 0.30, p < 0.01) but not with muscle CSA. Lower VFF also correlated with greater extensor muscle endurance (r = - 0.26, p < 0.05) and habitual PA (MET-mins per week) (r = - 0.24, p < 0.05)., Conclusion: This is the first study to show that better IVD hydration is associated with lower VFF and that greater physical activity is associated with favourable levels of vertebral marrow adipose tissue in young healthy individuals. Reduced vertebral marrow adipose tissue may specifically improve IVD hydration via improved nutrient supply. These slides can be retrieved under Electronic Supplementary Material.

Muscles work most effectively along their anatomically defined action vector(s) which has implications in training and therapeutics. Action vectors can easily be identified in extremity muscles and smaller muscles of the trunk, but are less clear in larger trunk muscles. Trunk muscle exercises and diagnostics have traditionally relied on tasks in the sagittal plane - a practice that is being reconsidered. Therefore, this study aimed at identifying main force directions (MFDs) of major trunk muscles expressed in terms of deviation from the sagittal plane. 20 healthy male subjects underwent graded isometric submaximal static load applications on their trunk by application of simultaneous and incremental tilting and rotating from vertical to horizontal at rotational angles of 45° starting from 0° (forward tilting) around 360° with only the lower body secured. Surface EMG (SEMG) from six trunk muscles on each body side was recorded. The MFD of each trunk muscle was estimated by considering SEMG amplitudes of all rotational angles, separately for all tilt angles, and was expressed as angular deviation from sagittal plane. The calculated MFDs of trunk muscles deviated from sagittal plane to differing extents. Mean MFD angle was smallest (more parallel to sagittal plane) for rectus abdominis muscle (±14°), becoming more lateral for external oblique (OE, ±32°) and internal oblique abdominal muscles (OI, ±47°). As tilt angle increased, MFD angles increased for OE, but decreased for OI. Iliocostalis muscle showed an almost laterally directed MFD with systematic dependency on body side (-90° for left and +75° for right side). Both paravertebral muscles (longissimus and multifidus muscles) showed almost identical MFD angles of about ±145° and varied the least with tilt angle. All trunk muscles' MFDs deviate from sagittal plane and, in addition to flexing and extending, have both bending and/or rotational capabilities. MFDs of oblique abdominal muscles are systematically altered by tilt angle in accordance with their more divergent fiber directionality. The results provide a basis for specifically targeted diagnostics and training of trunk muscles., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Information on spinal loading for using lift assist systems for airport baggage handling is lacking. We conducted a laboratory study to evaluate a vacuum lift system for reducing lumbar spinal loads during baggage loading/unloading tasks. Ten subjects performed the tasks using the industry average baggage weight of 14.5 kg on a typical two-shelved baggage cart with or without using the lift system (i.e. lifting technique). Repeated measures analysis of variance (2 tasks × 2 shelf heights x 2 techniques) was used. Spinal loads were estimated by an electromyography-driven biomechanical model. On average, the vacuum lift system reduced spinal compressive forces on the lumbar spine by 39% and below the 3400 N damage threshold. The system also resulted in a 25% reduction in the anterior-posterior shear force at the L5/S1 inferior endplate level. This study provides evidence for the potential to reduce spinal loads when using a vacuum lift system., (Published by Elsevier Ltd.)

The epaxial muscles produce intervertebral rotation in the transverse, vertical and axial axes. These muscles also counteract the movements induced by gravitational and inertial forces and movements produced by antagonistic muscles and the intrinsic muscles of the pelvic limb. Their fascicles are innervated by the dorsal branch of the spinal nerve, which corresponds to the metamere of its cranial insertion in the spinous process. The structure allows the function of the muscles to be predicted: those with long and parallel fibres have a shortening function, whereas the muscles with short and oblique fibres have an antigravity action. In the horse, the multifidus muscle of the thoracolumbar region extends in multiple segments of two to eight vertebral motion segments (VMS). Functionally, the multifidus muscle is considered a spine stabiliser, maintaining VMS neutrality during spine rotations. However, there is evidence of the structural and functional heterogeneity of the equine thoracolumbar multifidus muscle, depending on the VMS considered, related to the complex control of the required neuromuscular activity. Osteoarticular lesions of the spine have been directly related to asymmetries of the multifidus muscle. The lateral (LDSM) and medial (MDSM) dorsal sacrocaudal muscles may be included in the multifidus complex, the function of which is also unclear in the lumbosacral region. The functional parameters of maximum force (F max ), maximum velocity of contraction (V max ) and joint moment (M) of the multifidus muscles inserted in the 4th, 9th, 12th and 17th thoracic and 3rd and 4th lumbar vertebrae of six horses were studied postmortem (for example: 4MT4 indicates the multifidus muscle that crosses four metameres with cranial insertion in the T4 vertebra). Furthermore, the structural and functional characteristics of LDSM and MDSM were determined. Data were analysed by analysis of variance (anova) in a randomised complete block design (P ≤ 0.05). For some muscles, the ordering of V max values was almost opposite to that of F max values, generally indicating antigravity or dynamic functions, depending on the muscle and VMS. The muscles 3MT12, 3ML3 and 4ML4 exhibited high F max and low V max values, indicating a stabilising action. The very long 7MT4 and 8MT4 multifidus had low F max and high V max values, suggesting a shortening action. However, some functional characteristics of interest did not fall within these general observations, also indicating a dual action. In summary, the results of the analysis of various structural and functional parameters confirm the structural and functional heterogeneity of the equine thoracolumbar multifidus complex, depending on the VMS, regardless of the number of metameres crossing each fascicle. To clarify the functions of the equine multifidus muscle complex, this study aimed to assess its functional parameters in thoracolumbar VMSs with different movement characteristics and in the MDSM and LDSM muscles, hypothesising that the functional parameters vary significantly when the VMS is considered., (© 2018 Anatomical Society.)

Context: Strength/resistance training volume has historically been supported in the American College of Sports Medicine recommendations. However, for the back muscles, exercise prescription related to the number of sets, such as single versus multiple, is not well established in the literature., Objective: The purpose of this study was to compare the effects of 2 training volumes on strength and endurance of back-extensor muscles in untrained young participants with regard to a repeated-measures design., Design: Randomized controlled trial., Setting: Laboratory of functional evaluation and human motor performance., Participants: Forty-four untrained young participants (mean age = 21 y) were randomized into single-set (n = 14), multiple-set (MSG, n = 15), and untrained control (n = 15) groups., Intervention: The single-set group and MSG underwent a 10-week progressive resistance training program (2 d/wk) using a 45° Roman chair., Main Outcome Measures: Back maximal strength (dynamometer) and isometric and dynamic endurance (time limit, trunk extension-flexion cycles, and electromyography muscle fatigue estimates)., Results: The results showed differences between the MSG and control group for isometric endurance time (mean = 19.8 s; 95% confidence interval, -44.1 to 4.8), but without time intervention significance. Significant improvement after training (P < .05) was found predominantly during dynamic endurance (number of repetitions) for both the MSG (+61%) and single-set group (+26%) compared with preintervention, whereas the control group reported no benefit. There was no significant (P > .05) difference in either strength or electromyography estimates after training., Conclusions: Both multiple and single volume training were efficient in promoting better back endurance during dynamic performance based on mechanical variables (time and number of repetitions).

Purpose: Tensiomyography™ (TMG) and MyotonPRO ® (MMT) are two non-invasive devices for monitoring muscle contractile and mechanical characteristics. This study aimed to evaluate the test-retest reliability of TMG and MMT parameters for measuring (TMG:) muscle displacement (D m ), contraction time (T c ), and velocity (V c ) and (MMT:) frequency (F), stiffness (S), and decrement (D) of the erector spinae muscles (ES) in healthy adults. A particular focus was set on the establishment of reliability measures for the previously barely evaluated secondary TMG parameter V c ., Methods: Twenty-four subjects (13 female and 11 male, mean ± SD, 38.0 ± 12.0 years) were measured using TMG and MMT over 2 consecutive days. Absolute and relative reliability was calculated by standard error of measurement (SEM, SEM%), Minimum detectable change (MDC, MDC%), coefficient of variation (CV%) and intraclass correlation coefficient (ICC, 3.1) with a 95% confidence interval (CI)., Results: The ICCs for all variables and test-retest intervals ranged from 0.75 to 0.99 indicating a good to excellent relative reliability for both TMG and MMT, demonstrating the lowest values for TMG T c and between-day MMT D (ICC < 0.90). Absolute reliability was suitable for all parameters (CV 2-8%) except for D m (10-12%). V c demonstrated to be the most reliable and repeatable TMG parameter (ICC > 0.95, CV < 8%)., Conclusion: The reliability for TMG V c could be established successfully. Its further applicability needs to be confirmed in future studies. MMT was found to be more reliable on repeated testing than the two other TMG parameters D m and T c .

Background/aim: Resting scapular asymmetry with a more protracted and depressed position of the scapula in the dominant throwing side relative to the scapula of the contralateral side is commonly detected in overhead athletes with both healthy and disabled shoulders. It has been proposed that possible alterations in the EMG activity of periscapular muscles due to asymmetric position of the scapula may alter its kinematics leading to shoulder pathology. The aim of the current study was to identify possible alterations in the activation of periscapular muscles of healthy female volleyball players with scapular asymmetry in the resting position., Methods: Resting position of the scapula was determined in 37 healthy professional female volleyball players. Twenty-two players, with the scapula of the dominant side in a more protracted and depressed position compared to the non-dominant side, were classified as the asymmetry group. Fifteen players with almost symmetrical position of both scapulae comprised the control group. All participants performed an upper extremity closed chain exercise (knee push-ups) on a stable (floor) and an unstable surface (BOSU platform), while the EMG activity of serratus anterior (SA), upper trapezius (UT) and middle trapezius (MT) was recorded bilaterally., Results: No significant group (asymmetry vs. control) by side (dominant vs. non-dominant) by surface condition (floor vs. BOSU platform) interaction was detected with regard to the EMG activity of SA, UT and MT. Although not statistically significant the asymmetry group demonstrated a tendency for reduced EMG activity of the SA on the dominant compared to the contra-lateral side and compared to the dominant side of the control group., Conclusions: The EMG activity of periscapular muscles (SA, UT and MT) was not affected during execution of a close chain exercise in healthy female volleyball players with the scapula of the dominant side in a more protracted and depressed resting position., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: The aim of the study was to describe and correlate the skin, subcutaneous tissue, and superficial fascia thickness assessed by ultrasonography (US) with the lumbar erector spinae muscles contractile properties evaluated by tensiomyography (TMG)., Methods: A cross-sectional descriptive study with 50 healthy participants was performed. The point of maximum lordosis in the lumbar region of the right erector spinae was evaluated by US and TMG. First, the skin, subcutaneous tissue, and superficial fascia thicknesses (cm) were assessed by US. Second, the five contractile TMG parameters were analyzed from the right erector spinae muscles belly displacement-time curves: maximal radial displacement (Dm), contraction time (Tc), sustain time (Ts), delay time (Td), and half-relaxation time (Tr). Finally, correlation analyses using Pearson (r for parametric data) and Spearman (rs for non-parametric data) coefficients were performed., Results: A strong negative correlation was shown between Dm and subcutaneous tissue thickness (rs=-0.668; P<.001). Furthermore, moderate negative correlations were observed between Dm and skin thickness (r=-0.329; P=0.020) as well as Tr and subcutaneous tissue thickness (rs=-0.369; P=0.008). The rest of the parameters did not show statistically significant correlations (P >.05)., Conclusion: Therefore, the lumbar erector spinae contractile properties during TMG assessments, especially Dm and Tr, may be widely correlated by the skin and subcutaneous tissue thickness.

Lacrosse is a fast-paced game that incorporates elements from multiple sports, such as soccer, basketball, baseball, tennis, and hockey. The sport involves rapid changes of direction, endurance, sprinting, physical contact, rotational movement, passing, and shooting. Passing and shooting are further complicated by having a weighted object (ball) at the end of a long moment arm (crosse) which places increased stress on the body segments. Thus, it is important to properly prepare for sport participation by improving strength, endurance, and dynamic stability of the postural and core stability muscles. Because high mechanical loads are experienced during play, (re)establishment of symmetric strength and flexibility is essential for rehabilitation and injury prevention. This article will focus on the musculoskeletal demands placed on the body in lacrosse, the importance of core strength and dynamic stability to prevent injury, and the elements of both prehabilitation and rehabilitation programs to properly prepare the athlete for participation.

The aim of this study was to evaluate the effect of an industrial exoskeleton on muscle activity, perceived musculoskeletal effort, measured and perceived contact pressure at the trunk, thighs and shoulders, and subjective usability for simple sagittal plane lifting and lowering conditions. Twelve male participants lifted and lowered a box of 7.5 kg and 15 kg, respectively, from mid-shin height to waist height, five times, both with and without the exoskeleton. The device significantly reduced muscle activity of the Erector Spinae (12%-15%) and Biceps Femoris (5%). Ratings of perceived musculoskeletal effort in the trunk region were significantly less with the device (9.5%-11.4%). The measured contact pressure was highest on the trunk (91.7 kPa-93.8 kPa) and least on shoulders (47.6 kPa-51.7 kPa), whereas pressure was perceived highest on the thighs (35-44% of Max LPP). Six of the users rated the device usability as acceptable. The exoskeleton reduced musculoskeletal loading on the lower back and assisted with hip extensor torque during lifting and lowering. Contact pressures fell below the Pain Pressure Threshold. Perceived pressure was not exceptionally high, but sufficiently high to cause discomfort if used for long durations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Patients with low back pain commonly exhibit impaired morphology and function of spinal musculature that may be quantifiable using shear-wave elastography (SWE). The purpose of this study was to assess the intra-rater and test-retest reliability of SWE elasticity measures of the lumbar erector spinae and multifidus muscles during rest and differing levels of contraction in asymptomatic individuals. This single-group repeated-measures design involved a baseline measurement session and a follow-up session 3 days later. The lumbar multifidus was imaged at rest and during three levels of contraction (minimal, moderate, and maximum). The lumbar erector spinae (illiocostalis and longissimus muscles) were imaged at rest only. Overall reliability estimates were fair to excellent with ICCs ranging from 0.44 to 0.92. Reliability was higher in the lumbar multifidus muscles than the erector spinae muscles, slightly higher during contraction than during rest, and substantially improved by using the mean of 3 measurements. By reliably quantifying impaired spinal musculature, SWE may facilitate an improved understanding of the etiology and treatment of low back pain and other muscle pain-related conditions such as trigger points and fibromyalgia., (Published by Elsevier Ltd.)

Objective: Numerous devices have been designed to support the back during lifting tasks. To improve the utility of such devices, this research explores the use of preparatory muscle activity to classify muscle loading and initiate appropriate device activation. The goal of this study was to determine the earliest time window that enabled accurate load classification during a dynamic lifting task., Methods: Nine subjects performed thirty symmetrical lifts, split evenly across three weight conditions (no-weight, 10-lbs and 24-lbs), while low-back muscle activity data was collected. Seven descriptive statistics features were extracted from 100 ms windows of data. A multinomial logistic regression (MLR) classifier was trained and tested, employing leave-one subject out cross-validation, to classify lifted load values. Dimensionality reduction was achieved through feature cross-correlation analysis and greedy feedforward selection. The time of full load support by the subject was defined as load-onset., Results: Regions of highest average classification accuracy started at 200 ms before until 200 ms after load-onset with average accuracies ranging from 80% (±10%) to 81% (±7%). The average recall for each class ranged from 69-92%., Conclusion: These inter-subject classification results indicate that preparatory muscle activity can be leveraged to identify the intent to lift a weight up to 100 ms prior to load-onset. The high accuracies shown indicate the potential to utilize intent classification for assistive device applications., Significance: Active assistive devices, e.g. exoskeletons, could prevent back injury by off-loading low-back muscles. Early intent classification allows more time for actuators to respond and integrate seamlessly with the user.

The aims of this study were to research the amplitude and median frequency characteristics of selected abdominal, back, and hip muscles of healthy subjects during a prone bridging endurance test, based on surface electromyography (sEMG), (a) to determine if the prone bridging test is a valid field test to measure abdominal muscle fatigue, and (b) to evaluate if the current method of administrating the prone bridging test is reliable. Thirty healthy subjects participated in this experiment. The sEMG activity of seven abdominal, back, and hip muscles was bilaterally measured. Normalized median frequencies were computed from the EMG power spectra. The prone bridging tests were repeated on separate days to evaluate inter and intratester reliability. Significant differences in normalized median frequency slope (NMF slope ) values between several abdominal, back, and hip muscles could be demonstrated. Moderate-to-high correlation coefficients were shown between NMF slope values and endurance time. Multiple backward linear regression revealed that the test endurance time could only be significantly predicted by the NMF slope of the rectus abdominis. Statistical analysis showed excellent reliability (ICC=0.87-0.89). The findings of this study support the validity and reliability of the prone bridging test for evaluating abdominal muscle fatigue., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: The question that was asked in the study was whether a training routine based on curl-up exercises with a load provided by body mass of the person increases local muscle strength or local muscle endurance., Objective: The aim of this study was to evaluate the effect of 4 weeks training based on a small load and low movement velocity on electrical activity (EMG), cross-sectional area (CSA) of core stabilisers., Methods: The EMG activity was measured in the rectus abdominis (RA), obliquus abdominis externus and erector spinae (ES) muscles. CSA of the muscles: RA, anterolateral abdominal, psoas major, quadratus lumborum, ES, and multifidus at the level of L3-L4 were measured too., Results: The training increased the CSA and thickness in most of the muscles studied. Statistically significant correlation was found only for the ES circumference (left side) and EMG activity for the right side (r= 0.627, p= 0.022) and left side (r= 0.624, p= 0.023)., Conclusions: The training programme resulted in a increase in the number of curl-up repetitions revealing an endurance increase in abdominal muscles. Furthermore, there was a increase in the EMG activity of the RA. An increase of the CSA of all tested muscles showed an increase of muscle active force.

Background: The aim of the present study is to propose a subject-specific biomechanical control model for the estimation of active cervical spine muscle forces., Methods: The proprioception-based regulation model developed by Pomero et al. (2004) for the lumbar spine was adapted to the cervical spine. The model assumption is that the control strategy drives muscular activation to maintain the spinal joint load below the physiological threshold, thus avoiding excessive intervertebral displacements. Model evaluation was based on the comparison with the results of two reference studies. The effect of the uncertainty on the main model input parameters on the predicted force pattern was assessed. The feasibility of building this subject-specific model was illustrated with a case study of one subject., Findings: The model muscle force predictions, although independent from EMG recordings, were consistent with the available literature, with mean differences of 20%. Spinal loads generally remained below the physiological thresholds. Moreover, the model behavior was found robust against the uncertainty on the muscle orientation, with a maximum coefficient of variation (CV) of 10%., Interpretation: After full validation, this model should offer a relevant and efficient tool for the biomechanical and clinical study of the cervical spine, which might improve the understanding of cervical spine disorders., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The serratus anterior is portrayed as a homogeneous muscle in textbooks and during functional activities and rehabilitation exercises. It is unclear whether the serratus anterior is composed of subdivisions with distinctive morphology and functions. The purpose of this study was to determine whether the serratus anterior could be subdivided into different structural parts on the basis of its segmental architectural parameters. Eight formalin-embalmed serratus anterior muscles were dissected and the attachments of each fascicle documented. Orientation and size of each fascicle were measured and the physiological cross-sectional area (PCSA) calculated. Three subdivisions of the serratus anterior were identified. A new finding was the discovery of two distinctive fascicles attached to the superior and inferior aspects of rib 2. The rib 2 inferior fascicle had the largest PCSA (mean 1.6 cm 2 ) and attached, with the rib 3 fascicle, along the medial border of the scapula to form the middle division. The rib 2 superior and rib 1 fascicles attached to the superior angle of the scapula (upper division). Fascicles from ribs 4-8/9 attached to the inferior angle of the scapula (lower division). Mean fascicle angle relative to a vertical midline reference and PCSA for each division were 29° and 1.3 cm 2 (upper), 90° and 2.2 cm 2 (middle) and 59° and 3.0 cm 2 (lower). This novel study demonstrated the presence of morphologically distinct serratus anterior subdivisions. The results of this study will inform the development of optimal techniques for the assessment, treatment and rehabilitation of this architecturally complex muscle in shoulder and neck pain.

Background: Lumbar mobilizations are used to clinically treat the lumbar and hamstring region. However, evidence is limited regarding the effectiveness of specific mobilization methods., Objective: To compare central and unilateral posterior-anterior mobilizations (CPA, UPA) of the lumbar spine on lumbar and hamstring range of motion (ROM), and muscle activity (sEMG)., Methods: Twenty participants received CPA, UPA, or no mobilization (CON) on separate occasions (crossover design). Post-treatment outcome measures were ROM during active lumbar flexion (ALF) and active knee extension (AKE), as well as sEMG of the Erector Spinae (ES) and Biceps Femoris (BF) during these movements., Results: sEMG was possibly to very likely lower following CPA (mean difference range =-5% to -21%) and UPA (-7% to -36%), while ROM was most likely greater (-12% to 25% and -17% to 24%, respectively). Most sEMG measures were possibly to likely lower following UPA versus CPA (-18% to -11%), while AKE ROM was possibly greater (-5.5%). Differences in ES sEMG (-2.5%) and ROM (-1.4%) during ALF were unclear and most likely trivial, respectively., Conclusions: CPA and UPA mobilizations increase lumbar and hamstring ROM whilst reducing local muscle activity. These effects appear to be greater for UPA mobilizations when compared with CPA.

Background: Spinal muscles endurance is fundamental for providing adequate trunk stability., Objective: The purpose of this study was to compare the side bridge static endurance ability of the right versus left side., Methods: Forty right hand dominant students, aged between 18 and 25 years, were recruited from Taibah University. Every participant had to lie down on his side and bear trunk weight on the arm with shoulder abducted to 90∘ and elbow flexed to 90∘. Every participant had to lift off his trunk of the supporting surface, keeping the trunk straight in neutral position, breathing normally and holding on that position as long as tolerated., Results: A paired sample t test was calculated. The mean score, in seconds, for right side bridge was 41.6 (SD = 30.08), and for left side bridge was 38.00 (SD = 26.93). No significant difference was found between right and left side bridge endurance ability [t (39) = 1.67, p> 0.05]. Pearson correlation showed high positive correlation [r (38) = 0.89, p< 0.001]., Conclusions: Among healthy participants, clinicians should expect very close endurance profile for the musculature of the two sides of trunk. Clinicians should equally train both sides of trunk muscles stabilizers in order to enhance tolerance.

Introduction: Muscle force generation involves recruitment and firing rate modulation of motor units (MUs). The control of MUs in producing multidirectional forces remains unclear., Methods: We studied MU recruitment and firing properties, recorded from the first dorsal interosseous muscle, for 3 different directions of contraction: abduction; abduction/flexion combination; and flexion., Results: MUs were recruited systematically at higher threshold force during flexion. Larger MUs were recruited and firing rates of MUs were lower during abduction. There was an orderly recruitment of MUs according to MU size regardless of contraction direction, obeying the "size principle." Firing rates of earlier-recruited MUs were consistently higher than later-recruited MUs, affirming the "onion-skin" property., Discussion: Our findings suggest that the size principle and onion-skin organization together provide a general description of MU recruitment patterns and firing properties. The directional alternations of MU control properties likely reflect changes in neural drive to the muscle. Muscle Nerve 57: E85-E93, 2018., (© 2017 Wiley Periodicals, Inc.)

Background: Diaphragm is an important component of spinal stability. In presence of low back pain, there may be some alterations in this muscle like other muscles that are responsible for lumbal stabilization., Objective: This study aims to assess the effects of stabilization exercises on diaphragm muscle thickness and motion along with lumbopelvic stability., Methods: Twenty-one women with low back pain participated in the study. Stabilization exercises including motor control training were performed on treatment group (n= 11). In control group (n= 10), strentghening exercises were peformed for back muscles, abdominal muscles and hip muscles. The patients underwent a total of 30 sessions of treatment, 3 days in a week for 10 weeks. The diaphragm muscle thickness and motion was evaluated using ultrasound (US), and lumbopelvic stability was evaluated using lumbopelvic stability tests., Results: After the treatment, in the treatment group, increase in diaphragm thickness and improvement in lumbopelvic stability were statically significant (p< 0.05). However, there were no significant changes in diaphragm motion in both groups (p> 0.05)., Conclusions: As a result, stabilization exercises increase diaphragm muscle thickness and improve lumbopelvic stability in women with low back pain. Therefore, stabilization exercises should be considered as a part of the treatment program in low back pain.

Background: Longus capitis and colli are proposed to play a role in stabilising the cervical spine, targeted in clinical and research practice with cranio-cervical flexion. However, it is not clear if these muscles are anatomically or biomechanically suited to a stabilising role., Objectives: To describe the fascicular morphology of the longus capitis and colli, and estimate their peak force generating capabilities across the individual cervical motion segments., Study Design: Biomechanical force modelling based on anatomical data., Methods: Three-part design including cadaveric dissection (n = 7), in vivo MRI muscle volume calculation from serial slices in young healthy volunteers (n = 6), and biomechanical modelling of the peak force generating capacities based on computed tomography scans of the head and neck., Results: Longus capitis and colli are small muscles spanning multiple cervical motion segments. Bilateral peak flexion torque estimates were higher in the upper cervical spine (0.5 Nm), and unlikely to affect motion below the level of C5 (<0.2 Nm). Peak shear estimates were negligible (<20 N), while peak compression estimates were small (<80 N)., Conclusions: These data highlight the complex anatomy and small force capacity of longus capitis and colli, and have implications for their function. In particular, the small peak compression forces indicate that these muscles have a limited capacity to contribute to cervical stability via traditional mechanisms. This implies that the mechanism(s) by which cranio-cervical flexion exercises produce clinical benefits is worth exploring further., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Introduction: This single-blind randomized trial was conducted to compare the treatment effect of lower limb (LL) exercises versus conventional lumbar extensor (LE) and lumbar stabilization (LS) exercises in recreational runners with chronic low back pain (cLBP), because there is currently no specific protocol for managing runners with cLBP., Methods: Eighty-four recreational runners with cLBP were allocated to three exercise groups (LL, LE, LS) for an 8-wk intervention. Outcome measures included self-rated pain and running capability, LL strength, back muscle function, and running gait. Participants were assessed at preintervention, mid-intervention, and end-intervention; selected outcomes also followed up at 3 and 6 months. Generalized estimating equation was adopted to examine group-time interaction., Results: The LL group improved 0.949 points per time point in Patient-Specific Functional Scale (P < 0.001), which was higher than the LE (B = -0.198, P = 0.001) and LS groups (B = -0.263, P < 0.001). All three groups improved on average 0.746 points per time point in Numeric Pain Rating Scale for running-induced pain (P < 0.001). Knee extension strength increased 0.260 N·m·kg per time point (P < 0.001) in the LL group, which was higher than the LE (B = -0.220, P < 0.001) and LS groups (B = -0.206, P < 0.001). The LL group also showed a greater increase in running step length (2.464 cm per time point, P = 0.001) compared with LS group (B = -2.213, P = 0.013). All three groups improved similarly in back muscle function., Conclusion: LL exercise therapy could be a new option for cLPB management given its superior effects in improving running capability, knee extension strength, and running gait.

The abdominal draw-in maneuver (ADIM) is a method commonly used to reestablish neuromuscular control of the deep spine muscles among individuals with musculoskeletal problems. The purpose of this study was to evaluate the effect of ADIM combined with simulated weight-bearing (SWB) activities in the facilitation of the deep spine muscles. The subjects were 30 young healthy individuals. Ultrasound images were used to measure the relative changes in transverse abdominal (TrA), internal oblique (IO) and external oblique (EO) muscle thickness during a simulated weight-bearing ADIM (SWB-ADIM). A paired t-test was used to determine the differences between the ADIM and SWB-ADIM conditions. The results showed that the thickness of the TrA and IO muscles in the SWB-ADIM condition was significantly higher than in the ADIM-alone condition. Our findings suggest that SWB-ADIM is more effective than ADIM alone for improving the deep spine muscles in real-life situations.

Load carriage can be harmful for workers, and alternative interventions to reduce back pain while walking and carrying loads are necessary. Unstable shoes have been used to improve balance and reduce back pain, but it is unknown whether walking wearing unstable shoes while carrying loads anteriorly causes excessive trunk extensors muscle activation. The aim of this study was to investigate the effects of different shoe types and anterior load carriage on gait kinematics and lumbar electromyographic (EMG) activity. Fourteen adults that predominantly walk or stand during the work day were asked to walk with and without carrying 10% of body mass anteriorly while wearing regular walking shoes (REG) and unstable shoes (MBT). The effects of shoe type, load carriage, and shoe × load interactions on the longissimus thoracis (LT) and iliocostalis lumborum (IC) EMG, stride duration, and stride frequency were assessed. MBT shoes induced a significant increase in LT (44.4 ± 35%) and IC EMG (33.0 ± 32%, p < .005), while load carriage increased LT (58.5 ± 41%) and IC EMG (55.1 ± 32%, p < .001). No significant shoe × load interaction was found (p>.05). However, walking wearing MBT shoes while carrying loads induced a 46 ± 40% higher EMG activity compared to walking wearing MBT shoes without load carriage. No effects of shoes or load carriage were found on stride duration and stride frequency. It was concluded that walking wearing MBT shoes and carrying 10% of total body mass induced greater activation of trunk extensors muscle compared to these factors in isolation, such a combination may not influence gait patterns., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Bed pushing during patient transfer is one of the most physically demanding and yet common tasks in the hospital setting. Powered bed movers have been increasingly introduced to hospitals to reduce physiological strains on the users. This study introduces and quantifies the manpower efficiency and health benefits of a novel robotic-assisted omni-directional hospital bed transporter (SESTO Bed Mover) in comparison with a conventional manual transport stretcher (Stryker Trauma Stretcher 1037) and a powered transport stretcher (HOSPIMEK HMPT 740), which has a fifth powered wheel providing power assistance only in the forward direction. A total of 14 subjects were recruited (7 porters and 7 students) and were tasked to complete a course within a controlled lab environment. It is concluded that the robotic bed mover is able to halve the required manpower to push hospital beds as compared to conventional bed pushing without any additional physiological strain, potentially improving efficiency by two-fold. Electromyography (EMG) patterns showed that users relied on the shoulder and back muscles in a fashion similar to conventional pushing, further confirming the intuitive drive of the robotic bed mover. Overall, the robotic bed mover shows reduced physical demands, less manpower required for patient transport and reduced back muscle activities, which strongly suggest health benefits for workers in the hospital., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objective: The aim of this cross-sectional study was to evaluate a variety of isometric plank exercises., Design: Twenty university students performed the following eight different variants of plank exercises in random order and with 1-min rest intervals: stable prone plank, suspended prone plank, stable roll-out plank, suspended roll-out plank, unilateral stable prone plank, unilateral suspended prone plank, stable lateral plank, and suspended lateral plank. Surface electromyography signals were recorded for the upper rectus abdominis, lower rectus abdominis, external oblique, lumbar erector spinae, and normalized to the maximum voluntary isometric contraction., Results: The suspended prone plank and the suspended roll-out plank provided the greatest upper rectus abdominis activity. The greatest lower rectus abdominis activity was induced by the suspended roll-out plank. The highest lumbar erector spinae activity was provided by the suspended and stable lateral planks. The suspended prone plank and the suspended roll-out plank provided the greatest external oblique activity, although not significantly different from the suspended lateral plank., Conclusions: Muscle activity could be progressed using the different exercises. Although suspended prone plank and the suspended roll-out plank were most efficient for the abdominal muscles, suspended and stable lateral planks were most efficient for the lumbar muscles.

Objective: To examine the effect of a trunk exercise program on pain, quality of life (QoL) and physical health (PH) in the late pregnancy and post-partum periods as well as baby weight and size and delivery., Methods: 90 nulliparous women were allocated based on voluntarism to a training group (TG) or to a control group (CG). TG carried out a structured program with exercises for flexibility, balance and strengthening for the majority of skeletal muscles specifically for the spinal ones, between the 24th and 36th week of pregnancy. Both TG and CG were evaluated for pain at the beginning of the program (T1), at the end of the program (T2) and two months' post-partum (T3). QoL was assessed at T1,T2 and T3, and PH at T1 and T3. Mann-Whitney test was utilized to compare TG and CG on each period and to compare the periods two by two., Results: At T1, no significant difference was found between the two groups in pain intensity (pain interference p = 0.317), QoL (p = 0.18) and PH (flexibility p = 0.06; walking p = 0.85). At T2, women of TG had a lower intensity of pain than CG (legs (p = 0.029), lower back (p < 0.0001), upper back (p = 0.022), pelvis (p = 0.017), groins (p = 0.043), lower pelvis (p = 0.009) and interference of pain (p < 0.0001)). At T3, TG had a lower intensity of pain than CG, in lower back and upper back (p < 0.0001) and interference of pain (p < 0.0001). Best scores of QoL were observed in TG compared to CG at T2 (p < 0.0001) and at T3 (p < 0.0001). PH in TG compared to CG was not different between the groups in T1 but was different in in T3 (flexibility p = 0.002, walking, balance, curling-ups and Ruffier p < 0.0001). TG were four times less likely to have a caesarean (p = 0.049) and had 4.5 h less of labor time (p < 0.0001). No difference was observed between the TG vs CG concerning the weight (p = 0.22) and the baby's size (p = 0.11)., Conclusion: Strengthening exercises centered on the trunk reduce pain, improve QoL and PH in late pregnancy and at two months in the post-partum period. Strengthening exercises also ease the delivery.