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The flexion-relaxation phenomenon (FRP) refers to the deactivation of back muscles during deep forward trunk bending. This study examined the effects of back muscle strength, individual flexibility, and trunk angle on FRP in the back muscles. Forty male participants were classified into four groups according to toe-touch flexibility and back muscle strength. Lumbar erector spinae (LES) activity and the lumbosacral angle (LSA) were measured at incremental trunk flexion angles (0°-90°, with increments of 15°) to analyze FRP. Results indicated significant effects of back muscle strength, flexibility, and trunk angle on LES activity (all p < 0.001). Flexibility (p < 0.05) and trunk angle (p < 0.001) also influenced LSA. Additionally, an interaction between flexibility and trunk angle impacted LES activation (p < 0.001). Flexibility mainly determined FRP onset, while back muscle strength influenced efforts during moderate trunk flexion (30°-60°). These findings indicate that differences in lower back load among individuals with varying back muscle strengths become apparent even at relatively small trunk flexion angles (approximately 30°). When prolonged static trunk flexion in workplace settings places considerable strain on the lower back, we recommend utilizing toe-touch flexibility and back muscle strength assessments as practical screening tools for identifying early and subtle indicators of the FRP in workers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Alterations of trunk muscle activity can be objectified using surface electromyography (sEMG). But for diagnostic purposes reliable reference values are needed. Therefore, the present study evaluated sEMG measurements of representative back muscles concerning their reliability. For this purpose, 49 healthy individuals (24 women) were subjected to static loads with defined portions of their upper body weight by applying whole-body tilts up to 90° in upright posture. Reliability analyses were carried out for amplitude values and normalized values according 90° tilt angle. Reliability measures included intraclass correlation coefficient (ICC), standard error of measurement (SEm), standard error of the mean (SEM), and coefficient of variation of method errors (CVME). ICC values for the amplitude values were > 0.79 for M. multifidus (MF) and M. longissimus (LO). For the normalized values, distinctively lower ICC levels were generally detected (0.33-0.81). The values of SEm and SEM also increased with increasing load, while CVME levels of the amplitude values maintained similar levels. For defined static extension loads, good to excellent reliability can be demonstrated for back muscles. The established normative values for SEm, SEM and CVME parameters may be used for diagnostic purposes during defined submaximal load situations. This does not apply to normalized data., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Over the course of the physical activity transition, machines have largely replaced skeletal muscle as the source of work for locomotion and other forms of occupational physical activity in industrial environments. To better characterize this transition and its effect on back muscles and the spine, we tested to what extent typical occupational activities of rural subsistence farmers demand higher magnitudes and increased variability of back muscle activity and spinal loading compared to occupational activities of urban office workers in Rwanda, and whether these differences were associated with back muscle endurance, the dominant risk factor for back pain. Using electromyography, inertial measurement units, and OpenSim musculoskeletal modeling, we measured back muscle activity and spinal loading continuously while participants performed occupational activities for one hour. We measured back muscle endurance using electromyography median frequency analysis. During occupational work, subsistence farmers activate their back muscles and load their spines at 390% higher magnitudes and with 193% greater variability than office workers. Partial correlations accounting for body mass show magnitude and variability response variables are positively associated with back muscle endurance (R = 0.39-0.90 [P < 0.001-0.210] and R = 0.54-0.72 [P = 0.007-0.071], respectively). Body mass is negatively correlated with back muscle endurance (R = -0.60, P = 0.031), suggesting higher back muscle endurance may be also partly attributable to having lower body mass. Because higher back muscle endurance is a major factor that prevents back pain, these results reinforce evidence that under-activating back muscles and under-loading spines at work increases vulnerability to back pain and may be an evolutionary mismatch. As sedentary occupations become more common, there is a need to study the extent to which occupational and leisure time physical activities that increase back muscle endurance helps prevent back pain., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Sibson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

This mixed-method study evaluated the efficacy of lift assist device use (Binder®, Eagle®, Maxi Air®) relative to manual lifting/care-as-usual in reducing low back muscle activity and perceived exertion during simulated patient extrication tasks. User feedback was recorded to identify factors that might influence use. Twenty paramedics performed a floor to stretcher lift, lateral transfer, and confined space extrication care-as-usual and with lift assist devices. Use of a lift assist reduced low back muscle activity during floor to stretcher and confined space tasks by 34-47%. Paramedics perceived exertion decreased from 'somewhat hard' to 'light' or 'very light' when using an assistive device. Paramedics noted that ease of use, patient comfort, task time, patient acuity, among other considerations would influence use decisions. Lift assist devices were efficacious at reducing low back muscle activity and perceived exertion during floor to stretcher and patient extrication tasks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Motion Tape (MT) is a low-profile, disposable, self-adhesive wearable sensor that measures skin strain. Preliminary studies have validated MT for measuring lower back movement. However, further analysis is needed to determine if MT can be used to measure lower back muscle engagement. The purpose of this study was to measure differences in MT strain between conditions in which the lower back muscles were relaxed versus maximally activated., Methods: Ten participants without low back pain were tested. A matrix of six MTs was placed on the lower back, and strain data were captured under a series of conditions. The first condition was a baseline trial, in which participants lay prone and the muscles of the lower back were relaxed. The subsequent trials were maximum voluntary isometric contractions (MVICs), in which participants did not move, but resisted the examiner force in extension or rotational directions to maximally engage their lower back muscles. The mean MT strain was calculated for each condition. A repeated measures ANOVA was conducted to analyze the effects of conditions (baseline, extension, right rotation, and left rotation) and MT position (1-6) on the MT strain. Post hoc analyses were conducted for significant effects from the overall analysis., Results: The results of the ANOVA revealed a significant main effect of condition ( p < 0.001) and a significant interaction effect of sensor and condition ( p = 0.01). There were significant differences in MT strain between the baseline condition and the extension and rotation MVIC conditions, respectively, for sensors 4, 5, and 6 ( p = 0.01-0.04). The largest differences in MT strain were observed between baseline and rotation conditions for sensors 4, 5, and 6., Conclusions: MT can capture maximal lower back muscle engagement while the trunk remains in a stationary position. Lower sensors are better able to capture muscle engagement than upper sensors. Furthermore, MT captured muscle engagement during rotation conditions better than during extension.

Background: Different treatments have been proposed for patients with deep gluteal syndrome (DGS). Stretching and compression exercises are commonly used to treat DGS., Objective: To compare the effects of compression or stretching exercises on the flexion-relaxation response (electromyography signals of back muscles) in patients with DGS., Methods: In this clinical trial with parallel groups, forty-five eligible patients were randomly allocated into three groups; compression exercise (ICE) (n = 15), stretching exercise (ISE) (n = 15) and control group (n = 15). All treatment groups (control, ICE and ISE) underwent 10 sessions of physiotherapy treatment at a frequency of three per week. The flexion-relaxation ratio (FRR) for back muscles was investigated as the primary outcome measure., Results: No significant differences were detected in FRR of back muscles at the end of the study between three study groups (all p > 0.05). In all groups after interventions, no significant changes in FRR compared to the baseline values were observed (within changes were not significant; all p > 0.05). The pairwise comparisons of the between groups revealed that the disability scores in the ISE group compared to ICE, were significantly lower (F = 5.53; df = 2; P = 0.009)., Conclusion: Neither stretching nor compression exercises affected FRR more than the control group in DGS patients. Between-group analyses suggest that ISE only has a more significant effect on improving the disability of patients with the deep gluteal syndrome., Clinical Trial Registration: The trial was retrospectively registered in the "IRANIAN" Registry of Clinical Trials (www.irct.ir) on January 10, 2017 as IRCT201604178035N4. URL of the record: https://en.irct.ir/trial/8473., Competing Interests: Declaration of competing interest There are no known conflicts of interest associated with this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Sedentary lifestyles lead to postural deformities, Lower Back Pain(LBP) and Colorectal cancer(CRC). Practicing Yoga attains definite strength in muscles by activating muscle fibers. The Yoga poses analyzed are often used in strengthening and stability programs for the abdomen and back muscles., Objective: To determine the potential use of Dolphin pose and Dolphin plank in specific strengthening endurance and rehabilitation programs via sEMG analysis in the selected bilateral abdomen and lower back muscles., Methods: Surface electromyographic analysis was conducted on bilateral muscles, including the Rectus Abdominis(RA), External oblique(EO), Internal oblique(IO), and Erector Spinae(ES), resulting in Dolphin pose(DS), Dolphin plank(DP), and High plank(HP). Data were expressed by Root Mean Square(RMS) of each bilateral muscle during each Pose normalized as 100% of maximum voluntary isometric contraction(MVIC)., Results: Dolphin plank(DP) generated a very high-level muscle activation than 100% MVIC in all bilateral muscles, and there was a significant main effect of Pose e (p < 0.001). Erector spinae generated more activation in the Dolphin pose (p < 0.05) than in the HP and DS. No significant difference between bilateral activity differences in DP and DS. There was a significant difference between RRA and LRA (p < 0.001) and RIO and LIO (p < 0.0001)., Conclusion: Findings have suggested that the Dolphin plank could be used for abdomen strengthening, performance enhancement, and rehabilitation programs. Dolphin pose may benefit lower back stability by providing endurance to the Erector spinae muscle. So, this yoga pose can be incorporated into the yoga training module for addressing lower back pain(LBP) caused by longer sitting in a sedentary lifestyle., Competing Interests: Declaration of competing interest None. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2024. Published by Elsevier Ltd.)

Background and Aim: Research has documented chronic non-specific low back pain (CNSLBP) as one of the primary causes of absenteeism at work, often accompanied by the use of health insurance and healthcare services. Considering little research on the consequences of open/closed kinetic chain (O/CKC) exercises in water on CNSLBP improvement, the present study is to investigate the effects of such interventions on the electrical activity of selected lumbar muscles, pain, lumbopelvic control (LPC), ground reaction force (GRF), and psychological factors in men with CNSLBP., Materials and Methods: This is a randomized controlled trial that involves individuals with CNSLBP between the ages of 40 and 60 years. Participants are randomly assigned, using block randomization, to one of the following groups: open kinetic chain (OKC) exercises, closed kinetic chain (CKC) exercises, or controls. The training groups engage in the exercises for eight weeks, with three sessions per week and 60 min each at the University of Bu-Ali Sina pool, following the prescribed workout routine. The primary outcomes of the electrical activity of the multifidus (MF), transversus abdominis (TrA), gluteus medius (GM), and quadratus lumborum (QL) muscles are measured by an electromyography (EMG) device. Additionally, the pressure biofeedback (BFB) device and the visual analog scale (VAS) are utilized to assess LPC and pain intensity, respectively. The secondary outcomes of the GRF, along with foot pressure and kinesiophobia, are subsequently measured by the Tampa Scale of Kinesiophobia (TSK)., Conclusion: By comparing the outcomes between the OKC exercise group, CKC exercise group, and control group, this study aims to determine the differential effects of these two water-based exercise interventions on the various physical and psychological parameters in individuals with CNSLBP. The findings provide valuable insights into the most effective approach to water-based rehabilitation for individuals with CNSLBP. By comparing the outcomes of OKC and CKC exercises, healthcare professionals can make informed decisions when designing tailored rehabilitation programs for this patient population. The results also contribute to the development of evidence-based guidelines for the management of CNSLBP using water-based exercises., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Introduction: Sedentary lifestyles is linked to a reduction in back muscle strength, endurance, and balance, consequently increasing the risk of experiencing low back pain. Kinesio taping has been shown to be effective in enhancing endurance, flexibility, and balance. This study aimed to investigate the effects of Kinesio taping on measures of lumbar function in sedentary individuals., Method: Forty-four sedentary young adults were randomly assigned into intervention and control groups. The intervention group received Kinesio tape to the lumbar region while the control group received health education. The Schober's test, Single-leg stance test, Y Balance Test, and Biering-Sorensen test were performed at baseline and 30 min and 24 h after the taping intervention., Results: There was a statistically significant increase in static balance (single-leg stance test) in the intervention group compared to the control group (p ≤ 0.05). In the Y Balance Test and Biering-Sorensen test, there was no significant difference between the intervention group and control group, though there was a significant increase in both groups from baseline to 24 h after taping. Though low back flexibility (Schober's test) significantly decreased in the intervention group, there was no significant difference between the two groups., Conclusion: Kinesio taping can immediately improve static balance in people with sedentary behavior. The application of Kinesio tape had no impact on dynamic balance, low back flexibility, or low back muscle endurance., Competing Interests: Declaration of competing interest There are no known conflicts of interest associated with this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study assessed the effect of a small-torque generating passive back-support exoskeleton during a low demanding occupational task, namely a repetitive lifting/lowering of an empty crate between the knee and shoulder heights. A comprehensive set of outcomes was considered, ranging from the measured trunk muscle activation and trunk movement to the estimated muscle group forces/coordination, spine loading and spine stability, using a dynamic subject-specific EMG-assisted musculoskeletal model. The exoskeleton decreased back muscle activation and corresponding muscle forces in the lowering phase and reduced spinal loading at larger trunk flexion angles (decreased peak compression and shear forces by ∼ 15%). However, the effect sizes were small (η G 2  < .06), questioning the usefulness of this type of exoskeleton, even for light tasks. On the other hand, the unique results of the present study showed that coordination between the main muscle groups as well as spinal stability remained unchanged with low effect sizes, suggesting that the use of this exoskeleton is safe., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Lumbar spine injuries resulting from heavy or repetitive lifting remain a prevalent concern in workplaces. Back-support devices have been developed to mitigate these injuries by aiding workers during lifting tasks. However, existing devices often fall short in providing multidimensional force assistance for asymmetric lifting, an essential feature for practical workplace use. In addition, validation of device safety across the entire human spine has been lacking. This paper introduces the Bilateral Back Extensor Exosuit (BBEX), a robotic back-support device designed to address both functionality and safety concerns. The design of the BBEX draws inspiration from the anatomical characteristics of the human spine and back extensor muscles. Using a multi-degree-of-freedom architecture and serially connected linear actuators, the device's components are strategically arranged to closely mimic the biomechanics of the human spine and back extensor muscles. To establish the efficacy and safety of the BBEX, a series of experiments with human participants was conducted. Eleven healthy male participants engaged in symmetric and asymmetric lifting tasks while wearing the BBEX. The results confirm the ability of the BBEX to provide effective multidimensional force assistance. Moreover, comprehensive safety validation was achieved through analyses of muscle fatigue in the upper and the lower erector spinae muscles, as well as mechanical loading on spinal joints during both lifting scenarios. By seamlessly integrating functionality inspired by human biomechanics with a focus on safety, this study offers a promising solution to address the persistent challenge of preventing lumbar spine injuries in demanding work environments.

Commonly used risk indexes, such as the NIOSH Lifting Index, do not capture the effect of exoskeletons. This makes it difficult for Health and Safety professionals to rigorously assess the benefit of such devices. The community requires a simple method to assess the effectiveness of back-support exoskeleton's (BSE) in possibly reducing ergonomic risk. The method introduced in this work is termed "Equivalent Weight" (EqW) and it proposes an interpretation of the effect built on the benefit delivered through reduced activation of the erector spinae (ES). This manifests itself as an apparent reduction of the lifted load perceived by the wearer. This work presents a pilot study where a practical application of the EqW method is used to assess the ergonomic risk in manual material handling (MMH) when using a back support exoskeleton (StreamEXO). The results are assessed by combining observational measurements from on-site testing with five different workers and quantitative measures of the muscle activity reduction achieved during laboratory evaluation with ten workers. These results will show that when lifting, lowering, and carrying a 19 kg load the StreamEXO can reduce risk by up to two levels (from "high" to "low") in the target sub-tasks. The Lifting index (LI) was reduced up to 64% when examining specific sub-tasks and the worker's movement conduction., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: An author (Christian Di Natali) is cofounder of a startup that aims to commercialize occupational exoskeletons. The other coauthors have not conflict of interest., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

OCCUPATIONAL APPLICATIONSOccupational exoskeletons receive rising interest in industry as these devices diminish the biomechanical load during manual materials handling. Still, we have limited knowledge when it comes to in-field use. This gap often contributes to failure in the implementation of exoskeleton in industry. In this study, we investigated how a training protocol consisting of in-field use of a passive back exoskeleton affected the biomechanics of logistic workers. More specifically, we focused on how the variation of the muscular and kinematic patterns of the user was altered after exoskeleton training. We found that training had a positive effect on exoskeleton use, as a relative decrease of 6-9% in peak back muscle activity was observed post-training. Additionally, training decreased knee flexion by 6°-16°, indicating a more stoop lifting technique. The findings point at the potential benefits of applying a training approach when implementing a back-supporting exoskeleton in logistics.

Lumbar exoskeleton is an assistive robot, which can reduce the risk of injury and pain in low back muscles when lifting heavy objects. An important challenge it faces involves enhancing assistance with minimal muscle energy consumption. One of the viable solutions is to adjust the force or torque of assistance in response to changes in the load on the low back muscles. It requires accurate loading recognition, which has yet to yield satisfactory outcomes due to the limitations of available measurement tools and load classification methods. This study aimed to precisely identify muscle loading using a multi-channel surface electromyographic (sEMG) electrode array on the low back muscles, combined with a participant-specific load classification method. Ten healthy participants performed a stoop lifting task with objects of varying weights, while sEMG data was collected from the low back muscles using a 3x7 electrode array. Nineteen time segments of the lifting phase were identified, and time-domain sEMG features were extracted from each segment. Participant-specific classifiers were built using four classification algorithms to determine the object weight in each time segment, and the classification performance was evaluated using a 5-fold cross-validation method. The artificial neural network classifier achieved an impressive accuracy of up to 96%, consistently improving as the lifting phase progressed, peaking towards the end of the lifting movement. This study successfully achieves accurate recognition of load on low back muscles during the object lifting task. The obtained results hold significant potential in effectively reducing muscle energy consumption when wearing a lumbar exoskeleton.

Industrial back support exoskeletons (BSEs) are a promising approach to addressing low back pain (LBP) which still affect a significant proportion of the workforce. They aim to reduce lumbar loading, the main biomechanical risk factor for LBP, by providing external support to the lumbar spine. The aim of this study was to determine the supporting effect of one active (A1) and two passive (P1 and P2) BSEs during different manual material handling tasks. Kinematic data and back muscle activity were collected from 12 subjects during dynamic lifting and static holding of 10 kg. Mean and peak L5/S1 extension moments, L5/S1 compression forces and muscle activation were included in the analysis. During dynamic lifting all BSEs reduced peak (12-26 %) and mean (4-17 %) extension moments and peak (10-22 %) and mean (4-15 %) compression forces in the lumbar spine. The peak (13-28 %) and mean (4-32 %) activity of the back extensor muscles was reduced accordingly. In the static holding task, analogous mean reductions for P1 and P2 of L5/S1 extension moments (12-20 %), compression forces (13-23 %) and muscular activity (16-23 %) were found. A1 showed a greater reduction during static holding for extension moments (46 %), compression forces (41 %) and muscular activity (54 %). This pronounced difference in the performance of the BSEs between tasks was attributed to the actuators used by the different BSEs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study aimed to establish an ambulatory field-friendly system based on miniaturised wireless flexible sensors for studying the biomechanics of human-exoskeleton interactions. Twelve healthy adults performed symmetric lifting with and without a passive low-back exoskeleton, while their movements were tracked using both a flexible sensor system and a conventional motion capture (MoCap) system synchronously. Novel algorithms were developed to convert the raw acceleration, gyroscope, and biopotential signals from the flexible sensors into kinematic and dynamic measures. Results showed that these measures were highly correlated with those obtained from the MoCap system and discerned the effects of the exoskeleton, including increased peak lumbar flexion, decreased peak hip flexion, and decreased lumbar flexion moment and back muscle activities. The study demonstrated the promise of an integrated flexible sensor-based system for biomechanics and ergonomics field studies as well as the efficacy of exoskeleton in relieving the low-back stress associated with manual lifting.

Background: Weakness and atrophy in trunk muscles have been associated with chronic low back pain (CLBP)., Objective: This study aimed to identify isometric exercises resulting the highest trunk muscle activity for individuals with and without CLBP., Methods: Fourteen males with CLBP and 15 healthy age-matched healthy subjects were recruited for this study. Muscle activity during maximal voluntary isometric contraction (MVIC) was measured for a comparative reference with surface electromyography (sEMG) from six trunk muscles. Thereafter maximum EMG amplitude values were measured during eleven trunk stability exercises. The maximal EMG activity in each exercise relative to the MVICs was analyzed using generalizing estimating equations (GEE) models with the unstructured correlation structure., Results: The GEE models showed statistically significant differences in muscle activity between exercises within both groups (p< 0.001), with no significant differences between groups (p> 0.05). The highest muscle activity was achieved with the hip flexion machine for multifidus, side pull with a resistance band for lumbar extensors, side and single-arm cable pull exercises for thoracic extensors, rotary plank and the hip flexion machine for abdominal., Conclusion: This study found five isometric trunk exercises that exhibited highest muscle activity depending on muscle tested, with no significant difference between individuals with and without CLBP.

Lumbar exoskeleton has potential to assist in lumbar movements and thereby prevent impairment of back muscles. However, due to limitations of evaluation tools, the effect of lumbar exoskeletons on coordinated activities of back muscles is seldom investigated. This study used the surface electromyography (sEMG) topographic map based on multi-channel electrodes from low back muscles to analyze the effects. Thirteen subjects conducted two tasks, namely lifting and holding a 20kg-weight box. For each task, three different trials, not wearing exoskeleton (NoExo), wearing exoskeleton but power-off (OffExo), and wearing exoskeleton and power-on (OnExo), were randomly conducted. Root-mean-square (RMS) and median-frequency (MDF) topographic maps of the recorded sEMG were constructed. Three parameters, average pixel values, distribution of center of gravity (CoG), and entropy, were extracted from the maps to assess the muscle coordinated activities. In the lifting task, results showed the average pixel values of RMS maps for the NoExo trial were lower than those for the OffExo trial ( [Formula: see text]) but the same as those for the OnExo trial ( [Formula: see text]0.05). The distribution of CoG showed a significant difference between NoExo and OnExo trials ( [Formula: see text]). In the holding task, RMS and MDF maps' average pixel values showed significant differences between NoExo and OnExo trials ( [Formula: see text]). These findings suggest that active lumbar exoskeletons can reduce the load on low back muscles in the static holding task rather than in the dynamic lifting task. This proves sEMG topographic maps offer a new way to evaluate such effects, thereby helping improve the design of lumbar exoskeleton systems.

The aim of this study was to assess, for both men and women, the consequences of using different back-support exoskeletons during various manual material tasks (MMH) on the activity of back muscles and trunk kinematics. Fifteen men and fourteen women performed MMH involving a 15 kg load (a static task, a symmetric lifting task, and an asymmetric lifting task). Four exoskeleton conditions were tested: without equipment (CON) and with three exoskeletons passive (P-EXO), and active (A-EXO1 and A-EXO2)). The electromyographic activity of the lower trapezius (TZ), latissimus dorsi (LD), erector spinae (ES), gluteus maximus (GM), and biceps femoris (BF) muscles was recorded. Trunk kinematics were evaluated to provide average thoracic, lumbar, and hip angles. The use of the P-EXO decreased the activity of LD, GM, and BF from -12 to -27% ( p < 0.01) compared to CON, mostly during the static task. The A-EXO1 and A-EXO2 reduced the muscle activity of all studied muscles from -7 to -62% ( p < 0.01) compared to CON and from -10 to -52% ( p < 0.005) compared to the P-EXO, independently of the modalities of the experimental tasks. A statistical interaction between the sex and exoskeleton was only observed in a few rare conditions. Occupational back-support exoskeletons can reduce trunk extensor muscle activity compared to no equipment being used. However, these reductions were modulated by the exoskeleton technology (passive vs. active), design (weight and anthropomorphism), and the modalities of the task performed (static vs. dynamic). Our results also showed that the active exoskeletons could modify the trunk kinematics.

Musculoskeletal disorders affecting the back are highly prevalent in fields of occupation involving repetitive lifting and working in forward leaning postures. Back-support exoskeletons are developed to relieve workers in physically demanding occupations. This study investigates the physiological effects of a lightweight exoskeleton which provides support through textile springs worn on the back. We hypothesized that wearing such a passive back-support exoskeleton reduces muscle activity of the back and hip muscles, while not influencing abdominal muscle activity and movement kinematics during typical occupational tasks. We collected electromyography data from the main back and hip muscles as well as whole body kinematics data via optical motion tracking during a set of relevant weight lifting tasks corresponding to typical work conditions. In our sample of 30 healthy volunteers, wearing the exoskeleton significantly reduced muscle activity, with reductions up to 25.59% during forward leaning and 20.52% during lifting in the main back and hip muscles (Erector Spinae at thoracic and lumbar level and Quadratus Lumborum). Simultaneously, no changes in knee and hip range of motion were observed. The stretch of the textile springs correlated with the body mass index and chest circumference of the wearer, and depended on posture, but not on the lifted load. The LiftSuit exoskeleton relieved back and hip muscles during typically straining occupational tasks, while biomechanical parameters were preserved. This suggests that passive lift-support exoskeletons can be safely used to relieve workers during lifting and forward leaning tasks., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Rachel van Sluijs is employed by Auxivo AG. Olivier Lambercy is an academic advisor to Auxivo AG., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: The prevalence of low back pain is lower when physical fitness (aerobic and muscular) is higher. Strength exercises are important for subjects with low back pain, but there are few studies on the inclusion of aerobic exercise in low back pain programs. The aim of this study was to compare the effects of aquatic exercises with or without high-intensity component on the functional status, lumbar and abdominal muscle endurance, and performance of subjects with chronic low back pain., Methods: Forty-eight volunteers between 20 and 60 years old were randomly allocated to an experimental group AEDWR (aquatic exercises plus deep-water running group, N.=25) or to a control group AE (aquatic exercises only group, N.=23). The dependent variables included functional status (Repeated Sit-to-Stand test), lumbar (Sorensen test) and abdominal (One Minute Abdominal test) muscle endurance, and physical performance (Maximum Physical Fitness test), which were measured before and after the 9-week intervention and at 21 weeks of follow-up., Results: Lumbar endurance was higher in the AEDWR group at the end of the treatment, with a mean difference (MD) of 43.2 seconds, 95% confidence intervals (CI) (9.6; 76.7), P=0.01, d̅=0.74, and better in the follow-up with MD=40.2 seconds, 95% CI (7.1; 73.3), P=0.02, d̅=0.71, than in the AE group. Participant performance also improved on the 9 th week in the AEDWR group, with an MD=0.53 kgf, 95% CI (0.008; 0.98), P=0.02, d̅=0.60., Conclusions: The addition of deep-water running exercise to aquatic exercises improved lumbar muscle endurance and performance when compared with aquatic exercises only, and this effect was maintained during the follow-up to lumbar muscle endurance.

While occupational back-support exoskeletons (BSEs) are considered as potential workplace interventions, BSE use may compromise postural control. Thus, we investigated the effects of passive BSEs on postural balance during quiet upright stance and functional limits of stability. Twenty healthy adults completed trials of quiet upright stance with differing levels of difficulty (bipedal and unipedal stance; each with eyes open and closed), and executed maximal voluntary leans. Trials were done while wearing two different BSEs (SuitX™, Laevo™) and in a control (no-BSE) condition. BSE use significantly increased center-of-pressure (COP) median frequency and mean velocity during bipedal stance. In unipedal stance, using the Laevo™ was associated with a significant improvement in postural balance, especially among males, as indicated by smaller COP displacement and sway area, and a longer time to contact the stability boundary. BSE use may affect postural balance, through translation of the human + BSE center-of-mass, restricted motion, and added supportive torques. Furthermore, larger effects of BSEs on postural balance were evident among males. Future work should further investigate the gender-specificity of BSE effects on postural balance and consider the effects of BSEs on dynamic stability., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objective: The purpose of this study was to investigate the effects of ischemic pressure (IP) vs postisometric relaxation (PIR) on rhomboid-muscle latent trigger points (LTrPs)., Methods: Forty-five participants with rhomboid-muscle LTrPs were randomly assigned into 3 groups and received 3 weeks of treatment-group A: IP and traditional treatment (infrared radiation, ultrasonic therapy, and transcutaneous electrical nerve stimulation); group B: PIR and traditional treatment; and group C: traditional treatment. Shoulder pain and disability, neck pain and disability, and pressure pain threshold (PPT) of 3 points on each side were measured before and after treatment., Results: Multivariate analysis of variance indicated a statistically significant Group × Time interaction (P = .005). The PPT for the right lower point was increased in group A more than in groups B or C. Neck pain was reduced in group B more than in group C. Moreover, shoulder and neck disability were reduced in both groups A and B more than in group C. The PPTs of the left lower and middle points were increased in group B compared with groups A and C. The PPT of the left upper point was increased in group A more than in group C. There were significant changes in all outcomes in the 2 experimental groups (P < .05). No changes were found in the control group except in pain intensity, shoulder disability, and PPT of the left lower point., Conclusion: This study found that IP may be more effective than PIR regarding PPT, but both techniques showed changes in the treatment of rhomboid-muscle LTrPs., (Copyright © 2020. Published by Elsevier Inc.)

Background: Stimulating electrodes for lower extremity motor-evoked potential (LE-MEP) monitoring with transcortical stimulation are usually placed on the medial side of motor cortex convexity, which is not lower extremity but lumbar motor area. Lumbar MEP may be elicited with lower stimulation intensity than LE-MEP through this location, and it is useful to monitor lower extremity motor function intraoperatively., Methods: Intraoperative lumbar and LE-MEP monitoring with transcortical stimulation during surgery of 12 patients with lesions involving the motor cortex from January 2012 to February 2019 at Shinshu University Hospital were reviewed retrospectively. Stimulations were delivered by a train of 5 pulses of anodal constant current stimulation. Stimulating electrode position was determined by motor cortex mapping. Recording needle electrodes were placed on bilateral lumbar muscles and contralateral leg muscles. The threshold-level stimulation method was used for MEP monitoring. The thresholds, monitoring result, and postoperative motor function of lumbar and lower extremities were compared., Results: The mean baseline thresholds were 19.9 ± 8.9 mA for lumbar MEP and 26.5 ± 11.5 mA for LE-MEP (P = 0.02). Patterns of intraoperative monitoring changes were the same between lumbar and LE-MEP monitoring., Conclusions: Lumbar MEP was stimulated with lower stimulation intensity than the LE-MEP with the same intraoperative pattern of waveform changes in 12 patients. Lumbar MEP monitoring may be useful for preserving the corticospinal tract of lower extremities intraoperatively., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The purpose of this study was to investigate fatigue-related changes in spinal kinematics, kinetics, and muscle activity of back muscles during a 2000 m all-out ergometer rowing performance. We analyzed ten male subjects with experience in both rowing and CrossFit exercises. We applied a novel kinematic method to describe spine curvature, determined bending moments at the spine using inverse dynamics and collected EMG data. We identified significant increases in spine curvature of the thoracic spine (i.e. vertebrae Th6 to Th11). Significant increases in peak moments were found only at the upper spine (i.e. Th2). We found no significant changes in EMG amplitudes, while the frequency analysis showed significant decreases in the mean frequencies (MNF) for the M. latissimus dorsi, the M. trapezius descendens and the M. deltoideus posterior. No significant changes on MNF were found for the Mm. erector spinae. We hypothesize that the significant increase in curvature for the thoracic spine is connected to the fatigued back muscles, especially the Mm. trapezius descendens, and might lead to an unbalanced loading of intervertebral discs and other structures. These findings are particularly important for athletes and coaches in CrossFit as strenuous rowing intervals are combined with technical exercises with high loads on the back and spine (e.g. power and Olympic lifting) leading to impaired muscular stabilization and potentially to an increased injury risk.

Compensatory mechanisms, such as a decrease in thoracic spine kyphosis and posterior tilting or rotation of the pelvis, aim to achieve optimal alignment of the spine. However, the effect of muscle strength on these compensatory mechanisms has not been elucidated. This study aimed to investigate the impact of back muscle and lower extremity strength on compensatory mechanisms in elderly people. Overall, 409 community-dwelling elderly participants (164 men, 245 women) were included. Age, disc degeneration, and 2 or more vertebral fractures showed a significant increase of risk for sagittal vertical axis (SVA) deterioration. Conversely, stronger back, hip flexor, and knee extensor muscles reduced the risk for SVA deterioration. To investigate the association of each muscle's strength with compensatory mechanisms, 162 subjects with pelvic incidence-lumbar lordosis > 10° were selected. The linear regression model for thoracic kyphosis demonstrated a negative correlation with back muscle strength and positive correlation with vertebral fracture. The regression analysis for pelvic tilt demonstrated a positive correlation with knee extensor strength. Back, hip flexor, and knee extensor muscle strength were associated with sagittal spinal alignment. Back muscle strength was important for the decrease in thoracic kyphosis, and knee extensor strength was associated with pelvic tilt.

Background: There are currently no reports of biomechanical changes in patients with forward head posture (FHP) that result in altered muscle activation throughout various functions with muscle activation response during diverse sleep postures., Objective: This study investigated neck and back muscle activity in individuals with and without FHP during a maintained side-sleeping position by incorporating various pillow designs., Methods: Thirty-four participants (i.e., 17 in each group) were enrolled. The muscle activity was investigated via surface electromyography during the use of three trial pillows: orthopedic pillow, hollow pillow, and Thai neck support pillow., Results: With the application of all three trial pillow, the FHP group demonstrated significantly greater middle-lower trapezius muscle activity than the normal head posture group (p< 0.05). Sternocleidomastoid and upper trapezius (UT) muscle activity were similar between the two groups (p> 0.05). Only UT muscle activity was affected by variations in pillow design. In the normal group, no difference was observed in the muscle activity between all three pillows (p> 0.05)., Conclusions: Feasibly, the ability to appropriately modify a pillow configuration without creating undesired muscle activation was limited to those exhibiting FHP. Therefore, specially designed pillows or mattresses should be investigated in terms of their relevance to muscle fatigue and potential musculoskeletal pain in FHP patients.

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

Objective: Pelvic tilt exercises are used clinically to correct lumbopelvic alignment. The anterior and posterior layers of the quadratus lumborum are important for pelvic motor control in the coronal plane. This study aimed to evaluate whether the anterior and posterior activity is related to the pelvic tilt angle during pelvic tilt exercises., Design: The study design was single-occasion repeated measures in a randomized manner. Twelve healthy men performed the four directions of the pelvic tilt exercises (anterior or posterior pelvic tilt and lateral pelvic elevation on the ipsilateral or contralateral measurement side). The electromyographies of the anterior and posterior were recorded using intramuscular fine-wire electrodes and normalized to isometric peak electromyography., Results: The activity of the anterior and posterior during lateral pelvic elevation on the ipsilateral measurement side (19.0 ± 16.0 percent of maximal voluntary isometric contraction) was significantly higher than that during other directions of the pelvic tilt exercises (P < 0.01). There was a significant positive correlation between the anterior activity and the maximum change angles of pelvic tilt during lateral pelvic elevation on the ipsilateral measurement side (r = 0.674, P = 0.016)., Conclusions: The anterior activity was related to a large lateral pelvic elevation angle on the ipsilateral side during pelvic tilt exercises.

Objective: The purpose of this study was to investigate the difference in back extensor muscle endurance before and after kinesiology tape application to all back stabilizer muscles and to the erector spinae alone., Methods: We assessed 32 adults (16 men and 16 women), randomly divided into two groups. In the erector spinae taping (EST) group, kinesiology tape was applied only to the erector spinae, and in the total muscle taping (TMT) group, kinesiology tape was applied to the erector spinae, latissimus dorsi, lower trapezius, internal oblique abdominis, and external oblique abdominis., Results: Both groups showed significant difference in terms of back extensor muscle endurance after kinesiology tape application (p<0.05). Between-group comparison revealed that the TMT group had more back extensor muscle endurance than the EST group (p<0.05) after kinesiology tape application., Conclusions: These findings indicate that, to improve back extensor muscle endurance, kinesiology tape should be applied to all back stabilizer muscles, rather than to the erector spinae muscles alone., Competing Interests: The authors have no conflict of interest.

Today's office chairs are not known to promote active sitting or to activate the lumbar trunk muscles, both of which functions are ergonomically recommended. This study investigated a newly developed dynamic office chair with a moveable seat, specifically designed to promote trunk muscle controlled active sitting. The study aimed to determine the means by which the seat movement was controlled during active sitting. This was accomplished by quantifying trunk and thigh muscular activity and body kinematics. Additionally, the effect of increased spinal motion on muscular activity and body kinematics was analysed. Ten subjects were equipped with reflective body markers and surface electromyography on three lumbar back muscles (multifidus, iliocostalis, longissimus) and two thigh muscles (vastus lateralis and medialis). Subjects performed a reading task during static and active sitting in spontaneous and maximum ranges of motion in a simulated office laboratory setting. The temporal muscle activation pattern, average muscle activity and body segment kinematics were analysed and compared using Friedman and post-hoc Wilcoxon tests (p≤0.05). Active sitting on the new chair significantly affected the lumbar trunk muscles, with characteristic cyclic unloading/loading in response to the seat movement. Neither thigh muscle activity nor lateral body weight shift were substantially affected by active sitting. When participants increased their range of motion, the lumbar back muscles were activated for longer and relaxation times were shorter. The characteristic activity pattern of the lumbar trunk muscles was shown to be the most likely dominant factor in controlling seat movement during active sitting. Consequently, the new chair may have a potential positive impact on back health during prolonged sitting. Further studies are necessary to analyse the frequency and intensity of active sitting during daily office work., Competing Interests: One of the authors (DB) is the inventor of the new seat motion and owner of rotavis AG who holds the right for commercial use of the intellectual property right. The intellectual property right belongs to ETH Zurich which has approved the present study. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Background: As the sustainability of the agricultural workforce has been threatened by the high prevalence of back pain, developing effective interventions to reduce its burden within farming will contribute to the long-term health and productivity of workers. Passive back-support exoskeletons are being explored as an intervention to reduce the physical demands on the back muscles, and consequently mitigate the risk of back pain, in many industrial sectors., Methods: This study investigated whether exoskeleton use could reduce farmers' low back muscle load. Electromyography was used to evaluate exoskeleton use in field and laboratory settings. A total of 14 farmers (13 males and 1 female) with a mean age of 49 (SD = 12) years and 6 female nonfarmers (mean age 28, SD = 5 years) performed a standardized set of tasks that included symmetric and asymmetric lifting and sustained trunk flexion. Following the standardized tasks, 14 farmers also performed regular, real-world, farm tasks with and without use of the exoskeleton at their farms., Results: Exoskeleton use decreased back muscular load during farming activities up to 65%, 56%, and 48% in static, median, and peak muscle activity, respectively. This indicates potential benefits of exoskeleton use to help farmers work under less muscular load. Paradoxically, exoskeleton use during standardized tasks increased muscle activity for some participants., Conclusions: This study demonstrates the potential effects of using passive exoskeletons in agriculture through observational and experimental research, and is among the first that explores the potential for using exoskeletons during actual work tasks in farm settings., (© 2020 Wiley Periodicals LLC.)

Background: The use of Pilates in various fields of sport sciences and rehabilitation is increasing; however, little is known about the muscle adaptations induced by this training method., Hypothesis: A standardized Pilates training program for beginners (9 months; 2 sessions of 55 minutes per week) will increase the muscle volume and reduce potential side-to-side asymmetries of the quadratus lumborum, iliopsoas, piriformis, and gluteus muscles (gluteus maximus, medius, and minimus)., Study Design: Controlled laboratory study., Level of Evidence: Level 3., Method: A total of 12 inactive, healthy women (35.7 ± 5.4 years) without previous experience in Pilates were randomly selected to participate in a supervised Pilates program (36 weeks, twice weekly). Muscle volume (cm 3 ) was determined using magnetic resonance imaging at the beginning and end of the intervention program. Side-to-side asymmetry was calculated as [(left - right volume) × 100/right volume]., Results: Small, nonsignificant ( P > 0.05) differences in the volume of the quadratus lumborum, iliopsoas, piriformis, and gluteus muscles were observed between pre- and post-Pilates program timepoints. Before and after Pilates, side-to-side asymmetry was less than 6% and nonsignificant in all muscles analyzed., Conclusion: Modern Pilates performed twice weekly for 9 months did not elicit substantial changes in the volume and degree of asymmetry of the selected lumbopelvic muscles in inactive women., Clinical Relevance: The benefits of Pilates in rehabilitation or training are likely elicited by neuromuscular rather than morphological adaptations. Pilates has no significant impact on muscle volume and does not alter side-to-side ratios in muscle volume (degree of asymmetry) of the lumbopelvic muscles.

Two passive back-support exoskeleton (BSE) designs were assessed in terms of muscular activity, energy expenditure, joint kinematics, and subjective responses. Eighteen participants (gender-balanced) completed repetitive lifting tasks in nine different conditions, involving symmetric and asymmetric postures and using two BSEs (along with no BSE as a control condition). Wearing both BSEs significantly reduced peak levels of trunk extensor muscle activity (by ~9-20%) and reduced energy expenditure (by ~8-14%). Such reductions, though, were more pronounced in the symmetric conditions and differed between the two BSEs tested. Participants reported lower perceived exertion using either BSE yet raised concerns regarding localized discomfort. Minimal changes in lifting behaviors were evident when using either BSE, and use of both BSEs led to generally positive usability ratings. While these results are promising regarding the occupational use of BSEs, future work is recommended to consider inter-individual differences to accommodate diverse user needs and preferences., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study aimed to clarify the difference in the onset of EMG activity between eight trunk muscles, including the anterior (QL-a) and posterior (QL-p) layers of the quadratus lumborum during rapid shoulder joint abduction. Thirteen healthy men participated in this study. Electromyography of the QL-a, QL-p, transversus abdominis (TrA), internal oblique (IO), external oblique (EO), rectus abdominis (RA), lumbar multifidus (LMF), lumbar erector spinae (LES) on non-movement side, and middle deltoid (MD) on the movement side were measured. Subjects who were standing in a relaxed position performed rapid shoulder abduction with the dominant hand after light stimulus with or without a 3 kg wrist weight. Two-way ANOVA (muscles × weight conditions) was used to compare the onset of trunk muscles relative to that of MD. There was a significant main effect of the muscles. The onset of the QL-a, QL-p, and TrA was significantly earlier than that of the IO, EO, LMF, and LES (P < 0.01). This result suggests that the activities of the QL-a, QL-p, and TrA have a crucial role in controlling the center of mass within the base of support and stabilizing the lumbar spine in the coronal plane during shoulder abduction., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest. Koji Kaneoka is currently receiving a grant-in-aid for Scientific Research (C) from the Japan Society for the Promotion of Science. None of the remaining authors have received funding., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Abdominal bracing is a voluntary method of increasing spine stiffness to restrict spine displacement. Previous investigations of abdominal bracing have measured effects on whole lumbar motion; however, how this effect is distributed across the lumbar spine is unknown. Therefore, this study was designed to test the influence of abdominal bracing on spine intersegmental (T9/T10 to L5/S1) flexion, measured via skin surface markers, in response to sudden loading perturbations applied through the hands in 16 young healthy participants. Abdominal and back muscle activation responses were also measured. The results demonstrated that abdominal bracing significantly reduced sagittal plane motion at intersegmental levels T12/L1 to L4/L5, by 45% (0.74 degrees) at L4/L5 to 94% (0.71 degrees) at L1/L2 compared to control. L5/S1 experienced a 50% (0.36 degrees) reduction, but this was not statistically significant. Additionally, abdominal bracing resulted in greater baseline activation of all abdominal and back muscles, but did not affect onset times or response magnitudes of any of the back muscles acting counter to the perturbation. Therefore, the elevated baseline activation of trunk musculature during an abdominal brace serves to restrict flexion motion at the majority of the intersegmental lumbar spine (T12/L1 to L4/5) in response to sudden trunk flexion perturbations., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The supraspinatus and infraspinatus muscles each have multiple sub-regions that may activate differentially in activities of daily living. Awareness of these differential demands critically informs rehabilitation of rotator cuff muscle following injury, particularly if centered on recovering and strengthening the rotator cuff to perform daily tasks. This study quantified muscle activation of supraspinatus and infraspinatus sub-regions during the performance of six activities of daily living. Twenty-three participants (mean: 22.6 ± 2.6 years) completed the following tasks: opening a jar, reaching at shoulder height, overhead reaching, pouring water from a pitcher, eating with a spoon, and combing hair. Indwelling electromyography was collected from the anterior and posterior supraspinatus and superior, middle, and inferior infraspinatus. Tasks requiring high arm elevations (e.g. reaching at shoulder and overhead height) activated anterior supraspinatus between 21 and 28% MVC. The posterior supraspinatus consistently activated between 10 and 30% MVC across all tasks. All sub-regions of infraspinatus activated highly (between 18 and 25% MVC) in tasks requiring high arm elevations in flexion. These findings may be leveraged to define effective measures to increase rotator cuff function in daily tasks., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Fractionated reaction time can be used to determine distinct epochs known as pre-motor, response and movement times (MTs) of a reaction time task. The purpose of this study was to compare elite and novice athletes performing a taekwondo kick in terms of the fractionated reaction time and electromyography (EMG) activation patterns of the muscles of the striking lower limb and the lower back. We hypothesised that the pre-motor time, response time (RT) and MT would be the shorter for elite athletes compared to novices. We collected data on 13 elite and 10 novice athletes when performing a roundhouse kick. The experiment included EMG electrodes placed on five low back and lower extremity muscles and an electrogoniometer placed on the kicking knee. We found that pre-motor time was shorter and the RT was longer for elite athletes than novice athletes. Moreover, the integrated EMG of the main knee extensor does not differ between groups though other leg and trunk muscles do. The results allow coaches and teachers to understand this particular taekwondo kicking movement which could ultimately improve the technique in order to establish training and teaching goals.

The purpose of this study was to compare caregiver muscle activation and joint angles between two ergonomic transport chairs designed to mitigate discomfort and safety risks associated with patient transport, the Stryker® Prime TC and the Staxi® Medical Chair, and a depot wheelchair. Twenty-three caregivers completed level walking and ramped tasks with each device and an 84 kg manikin. Surface electromyography for the upper extremities and back muscles and motion data were collected. The Staxi showed a statistical trend for higher wrist extensor and flexor carpi ulnaris activity compared to the Stryker chair (p ≤ 0.078) and greater wrist flexion than the Stryker and depot chairs (p ≤ 0.004). The depot chair showed greater peak trunk flexion than the Stryker chair (p = 0.004). Overall results suggest that ergonomic chair design may improve joint positioning of the trunk and elbows when operating patient transport chairs over level and ramped surfaces., Competing Interests: Declaration of competing interest The authors do not have any competing interests in this work., (Published by Elsevier Ltd.)

Background: Abdominal draw-in maneuver (ADIM) has been recommended to achieve appropriate trunk muscle response for patients with non-specific chronic low back pain (CLBP). However, it has remained unclear whether the intervention with ADIM could change the trunk muscle response to sudden release from loading, which is considered to contribute mechanical circumstances to low back pain. The purpose of the present study was to investigate the effects of the intervention with ADIM on electromyography (EMG) activities of trunk muscles following sudden release from loading., Methods: Seventeen subjects with non-specific CLBP participated. Subjects resisted trunk flexion or extension loading in semi-seated position, and then the loading was suddenly released. EMG recordings of 6 trunk muscles were acquired using a wireless surface EMG system. Onset and offset times were calculated from the EMG data. The intervention with ADIM was provided for 4 weeks. The onset and offset times were compared between pre- and post-intervention with ADIM., Results: At the post-intervention, the onset of trunk flexors following release from trunk flexion loading became significantly earlier than pre-intervention (P = 0.028). The offset of flexors following release from trunk extension loading of post-intervention was significantly earlier than that of pre-intervention (P = 0.001)., Conclusions: We showed that the intervention with ADIM changed the EMG activity of trunk flexors in response to sudden release from loading. These results suggest a possibility that ADIM might be effective to improve the neuromuscular control of trunk flexors for the treatment of young patients with non-specific CLBP., Competing Interests: Declaration of Competing Interest H Tohyama was supported by grants from Nipro Corporation and Harada Electronic Industry Ltd. outside the submitted work. The other authors declare no conflict of interest., (Copyright © 2019 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.)

Competing Interests: Competing interests: None declared.

Lumbar and pelvic alignment may have a huge impact on the posture of the spine and other parts. The aim of this study were to compare the spinal curvature of the cervical, thoracic, and lumbar spine and the muscle activity of the cervical erector spinae muscle, upper trapezius muscle, and thoracic erector spinae muscle when sitting at 3 different sloped, seating surfaces. A 10° wedge was used as the seating surface and we compared a forward sloping seat surface, a flat seating surface, and a rear sloping seat surface, in that order. Twenty healthy officers were recruited for this study. The subjects sat on the seat of 3 different slopes and watched a total of 3 videos, 10 minutes each. The rest time was 10 minutes. Subjects were photographed while viewing videos and muscle activity was measured. There were significant differences in cervical, thoracic, lumbar curvatures, and muscle activity in the 3 different sitting positions according to seat tilt (P < .05). Among the 3 slopes, the forward slope decreased forward head posture and cervical erector spinae muscle activity (P < .05). The activity of the cervical erector spinae muscle was 2.67% with a forward sloping seat, 5.45% with a flat sloping seat, and 6.77% with a rear sloping seat, revealing a significant difference (P < .05). This suggests that a forward sloping seat surface was effective in maintaining a neutral alignment of the spine, and this decreased the cervical spine erector muscle activity. Based on this result, equipment and chair development to incline seats forward may improve posture and health, and prevent chronic pain.

Recent literature has indicated altered motor control in individuals with non-specific low back pain (NSLBP). These individuals present variations in back muscular activity and center of mass (CoM) oscillations. The aim of this study is to explore the possibility of quantitatively measuring these differences using standard parameters with electronic devices. Twenty individuals with NSLBP and 20 healthy controls, matched by sex and age, performed a total of three trials under three different conditions for 90 seconds each. These conditions were standing on firm ground with eyes open, with eyes closed and standing on unstable foam with eyes open. Balance data was acquired via a Kistler force platform and muscular activity was measured by electromyography derived bilaterally from the erector spinae. Afterwards, participants were asked to complete a questionnaire on their current mood, pain rating, well-being, disability and physical activity. Descriptive data from the questionnaire showed an average acute pain score of 2.6 and an average pain score of 5.1 for the prior six weeks in the NSLBP group, while the control group reported an acute pain of 0.1 and an average pain of 0.5. For wellbeing, differences were found only for the physical scale. Average disability was low for the NSLBP group. No differences in physical activity were found among groups. A repeated measures ANOVA did not show significant differences between groups for any parameter. There was also no main effect for the standing conditions and no interaction between group and condition. Simultaneously measuring biomechanical and neuromuscular parameters, allowed for a fine grain approach to understanding motor control in individuals with NSLBP. This study did not find differences as described in the literature, and suggests further examination of factors involved in pain and control processes to better understand implications of NSLBP and possible avenues for support., Competing Interests: The authors have declared that no competing interests exist.

Objective: This study evaluated whether the use of kinesio taping (KT) would enhance the effect of physical therapy in relieving pain, improving muscle endurance, and boosting functional capacity in adolescents with hemophilia who experience low back pain., Methods: Forty-five adolescents with hemophilia (age; 10-13 years) assigned randomly into three treatment arms; KT applied paraspinal alongside a physical exercise program conducted three times/week for three successive months (KT group; n=15), placebo taping plus physical exercise (Placebo group; n=15), or physical exercise only (Control group; n=15). Lower back pain, back muscle endurance, and functional capacity assessed pre- and post-treatment., Results: Lower back pain reduced significantly in the KT group as compared to the control group (P=.001), but not to the placebo group (P=.19). Back muscle endurance increased significantly in the KT group relative to either the placebo (P=.004) or the control group (P=.043). Additionally, functional capacity improved significantly in the KT group as compared to the control (P=.039) group but not to the placebo group (P=.58)., Conclusion: KT is an effective adjunctive therapy to reduce lower back pain, improve back muscle endurance, and enhance functional capacity in adolescents with hemophilia., Competing Interests: The authors have no conflict of interest.

A 40-year-old woman was referred to physical therapy with complaints of headaches. Examination raised suspicion of a "thunderclap headache," a condition characterized by sudden, intense headaches correlated with bleeding in and around the brain. The patient was referred to a neurologist, who ordered magnetic resonance angiography of the head and neck, which identified a partial dissection of the right vertebral artery. A subsequent computed tomography angiogram confirmed the dissection. J Orthop Sports Phys Ther 2020;50(6):344. doi:10.2519/jospt.2020.8858 .

Carrying a heavy school backpack has extensively been reported as a prime cause of children's body strain. It is suggested that the load should not exceed 10 percent of the child's body weight; however, ensuring this requires continuous monitoring. The study explores how ergonomically designed school backpack based on the user anthropometric data ( n = 280) and ergonomic parameters help reduce force concentration on shoulders and back. It provides a validation process of the developed prototype by experimental verification. The developed design was assessed in a comparison experiment with a commercially available local school backpack. An experimental study was used which recruited thirty healthy college students (aged 19 to 23 years). Two independent variables evaluated were school backpack type (developed backpack versus commercial one) and load levels as a percentage of body weight. Three load levels were employed 10%, 15%, and 20%. These variables were measured on the responses: bag comfort scale and the percent of maximum voluntary contraction (%MVC) of six muscles (right and left of erector spine, right and left of external abdominal oblique muscle, and right and left of trapezius). The developed backpack provided astonishing performance at levels of 15% and 20% of body weight in terms of subjective measure and electromyography (EMG) responses. It also showed that increasing the carried weight more than 10% result in reducing activity on the erector spinal muscles, while it increases on abdominal oblique muscles. The developed backpack design confirmed the efficiency of its bases by distributing the carried weight among the trunk through side pockets, attached to the body through two upper and lower straps. It helped the body to distribute the carried weight and avoid concentrating pressure on specific areas., Competing Interests: The authors declare no conflict of interest., (Copyright © 2020 Mohamed Z. Ramadan and Sultan N. Al-Tayyar.)

Low-back pain is the number one cause of disability in the world, with mechanical loading as one of the major risk factors. Exoskeletons have been introduced in the workplace to reduce low back loading. During static forward bending, exoskeletons have been shown to reduce back muscle activity by 10% to 40%. However, effects during dynamic lifting are not well documented. Relative support of the exoskeleton might be smaller in lifting compared to static bending due to higher peak loads. In addition, exoskeletons might also result in changes in lifting behavior, which in turn could affect low back loading. The present study investigated the effect of a passive exoskeleton on peak compression forces, moments, muscle activity and kinematics during symmetric lifting. Two types (LOW and HIGH) of the device, which generate peak support moments at large and moderate flexion angles, respectively, were tested during lifts from knee and ankle height from a near and far horizontal position, with a load of 10 kg. Both types of the trunk exoskeleton tested here reduced the peak L5S1 compression force by around 5-10% for lifts from the FAR position from both KNEE and ANKLE height. Subjects did adjust their lifting style when wearing the device with a 17% reduced peak trunk angular velocity and 5 degrees increased lumbar flexion, especially during ANKLE height lifts. In conclusion, the exoskeleton had a minor and varying effect on the peak L5S1 compression force with only significant differences in the FAR lifts., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier Ltd.)

When an individual enters a maximally flexed spine position, their largest extensor muscles become electrically inactive despite a substantial extensor moment demand being placed on the low back; this is termed flexion relaxation. Stresses within intervertebral discs, ligaments, and passive muscles are thought to support this moment thereby allowing the extensor muscles to 'turn off'. While the mechanical behaviour of the intervertebral disc and ligaments have been studied extensively, less is known regarding the moment supported by passive muscle tissue during spine flexion. Here we estimated the L4/L5 moment supported by the passive musculature during spine flexion based on experimentally derived architectural and material properties. We then tested the validity of the passive muscle prediction by determining whether the cumulative passive tissue moment (including passive muscle, intervertebral discs, and ligaments) would support the extensor moment demand-calculated with inverse dynamics-near maximum spine flexion. The model predicted that the passive tissues were able to support the entire extensor moment demand, indicating that muscle activity was not required to support the weight of the upper body, consistent with the mechanism of flexion relaxation. The model further demonstrated that despite being inactive, spine muscles still greatly contribute to flexion relaxation by passively supporting ~47% of the extensor moment demand on the spine. Finally, there was strong agreement between the predicted active muscle moments and the recorded spine muscle activity (EMG); this strong agreement persisted when the external moment was manipulated using a pulley-system. These findings provide additional confidence that the estimated passive muscle moments are reasonably accurate throughout spine flexion., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest associated with the work presented in this manuscript., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Back support exoskeletons are designed to prevent work-related low-back pain by reducing mechanical loading. For actuated exoskeletons, support based on moments actively produced by the trunk muscles appears a viable approach. The moment can be estimated by a biomechanical model. However, one of the main challenges here is the feasibility of recording the required input variables (kinematics, EMG data, ground reaction forces) to run the model. The aim of this study was to evaluate how accurate different selections of input variables can estimate actively generated moments around L5/S1. Different multivariate regression analyses were performed using a dataset consisting of spinal load, body kinematics and trunk muscle activation levels during different lifting conditions with and without an exoskeleton. The accuracy of the resulting models depended on the number and type of input variables and the regression model order. The current study suggests that third-order polynomial regression of EMG signals of one or two bilateral back muscle pairs together with exoskeleton trunk and hip angle suffices to accurately estimate the actively generated muscle moment around L5/S1, and thereby design a proper control system for back support exoskeletons., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Limitations of shoulder range of motion (ROM) have been reported to be at high risk for shoulder disorders in baseball players. In this study, we assessed posterior shoulder muscle stiffness using shear wave elastography in baseball players with and without posterior shoulder tightness., Materials and Methods: In total, 21 college baseball players volunteered to participate in this study. Passive ROMs for shoulder abduction and horizontal adduction were measured using a goniometer. Subsequently, we divided all participants into 2 groups based on the differences between bilateral shoulder ROMs: STIFF+ and STIFF- groups. Thickness and elasticity of the posterior and inferior shoulder muscles were assessed using ultrasound., Results: Shoulder abduction ROM on the throwing side was 114.5° ± 5.3° and 131.3° ± 5.7° in the STIFF+ and STIFF- groups, respectively, which was significantly different between the 2 groups (P = .023). Horizontal adduction ROM on the throwing side was 96.6° ± 4.9° and 110.9° ± 4.8° in the STIFF+ and STIFF- groups, respectively, which was also significantly different between the 2 groups (P = .014). The elasticity of infraspinatus and lower trapezius in the STIFF+ group was significantly greater than that in the STIFF- group (P = .018 and .033, respectively)., Discussion: In this study, we found that the elasticity of infraspinatus and lower trapezius in stiff shoulders was significantly greater than that in nonstiff shoulders, which indicated that the infraspinatus and lower trapezius could be the key muscles in posterior shoulder tightness., (Copyright © 2019. Published by Elsevier Inc.)