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This study investigated the effect of the prone trunk extension test (PTE) on lumbar and lower limb muscle stiffness to explore the optimal angle for lumbar muscle training, understand the peripheral muscle force transmission effect, and determine the modulation strategy and interaction mode of different muscles during PTE. Twenty healthy young females were recruited for this study, and the stiffness of the erector spinae (ES), semitendinosus (ST), biceps femoris (BF), medial head of the gastrocnemius (MG), and lateral head of the gastrocnemius (LG) was measured by MyotonPRO under four angular PTE conditions (0° horizontal position, 10°, 20°, and 30°). With the increasing angle, the stiffness of ES decreased gradually, while ST and BF increased first and then decreased. The stiffness of MG and LG increased first, then decreased, then increased. There was a moderate to strong negative correlation between ES stiffness variation and ST (r = -0.819 to -0.728, p < 0.001), BF (r = -0.620 to -0.527, p < 0.05), MG (r = -788 to -0.611, p < 0.01), and LG (r = -0.616 to -0.450, p < 0.05). Horizontal PTE maximizes the activation of ES. There is a tension transfer between the ES, hamstrings, and gastrocnemius, mainly between the ES, ST, and LG. The study provides data to explore the effect of peripheral muscle force transmission and the modulation strategies of different muscles during trunk extension., (© 2023 American Association of Clinical Anatomists and British Association of Clinical Anatomists.)

This study aims to identify how spatial distribution of lumbar muscle activity is modulated by different fatigue tasks. Twenty healthy adults performed two different isometric trunk extension endurance tasks (the modified Sorensen test and the inverted modified Sorensen test) until exhaustion. During these tasks, bilateral superficial lumbar muscle activity was recorded using high-density electromyography. The spatial distribution of activation within these muscles was obtained using the centroid coordinates in the medio-lateral and cranio-caudal directions. The effects of task and endurance time (left and right sides) were investigated using repeated measures ANOVA. Results revealed a significant lateral shift of the centroid throughout the fatigue tasks on both sides and no difference between tasks. Significant task × time interaction effects were found for the cranio-caudal direction on both sides showing a significantly more caudal location of the centroid in the modified Sorensen test compared to the inverted test at the beginning of the tasks. Our findings suggest that spatial distribution of lumbar muscle activity is task-dependent in a pre-fatigue stage while an alternative but similar muscle recruitment strategy is used in both tasks to maintain performance in the later stages of muscle fatigue., 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 © 2023 Elsevier Ltd. All rights reserved.)

Quantifying the trunk flexion angles at which wearable support systems (exoskeletons/exosuits) provide substantial trunk extension moment during posture maintenance tasks (such as those seen in surgical environments) can provide a deeper understanding of this potential intervention strategy. Understanding how time (i.e. adaptation/learning) might impact the reliance on wearable support is also of value. Sixteen participants were asked to maintain specific trunk flexion angles (range 0-60°) with and without an exosuit system while erector spinae and rectus abdominis muscle activity were captured using surface electromyography. The effects of the exosuit showed a statistically significant ( p  < 0.007) effect on the activity of the erector spinae muscles at 10-60°-an effect that became 'large' (Cohen's d = 0.84) after 20° of trunk flexion. There were no meaningful time-dependent trends in the levels of muscle activation indicating there was no adaptation/learning effect of the exosuit in the task studied. Practitioner summary: This study examined the effectiveness of a back-support exosuit as a function of trunk flexion angle and time of use. The results revealed that the exosuit significantly reduced erector spinae muscle activity beyond 20° of trunk flexion but did not show a meaningful adaption/learning effect. Abbreviations: LBP: low back pain; EMG: electromyography; NEMG: normalized electromyography; IMU: inertial measurement unit; ES: erector spinae; RA: rectus abdominis; MVC: maximum voluntary contraction; FFT: Fast Fourier Transform.

Previous studies that tested passive back-support exoskeletons focused only on active low-back tissue. Therefore, this study examines the effect from a passive back-support exoskeleton by investigating changes in the load transfer mechanism between active and passive tissue in the low back. Twelve healthy male participants performed a full range of trunk flexion-extension movements under three conditions-FREE (no exoskeleton), the backX, or the CoreBot exoskeleton-while holding 0 kg, 4 kg, and 8 kg loads. Body kinematics and electromyography were recorded. Results showed that the average muscle activity of the lumbar erector spinae (LES) was significantly reduced while wearing the exoskeletons, with a 5.9%MVC reduction with the backX and a 3.3%MVC reduction with the CoreBot. Earlier occurrence of the flexion-relaxation phenomenon induced by the trunk extension moment of exoskeletons played an important role in reducing LES muscle activity because the LES returned to a relaxed state earlier (EMG-Off: a 3.1° reduction with the backX, and a 1.8° reduction with the CoreBot; EMG-On: a 2.3° reduction with the backX, and a 1.4° reduction with the CoreBot). In addition, the maximum lumbar flexion angle (a 2.2° reduction with the backX and a 1.5° reduction with the CoreBot) showed significant decreases compared to the FREE condition, indicating that exoskeleton use can prevent low-back passive tissue from being fully activated. These results suggested the overall effects of passive back-support exoskeletons in reducing loads on both active and passive tissue in the low back., 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 © 2023 Elsevier Ltd. All rights reserved.)

Purpose: In this study we measured neural activation (EMG) in four trunk stabilizer muscles and vastus lateralis (VL) in trained and novice participants during a set of squat repetitions to volitional fatigue at 85% 1RM., Methods: Forty males were recruited into two groups, novice (NG: n = 21) and experienced (EG: n = 19), according to relative squat 1RM. Participants were tested twice to: (1) determine squat 1RM, and (2) complete a single set of repetitions to volitional fatigue at 85% 1RM. Relative squat 1RM; NG < 140% body mass, EG > 160% body mass. Neuromuscular activation was measured by EMG for the following: rectus abdominus (RA), external oblique (EO), lumbar sacral erector spinae (LSES), upper lumbar erector spinae (ULES) and VL in eccentric and concentric phase. Completed repetitions, RPE and EMG in repetition 1 and at 20, 40, 60, 80 and 100% of completed repetitions were analysed., Results: No group differences were found between number repetitions completed and RPE in repetitions to volitional fatigue at 85% 1RM. Neuromuscular activation increased significantly in all muscle groups in eccentric and concentric phase apart from RA in the eccentric phase. Trunk neuromuscular activation was higher in NG compared to EG and this was significant in EO, LSES and ULES in eccentric phase and LSES in the concentric phase. VL activation increased in both phases with no group differences., Conclusion: Trunk neuromuscular activation increases in a fatiguing set of heavy squats regardless of training status. Increased back squat strength through training results in lower neuromuscular activation despite greater absolute external squat loads.

Wasserberger, KW, Downs, JL, Barfield, JW, Williams, TK, and Oliver, GD. Lumbopelvic-hip complex and scapular stabilizing muscle activations during full-body exercises with and without resistance bands. J Strength Cond Res 34(10): 2840-2848, 2020-Inefficient sequencing in the kinetic chain has been linked to decreased performance and increased injury risk. Resistance band usage is very common in baseball/softball due to accessibility and low cost. However, resistance band use has primarily focused on the rotator cuff and surrounding shoulder musculature, thereby ignoring the rest of the kinetic chain. Currently, it is unclear whether resistance bands are effective tools for training musculature outside the throwing extremity. Thus, the purpose of this study was to examine muscle activations of the lumbopelvic-hip complex (LPHC) and scapular stabilizing musculature during 4 full-body exercises with and without the use of a resistance band. Twenty healthy, active individuals (174.39 ± 1.58 cm; 74.10 ± 1.75 kg; 21.85 ± 1.13 years) participated. Data were collected through surface electromyography for the LPHC and scapular stabilizing musculature during 4 full-body exercises with and without a resistance band. Statistical analyses were used to determine significant differences in activation levels between exercises and within exercises between conditions. Data showed a significant difference on muscle activation based on the interaction between resistance band usage and exercise choice (Λ = 0.276, F24, 136.92 = 3.19, p < 0.001). Adding a resistance band was effective in increasing muscle activation within the scapular stabilizing musculature. Conversely, the use of a resistance band was not as effective in increasing the activation of LPHC musculature. Future studies should investigate exercises that increase LPHC musculature activation. Coaches and clinicians can use these results to make more informed decisions when prescribing exercises to athletes for performance enhancement and rehabilitation.

The study aimed to quantify the measurement error / reliability of a musculoskeletal profiling test battery administered in young, elite academy soccer players, and to examine if the order in which the test battery was administered, and who it was administered by, influenced reliability. Players (n = 75; age 12-20 years; stature 1.47-1.95 m; body mass 36-89 kg) from U-12 to U-23 age groups were assigned to either: 1) intra-rater-fixed order; 2) intra-rater-non-fixed order; 3) inter-rater-fixed order; or, 4) inter-rater-non-fixed order groups. On two separate occasions separated by 3 to 7 days, 12 raters conducted a musculoskeletal profiling test battery comprising 10 tests (Supine Medial Hip Rotation, Supine Lateral Hip Rotation, Hamstring 90/90, Prone Medial Hip Rotation [degrees]; Combined Elevation, Thoracic Rotation, Weight-Bearing Dorsiflexion, Y-Balance [centimetres]; Beighton, Lumbar Quadrant [categorical]). The measurement error / reliability for tests measured in degrees and centimetres was evaluated using the intraclass correlation (relative reliability), coefficient of variation and ratio limits of agreement (absolute reliability). Intraclass correlations varied from 0.04 ("poor") to 0.95 ("excellent"), coefficient of variation from 2.9 to 43.4%, and the ratio limits of agreement from 1.058 (*/÷ 1.020) to 2.026 (*/÷ 1.319) for the tests measured in degrees and centimetres. The intraclass correlation, coefficient of variation and ratio limits of agreement were smallest for five out of eight tests measured in degrees and centimetres when the tests were administered in an intra-rater-fixed test order. These findings emphasise that different testing methods, and the administration of a musculoskeletal profiling test battery using a less than optimal design, will influence measurement error and hence test reliability. These observations need to be considered when investigating musculoskeletal function and age, injury, training or asymmetry in young, elite academy soccer players., Competing Interests: City Football Group provided support in the form of salaries for authors CWO and SM, but they did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

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

Key Points: •Longissimus activity in the lumbar region was measured using indwelling electromyography to characterize the territory of its motor units. •The distribution of motor units in the longissimus pars lumborum muscle was mainly grouped into two distinct regions. •Regional activation of the longissimus pars lumborum was also observed during functional tasks involving trunk movements. •The regional activation of the longissimus pars lumborum muscle may play a role in segmental stabilization of the lumbar spine., Abstract: The longissimus pars lumborum contributes to lumbar postural control and movement. While animal studies suggest a segmental control of this muscle, the territory of motor units constituting the human longissimus pars lumborum remains unknown. The aims of this study were to identify the localization of motor unit territories in the longissimus and assess the activation of this muscle during functional tasks. Eight healthy participants were recruited. During isometric back extension contractions, single motor-unit (at L1, L2, L3 and L4) and multi-unit indwelling recordings (at L1, L1-L2, L2, L2-L3, L3, L3-L4 and L4) were used to estimate motor unit territories in the longissimus pars lumborum based on the motor-unit spike-triggered averages from fine-wire electrodes. A series of functional tasks involving trunk and arm movements were also performed. A total of 73 distinct motor units were identified along the length of the longissimus: only two motor units spanned all recording sites. The majority of the recorded motor units had muscle fibres located in two main rostro-caudal territories (32 motor units spanned L1 to L3 and 30 spanned ∼L3 to L4) and 11 had muscle fibres outside these two main territories. We also observed distinct muscle activation between the rostral and caudal regions of the longissimus pars lumborum during a trunk rotation task. Our results show clear rostral and caudal motor unit territories in the longissimus pars lumborum muscle and suggest that the central nervous system can selectively activate regions of the superficial lumbar muscles to provide local stabilization of the spine., (© 2019 The Authors. The Journal of Physiology © 2019 The Physiological Society.)

Mettler, JH, Shapiro, R, and Pohl, MB. Effects of a hip flexor stretching program on running kinematics in individuals with limited passive hip extension. J Strength Cond Res 33(12): 3338-3344, 2019-Tightness of the hip flexor muscle group may theoretically contribute to altered kinematics of the lumbo-pelvic-hip (LPH) complex during dynamic movements. Therefore, the purpose of this study was to analyze the effects of a 3-week home-based stretching program on passive hip extension and sagittal plane kinematics of the LPH complex when running. Twenty healthy subjects with limited passive hip extension underwent a 3D gait analysis both before (PRE) and after (POST) a hip flexor stretching program. After the stretching program, passive hip extension increased significantly (p < 0.001), whereas no improvements during running were reported for active hip extension, anterior pelvic tilt, or lumbar spine extension (p ≥ 0.05). In addition, no relationship was found between the change in passive hip extension with either the change in active hip extension, anterior pelvic tilt, or lumbar spine extension. A 3-week static stretching program of the hip flexor muscle group resulted in an increase in passive hip extension, but the sagittal plane kinematics of the LPH complex during running remained unchanged. The results suggest that passive hip joint flexibility may be of limited importance in determining the kinematics of the LPH complex during submaximal running. However, it is possible that an increase in the range of motion at the hip may be beneficial when running at or near maximal speeds.

Background: Although altered muscular control of the lumbopelvic region is one of the main risk factors for the development of low back pain and dysfunction, the influence of abnormal foot posture on lumbopelvic muscular function has not been investigated., Research Question: To determine possible functional changes due to hyperpronation in the main muscles that control the lumbopelvic segment., Methods: Kinematic and kinetic data were collected from 15 persons with hyperpronated feet and compared to a control group of 15 persons with normally aligned feet during the stance phase of gait. A generic OpenSim musculoskeletal model was scaled for each participant. A computed muscle control approach was used to produce a forward dynamic simulation of walking to determine muscle function., Results: In the hyperpronation group significantly greater peak forces were observed in the erector spinae, iliopsoas and abdominals compared to controls. The former group showed peak latencies for abdominal muscles during early stance, and for erector spinae muscles during both early and late stance. No significant between-group differences were found in gluteus maximus muscle activation in the stance phase of gait., Significance: Abnormal foot pronation can change the timing and intensity of lumbopelvic muscle activation. These changes may predispose people to develop secondary dysfunctions., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Lawrence, MA, Chin, A, and Swanson, BT. Biomechanical comparison of the reverse hyperextension machine and the hyperextension exercise. J Strength Cond Res 33(8): 2053-2056, 2019-The purpose of this study was to compare activation of the erector spinae, gluteus maximus, and biceps femoris muscles, lower back extension moment, and lower extremity range of motion (ROM) between the reverse hyperextension (RHE) and hyperextension (HE) exercises. Motion and muscle activation of the trunk and lower extremity were measured while 20 recreationally active individuals performed 2 sets of 10 repetitions of each exercise. Equivalent loads were used for each exercise. Peak, average, and integrated muscle activity, low back moment, and ROM between the trunk and pelvis and the thigh and trunk were calculated. A Wilcoxon signed-rank test (p = 0.05) revealed significantly greater integrated activity of the biceps femoris and gluteus maximus during the HE exercise. The RHE exercise generated greater peak (+129%), integrated (+63%), and mean (+78%) low back moment as compared to the HE exercise. The RHE resulted in a significantly greater thigh to trunk ROM, 76.6 compared with 64.7. However, the RHE used less lumbar flexion, 20.4 compared with 31.1 for the HE. The RHE movement profile is preferable because it provides greater hip ROM with less angular stress and equivalent erector spinae activity.

Background: Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this is associated with trunk muscle co-contraction, which would increase the compression on the spine. It has been hypothesized that lumbar belts increase lumbar stiffness by increasing intra-abdominal pressure, which would increase spinal stability without increasing the compressive load on the spine., Methods: Trunk muscle activity and lumbar stiffness and damping were measured in healthy and low-back pain subjects during three conditions: no lumbar belt; wearing an extensible lumbar belt; wearing a non-extensible lumbar belt. Muscle activity was measured while subjects performed controlled forward and backward 20° trunk sways. Lumbar stiffness and damping were measured by applying random continuous perturbation to the chest., Findings: External oblique activity was decreased when wearing either lumbar belt during all phases of movement, while rectus abdominis and iliocostalis activity were decreased during the phase of movement where the muscles were maximally active while wearing either belt. Trunk stiffness was greatly increased by wearing either belt. There were no consistent differences in either lumbar stiffness or muscle activity between the two belts. Wearing a lumbar belt had little to no effect on damping. There were no group differences in any of the measures between healthy and low-back pain populations., Interpretation: The findings are consistent with the hypothesis that lumbar belts can increase spinal stability by increasing intra-abdominal pressure, without any increase in the compressive load on the spine. The findings can also be generalized, for the first time, to subjects with low-back pain., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Repetitive lumbopelvic rotation (LPR) during active limb movements has been indicated as a factor that contributes to low back pain (LBP). Prior studies suggest that people with LBP demonstrate greater and earlier LPR during limb movements in prone. We examined timing and magnitude of LPR during sitting active knee extension in people with and without LBP. We also investigated differences of LPR during active and passive knee extension in LBP group. 38 men (mean age: 38.4)10.6) years) with chronic mechanical LBP and 38 matched healthy men (mean age: 36.6(8.4) years) were examined. Kinematic data were collected by motion capture system and analyzed using OpenSim software. The difference between the start time of knee extension and start time of LPR was calculated and was normalized to knee extension movement time. Maximum angular displacement for LPR was also calculated across time. People with LBP demonstrated earlier LPR during knee extension than healthy subjects (P < 0.01). There was, however, no difference in maximum LPR between groups. LBP group also demonstrated greater and earlier LPR during active than during passive knee extension (P < 0.01). Earlier LPR during limb movements in sitting may be related to LBP. Quadriceps muscle activity and inefficient trunk muscles activation may contribute to early LPR in LBP group. A greater understanding of the factors that may contribute to early LPR during daily activities can provide information to guide rehabilitation treatment for people with LBP., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Quantifying stiffness of the lumbar spine musculature using shear-wave elastography (SWE) maybe beneficial in the diagnosis and treatment of non-specific low back pain (LBP). The primary purpose of this study was to establish normative parameter and variance estimates of lumbar spine muscle stiffness at rest and during submaximal contraction levels using SWE in healthy individuals. A second aim was to determine the relationship between lumbar spine muscle stiffness and a variety of demographic, anthropometric, and medical history variables., Methods: This cross-sectional study included stiffness measurements of the lumbar musculature in 120 asymptomatic individuals using ultrasound SWE. The lumbar erector spinae muscle was measured during rest only and lumbar multifidus muscle was measured during rest and during submaximal contraction using a prone contralateral arm lift. Statistical comparisons of shear modulus were made between sex (male vs. female) and muscle condition (erector spinae rest, lumbar multifidus rest, lumbar multifidus contracted) using 2 × 3 repeated measures analysis of variance (ANOVA). Univariate associations between shear modulus and age, sex, BMI, activity level, and history of back pain were assessed using correlation analysis., Findings: Shear modulus at rest was approximately 4 kPa for the erector spinae muscles and approximately 6 kPa for the lumbar multifidus muscles. Shear modulus substantially increased during contraction, and varied by sex, BMI, and self-reported activity level, with men and more active individuals generally having stiffer muscles., Interpretation: Variability in shear modulus of the lumbar musculature may be mediated through a combination of muscle size and contractile state, which is consistent with our findings of higher stiffness in the more postural lumbar multifidi muscles, during contraction, and in larger and more active individuals. These findings should inform and be accounted for in future comparative clinical studies., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background Context: The kinematics of the lumbar region and the activation patterns of the erector spinae muscle have been associated with the genesis of low back pain, which is one of the most common complications associated with pregnancy. Despite the high prevalence of pregnancy-related low back pain, the biomechanical adaptations of the lumbar region during pregnancy remain unknown., Purpose: This study analyzes lumbar spine motion and the activation pattern of the lumbar erector spinae muscle in healthy pregnant women., Study Design: A case-control study., Patient Sample: The study involved 34 nulliparous women (control group) and 34 pregnant women in the third trimester (week 36 ± 1)., Outcome Measures: We recorded the parameters of angular displacement of the lumbar spine in the sagittal plane during trunk flexion-extension, and the EMG activity of the erector spinae muscles during flexion, extension, eccentric and concentric contractions, and the myolectrical silence., Methods: The participants performed several series of trunk flexion-extension movements, which were repeated 2 months postpartum. The position of the lumbar spine was recorded using an electromagnetic motion capture system. EMG activity was recorded by a surface EMG system and expressed as a percentage of a submaximal reference contraction., Results: Antepartum measurements showed a decrease (relative to control and postpartum measurements) in lumbar maximum flexion (52.5 ± 10.5° vs 57.3 ± 7.7° and 58.7 ± 8.6°; p < .01), the percentage of lumbar flexion during forward bending (56.4 ± 5.6% vs 59.4 ± 6.8% and 59.7 ± 5.6%; p < .01), and the time keeping maximum levels of lumbar flexion (35.7 ± 6.7% vs 43.8 ± 5.3% and 50.1 ± 3.7%; p < .01). Higher levels of erector spinae activation were observed in pregnant women during forward bending (10.1 ± 4.8% vs 6.3 ± 2.4% and 6.6 ± 2.7%; p < .01) and eccentric contraction (12.1 ± 5.2% vs 9.4 ± 3.1% and 9.1 ± 2.9%; p < .01), as well as a shortened erector spinae myoelectric silence during flexion., Conclusions: Pregnant women show adaptations in their patterns of lumbar motion and erector spinae activity during trunk flexion-extension. These changes could be associated with the genesis of pregnancy-related low back pain, by means of biomechanical protection mechanisms against the increase on abdominal mass and ligamentous laxity., (Copyright © 2018. Published by Elsevier Inc.)

High impact exercise can reduce postmenopausal bone loss, however stimulus frequency (loading cycles per second) can affect osteogenesis. We aimed to examine the effect of stimulus frequency on the mechanical loading of four common osteoporosis prevention exercises, measuring body acceleration and muscle activation with accelerometry and electromyography (EMG), respectively. Fourteen early postmenopausal women completed randomised countermovement jumps (CMJ), box-drops (BD), heel-drops (HD) and stamp (STP) exercises for continuous and intermittent stimulus frequencies. Sacrum accelerometry and surface electromyography (EMG) of four muscles were recorded. CMJ (mean ± SD: 10.7 ± 4.8 g & 10.0 ± 5.0 g), BD (9.6 ± 4.1 g & 9.5 ± 4.0 g) and HD (7.3 ± 3.8 g & 8.6 ± 4.4 g) conditions generated greater peak acceleration than STP (3.5 ± 1.4 g & 3.6 ± 1.7 g) across continuous and intermittent trials. CMJ and BD generated greater acceleration gradients than STP across continuous and intermittent trials. CMJ generated greater rectus femoris EMG than all other exercises, CMJ and BD generated greater semitendinosus and tibialis anterior EMG than HD across continuous and intermittent trials. CMJ and BD provide greater peak acceleration than STP and remain similar during different stimulus frequencies. CMJ, BD and HD may exceed STP in maintaining postmenopausal bone health., (Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.)

In humans, hip abductor and lumbar lateral flexor muscles are well-developed as side-to-side lumbopelvic stabilizers. We hypothesized that the hip abductors and lumbar lateral flexors act as energy generators during a running single-leg jump, although they are generally recognized as stabilizers. We collected kinematics and ground reaction force data in running single-leg jumps by 13 male high jumpers and calculated three-dimensional kinetic variables. Hip abduction and lumbosacral lateral flexion towards free leg side torques were exerted during almost the entire take-off phase, exerting positive power during the terminal 2/3 of the phase. The positive work of the hip abductors (1.08±0.30 J/kg) was as large as that of the ankle plantar-flexors, suggesting that the energy-generating potential of the hip abductors compares with that of the extensors of the stance-leg joints. The lumbosacral lateral flexors also performed positive work (0.36±0.18 J/kg), which was 47±25% of the knee extensors, albeit less than the extensors of the stance leg joints. The results implied that the hip abductors and lumbar lateral flexors have substantial potentials not only as stabilizers but also as energy generators and that they act as substantial energy generators during running single-leg jumps., Competing Interests: No conflict of interest has been declared by the author(s)., (© Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: The ratio of fat within skeletal muscle is an important parameter that is indicative of muscle quality, and can be assessed using ultrasonography to measure echo intensity (EI). Muscle EI indicates muscle strength and risk of physical dysfunction; however, this observation was determined following examinations of only selected muscle. The purpose of this study was to investigate the EI characteristics of muscles in several regions in elderly men and women, using physical function tests and serum cholesterol levels., Methods: Twenty-two men and women (age 78 ± 8 years) participated in this study. The EIs were calculated from rectus femoris (RF), biceps femoris (BF) triceps brachii (TB) and multifidus (MF) using B-mode transverse ultrasound images. Seven functional tests (isometric knee-extension peak torque, functional reach, sit-to-stand, 5-m normal/maximal speed walking, handgrip strength and timed up-and-go) and blood lipid components including adipocytokines were measured in all participants., Results: A statistically significant correlation between EI of the RF, TB and BF was observed (r = 0.46-0.50, P < 0.05), but not between EI of the MF and that of other muscles. EI of muscles of the limbs, which was averaged EI for RF, TB and BF, was negatively correlated with leptin levels (adjusted R 2  = 0.27, P < 0.01), and EI of the MF was correlated with muscle mass and performance in the timed up-and-go test (adjusted R 2  = 0.61, P < 0.01)., Conclusion: These results suggest that EI might be influenced by specific parameters depending on the location of the muscle.

Adopting a new technology (exoskeletal vest designed to support overhead work) in the workplace can be challenging since the technology may pose unexpected safety and health consequences. A prototype exoskeletal vest was evaluated for potential unexpected consequences with a set of evaluation tests for: usability (especially, donning & doffing), shoulder range of motion (ROM), postural control, slip & trip risks, and spine loading during overhead work simulations. Donning/doffing the vest was easily done by a wearer alone. The vest reduced the max. shoulder abduction ROM by ∼10%, and increased the mean center of pressure velocity in the anteroposterior direction by ∼12%. However, vest use had minimal influences on trip-/slip-related fall risks during level walking, and significantly reduced spine loadings (up to ∼30%) especially during the drilling task. Use of an exoskeletal vest can be beneficial, yet the current evaluation tests should be expanded for more comprehensiveness, to enable the safe adoption of the technology., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The aims of this pilot study were to verify which muscle strength tests better explain bone mineral content (BMC) of the femoral neck and lumbar spine and to develop predictive equations to estimate femoral neck and lumbar spine BMC. Twenty-nine subjects aged 56-76 years old (12 women and 17 men) participated in the study. Femoral neck and lumbar spine BMC was evaluated by Dual X-ray absorptiometry (DXA). Muscle strength measurements included maximal isometric voluntary contractions of knee extensors and flexors, vertical jump, 5-repetition maximum of the leg press (5-RM LP ) and seated leg curl (5-RM LC ), and handgrip strength. Women presented a moderate to strong correlation between femoral neck BMC and 5-RM LP (r = 0.819), 5-RM LC (r = 0.879), knee extensors peak torque (r = 0.699), and handgrip strength (r = 0.663), as well as between lumbar spine BMC and the 5-RM LP test (r = 0.845) and manual grip strength (r = 0.699). For females, the 5-RM LP and 5-RM LC tests most fully explained femoral neck BMC (R 2  = 0.859) and the 5-RM LP test and body mass explained lumbar spine density (R 2  = 0.757) for females. Men did not present correlations between BMC and strength variables. For females, the 5-RM LP and 5-RM LC variables explained the variations of femoral neck BMC, while 5-RM LP and body mass explained lumbar spine BMC. Future studies should evaluate a larger sample size and prioritize the strength tests with a greater predictive capacity., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objectives: The purpose of this study was to investigate between movement patterns of trunk extension from full unloaded flexion and lifting techniques, which could provide valuable information to physical therapists, doctors of chiropractic, and other manual therapists., Methods: A within-participant study design was used. Whole-body kinematic and kinetic data during lifting and full trunk flexion were collected from 16 healthy male participants using a 3-dimensional motion analysis system (Vicon Motion Systems). To evaluate the relationships of joint movement between lifting and full trunk flexion, Pearson correlation coefficients were calculated., Results: There was no significant correlation between the amount of change in the lumbar extension angle during the first half of the lifting trials and lumbar movement during unloaded trunk flexion and extension. However, the amount of change in the lumbar extension angle during lifting was significantly negatively correlated with hip movement during unloaded trunk flexion and extension (P < .05)., Conclusions: The findings that the maximum hip flexion angle during full trunk flexion had a greater influence on kinematics of lumbar-hip complex during lifting provides new insight into human movement during lifting. All study participants were healthy men; thus, findings are limited to this group., (Copyright © 2018. Published by Elsevier Inc.)

Static trunk bending is an occupational risk factor for lower back pain (LBP). When assessing relative short duration trunk bending tasks, existing studies mostly assumed unchanged spine biomechanical responses during task performance. The purpose of the current study was to assess the biomechanical changes of lumbar spine during the performance of relatively short duration, sustained trunk bending tasks. Fifteen participants performed 40-s static trunk bending tasks in two different trunk angles (30° or 60°) with two different hand load levels (0 or 6.8 kg). Results of the current study revealed significantly increased lumbar flexion and lumbar passive moment during the 40 s of trunk bending. Significantly reduced lumbar and abdominal muscle activities were also observed in most conditions. These findings suggest that, during the performance of short duration, static trunk bending tasks, a shift of loading from lumbar active tissues to passive tissues occurs naturally. This mechanism is beneficial in reducing the accumulation of lumbar muscle fatigue; however, lumbar passive tissue creep could be introduced due to prolonged or repetitive exposure., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The normal physiological loads from muscles experienced by the spine are largely unknown due to a lack of data. The aim of this study is to investigate the effects of varying muscle directions on the outcomes predicted from finite element models of human lumbar spine. A nonlinear finite element model of L3-L5 was employed. The force of the erector spinae muscle, the force of the rectus abdominis muscle, follower loads, and upper body weight were applied. The model was fixed in a neural standing position and the direction of the force of the erector spinae muscle and rectus abdominis muscle was varied in three directions. The intradiscal pressure, reaction moments, and intervertebral rotations were calculated. The intradiscal pressure of L4-L5 was 0.56-0.57 MPa, which agrees with the in vivo pressure of 0.5 MPa from the literatures. The models with the erector spinae muscle loaded in anterior-oblique direction showed the smallest reaction moments (less than 0.6 Nm) and intervertebral rotations of L3-L4 and L4-L5 (less than 0.2 degrees). In comparison with loading in the vertical direction and posterior-oblique direction, the erector spinae muscle loaded in the anterior-oblique direction required lower external force or moment to keep the lumbar spine in the neutral position.

The authors investigated postural and arm control in seated reaches while providing trunk support at midribs and pelvic levels in adults. Kinematics and electromyography of the arm and ipsiliateral and contralateral paraspinal muscles were examined before and during reaching. Kinematics remained constant across conditions, but changes were observed in neuromuscular control. With midribs support, the ipsilateral cervical muscle showed either increased anticipatory activity or earlier compensatory muscle responses, suggesting its major role in head stabilization. The baseline activity of bilateral lumbar muscles was enhanced with midribs support, whereas with pelvic support, the activation frequency of paraspinal muscles increased during reaching. The results suggest that segmental trunk support in healthy adults modulates ipsilateral or contralateral paraspinal activity while overall kinematic outputs remain invariant.

Background: Low back pain is highly prevalent in the general population and is even reported as early as at primary school. A poor sitting position has been suggested as an etiologic factor. This study analysed, in primary schoolchildren, the influence of a triangular dynamic cushion that aims to help children maintain their physiological lumbar lordosis and to induce movement to reduce the static effect of the sitting position., Methods: Thirty 8-year-old children took part in this study. A 3D analysis combined with electromyography was used to evaluate the biomechanics and the related muscle activation in two sitting positions (with and without a triangular cushion on a horizontal stool) during a 15-minute working task. In addition, the force of the feet on the ground was assessed with a force plate., Findings: The cushion improved the trunk-thighs angle, lumbar lordosis, anterior pelvis tilt, and feet support on the ground (p<0.0001). In addition, sitting on the cushion appeared to be more dynamic (p<0.05) and induced a decrease of the lumbar paravertebral muscle activity (p<0.01)., Interpretation: Sitting on a dynamic triangular cushion tends to favour the "ideal" siting position usually described in the literature and to decrease the level of paravertebral muscle recruitment. Seeing that sitting position is a risk factor to develop low back pain, the cushion could be a solution to prevent it., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The deadlift exercise is one of the most effective exercises for developing lower-body strength; however, technique errors can lead to low back injuries. The use of a "walk-in" deadlift machine removes the weight bar by using a lever system with independent handles on either side of the body. Theoretically, this would allow alignment of the load with the center of gravity, encouraging a more upright torso and decreasing the involvement of the low back extensors. This study compared trunk angle, knee angle, and electrical activity of key muscles between the conventional deadlift (CDL) and 2 foot positions (ball of foot or toe alignment) with pronated grip (called BallPro and ToePro) of a walk-in deadlift machine among high-skilled and low-skilled lifters. Although there were no skill group differences, in the combined groups, the walk-in deadlift resulted in a significantly more upright trunk angle (p ≤ 0.05) for both the BallPro (29.9° ± 12.0 SD) and the ToePro (32.4° ± 10.4) compared with the CDL (23.7° ± 11.3) at the start of the lift. Similar results were noted in the midconcentric phase, with trunk angles for the ToePro (46.9° ± 6.8) significantly different from CDL (42.66° ± 3.7), and for the mideccentric phase of the lift, with ToePro (47.2° ± 7.0) significantly higher than CDL (42.9° ± 6.5). ToePro knee angle was significantly more flexed (101.6° ± 10.6) than CDL (110.8° ± 11.5) at the starting position, with both BallPro (135.7° ± 14.2) and ToePro (136.5° ± 8.8) significantly more flexed than CDL (159.3° ± 5.9) in both the midconcentric phase and the mideccentric phase (BallPro 129.2° ± 14.0, ToePro 127.7° ± 8.9, and CDL 150.5° ± 7.8). In the combined low- and high-skilled groups, electrical activity as a percent of maximum isometric root mean square activity of the erector spinae during the BallPro variation (53.1% ± 33.8) was significantly lower than CDL (73.19% ± 23.9), whereas vastus lateralis activity was significantly higher in both BallPro (79.9% ± 26.3) and ToePro (64.3 ± 22.4) compared with CDL (48.6% ± 13.0). Gluteus maximus (GM) activity was significantly lower for BallPro (30.1% ± 16.6) and ToePro (30.2% ± 15.0) than CDL (47.1% ± 27.6). Together, the results indicate that the walk-in deadlift machine has potential to reduce the stress on the low back during the deadlift activity, with subjects generally exhibiting a more upright posture and erector spinae muscle activity, depending on the foot position. However, there was also a shift in muscle activity away from the GM and towards the knee extensors, which may limit the machine's long-term usefulness as a deadlift replacement.

Objectives: To investigate the effects of elastic therapeutic tape when applied overlaying the lumbar extensors on different measures of muscle performance, compared to a placebo taping technique and a no-tape control., Design: A cross-sectional experimental study., Setting: A biomechanics laboratory., Participants: Twenty one participants received three taping conditions in a randomised order: elastic therapeutic tape, a placebo tape and a no-tape control. Peak torque, the time taken to reach peak torque and peak velocity were measured using an isokinetic dynamometer., Main Outcome Measures: Concentric lumbar extension peak torque at 60°/s, time taken to reach peak torque and peak velocity was measured using an isokinetic dynamometer. Friedman's test and post-hoc Wilcoxon signed-rank test were used to determine the statistical differences between the three taping conditions. Level of signicance was set at 0.05.fi., Results: A statistically significant improvement in peak lumbar extensor torque was observed when comparing elastic therapeutic tape with the no-tape control (p < 0.05). However, there was no significant differences in time taken to reach peak torque and peak velocity (p > 0.05)., Conclusions: Results demonstrate that the application of elastic therapeutic tape overlaying the primary lumbar extensors significantly improves the maximal lumbar extension peak torque in healthy, asymptomatic adults., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Introduction: Changes in movement variability and complexity may reflect an adaptation strategy to fatigue. One unresolved question is whether this adaptation is hampered by the presence of low back pain (LBP). This study investigated if changes in movement variability and complexity after fatigue are influenced by the presence of LBP. It is hypothesised that pain free people and people suffering from LBP differ in their response to fatigue., Methods: The effect of an isometric endurance test on lumbar movement was tested in 27 pain free participants and 59 participants suffering from LBP. Movement variability and complexity were quantified with %determinism and sample entropy of lumbar angular displacement and velocity. Generalized linear models were fitted for each outcome. Bayesian estimation of the group-fatigue effect with 95% highest posterior density intervals (95%HPDI) was performed., Results: After fatiguing %determinism decreased and sample entropy increased in the pain free group, compared to the LBP group. The corresponding group-fatigue effects were 3.7 (95%HPDI: 2.3-7.1) and -1.4 (95%HPDI: -2.7 to -0.1). These effects manifested in angular velocity, but not in angular displacement., Discussion: The effects indicate that pain free participants showed more complex and less predictable lumbar movement with a lower degree of structure in its variability following fatigue while participants suffering from LBP did not. This may be physiological responses to avoid overload of fatigued tissue, increase endurance, or a consequence of reduced movement control caused by fatigue., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objective: The purpose of this study was to compare the effect of abdominal hollowing (AH) and abdominal bracing (AB) maneuvers on the activity pattern of lumbopelvic muscles during prone hip extension (PHE) in participants with or without nonspecific chronic low back pain (CLBP)., Methods: Twenty women with or without CLBP participated in this cross-sectional observational study. The electromyographic activity (amplitude and onset time) of the contralateral erector spinae (CES), ipsilateral erector spinae (IES), gluteus maximus, and biceps femoris muscles was measured during PHE with and without abdominal maneuvers. A 3-way mixed model analysis of variance and post hoc tests were used for statistical analysis., Results: Between-group comparisons showed that the CES onset delay during PHE alone was greater (P = .03) and the activity level of IES, CES, and biceps femoris in all maneuvers (P < .05) was higher in patients with CLBP than in asymptomatic participants. In asymptomatic participants, PHE + AH significantly decreased the signal amplitude (AMP) of IES (P = .01) and CES (P = .02) muscles. In participants with CLBP, IES muscle AMP was lower during PHE + AH compared with PHE + AB and PHE alone. With regard to onset delay, the results also showed no significant difference between maneuvers within either of the 2 groups (P > .05)., Conclusions: Performance of the AH maneuver decreased the erector spinae muscle AMP in both groups, and neither maneuver altered the onset delay of any of the muscles in either group. The low back pain group showed higher levels of activity in all muscles (not statistically significant in gluteus maximus during all maneuvers). The groups were similar according to the onset delay of any of the muscles during either maneuver., (Copyright © 2016. Published by Elsevier Inc.)

Objectives: The aim of the present study was to examine the intra- and inter-rater reliabilities of the leg lateral reach test as a screening tool for thoraco-lumbo-pelvic rotation and to assess the relationship between leg lateral reach distance and thoraco-lumbo-pelvic rotation range in a supine position., Design: Controlled laboratory study., Methods: Thirty-six physically active participants were recruited. The leg lateral reach test was performed over 2 days. In the first session, two testers measured the distance of the leg lateral reach to determine the within-day inter-rater reliability, and one tester repeated the measurement on day 2 to determine the intra-rater reliability between days. The leg lateral reach test was performed three times per leg, and the mean value was used for data analysis. Reliability was determined using the intraclass correlation coefficient, standard error of measurement, and minimal detectable change. The correlation between leg lateral reach distance and thoraco-lumbo-pelvic rotation range was determined using Pearson correlation., Results: Almost perfect intra- and inter-rater reliabilities were shown for the test [intraclass correlation coefficient 2,3 =0.97 (95% confidence interval=0.914-0.984) and 0.99 (0.974-0.996), respectively]. The within-day inter-rater standard error of measurement was 1.40cm, and the minimal detectable change was 3.87cm. The between-day intra-rater standard error of measurement was 2.66cm, and the minimal detectable change was 7.37cm. The Pearson correlation showed a moderate to good correlation between the leg lateral reach distance and the thoraco-lumbo-pelvic rotation range (r=0.73)., Conclusions: The leg lateral reach screening test is reliable for measuring thoraco-lumbo-pelvic rotation range and allows for practical measurement of the thoraco-lumbo-pelvic rotation range in a supine position., (Copyright © 2016. Published by Elsevier Ltd.)

Introduction: Adolescent fast bowlers are prone to sustaining lumbar injuries. Numerous components have been identified as contributing factors; however, there is limited empirical evidence outlining how the muscles of the lumbopelvic region, which play a vital role in stabilising the spine, function during the bowling action and the influence of such activation on injuries in the fast bowler., Methods: Surface electromyography was utilised to measure the function of the lumbar erector spinae, lumbar multifidus, gluteus medius and gluteus maximus muscles bilaterally during the fast bowling action in a group of 35 cricket fast bowlers aged 12-16 years., Results: Two prominent periods of activation occurred in each of the muscles examined. The period of greatest mean activation in the erector spinae and multifidus occurred near back foot contact (BFC) and within the post-ball-release (BR) phase. The period of greatest mean activation for the gluteus medius and gluteus maximus occurred during phases of ipsilateral foot contact., Discussion: The greatest periods of muscle activation in the paraspinal and gluteal muscles occurred at times where vertical forces were high such as BFC, and in the phases near BR where substantial shear forces are present., Conclusion: The posterior muscles within the lumbopelvic region appear to play a prominent role during the bowling action, specifically when compressive and shear forces are high. Further research is required to substantiate these findings and establish the role of the lumbopelvic muscles in the aetiology of lumbar injury in the cricket fast bowler.

Background: Biomechanical models have been developed to assess the spine tissue loads of individuals. However, most models have assumed trunk muscle lines of action as straight-lines, which might be less reliable during occupational tasks that require complex lumbar motions. The objective of this study was to describe the model structure and underlying logic of a biologically-assisted curved muscle model of the lumbar spine., Methods: The developed model structure including curved muscle geometry, separation of active and passive muscle forces, and personalization of muscle properties was described. An example of the model procedure including data collection, personalization, and data evaluation was also illustrated., Findings: Three-dimensional curved muscle geometry was developed based on a predictive model using magnetic resonance imaging and anthropometric measures to personalize the model for each individual. Calibration algorithms were able to reverse-engineer personalized muscle properties to calculate active and passive muscle forces of each individual., Interpretation: This biologically-assisted curved muscle model will significantly increase the accuracy of spinal tissue load predictions for the entire lumbar spine during complex dynamic occupational tasks. Personalized active and passive muscle force algorithms will help to more robustly investigate person-specific muscle forces and spinal tissue loads., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: Accurate geometry of the trunk musculature is essential for reliably estimating spinal loads in biomechanical models. Currently, many models employ straight muscle path assumptions that yield far less accurate tissue loads, particularly in extreme postures. Precise muscle moment-arms and physiological cross-sectional areas are important when incorporating curved muscle geometry in biomechanical models. The objective of this study was to develop a predictive model of moment arms and physiological cross-sectional areas of trunk musculature at multiple levels in the thoracic/lumbar spine as a function of anthropometric measures., Methods: Based on magnetic resonance imaging data from thirty subjects (10 male and 20 female) reported in a previous study, a polynomial regression analysis was conducted to estimate the muscle moment-arms and physiological cross-sectional areas of trunk muscles through thoracic/lumbar spine as a function of vertebral level, gender, age, height, and body mass., Findings: Gender, body mass, and height were the best predictors of muscle moment-arms and physiological cross-sectional areas. The predictability of muscle parameters tended to be higher for erector spinae than other muscles. Most muscles showed a curved muscle path along the thoracic/lumbar spine., Interpretation: The polynomial regression model of the muscle geometry in this study generally showed good predictability compared to previous reports. The predictive model in this study will be useful to develop personalized biomechanical models that incorporate curved trunk muscle geometries., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: The Sorensen test is commonly used to assess back muscle endurance capacity. However, the clinical value of this test, requiring compensation of the entire upper body mass, is limited if pain occurs. Therefore, a test variant using only portions of upper body mass could be an alternative., Objective: This study aimed to determine fatigue characteristics in lumbar muscles during a modified Sorensen test utilizing only 50% of the upper body mass and asked if localization-related effects of surface electrodes in the assessment of lumbar muscle fatigue should be considered., Methods: Thirty-two young (20-29 years) symptom-free men were enrolled and asked to maintain only 50% upper body mass for 10 minutes. Fatigue characteristics were bilaterally derived from four different lumbar levels using Surface EMG. Side-specific and SEMG parameter-independent repeated measures (four lumbar levels, nine time points) analyses of variance were conducted., Results: All participants were able to complete the test. Over time, a spatial effect of fatigue-related amplitude alterations at the respective segments could be observed., Conclusions: By using this modified Sorensen test, muscular fatigue can be evoked. Electrophysiological assessment of lumbar fatigue should consider spatial differences.

A hallmark of more advanced models is their higher details of trunk muscles represented by a larger number of muscles. The question is if in reality we control these muscles individually as independent agents or we control groups of them called "synergy". To address this, we employed a 3-D biomechanical model of the spine with 18 trunk muscles that satisfied equilibrium conditions at L4/5, with different cost functions. The solutions of several 2-D and 3-D tasks were arranged in a data matrix and the synergies were computed by using non-negative matrix factorization (NMF) algorithms. Variance accounted for (VAF) was used to evaluate the number of synergies that emerged by the analysis, which were used to reconstruct the original muscle activations. It was showed that four and six muscle synergies were adequate to reconstruct the input data of 2-D and 3-D torque space analysis. The synergies were different by choosing alternative cost functions as expected. The constraints affected the extracted muscle synergies, particularly muscles that participated in more than one functional tasks were influenced substantially. The compositions of extracted muscle synergies were in agreement with experimental studies on healthy participants. The following computational methods show that the synergies can reduce the complexity of load distributions and allow reduced dimensional space to be used in clinical settings., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Three different methodologies: work sampling, computer simulation and biomechanical modeling, were integrated to study the physical demands of drywall installation. PATH (Posture, Activity, Tools, and Handling), a work-sampling based method, was used to quantify the percent of time that the drywall installers were conducting different activities with different body segment (trunk, arm, and leg) postures. Utilizing Monte-Carlo simulation to convert the categorical PATH data into continuous variables as inputs for the biomechanical models, the required muscle contraction forces and joint reaction forces at the low back (L4/L5) and shoulder (glenohumeral and sternoclavicular joints) were estimated for a typical eight-hour workday. To demonstrate the robustness of this modeling approach, a sensitivity analysis was conducted to examine the impact of some quantitative assumptions that have been made to facilitate the modeling approach. The results indicated that the modeling approach seemed to be the most sensitive to both the distribution of work cycles for a typical eight-hour workday and the distribution and values of Euler angles that are used to determine the "shoulder rhythm." Other assumptions including the distribution of trunk postures did not appear to have a significant impact on the model outputs. It was concluded that the integrated approach might provide an applicable examination of physical loads during the non-routine construction work, especially for those operations/tasks that have certain patterns/sequences for the workers to follow., (Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.)

Background: The psoas major (PM) is important for stabilizing lumbopelvic region during active straight leg raising (ASLR). Uncontrolled lumbopelvic rotation (ULPR) frequently occurs during ASLR in subjects with poor lumbo-pelvic stability and may contribute to asymmetric symptoms including pain in lumbopelvic region., Objects: This study compared the thickness of contralateral PM (cPM) using ultrasound imaging during ASLR in subjects with and without ULPR., Method: Healthy male subjects (18 without ULPR, 19 with ULPR) were recruited. The thickness of the cPM during rest and ASLR without loading and with a 1-kg load was measured by ultrasound imaging. The relative muscle thickness was calculated as the thickness during ASLR/thickness at rest. Two-way mixed-model analysis of variance was used to identify significant differences in the relative thickness of the cPM between groups and within a loading status. The level of statistical significance was set at α = 0.05., Results: The resting thickness of the cPM in subjects without ULPR did not differ from that of subjects with ULPR. The relative thickness of the cPM in subjects without ULPR was significantly greater during ASLR than that in subjects with ULPR both without loading and with a load (p < 0.01). No significant change in thickness of the cPM was evident in those with ULPR., Conclusion: The thickness of the cPM was significantly greater during ASLR in subjects without ULPR than with ULPR. This result indicates that persons with ULPR have less activation of the cPM to stabilize the lumbar spine during ASLR., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In people with a history of low back pain (LBP), structural and functional alterations have been observed at several peripheral and central levels of the sensorimotor pathway. These existing alterations might interact with the way the sensorimotor system responds to pain. We examined this assumption by evaluating the lumbar motor responses to experimental nociceptive input of 15 participants during remission of unilateral recurrent LBP. Quantitative T2 images (muscle functional MRI) were taken bilaterally of multifidus, erector spinae, and psoas at several segmental levels (L3 upper and L4 upper and lower endplate) and during several conditions: 1) at rest, 2) upon trunk-extension exercise without pain, and 3) upon trunk-extension exercise with experimental induced pain at the clinical pain-side (1.5-ml intramuscular hypertonic saline injections in erector spinae). Following experimental pain induction, muscle activity levels similarly reduced for all three muscles, on both painful and nonpainful sides, and at multiple segmental levels (P = 0.038). Pain intensity and localization from experimental LBP were similar as during recalled clinical LBP episodes. In conclusion, unilateral and unisegmental experimental LBP exerts a generalized and widespread decrease in lumbar muscle activity during remission of recurrent LBP. This muscle response is consistent with previous observed patterns in healthy people subjected to the same experimental pain paradigm. It is striking that similar inhibitory patterns in response to pain could be observed, despite the presence of preexisting alterations in the lumbar musculature during remission of recurrent LBP. These results suggest that motor output can modify along the course of recurrent LBP., (Copyright © 2016 the American Physiological Society.)

Flexion relaxation (FR), a myoelectric silence of extensor muscles near end range of lumbar flexion, is commonly reported as the lumbar flexion angle at the instant the extensor muscles become silent. However, lumbar flexion angle alone is insufficient to characterize mechanisms that modulate FR. As FR requires the moment generated by passive lumbar extensor tissues to equilibrate the moment due to gravity, the inter-relationships between lumbar moment, flexion angle, and myoelectrical silence will provide added information in the understanding of FR. The purpose of this study was to examine the relationship between lumbar moment and flexion angle throughout various flexion manoeuvres. It was hypothesized that lumbar moment and flexion angle would not be linearly related and would be affected by lower limb position, range of motion, and the addition of mass to the torso. Eleven participants performed four different lumbar flexion trials. Results showed that lumbar flexion was correlated with the lumbar moment (r = 0.92); however an analysis of residuals found that these measures were not linearly related. The moment was, however, correlated (r = 0.99) and linearly related to the sine of trunk inclination (T12 rigid body with respect to global horizontal). Future studies of FR could use trunk inclination as a simple kinematic measure to predict relative changes in lumbar moment with flexion., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Rope and harness vertical dance takes place off the floor with the dancer suspended from his or her center of mass in a harness attached to a rope from a point overhead. Vertical dance represents a novel environment for training and performing in which expected stresses on the dancer's body are different from those that take place during dance on the floor. Two male and eleven female dancers with training in vertical dance performed six typical vertical dance movements with electromyography (EMG) electrodes placed bilaterally on rectus abdominus, external oblique, erector spinae, and latissimus dorsi. EMG data were expressed as a percentage of maximum voluntary isometric contraction (MVIC). A simplified musculoskeletal model based on muscle activation for these four muscle groups was used to estimate the compressive force on the spine. The greatest muscle activation for erector spinae and latissimus dorsi and the greatest trunk compressive forces were seen in vertical axis positions where the dancer was moving the trunk into a hyper-extended position. The greatest muscle activation for rectus abdominus and external oblique and the second highest compressive force were seen in a supine position with the arms and legs extended away from the center of mass (COM). The least muscle activation occurred in positions where the limbs were hanging below the torso. These movements also showed relatively low muscle activation compression forces. Post-test survey results revealed that dancers felt comfortable in these positions; however, observation of some positions indicated insufficient muscular control. Computing the relative contribution of muscles, expressed as muscle activation and estimated spinal compression, provided a measure of how much the muscle groups were working to support the spine and the rest of the dancer's body in the different movements tested. Additionally, identifying typical muscle recruitment patterns in each movement will help identify key exercises for training that should promote injury prevention.

Purpose: Postural alignment of elderly people becomes poor due to aging, possibly leading to low-back pain and spinal deformity. Although there are several interventions for treating these conditions, no previous study has reported the effectiveness of a spinal orthosis or lumbosacral orthosis (LSO) in healthy elderly people without specific spinal deformity. We therefore developed a trunk orthosis to decrease low-back muscle activity while training good postural alignment through resistive force provided by joints with springs (here, called the ORF, which stands for orthosis with joints providing resistive force) as a preventive method against abnormal posture and low-back pain in healthy elderly persons., Patients and Methods: Fifteen community-dwelling elderly men participated in this study. Participants stood freely for 10 seconds in a laboratory setting under three conditions: without an orthosis, with the ORF, and with an LSO. The Damen corset LSO was selected as it is frequently prescribed for patients with low-back pain. Postural alignment during static standing was recorded using a three-dimensional motion capture system employing infrared cameras. Two force plates were used to record center of pressure. Electromyograms were obtained for bilateral erector spinae (ES), left internal abdominal oblique, and right gluteus medius muscles., Results: Pelvis forward tilt angle tended to increase while wearing the ORF and decrease while wearing the LSO, but these results were not significant compared to no orthosis. Thorax extension angle and thorax angle on pelvis coordinate system significantly increased while wearing the ORF compared to the other two conditions. ES activity significantly decreased while wearing the ORF compared to the other two conditions. Internal oblique activity was significantly smaller while wearing the LSO than with no orthosis. Center of pressure did not significantly differ among the conditions., Conclusion: The ORF significantly improved trunk alignment and decreased ES activity in healthy elderly subjects during static standing.

Previous studies indicated that lumbar extensor muscle fatigue could potentially affect lumbar-pelvic rhythm and influence spinal loading during trunk motions. In this study, the effects of lumbar extensor muscle fatigue on the normalized lumbar-pelvic rotation rhythm and the associated L5/S1 joint loading during weight lifting and lowering tasks were investigated. Thirteen volunteers performed lifting and lowering of a 20-lbs box both before and after lumbar extensor muscle fatigue, which was generated through a static weight holding task. The normalized lumbar-pelvic motion ratio (L/P ratio) and the external moment on the L5/S1 joint were calculated and compared. Results showed that subjects demonstrated significantly larger normalized L/P ratios during both weight lifting and lowering tasks with the influence of fatigue. In addition, although the spinal loadings remain unchanged at the beginning and ending of both lifting and lowering motions, significantly larger L5/S1 joint moments were observed during both motions after fatigue. Such changes indicate potentially elevated risk of back injury. In a clinical setting, the current results demonstrated that lumbar muscle fatigue could cause transient changes in lumbar-pelvic motion rhythm. Therefore, lumbar muscle fatigue must be avoided when using lumbar-pelvic motion rhythms for patient diagnosis or rehabilitation assessment.

Objective: To develop a simple method of quantifying dynamic lumbar stability by evaluating postural changes of the lumbar spine during a wall plank-and-roll (WPR) activity while maintaining maximal trunk rigidity., Design: A descriptive, exploratory research with a convenience sample., Setting: A biomechanics laboratory of a tertiary university hospital., Participants: Sixteen healthy young subjects (8 men and 8 women; 30.7 ± 6.8 years old) and 3 patients (2 men 46 and 50 years old; 1 woman 54 years old) with low back pain (LBP)., Methods: The subjects performed the WPR activity with 2 inertial sensors attached on the thoracic spine and sacrum. Relative angles between the sensors were calculated to characterize lumbar posture in 3 anatomical planes: axial twist (AT), kyphosis-lordosis (KL), or lateral bending (LB). Isokinetic truncal flexion and extension power were measured., Main Outcome Measures: AT, KL, and LB were compared between the initial plank and maximal roll positions. Angular excursions were compared between males and females and between rolling sides, and tested for correlation with isokinetic truncal muscle power. Patterns and consistencies of the lumbar postural changes were determined. Lumbar postural changes of each patient were examined in the aspects of pattern and excursion, considering those from the healthy subjects as reference., Results: AT, KL, and LB were significantly changed from the initial plank to the maximal roll position (P < .01); that is, the thoracic spine rotated further, lumbar lordosis increased, and the thoracic spine was bent away from the wall by 6.9° ± 12.0°, 9.5° ± 6.5°, and 7.9° ± 4.9°, respectively. The patterns and amounts of lumbar postural changes were not significantly different between the rolling sides or between male and female participants, except that the excursion in AT was larger on the dominant rolling side. The excursions were not related to isokinetic truncal muscle power. The 3 LBP patients showed varied deviations in pattern and excursion from the average of the healthy subjects., Conclusions: Certain amounts and patterns of lumbar postural changes were observed in healthy young subjects, with no significant variations based on gender, rolling side, or truncal muscle power. Application of the evaluation on LBP patients revealed prominent deviations from the healthy postural changes, suggesting potential clinical applicability. Therefore, with appropriate development and case stratification, we believe that the quantification of lumbar postural changes during WPR activity can be used to assess dynamic lumbar stability in clinical practice., (Copyright © 2015 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.)

Trunk extension exercises are used to train endurance and strength of the trunk extensor muscles. Appropriate exercise dosage is crucial to achieve specific training effects, however literature describing the relation between the predetermined exercise intensity and the actual trunk extensors activity is scarce and inconclusive. To examine whether the actual activity of the thoracic and lumbar extensors during extensions exercises correspond with the predetermined intensity, electromyographic evaluation of the trunk extensors was performed during trunk extension exercises at various intensities expressed as percentages of 1-RM. The 1-RM was predetermined using 2 different methods: (1) through direct estimation by determining the maximum isometric force produced during semi-seated trunk extension on a Tergumed rehabilitation device, (2) through indirect estimation calculated based on the relation between the maximum number of repetitions of trunk extension from prone lying on a variable angle chair and the submaximal resistance at which the repetitions were performed as presented on the Holten-diagram. The total trunk muscle activity during extension exercises performed semi-seated on a rehabilitation device or from prone lying corresponds with the predetermined dosage using both estimation methods. The indirect estimation method more accurately predicts the actual trunk extensor activity for low load training than for high load training. However, the direct estimation method is suitable to closely predetermine the load and actual trunk extensors activity during high load exercises. A shift from a differential recruitment between the thoracic and lumbar extensors at low intensities to a more homogenous recruitment at high intensities is observed during semi-seated trunk extension exercises. During prone extension exercises both muscle groups equally contribute to the total muscle work regardless of the exercise intensity. Based on these findings suggestions regarding the appropriate choice of estimation and performance method are made., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Intramuscular electromyography (EMG) is commonly used to quantify activity in the trunk musculature. However, it is unclear if the discomfort or fear of pain associated with insertion of intramuscular EMG electrodes results in altered motor behavior. This study examined whether intramuscular EMG affects locomotor speed and trunk motion, and examined the anticipated and actual pain associated with electrode insertion in healthy individuals and individuals with a history of low back pain (LBP). Before and after insertion of intramuscular electrodes into the lumbar and thoracic paraspinals, participants performed multiple repetitions of a walking turn at self-selected and controlled average speed. Low levels of anticipated and actual pain were reported in both groups. Self-selected locomotor speed was significantly increased following insertion of the electrodes. At the controlled speed, the amplitude of sagittal plane lumbo-pelvic motion decreased significantly post-insertion, but the extent of this change was the same in both groups. Lumbo-pelvic motion in the frontal and axial planes and thoraco-lumbar motion in all planes were not affected by the insertions. This study demonstrates that intramuscular EMG is an appropriate methodology to selectively quantify the activation patterns of the individual muscles in the paraspinal group, both in healthy individuals and individuals with a history of LBP., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objective: The aim of this study was to determine whether side-lying hip abduction exercise while applying manual pelvic fixation is more effective than hip abduction without manual pelvic fixation for promoting deep trunk muscle activity., Design: This is a cross-sectional study comparing deep trunk muscle activation between hip abduction exercise without and with manual pelvic fixation in ten participants. Muscle activation was measured using fine-wire and surface electromyography., Results: Hip abduction with manual pelvic fixation was found to result in significantly more recruitment of all studied deep trunk muscles except the ipsilateral obliquus externus compared with hip abduction without manual pelvic fixation (P < 0.05). The greatest increased activation was seen in the ipsilateral deep and superficial multifidus. The increase in deep multifidus percentage of maximal voluntary contraction was greater than that of the rectus abdominis, the obliquus externus, the transversuus abdominis/obliquus internus, the lumbar erector spinae, the superficial multifidus, and the gluteus medius (P < 0.05). The superficial multifidus percentage of maximal voluntary contraction was significantly increased over that of the rectus abdominis and the obliquus externus (P < 0.05). Moderate correlation between deep and superficial multifidus activation was found (Pearson correlation coefficient, 0.537)., Conclusions: Hip abduction training in the side-lying position while applying manual pelvic fixation seems to be more effective for recruiting deep trunk muscles for dynamic lumbar spinal stabilization.

Background: The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from a standing position and task specific spine ranges of motion objectively assess muscle function in healthy young and middle age individuals. However, literature on neuromuscular activation and associated spine and hip kinematics in older individuals is sparse. This cross sectional study sought to examine the sex and age (<40 versus >60 years) related differences in the neuromuscular activation profiles of the lumbar extensors and the related spine and hip kinematics from healthy individuals during a standardized trunk flexion-extension task., Methods: Twenty five older (13 females, 60-90 years) and 24 younger (12 females, 18-40 years) healthy individuals performed trunk flexion-extension testing by holding static positions at half-flexion way and full range of motion between standing and maximum trunk flexion. The associated lumbar extensor muscle activity was derived from measurements at standing, half, and maximum flexion positions. The range of motion at the hip and lumbar spine was recorded using 3d accelerometers attached to the skin overlying the multifidus and semispinalis thoracis muscles lateral to the L5 and T4 spinous processes, respectively. Statistical calculations were performed using a permutation ANOVA with bootstrap confidence intervals., Results: The muscle activity in the half related to the maximum flexion position (half flexion relaxation ratio) was significantly smaller in older males when compared with younger males. Moreover, measurements revealed smaller activity changes from standing to the half and from half to the maximum flexion position in older compared to younger individuals. Older males displayed smaller gross trunk range of motion from standing to maximum flexion than any other group., Conclusions: Gender and normal aging significantly affect both the activation patterns of the lumbar extensor muscles and the kinematics of the trunk during a standardized trunk flexion-extension task. Measurement results from healthy young and middle age individuals should not be used for the assessment of individuals older than 60 years of age.

Lumbar muscle fatigue is a potential risk factor for the development of low back pain. In this study, we investigated the influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination patterns during weightlifting. Each of the 15 male subjects performed five repetitions of weightlifting tasks both before and after a lumbar extensor muscle fatiguing protocol. Lumbar muscle electromyography was collected to assess fatigue. Trunk kinematics was recorded to calculate lumbar-pelvic continuous relative phase (CRP) and CRP variability. Results showed that fatigue significantly reduced the average lumbar-pelvic CRP value (from 0.33 to 0.29 rad) during weightlifting. The average CRP variability reduced from 0.17 to 0.15 rad, yet this change ws statistically not significant. Further analyses also discovered elevated spinal loading during weightlifting after the development of lumbar extensor muscle fatigue. Our results suggest that frequently experienced lumbar extensor muscle fatigue should be avoided in an occupational environment., Practitioner Summary: Lumbar extensor muscle fatigue generates more in-phase lumbar-pelvic coordination patterns and elevated spinal loading during lifting. Such increase in spinal loading may indicate higher risk of back injury. Our results suggest that frequently experienced lumbar muscle fatigue should be avoided to reduce the risk of LBP.

Background: The abdominal drawing-in maneuver (ADIM) is used to prevent abnormal movements of the lumbar spine and pelvis during therapeutic exercises. This study compared the effects of ADIM on the muscle onset time of the hamstring, gluteus maximus, and erector spinae muscles during prone hip extension exercise in subjects with or without hyperlordotic lumbar angle. Forty healthy adults (18 male, 22 female) were recruited for this study., Methods: The lumbar lordotic angles and pelvic tilt angles of the subjects were measured using the Avaliação postural analysis software. The subjects were divided into two groups: the lumbar hyperlordotic angle (LHLA) and lumbar normal lordotic angle (LNLA) groups. The muscle contraction onset time of the hamstring, gluteus maximus, and erector spinae were assessed using surface electromyography., Results: During ADIM application, the muscle contraction onset time of the gluteus maximus was significantly increased in the LHLA group compared with the LNLA group., Conclusions: ADIM application during prone hip extension was more effective for gluteus maximus onset time in the LHLA group. Therefore, ADIM during prone hip extension may be useful for gluteus maximus training in individuals with lumbar hyperlordosis.