Irrespective of the lifting technique (squat or stoop), the lumbar spine posture (more kyphotic versus more lordotic) adopted during lifting activities is an important parameter affecting the ...active-passive spinal load distribution. The advantages in either posture while lifting remains, however, a matter of debate. To comprehensively investigate the role on the trunk biomechanics of changes in the lumbar posture (lordotic, free or kyphotic) during forward trunk flexion, validated musculoskeletal and finite element models, driven by in vivo kinematics data, were used to estimate detailed internal tissue stresses-forces in and load-sharing among various joint active-passive tissues. Findings indicated that the lordotic posture, as compared to the kyphotic one, resulted in marked increases in back global muscle activities (~14–19%), overall segmental compression (~7.5–46.1%) and shear (~5.4–47.5%) forces, and L5-S1 facet joint forces (by up to 80 N). At the L5-S1 level, the lordotic lumbar posture caused considerable decreases in the moment resisted by passive structures (spine and musculature, ~14–27%), negligible reductions in the maximum disc fiber strains (by ~0.4–4.7%) and small increases in intradiscal pressure (~1.8–3.4%). Collectively and with due consideration of the risk of fatigue and viscoelastic creep especially under repetitive lifts, current results support a free posture (in between the extreme kyphotic and lordotic postures) with moderate contributions from both active and passive structures during lifting activities involving trunk forward flexion.
Abstract Purpose Field study, cross-sectional study to measure the posture and sEMG of the lumbar spine during office work for a better understanding of the lumbar spine within such conditions. Scope ...There is high incidence of low back pain in office workers. Currently there is little information about lumbar posture and the activity of lumbar muscles during extended office work. Methods Thirteen volunteers were examined for around 2 h of their normal office work. Typical tasks were documented and synchronised to a portable long term measuring device for sEMG and posture examination. The correlation of lumbar spine posture and sEMG was tested statistically. Results The majority of time spent in office work was sedentary (82%). Only 5% of the measured time was undertaken in erect body position (standing or walking). The sEMG of the lumbar muscles under investigation was task dependent. A strong relation to lumbar spine posture was found within each task. The more the lumbar spine was flexed, the less there was activation of lumbar muscles ( P < .01). Periods of very low or no activation of lumbar muscles accounted for about 30% of relaxed sitting postures. Conclusion Because of very low activation of lumbar muscles while sitting, the load is transmitted by passive structures like ligaments and intervertebral discs. Due to the viscoelasticity of passive structures and low activation of lumbar muscles, the lumbar spine may incline into de-conditioning. This may be a reason for low back pain.
Aim: Low back pain (LBP) is one of the leading causes of disability worldwide, with a huge economic burden on public health. Neuromuscular (NMS) exercises may reduce LBP recurrence, but the most ...effective program has not been established. This narrative review aimed to collect evidence on the effect of NMS exercises in patients with LBP. Methods: A narrative review of the electronic literature from April 2000 to July 2023 was conducted. The electronic search was performed on five databases (PubMed, Scopus, Web of Science, Google Scholar, and Science Direct). All articles analysed in this study were randomized controlled trials (RCTs). The PEDro scale was used to assess the methodological quality of the articles. Results: Five RCTs were selected and included.The RCTs showed that NMS exercises reduce pain intensity, improve lumbar movement control and physical function, and prevent LBP. Studies also showed that NMS exercises are targeted to improve the control, flexibility, and strength of lumbar muscles. The PEDro score ranges from 5 to 7, highlighting several methodological issues. Conclusion: The findings of this narrative review indicate that NMS exercises can reduce pain intensity in LBP. However, the research on NMS exercises’ effects on LBP is very limited and should be interpreted with caution due to the methodological limitations.
Objetivo: La lumbalgia, una de las principales causas de discapacidad a nivel mundial, impone una considerable carga económica en el ámbito de la salud pública. Los ejercicios neuromusculares (NMS) pueden reducir la recurrencia del dolor lumbar, pero no se ha establecido el programa más eficáz. Esta revisión narrativa tuvo como objetivoevaluar la evidencia sobre el efecto de los ejercicios NMS en pacientes con dolor lumbar.
Métodos: Se realizó una revisión narrativa de la literatura electrónica desde abril de 2000 hasta julio de 2023. La búsqueda bibliografica se realizó en cinco bases de datos (PubMed, Scopus, Web of Science, Google Scholar y Science Direct). Todos los artículos analizados en este estudio fueron ensayos controlados aleatorios (ECA). Se utilizó la escala PEDro para evaluar la calidad metodológica de los artículos. Resultados: Se seleccionaron e incluyeron cinco ECA. Los ECA mostraron que los ejercicios NMS reducen la intensidad del dolor, mejoran el control del movimiento lumbar y la función física y previenen el dolor lumbar. Los estudios también demostraron que los ejercicios NMS son ejercicios dirigidos a mejorar el control, la flexibilidad y la fuerza de los músculos lumbares. La puntuación de PEDro oscila entre 5 y 7, lo que destaca varias cuestiones metodológicas.
Conclusión: Los resultados de este estudi sugiere que los ejercicios NMS pueden tener un impacto positivo en la intensidad del dolor en el dolor lumbar.
This study investigated the effects of age on upper erector spinae (UES), lower erector spinae (LES) and lower body (gluteus maximus; biceps femoris; and vastus lateralis) muscle activity during a ...repetitive lifting task. Twenty-four participants were assigned to two age groups: ‘younger’ (n = 12; mean age ± SD = 24.6 ± 3.6 yrs) and ‘older’ (n = 12; mean age = 46.5 ± 3.0 yrs). Participants lifted and lowered a box (13 kg) repetitively at a frequency of 10 lifts per minute for a maximum of 20 min. EMG signals were collected every minute and normalised to a maximum voluntary isometric contraction. A submaximal endurance test of UES and LES was used to assess fatigue. Older participants showed higher levels of UES and LES muscle activity (approximately 12–13%) throughout the task, but less fatigue compared to the younger group post-task completion. When lifting, lower-limb muscle activity was generally higher in older adults, although temporal changes were similar. While increased paraspinal muscle activity may increase the risk of back injury in older workers when repetitive lifting, younger workers may be more susceptible to fatigue-related effects. Education and training in manual materials handling should consider age-related differences when developing training programmes.
Although numerous studies have documented back muscle flexion-relaxation phenomenon (FRP) in standing postures, few studies have examined the FRP in various seated lumbar postures and individual ...flexibilities. This study, therefore, recruited 18 male students and assigned to low- and high-flexibility groups (9 in each). Activation of thoracic and lumbar erector spinae (ES) and lumbosacral angles were examined while participants sat in two postures (lordosis and kyphosis) and flexed their trunks at 15°, 30°, 45°, 60°, and maximum flexion. Results showed that kyphotic lumbar posture caused relatively low and unchangeable thoracic and lumbar ES activations, whereas lordotic lumbar posture engendered more contractive and varying thoracic and lumbar ES activations. Flexible participants exhibited higher thoracic ES activation than less flexible participants during lordotic sitting. Thoracic ES seemed to play a compensative role to stabilize the spine in the lordotic sitting posture, especially when the trunk was flexed over 45°. In lordotic lumbar posture, FRP occurred only in the lumbar ES; however, the activation and lumbosacral angles were still higher than those in kyphotic posture. The increased back muscle activation associated with lumbar lordosis may partially share the load on passive interspinous tissues, which are close to the discs during these flexed trunk positions.
This study suggests that various lumbar postures and individual flexibilities may cause different FRP patterns when sitting. While performing seated tasks, people should exercise caution about the lumbar posture.
•Back muscle activity reduces during trunk flexing means flexion-relaxation phenomenon (FRP).•This study was to determine the effects of flexibility and lumbar posture on FRP when sitting.•Eighteen males with low and high flexibility seated and flexed their trunk from 0° to the maximum.•Fewer back muscle contractions may lead to excessive passive issue stresses in a lumbar kyphosis.•Flexible group showed higher upper back muscle activity to stabilize spine in a lordotic sitting.
Purpose
This study aimed to compare differences in lumbosacral and spinopelvic parameters between pain developers and non-pain developers as well as the effects of various posture changes.
Methods
A ...total of 38 consecutive participants, 20 standing-induced low back pain developers (mean age: 27.7 ± 5.3; mean BMI: 22.64 ± 2.95) and 18 non-pain developers (mean age: 29.0 ± 7.5; mean BMI: 24.2 ± 1.87) (
p
> 0.05), were prospectively evaluated. Six sagittal plane radiographs were taken. Upright standing posture was used as the reference posture. Lumbar lordosis, lumbosacral lordosis, L1/L2 and L5/S1 intervertebral (IV) joint angles, pelvic incidence, pelvic tilt and sacral slope were measured on each radiograph.
Results
There were no significant differences in terms of age, BMI, SF-36 score, or Oswestry Disability Index scores between pain developer and non-pain developer groups (
p
> 0.05). Pain developers had significantly larger lumbar lordosis, larger L1/L2 intervertebral angles, larger pelvic incidences and sacral slopes in all postures (
p
< 0.05). The contribution of L5/S1 intervertebral angle to lumbar flexion was higher than that of the L1/L2 intervertebral angle during stair descent, the sitting and the leaning forward while sitting postures (
p
< 0.05).
Conclusion
The current study supports the assertion that increased lumbar lordosis is associated with increased pain. Lumbar spine angles change in various postures. The changes were more prominent in pain developers than in non-pain developers. Larger lumbar lordosis due to larger pelvic incidence may be a risk factor for the development of standing-induced low back pain.
Graphical abstract
These slides can be retrieved under Electronic Supplementary Material.
Abstract Background Age is considered a risk factor for manual handling-related injuries and older workers incur higher injury-related costs than younger co-workers. This study investigated the ...differences between the kinematics and kinetics of repetitive lifting in two groups of handlers of different ages. Methods Fourteen younger (mean 24.4 yr) and 14 older (mean 47.2 yr) males participated in the study. Participants repetitively lifted a box weighing 13 kg at a frequency of 10 lifts/min for a maximum of 20 min. Postural kinematics (joint and lumbosacral angles and angular velocities) and kinetics (joint moments) were measured throughout the lifting task using motion analysis and ground reaction forces. Muscle fatigue of the erector spinae was assessed using electromyography. Findings Peak lumbosacral, trunk, hip and knee flexion angles differed significantly between age groups over the duration of the task, as did lumbosacral and trunk angular velocities. The younger group increased peak lumbar flexion by approximately 18% and approached 99% of maximum lumbosacral flexion after 20 min, whereas the older group increased lumbar flexion by 4% and approached 82% maximum flexion. The younger group had a larger increase in peak lumbosacral and trunk angular velocities during extension, which may be related to the increased back muscle fatigue observed among the younger group. Interpretation Older participants appeared to control the detrimental effects of fatigue associated with repetitive lifting and limit lumbar spine range of motion. The higher rates of musculoskeletal injury among older workers may stem from a complex interaction of manual handling risk factors.
Abstract The goal of this study was to determine the effects of vision and lumbar posture on trunk neuromuscular control. Torso perturbations were applied with a pushing device while the subjects ...were restrained at the pelvis in a kneeling-seated position. Torso kinematics and the muscle activity of the lumbar part of the M. Longissimus were recorded for 14 healthy subjects. Four conditions were included: a flexion, extension and neutral lumbar posture with eyes closed and the neutral posture with eyes open. Frequency response functions of the admittance and reflexes showed that there was no significant difference between the eyes open and eyes closed conditions, thereby confirming that vision does not play a role in the stabilization of the trunk during small-amplitude trunk perturbations. In contrast, manipulating posture did lead to significant differences. In particular, the flexed condition led to a lower admittance and lower reflex contribution compared to the neutral condition. Furthermore, the muscle pre-activation (prior to the onset of the perturbation) was significantly lower in the flexed posture compared to neutral. This confirms that flexing the lumbar spine increases the passive tissue stiffness and decreases the contribution of reflex activity to trunk control.
In vivo measurements and model studies are combined to investigate the role of lumbar posture in static lifting tasks.
Identification of the role of changes in the lumbar posture on muscle forces, ...internal loads, and system stability in static lifting tasks with and without load in hands.
Despite the recognition of the causal role of lifting in spinal injuries, the advantages of preservation or flattening of the lumbar lordosis while performing lifting tasks is not yet clear.
Kinematics of the spine and surface EMG activity of selected muscles were measured in 15 healthy subjects under different forward trunk flexion angles and load cases. Apart from the freestyle lumbar posture, subjects were instructed to take either lordotic or kyphotic posture as well. A kinematics-based method along with a nonlinear finite element model were interactively used to compute muscle forces, internal loads and system stability margin under postures, and loads considered in in vivo investigations. RESULTS.: In comparison with the kyphotic postures, the lordotic postures increased the pelvic rotation, active component of extensor muscle forces, segmental axial compression and shear forces at L5-S1, and spinal stability margin while decreasing the passive muscle forces and segmental flexion moments.
Alterations in the lumbar lordosis in lifting resulted in significant changes in the muscle forces and internal spinal loads. Spinal shear forces at different segmental levels were influenced by changes in both the disc inclinations and extensor muscle lines of action as the posture altered. Considering internal spinal loads and active-passive muscle forces, the current study supports the freestyle posture or a posture with moderate flexion as the posture of choice in static lifting tasks.
Police officers spend large amounts of time performing duties within a police cruiser and report a high prevalence of musculoskeletal problems. This study evaluated the effects of driver seat and ...duty belt design on posture, pressure and discomfort. Ten male and 10 female university students attended two sessions involving simulated driving in a standard police seat (CV) and an active lumbar support (ALS) seat. Participants wore a full duty belt (FDB) or reduced duty belt (RDB) in each seat. Lumbar postures, driver-seat and driver-duty belt pressures and perceived discomfort were measured. Gender × Seat interactions were found for pelvic (p = 0.0001) and lumbar postures (p = 0.003). Females had more lumbar flexion than males and were more extended in the ALS seat (−9.8 ± 11.3°) than CV seat (−19.8 ± 9.6°). The FDB had greater seat pressure than the RDB (p < 0.0001), which corresponded to increased pelvis discomfort. This study supports the use of an ALS seat and RDB to reduce injury risk associated with prolonged sitting in police officers.
Practitioner Summary: Police officers report a high prevalence of musculoskeletal problems to the lower back, associated with prolonged driving and further investigation is needed to reduce injury risk. This simulated driving study investigated seat and duty belt configuration on biomechanical measures and discomfort. Seat design had the greatest impact, regardless of gender and males benefited more from a reduced belt configuration.
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