Although trunk muscles are involved in many important functions, evaluating trunk muscle strength is not an easy task. If trunk muscle mass and thickness could be used as indicators of trunk muscle ...strength, the burden of measurement would be reduced, but the relationship between trunk muscle strength and trunk muscle mass and thickness has not been clarified.
The purpose of this study was to clarify the relationship between trunk muscle strength and trunk muscle mass by bioelectrical impedance analysis and trunk muscle thickness by ultrasound imaging in healthy adults.
One hundred and twenty-one healthy university students were included in this study. Trunk flexion/extension muscle strength and trunk muscle mass by bioelectrical impedance analysis, and trunk muscle thickness by ultrasound imaging were measured.
Both trunk flexion strength and trunk extension strength were significantly correlated with trunk muscle mass and oblique and rectus abdominis muscle thickness. Multiple regression analysis showed that trunk extension muscle strength had an independent relationship with trunk muscle mass.
This study demonstrated that trunk muscle mass or trunk muscle thickness can be used as an alternative means for evaluating trunk muscle strength, making the evaluation of trunk muscles less burdensome.
The contribution of the trunk neuromuscular system (TNS) to spine stability has been shown in earlier studies by characterizing changes in antagonistic activity of trunk muscles following alterations ...in stability demands of a task. Whether and/or how much such changes in the response of TNS to alteration in stability demand of the task alter spinal stiffness remains unclear. To address this research gap, a repeated measure study was conducted on twenty gender-balanced asymptomatic individuals to evaluate changes in trunk bending stiffness throughout the lumbar spine’s range of flexion following alterations in both stability and equilibrium demands of a load holding task. Trunk bending stiffness was determined using trunk stiffness tests in upright posture on a rigid metal frame under different equilibrium and stability demands on the lower back. Increasing the stability demand by increasing the height of lifted load ∼30 cm only increased trunk bending stiffness (∼39%) over the lower range of lumbar flexion and under the low equilibrium demand condition. Similarly, increasing the equilibrium demand of the task by increasing the weight of lifted load by 3.5 kg only increased trunk bending stiffness (55%) over the low range of lumbar flexion and under the low stability demand condition. Our results suggest a non-linear relationship between changes in stability and equilibrium demands of a task and the contribution of TNS to trunk bending stiffness. Specifically, alterations in TNS response to changes in stability and equilibrium demand of a given task will increase stiffness of the trunk only if the background stiffness is low.
Objective
To assess the efficacy of two different passive back-support exoskeleton (BSE) designs, in terms of trunk muscle activity, perceived low-back exertion, and task performance.
Background
BSEs ...have the potential to be an effective intervention for reducing low-back physical demands, yet little is known about the impacts of different designs in work scenarios requiring varying degrees of symmetric and asymmetric trunk bending during manual assembly tasks.
Method
Eighteen participants (gender balanced) completed lab-based simulations of a precision manual assembly task using a “grooved pegboard.” This was done in 26 different conditions (20 unsupported; 6 supported, via a chair), which differed in vertical height, horizontal distance, and orientation.
Results
Using both BSEs reduced metrics of trunk muscle activity in many task conditions (≤47% reductions when using BackX™ and ≤24% reductions when using Laevo™). Such reductions, though, were more pronounced in the conditions closer to the mid-sagittal plane and differed between the two BSEs tested. Minimal effects on task completion times or ratings of perceived exertion were found for both BSEs.
Conclusion
Our findings suggest that using passive BSEs can be beneficial for quasi-static manual assembly tasks, yet their beneficial effects can be task specific and specific to BSE design approaches. Further work is needed, though, to better characterize this task specificity and to assess the generalizability of different BSE design approaches in terms of physical demands, perceived exertion, and task performance.
Application
These results can help guide the choice and application of passive BSE designs for diverse work scenarios involving nonneutral trunk postures.
Abstract Background Context Heterogeneity exists within the low back pain population. Some patients recover after every pain episode, whereas others suffer daily from LBP complaints. Until now, ...studies rarely make a distinction between recurrent low back pain (RLBP) and chronic low back pain (CLBP), although both are characterized by a different clinical picture. Clinical experiences also indicate that heterogeneity exists within the CLBP population. Muscle degeneration, like atrophy, fat infiltration, alterations in muscle fiber type and altered muscle activity, compromises proper biomechanics and motion of the spinal units in low back pain (LBP) patients. The amount of alterations in muscle structure and muscle function of the paraspinal muscles, might be related to the recurrence or chronicity of LBP. Purpose The aim of this experimental study is to evaluate differences in muscle structure (cross-sectional area and lean muscle fat index) and muscle activity of the multifidus (MF) and erector spinae (ES) during trunk extension, in patients with RLBP, non-continuous CLBP and continuous CLBP. Study Design and Setting This cross-sectional study took place in the University hospital of Ghent, Belgium. Muscle structure characteristics and muscle activity were assessed by magnetic resonance imaging (MRI). Patient Sample Fifty five adults with non-specific low back pain (24 RLBP in remission, 15 non-continuous CLBP, 16 continuous CLBP) participated in this study. Outcome Measures Total cross-sectional area, muscle cross-sectional area, fat cross-sectional area, lean muscle fat index, T2-rest and T2-shift were assessed. Methods A T1-weighted Dixon MRI scan was used to evaluate spinal muscle cross-sectional area and fat infiltration in the lumbar MF and ES. Muscle functional MRI was used to evaluate the muscle activity of the lumbar MF and ES during a lumbar extension exercise. Before and after the exercise, a pain assessment was performed. This study was supported by grants from the Special Research Fund of Ghent University (DEF12/AOP/022) without potential conflict of interest-associated biases in the text of the paper. Results Fat cross-sectional area and lean muscle fat index was significantly higher in MF and ES in continuous CLBP compared to non-continuous CLBP and RLBP (p<0.05). No differences between groups were found for total cross-sectional area and muscle cross-sectional area in MF or ES (p>0.05). Also no significant differences between groups for T2-rest were established. T2-shift, however, was significantly lower in MF and ES in RLBP compared to respectively non-continuous CLBP and continuous CLBP (p<0.05). Conclusion These results indicate a higher amount of fat infiltration in the lumbar muscles, in the absence of clear atrophy, in continuous CLBP compared to RLBP. A lower metabolic activity of the lumbar muscles was seen in RLBP replicating a relative lower intensity in contractions performed by the lumbar muscles in RLBP compared to non-continuous and continuous CLBP. In conclusion, RLBP differ from continuous CLBP for both muscle structure and muscle function, whereas non-continuous CLBP seem comparable with RLBP for lumbar muscle structure and with continuous CLBP for lumbar muscle function. These results underline the differences in muscle structure and muscle function between different LBP populations.
One of the primary changes in the neuromuscular system in response to microgravity is skeletal muscle atrophy, which occurs especially in muscles that maintain posture while being upright on Earth. ...Reduced size of paraspinal and abdominal muscles has been documented after spaceflight. Exercises are undertaken on the International Space Station (ISS) during and following space flight to remediate these effects. Understanding the adaptations which occur in trunk muscles in response to microgravity could inform the development of specific countermeasures, which may have applications for people with conditions on Earth such as low back pain (LBP).
The aim of this study was to examine the changes in muscle size and function of the lumbar multifidus (MF) and anterolateral abdominal muscles (1) in response to exposure to 6 months of microgravity on the ISS and (2) in response to a 15-day reconditioning program on Earth.
Prospective longitudinal series.
Data were collected from five astronauts who undertook seven long-duration missions on the ISS.
For the MF muscle, measures included cross-sectional area (CSA) and linear measures to assess voluntary isometric contractions at vertebral levels L2 to L5. For the abdominal muscles, the thickness of the transversus abdominis (TrA), obliquus internus abdominis (IO) and obliquus externus abdominis (EO) muscles at rest and on contraction were measured.
Ultrasound imaging of trunk muscles was conducted at four timepoints (preflight, postflight, mid-reconditioning, and post reconditioning). Data were analyzed using multilevel linear models to estimate the change in muscle parameters of interest across three time periods.
Beta-coefficients (estimates of the expected change in the measure across the specified time period, adjusted for the baseline measurement) indicated that the CSA of the MF muscles decreased significantly at all lumbar vertebral levels (except L2) in response to exposure to microgravity (L3=12.6%; L4=6.1%, L5=10.3%; p<.001), and CSAs at L3-L5 vertebral levels increased in the reconditioning period (p<.001). The thickness of the TrA decreased by 34.1% (p<.017), IO decreased by 15.4% (p=.04), and the combination of anterolateral abdominal muscles decreased by 16.2% (p<.001) between pre- and postflight assessment and increased (TrA<0.008; combined p=.035) during the postreconditioning period. Results showed decreased contraction of the MF muscles at the L2 (from 12.8% to 3.4%; p=.007) and L3 (from 12.2% to 5%; p=.032) vertebral levels following exposure to microgravity which increased (L2, p=.046) after the postreconditioning period. Comparison with preflight measures indicated that there were no residual changes in muscle size and function after the postreconditioning period, apart from CSA of MF at L2, which remained 15.3% larger than preflight values (p<.001).
In-flight exercise countermeasures mitigated, but did not completely prevent, changes in the size and function of the lumbar MF and anterolateral abdominal muscles. Many of the observed changes in size and control of the MF and abdominal muscles that occurred in response to prolonged exposure to microgravity paralleled those seen in people with LBP or exposed to prolonged bed rest on Earth. Daily individualized postflight reconditioning, which included both motor control training and weight-bearing exercises with an emphasis on retraining strength and endurance to re-establish normal postural alignment with respect to gravity, restored the decreased size and control of the MF (at the L3-L5 vertebral levels) and anterolateral abdominal muscles. Drawing parallels between changes which occur to the neuromuscular system in microgravity and which exercises best recover muscle size and function could help health professionals tailor improved interventions for terrestrial populations. Results suggested that the principles underpinning the exercises developed for astronauts following prolonged exposure to microgravity (emphasizing strength and endurance training to re-establish normal postural alignment and distribution of load with respect to gravity) can also be applied for people with chronic LBP, as the MF and anterolateral abdominal muscles were affected in similar ways in both populations. The results may also inform the development of new astronaut countermeasures targeting the MF and abdominal muscles.
Context:
Enhancing core stability through exercise is common to musculoskeletal injury prevention programs. Definitive evidence demonstrating an association between core instability and injury is ...lacking; however, multifaceted prevention programs including core stabilization exercises appear to be effective at reducing lower extremity injury rates.
Evidence Acquisition:
PubMed was searched for epidemiologic, biomechanic, and clinical studies of core stability for injury prevention (keywords: “core OR trunk” AND “training OR prevention OR exercise OR rehabilitation” AND “risk OR prevalence”) published between January 1980 and October 2012. Articles with relevance to core stability risk factors, assessment, and training were reviewed. Relevant sources from articles were also retrieved and reviewed.
Results:
Stabilizer, mobilizer, and load transfer core muscles assist in understanding injury risk, assessing core muscle function, and developing injury prevention programs. Moderate evidence of alterations in core muscle recruitment and injury risk exists. Assessment tools to identify deficits in volitional muscle contraction, isometric muscle endurance, stabilization, and movement patterns are available. Exercise programs to improve core stability should focus on muscle activation, neuromuscular control, static stabilization, and dynamic stability.
Conclusion:
Core stabilization relies on instantaneous integration among passive, active, and neural control subsystems. Core muscles are often categorized functionally on the basis of stabilizing or mobilizing roles. Neuromuscular control is critical in coordinating this complex system for dynamic stabilization. Comprehensive assessment and training require a multifaceted approach to address core muscle strength, endurance, and recruitment requirements for functional demands associated with daily activities, exercise, and sport.
This study aimed to investigate how skeletal muscle attenuation and adipose tissue (AT) attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle vary according to the ...targeted muscles, sex, and age.
Population-based cross-sectional study.
Community-dwelling old population in Reykjavik, Iceland.
A total of 5331 older adults (42.8% women), aged 66–96 years from the Age, Gene/Environment Susceptibility (AGES)- Reykjavik Study, who participated in the baseline visit (between 2002 and 2006) and had valid thigh and abdominal computed tomography (CT) scans were studied.
Muscle attenuation and AT attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle were determined using CT. Linear mixed model analysis of variance was performed for each sex, with skeletal muscle or AT attenuation as the dependent variable.
Muscle attenuation decreased, and AT attenuation increased with age in both sexes, and these differences were specific for each muscle, although not in all age groups. Age-related differences in muscle and AT attenuation varied with specific muscle. In general, for both sexes, skeletal muscle attenuation of the hamstrings declined more than average with age. Men and women displayed a different pattern in the age differences in AT attenuation for each muscle.
Our data support the hypotheses that skeletal muscle attenuation decreases, and AT attenuation increases with aging. In addition, our data add new evidence, supporting that age-related differences in skeletal muscle and AT attenuation vary between muscles.
•Overall, skeletal muscle attenuation decreases, and adipose tissue (AT) attenuation increases during aging.•Muscle and AT attenuation followed a distinctive pattern of change depending on the age group.•Muscle and AT attenuation are dependent on sex and muscle group.•The hamstrings muscle attenuation declined more than average with age.
We report the case of a man in his 80s who presented with left hemiplegia due to atherothrombotic cerebralinfarction. The man turned to the right side and tried to get out of bed but could not. This ...is because hewas unable to rotate the body to the right and was unable to swing both legs out to the edge of the bed. Wehypothesized that the cause of his inability to rotate the body to the right was deterioration of trunk functionon the paralyzed side. Physical therapy evaluation revealed hypotonia in the paralyzed rectus abdominismuscle and paralyzed external oblique muscle. Physical therapy was performed to improve muscle tone in theparalyzed trunk muscles. As a result of physical therapy, the muscle tone of the trunk muscle on the paralyzedside improved, and the man was able to get up from the bed on the right side.
We report the case of a man in his 80s who presented with left hemiplegia due to atherothrombotic cerebralinfarction. The man turned to the right side and tried to get out of bed but could not. This ...is because hewas unable to rotate the body to the right and was unable to swing both legs out to the edge of the bed. Wehypothesized that the cause of his inability to rotate the body to the right was deterioration of trunk functionon the paralyzed side. Physical therapy evaluation revealed hypotonia in the paralyzed rectus abdominismuscle and paralyzed external oblique muscle. Physical therapy was performed to improve muscle tone in theparalyzed trunk muscles. As a result of physical therapy, the muscle tone of the trunk muscle on the paralyzedside improved, and the man was able to get up from the bed on the right side.
Postural control during walking is maintained by the combination of various factors. Among these factors, adjustment of trunk movement is essential for maintaining postural control, and the response ...of muscles to unpredictable stimuli affects postural control. Loss of balance while walking increases the risk of accidents, the frequency of which depends on age and sex. In this study, we investigated whether there was a difference in the movement time of trunk muscles to sudden stimulation while walking according to age and sex. Fourteen healthy individuals aged 20–30 years (6 men, 8 women) and 12 individuals aged 50–70 years (4 men, 8 women) were included in the study. Movement time of bilateral erector spinae and rectus abdominis muscles in response to visual stimulation during walking was examined using surface electromyography. Movement time was calculated as the total muscle activation time excluding the reaction time. This study revealed no significant differences in movement time of the erector spinae muscles according to sex or age. The role of the rectus abdominis muscles in maintaining posture during walking was insignificant. In conclusion, the movement time of trunk muscles in response to sudden visual stimulation during walking did not differ by age or sex, and the difference in accident frequency may be associated with deterioration of other factors required to maintain posture.
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