Maintenance Of Upright Posture Research Articles

Skeletal Muscle Extracellular Matrix - What Do We Know About Its Composition, Regulation, and Physiological Roles? A Narrative Review.

Skeletal muscle represents the largest body-composition component in humans. In addition to its primary function in the maintenance of upright posture and the production of movement, it also plays important roles in many other physiological processes, including thermogenesis, metabolism and the secretion of peptides for communication with other tissues. Research attempting to unveil these processes has traditionally focused on muscle fibers, i.e., the contractile muscle cells. However, it is a frequently overlooked fact that muscle fibers reside in a three-dimensional scaffolding that consists of various collagens, glycoproteins, proteoglycans, and elastin, and is commonly referred to as extracellular matrix (ECM). While initially believed to be relatively inert, current research reveals the involvement of ECM cells in numerous important physiological processes. In interaction with other cells, such as fibroblasts or cells of the immune system, the ECM regulates muscle development, growth and repair and is essential for effective muscle contraction and force transmission. Since muscle ECM is highly malleable, its texture and, consequently, physiological roles may be affected by physical training and disuse, aging or various diseases, such as diabetes. With the aim to stimulate increased efforts to study this still poorly understood tissue, this narrative review summarizes the current body of knowledge on (i) the composition and structure of the ECM, (ii) molecular pathways involved in ECM remodeling, (iii) the physiological roles of muscle ECM, (iv) dysregulations of ECM with aging and disease as well as (v) the adaptations of muscle ECM to training and disuse.

Distinguishing Two Types of Variability in a Sit-to-Stand Task.

Variability is commonly observed in complex behavior, such as the maintenance of upright posture. The current study examines the value added by using nonlinear measures of variability to identify dynamic stability instead of linear measures that reflect average fluctuations about a mean state. The largest Lyapunov exponent (λ1) and SD were calculated on mediolateral movement as participants performed a sit-to-stand task on a stable and unstable platform. Both measures identified changes in movement across postures, but results diverged when participants stood on the unstable platform. Large SD indicated an increase in movement variability, but small λ1 identified those movements as stable and controlled. The results suggest that a combination of linear and nonlinear analyses is useful in identifying the proportion of observed variability that may be attributed to structured, controlled sources. Nonlinear measures of variability, like λ1, can further be used to make predictions about transitions between stable postures and to identify a system's resistance to disruption from external perturbations. Those features make nonlinear analyses highly applicable to both human movement research and clinical practice.

The Effect of Paravertebral Muscle on the Maintenance of Upright Posture in Patients With Adult Spinal Deformity

ObjectiveWe investigated the relationship between cross-sectional area (CSA) of paravertebral muscle and trunk tilt at standing and walking in adult spinal deformity (ASD) surgery. Summary of Background DataAlthough the importance of back muscles for the development of spinal kyphosis was well described, the influence on maintaining the sagittal balance was unclear. MethodsForty-five female patients (mean age, 68.8 years) with ASD were studied. We measured sagittal vertical axis [SVA], pelvic tilt [PT], and pelvic incidence–lumbar lordosis [PI-LL]) by lateral spine radiograph. For the assessment of trunk tilt standing-trunk tilt angle (STA) by lateral standing radiograph, gait-trunk tilt angle (GTA) by lateral gait images, and the increasing trunk tilt angle (ITA) by subtracting the STA from the GTA were calculated. Using L1/2 and L4/5 axial MRI, the CSAs of bilateral multifidus muscles (MF) and elector spinae (ES) removed fat by Image J software were calculated. We examined the correlation between trunk tilt angle (STA, GTA, and ITA) and spinopelvic parameters (SVA, PT, and PI minus LL) and also the correlation among muscle CSA, trunk tilt angle (STA, GTA, and ITA), and Oswestry Disability Index (ODI). ResultsThe mean STA, GTA, and ITA were 4.2°, 13.0°, and 8.8°, respectively. The CSAs of back muscles were 278 mm2 at L1/2 MF, 1,687 mm2 at L1/2 ES, 636 mm2 at L4/5 MF, and 1,355 mm2 at L4/5 ES, respectively. Trunk tilt angle had significant relations with spinopelvic parameters. Concerning about muscle CSA, significant correlations were observed between STA and L4/5 MF (r = −0.517), GTA and L1/2 ES (r = −0.461) and L4/5 MF (r = −0.476), and ITA and L1/2 ES(r = −0.429). ODI showed significant correlation with STA and GTA. ConclusionsParavertebral muscles were crucial to keep upright posture during walking as well as standing.

Effect of sensory-motor latencies and active muscular stiffness on stability for an ankle-hip model of balance on a balance board

To achieve human upright posture (UP) and avoid falls, the central nervous system processes visual, vestibular, and proprioceptive information to activate the appropriate muscles to accelerate or decelerate the body’s center of mass. In this process, sensory-motor (SM) latencies and muscular deficits, even in healthy older adults, may cause falls. This condition is worse for people with chronic neuromuscular deficits (stroke survivors, patients with multiple sclerosis or Parkinson’s disease). One therapeutic approach is to recover or improve quiet UP by utilizing a balance board (BB) (a rotating surface with a tunable stiffness and time delay), where a patient attempts to maintain UP while task difficulty is manipulated. While BBs are commonly used, it is unclear how UP is maintained or how changes in system parameters such as SM latencies and BB time delay affect UP stability. To understand these questions, it is important that mathematical models be developed with enough degrees-of-freedom to capture the many responses evoked during the maintenance of UP on a BB. This paper presents an ankle-hip model of balance on a BB, which is used to study the combined effect of SM latencies and active muscular stiffness of the ankle and hip joints, and the BB stiffness and time delay on UP stability. The analysis predicts that people with proprioceptive, visual, vestibular loss, or increased SM latencies may show either leaning postures or larger body-sway. The results show that the BB time delay and the visual and vestibular feedback have the largest impact on UP stability.

Influence of passive tactile contact of arms on the maintenance of upright posture in humans

The influence of light passive contact of the forearm with a pliable external object (flexible plate) on the maintenance of upright posture was studied in healthy subjects in several conditions, with the eyes closed and on immersion in a virtual visual environment (VVE). The visual environment was either stable or unstable as a result of a synphase (SP) or antiphase (AP) association between the environment and body sway. The posture maintenance analysis focused on estimating the amplitude and frequency characteristics of two elementary variables, which were calculated from the foot center of pressure (CoP) trajectories in the mediolateral and anteroposterior directions. The variables were trajectory of the vertical projection of the center of gravity (variable CG) and difference between the CoP and CG trajectories (variable CoP–CG). In both the absence and presence of passive tactile contact, the root mean square (RMS) values of the oscillation spectra of the two variables were the lowest in the stable visual environment and in the case of the antiphase association of the environment with body sways and the highest in the cases of the synphase association and standing with the eyes closed. Passive contact decreased body sways in both directions, and the RMSs of the spectra of the two variables decreased in all visual conditions. A greater decrease in RMS was observed for the CG variable. Body sways changed not only in amplitude, but also in frequency. Tactile contact increased the median frequencies (MFs) of the CG variable spectra calculated from the anteroposterior and mediolateral body sways. In contrast, a significant increase in MFs calculated for the CoP–CG variable was observed only for anteroposterior body sways. The results showed that passive contact of a forearm with a pliable external object, which does not provide a mechanical support for the subject, significantly improves the maintenance of the upright posture even in an unstable visual environment.

Impact of Fatigue on Maintenance of Upright Posture

Retrospective analysis of prospectively collected data. To assess global and regional spinal sagittal radiographic parameters in adults with loss of lumbar lordosis ("flatback") before and after walking 10 minutes. While routine activities of daily living may exacerbate functional disability of spinal sagittal-plane deformity, there is limited understanding of how sagittal parameters and compensatory mechanisms are affected by activity. Consecutive adults with "flatback" at a single institution who previously had full-length standing spinal radiographs before and after walking 10 minutes were reviewed. Changes in spinal deformity sagittal parameters before and after walking were evaluated for two groups: Compensated Sagittal Deformity ("Compensated": sagittal vertical axis [SVA] ≤4 cm and pelvic tilt [PT] >20°) and Decompensated Sagittal Deformity ("Decompensated": SVA>4 cm and PT>20°). Intra-group radiographic comparisons were performed with paired Student t tests. One hundred fifty-seven patients (143 females, 14 males; average age 67.9 ± 5.9 yr) met inclusion criteria. Initial average SVA was 1.7 ± 1.2 cm for "Compensated" and 11.5 ± 6.4 cm for "Decompensated." After walking 10 minutes, significant deteriorations in average SVA were observed for all "Decompensated" patients and 84.6% of "Compensated" patients. For both groups, this was accompanied by significant decreases in PT and LL and increases in PI-LL (P <0.01). Thoracic kyphosis increased after walking for only "Decompensated" (P <0.01). For "Compensated," the change in SVA was determined by decreases in PT and LL, while changes in SVA for "Decompensated" were correlated to worsening of all sagittal parameters. After walking, compensatory mechanisms to maintain sagittal balance in adults with spinal deformity are less pronounced than when the patient initially presents. This results in significant sagittal decompensation, irrespective of the initial SVA. As we postulate that loss of compensatory mechanisms is due to fatigue on pelvic and spinal extensor muscles, sagittal parameters can be re-evaluated with radiographs obtained after patients walk 10 minutes to unmask a hidden sagittal imbalance in compensated deformities. 3.

Coordination of body segments during turning in healthy adults: A review

Turning around to interact with the environment is a common activity of daily living. Coordination of body segments during turning is very important for the maintenance of upright posture. The aim of this review was to provide information about coordination of body segments during turning in health adults to serve as a yardstick for identifying turning problems in patients with neurological problems. Literature search was conducted through CINHAL, EMBASE, MEDLINE, and Google Scholar from inception to 2012 using the following search terms: coordination and turning, onset latency and turning, and peak velocity and turning. The present review has shown that turning to predictable targets results in a separate top to bottom sequence of onset of rotation of body segments, while turning to predictable targets results in a more simultaneous onset of rotation of the segments. On the contrary, the angle or direction a person turns to does not affect the sequence of rotation of body segments during turning. The peak velocity of the head was shown to be higher than that of the shoulder and pelvis when turning on-the-spot. The head was also shown to reach its peak velocity earlier than the shoulder and pelvis. However, the effect of the predictability of a target, turn angle, and turn direction on either the peak velocity or the time to reach the peak velocity has not been reported. The onset of rotation of body segments during turning while walking was shown to be in a top to bottom sequence. Alteration of the normal sequence of rotation of segments during turning could challenge the balance of an individual and may subsequently result into falls.

The Impact of Core Stabilization Exercise Therapy on Perception of Verticality in Adoescent Idiopathic Scoliosis

Accurate perception of verticality is important in maintenance of upright posture and gait. It is believed that abnormal postural sway present in patients with adolescent idiopathic scoliosis (AIS) may be related to their perception of body orientation in space. PURPOSE: To investigate the effects of core stabilization exercises on perception of verticality which is represented by subjective visual vertical (SVV), subjective postural vertical (SPV) and subjective haptic vertical (SHV) in patients with AIS. METHODS: Twelve female subjects with AIS were included in this study. Mean age was 14,5±1,7 years. The average Cobb angle of the major curve was 28±13° for thoracic and 24±7° for lumbar regions (range: 10°-54°). According to the King-Moe classification, Type I curve was evident in three patients, Type II in seven, Type III in one and Type IV in four. The SVV, SPV and SHV tests were assessed by seating subjects in a chair and instructing them to adjust laser line projections in the directions of vertical, horizontal and at the angles of 30°, 45°, and 60° in a dark room before and after training. The performance, expressed as the deviation from each line (measured in degrees), was calculated by the examiner. Training consists of core stabilization exercises and active self-correction performed two times per week for twelve weeks. RESULTS: In SVV test, accuracy of perception of horizontal, vertical, 30° right, 60° right was improved after treatment (p<0.05). Also in SPV test, better values seemed in vertical, 30° left and 60° left after treatment (p<0.05). In SHP, 45° left was improved (p<0.05). We found no significant difference in other subtests (p>0,05). CONCLUSION: The present study shows that perception of verticality in AIS can be improved with core stabilization exercise therapy.

Attentional influences on the performance of secondary physical tasks during posture control

We examined the influence of attentional focus and cognitive load on motor performance in a dynamic stick balancing task during the maintenance of upright posture. Dynamical analyses of postural fluctuations revealed the existence of a drift and correct mechanism, with correlational structure reflecting the demands of the stick balancing task. In contrast, experimentally manipulated attentional foci (internal, external) did not influence the variability of postural or fingertip trajectories. However, dual-task cognitive stick balancing performance resulted in decreased variability of postural and fingertip time series. These results are discussed in the context of dual timescale models for posture control and stick balancing.

Psoas Major Muscle In Elderly Female Rowers

The psoas major muscle (PM), which is recruited for hip/lumber stabilization and during hip joint flexion, plays an important role in maintenance of upright posture and walking. The age-related wasting of PM size is more remarkable than quadriceps femoris muscle. Rowing exercise, which includes hip joint flexion, may be categorized as one of the exercise mode for maintaining PM size and functions. We showed that elderly rowing trained men had larger PM than age-matched untrained men (MSSE, 40(5)suppl.:371, 2008). However, little is known whether rowing exercise can prevent the wasting and weakness of PM in elderly women. b>PURPOSE: The purpose of this study was to evaluate the effects of regularly performed-rowing exercise on the morphology and function of PM in elderly women. METHODS: Participants were 8 elderly female rowers (ER: age 64.1±4.6 yrs, BMI 20.7±0.8 kg/m2, mean±SD), 14 age-matched female walkers as active control group (EC: 62.8±3.8 yrs, 21.6±2.3 kg/m2) and 6 young untrained women (YC: 21.5±1.0 yrs, 20.2±0.9 kg/m2). Elderly rowers and walkers performed rowing or walking exercise regularly twice a week and each session 60-120 min. Muscle cross-sectional area (CSA) of PM scanned by magnetic resonance imaging and bilateral leg extension power were measured. RESULTS: The CSA of PM in EC was 33% lower than that in YC (p<0.001). ER had 74% higher CSA of PM than EC (p<0.001), which was comparable to that of YC (YC: 9.4±1.3 cm2, EC: 6.2±1.0 cm2, ER: 8.7±1.7 cm2, mean±SD). The leg extension power in EC was 28% lower than that in YC (YC: 853±221 W vs EC: 616±148 W, p<0.05), whereas there was no significant difference between ER and YC (ER: 704±154 W). The CSAs of PM was strongly associated with leg extension power (r=0.914, p<0.001). Furthermore, partial correlation analysis revealed that PM is strong independent predictor of leg extension power(r=0.585, p<0.001). CONCLUSIONS: These results provide the possibility that PM plays an important role in the muscle function of leg extension, and that rowing exercise can prevent age-related decline in PM in women as well as men.

Can tactile plantar stimulation improve postural control of persons with superficial plantar sensory deficit?

Complex interactions between visual, vestibular and somatosensory information and the cerebellar system are involved in the maintenance of upright posture. Previous studies have shown that normal aging and pathologies may lead to deterioration of the control of upright standing posture. In order to investigate postural control during quiet standing in the elderly, the center of pressure (CoP) was analysed on two force platforms in three different groups. The first group was composed of 13 healthy older adults (O), the second consisted of 9 older adults with plantar sole deficit (OD), and the third (control) group was composed of 8 young healthy subjects (Y). All subjects were tested with eyes closed, before and after tactile plantar stimulation lasting ten minutes. Center of pressure displacements were analyzed in terms of sway area, mean velocity, and mean root mean square (RMS) along both mediolateral and antero-posterior axes. Results showed that, before tactile plantar stimulation, the sway area and mean RMS were greater in O and OD subjects compared with Y ones. After tactile plantar stimulation, a decrease in the mean RMS was observed in OD subjects, this effect being significant only for the medio-lateral axis. These results suggest that application of tactile plantar stimulation may compensate a loss of superficial plantar sensitivity.

Musculature and biomechanics of the trunk in the maintenance of upright posture

Surface perturbation has been used for decades to study balance and postural control; however the behavior of the trunk in these postural responses has been largely overlooked. Thirteen healthy males (18–23 yrs) were exposed to horizontal support surface translations delivered randomly in one of eight different horizontal directions in both sitting and standing. A 4-segment model of the trunk was used to estimate the kinematics and kinetics associated with the postural response, while surface EMG was acquired, bilaterally, from seven trunk muscles and one hip muscle. Multi-segmental movement was observed in the trunk in both test postures. Both the biomechanical and neuromuscular aspects of the trunk response were significantly affected by translation direction and test posture, with an interaction effect between these variables. The response in sitting was closely tied to the movement of the support surface, while the response in standing occurred in two phases: the first related to the dynamic response in the lower limbs, and the second tied to the movement of the support surface. As such, the observed postural responses could be largely explained by the biomechanical constraints of the system, such that the neural control of trunk equilibrium is simplified.

Virtual time-to-contact of postural stability boundaries as a function of support surface compliance

This study investigated the hypothesis that virtual time-to-contact, which specifies the time to reach the functional stability boundary, is a variable controlled in the maintenance of upright posture. Three different levels of support surface compliance were used on a force platform (no foam, 5 cm of foam, and 15 cm of foam). The participant's task was to stand still under each surface support condition both with and without vision. The stability boundary was determined for each set of conditions where the participant was required to lean as far as possible in all directions of the horizontal plane without losing stability. The results showed that the no vision conditions had a significantly larger center of pressure displacement than the vision conditions. No vision and increasing support surface compliance also increased the velocity of the center of pressure trajectory. The distribution of the radial displacement of the center of pressure showed relatively equal frequency over spatial location with no central tendency. The virtual time-to-contact with the stability boundary decreased as platform surface support became more compliant. Furthermore, the distribution of virtual time over the effective scaling range was a power law with a larger exponent in the more unstable no vision and increasing surface foam conditions. The findings provide additional evidence for the hypothesis that virtual time-to-contact with stability boundaries is a postural control variable that is regulated rather than the preservation of minimal motion around the center of the stability region as proposed in pendulum models of posture.

Muscle length assessment of tightness-prone muscles

The muscles of the human body may be divided into two groups, postural and phasic. The postural muscles are those involved primarily in maintenance of upright posture while the phasic muscles are those primarily involved in movement. These two groups of muscles react in distinct ways to musculoskeletal injury and even to the ordinary stresses of daily life. The postural muscles tend to become short and tight while the phasic muscles tend to become weak and inhibited. Tightness of postural muscles is extremely common and can initiate a cascade of changes in locomotor system function which often lead to pain. In our desire to provide thorough and effective care to our patients, we may wish to include examination and treatment for loss of normal muscle length in our treatment protocol. A standardized, step-by-step procedure for length assessment of key postural muscles is presented, as developed by Professor Vladimir Janda, of the Department of Rehabilitation Medicine, Charles University Hospital in Prague.

How to Construct and Move a Cat's Neck

Extensive information has been accumulated over the past several years about the head-neck sensory-motor system, in particular that relating to cats. Using still x-ray and cineradiographic analysis, the skeletal geometry of head-neck posture in three dimensions--when an animal is resting, actively orienting, or locomoting--is described. From these descriptions, cervical, vertebral, and craniocervical joint biomechanics for all three rotational dimensions are quantified. These behavioral data on muscle and skeletal movements have been incorporated in a biomechanical, functional anatomical model of the head-neck movement system. Individual as well as groups of neck muscles have been measured in detail and their kinematics determined. The role of a number of these muscles will be described for several reflex and voluntary behavioral contexts, including muscle co-contractions. Having established how each movement is accomplished, the neuronal sensory-motor reflex basis of head-neck system stabilization in space is addressed. The vestibular system is largely responsible for acquisition and maintenance of upright posture. The bilateral semicircular canals (horizontal, anterior, posterior) and otoliths (sacculus, utriculus) feed information differentially to specific neck muscles: these connections are reviewed with regard to the origin of the reflex are from each receptor to its destination of specific muscles. Behavioral data from normal animals, and from animals whose vestibular receptor systems are selectively lesioned, will be reviewed to complement the functional interpretation of the sensory-motor transformations. Finally, the requirements for space-time coordinated cat head-neck movements will be synthesized, based on biomechanics, muscle kinematics, canal/otolith connectivity, and selective lesion experiments.

The roles of the labyrinth and proprioception in the maintenance of upright posture

The roles of the labyrinth and proprioception in the maintenance of upright posture

Comparison of level and up-hill gait after gastrocnemius/soleus muscle flap

The muscles of the human body may be divided into two groups, postural and phasic. The postural muscles are those involved primarily in maintenance of upright posture while the phasic muscles are those primarily involved in movement. These two groups of muscles react in distinct ways to musculoskeletal injury and even to the ordinary stresses of daily life. The postural muscles tend to become short and tight while the phasic muscles tend to become weak and inhibited. Tightness of postural muscles is extremely common and can initiate a cascade of changes in locomotor system function which often lead to pain. In our desire to provide thorough and effective care to our patients, we may wish to include examination and treatment for loss of normal muscle length in our treatment protocol. A standardized, step-by-step procedure for length assessment of key postural muscles is presented, as developed by Professor Vladimir Janda, of the Department of Rehabilitation Medicine, Charles University Hospital in Prague.

Dose–related effect of triazolam on postural sway

Measurement of clinically relevant benzodiazepine drug effects at hypnotic and anxiolytic doses has been difficult because most measures are subjective, difficult to interpret, or relate to anesthetic doses. A potentially useful measure of drug effect is postural sway, which is a manifestation of the corrective mechanisms associated with the maintenance of upright posture. Postural sway was measured over 8 hours, with a biomechanics force platform, in six healthy male volunteers who received triazolam, 0.125, 0.250, or 0.375 mg, or placebo in a randomized double-blind study. Our results show a dose-dependent increase in postural sway measured as the elliptical area or the 95% confidence ellipse for the area covered by the subjects' sway. After triazolam, 0.250 and 0.375 mg, the area under the sway-time curve and peak effect increased significantly compared with placebo (p less than 0.05). The number of losses of balance when subjects stood on one foot also showed a significant increase with increased dose (p less than 0.05). The rate of loss of balance was positively correlated with the extent of postural sway (r = 0.802; p less than 0.001). The extent of sway when the subjects were drug free predicted this increase in a subject's postural sway with triazolam. Thus at hypnotic or anxiolytic doses of triazolam, computer-assisted force platform measures of sway provide a clinically relevant measure of drug effect. Measurement of drug-induced postural sway may be useful in persons at risk for falls, such as the elderly.

Assessment of balance control in the elderly: major issues

One of the major concerns among the elderly is the high frequency of falls. As an initial step toward reducing falls, it is imperative to characterize those changes in the balance control system that are only "age-related." One approach is to identify the response characteristics to experimentally simulated conditions that can cause falls or near falls. The simulations used and the measures currently taken are varied. The tests include assessment of: (a) static unperturbed balance; (b) maintenance of upright posture under perturbation; (c) normal walking characteristics; and (d) maintenance of balance under perturbations introduced while the subjects are walking. The measurements range from simple time measures, centre of pressure, estimates of centre of gravity, and muscle activity levels. A number of important issues related to each of these paradigms are discussed, including the subject selection procedures. The advantages and limitations of the tests and measures used are discussed along with their potential predictive capabilities.

Visual Factors in the Maintenance of Upright Posture

Visual Factors in the Maintenance of Upright Posture