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PubMed1980

Influence of a diagonal postural pattern on parameters of movement and associated postural adjustment in the cat.

The aim of this study was to investigate the influence of initial posture on the latency and amplitude of a movement and the postural adjustment associated with it. The movement studied was a limb flexion induced by stimulation of the motor cortex in chronically implanted cats. Only weak stimulations were used and the motor activity was mainly isometric, which facilitated the quantification of responses, analysed by measuring vertical forces exerted at the level of each limb. The initial posture consisted of the diagonal force pattern induced by stimulation of another cortical site corresponding to a different limb. The choice of this cortical site depended on the desired direction of force changes for the initial posture, i.e. either in the same direction as those accompanying the movement or in the opposite direction. The conditioning stimulation leading to the initial posture was triggered only when the computer analysing postural parameters showed a stable and balanced posture. Within the limits of the experimental method utilized, the following results have been established: 1. The latency of onset of the test movement and its associated postural adjustment were independent of initial posture. 2. The peak forces recorded were constant for a given stimulation intensity, and independent of initial force values. This shows that the amplitudes of force variations depend on the initial values: in the case of a low initial value the force variation must be greater to reach the same extreme value as in the case of a high initial value. Thus, the same stimulus intensity can induce different motor activities depending on the initial conditions.

Animals↗
PubMed2005

Can stooped posture explain multidirectional postural instability in patients with Parkinson's disease?

To determine the effects of the stooped posture of patients with Parkinson's disease (PD) on postural stability, we compared the kinetic, kinematic, and electromyographic responses of seven subjects with PD and 11 control subjects to eight directions of surface translations. Control subjects were studied in an upright posture and in a stooped posture that mimicked the posture of the PD subjects. When control subjects adopted a stooped posture, peak center of pressure displacements slowed and decreased, reducing stability margins toward values observed in PD subjects. Stooped control subjects, however, responded to translations with large joint angle displacements, whereas PD subjects exhibited small joint angle displacements. Stooping in control subjects did not lead to abnormally directed horizontal forces under each foot or antagonistic muscle co-activation at the hip and trunk, as seen in PD subjects. Upright and stooped control subjects never fell during the trials, whereas PD subjects fell in 16% of the trials. We conclude that stooped posture is a destabilizing posture, but it does not account for abnormal postural responses in PD.

Aged↗
PubMedDate not supplied

Sitting posture of subjects with postural backache.

OBJECTIVE: To test the construct validity of postural backache. To identify if individuals with backache sit for longer periods of sustained sitting and have more flexed relaxed sitting posture than individuals in a no backache group. METHODS: Following an initial questionnaire, student volunteers without a history of 'serious' back pain were classified as either postural backache group or no backache group. With the use of an activity diary that plotted activity every 5 minutes over a 3-day period, the average time spent in different postures was established. Relaxed sitting posture was evaluated using Dartfish software to analyze videotape after 10 minutes of sitting. RESULTS: The most common daytime activity of both groups was sitting, with average sitting time not significantly different between groups. Periods of uninterrupted sustained sitting and uninterrupted sustained studying were significantly longer, and the degree of flexion in relaxed sitting was significantly greater in the postural backache group (all P < .024). CONCLUSION: In a group of student volunteers, half reported postural backache. The group with backache sat for longer periods without interruption and had a more flexed relaxed sitting posture than the no backache group. These findings appear to validate McKenzie's concept of a postural syndrome.

Adult↗
PubMed1990

Observations of working postures in garages using the Ovako Working posture Analysing System (OWAS) and consequent workload reduction recommendations.

The working postures of mechanics (n = 84) in 42 garages were observed using the Ovako Working posture Analysis System (OWAS). During observation, both working postures and work activities were recorded. A computer program was developed for the data analyses. Using this program it is possible to calculate the working posture load for each work activity and the contribution of a specific activity to the total working posture load. This is a substantial extension of the original OWAS method. Five out of 19 observed postures of the body members were classified as Action Category 2, which suggests they were slightly harmful to the musculoskeletal system and likely to cause discomfort. Of the so-called typical working postures, 31.9% was classified in Action Category 2, suggesting that during a substantial part of the working day typical working postures occur which are at least slightly harmful to the musculoskeletal system. Moreover, those work activities principally causing the workload to fall in OWAS' higher Action Categories were identified. For each of these three work activities an alternative work method was observed. The data show that in all three work activities the use of a vehicle lift reduces the number of poor working postures thereby reducing the load on the musculoskeletal system.

Accidents, Occupational↗
PubMed2003

[Effect of a posture training program on cobb angle and knowledge of posture of elementary school students].

PURPOSE: This study was conducted to examine the effect of a posture training program, including posture education and spinal exercise as implemented on the elementary school students with scoliosis. METHOD: The design of this study is nonequivalent sample control group pretest-posttest design. The study subjects were elementary school students attending 7 elementary schools located in G city in Gyungsangbuk-Do. Among them, those who had the Cobb angle between 4~10 degrees in spine x-ray who agreed to participate in the study program were selected as the study subjects. The research instruments included the degree of spinal scoliosis(cobb angle), the level of knowledge on posture, and an evaluation following the posture training program. The data were collected from March 1, 2002 to July 30, 2002. The collected data were analyzed by frequency, percentile, mean, standard deviation, t-test, chi(2) test and Mann-Whitney U test were using SPSS WIN10.0 program. RESULT: The elementary school students with scoliosis who received the posture training program have a lower Cobb angle and higher level of knowledge of posture than the elementary school students with scoliosis who did not receive the posture training program. CONCLUSION: The posture training program was effective on the on Cobb angle and Knowledge of posture in the elementary school students with scoliosis in this study. Therefore, the program training program can be usefully utilized for the students with mild scoliosis in the field of school health.

English Abstract↗
PubMed1995

Directional specificity of postural muscles in feed-forward postural reactions during fast voluntary arm movements.

Healthy subjects performed bilateral fast shoulder movements in different directions while standing on a force platform. Anticipatory postural adjustments were seen as changes in the electrical activity of postural muscles as well as displacements of the center of pressure and center of gravity. Postural muscle pairs of agonist-antagonist commonly demonstrated triphasic patterns starting prior to the first electromyographic (EMG) burst in the prime-mover muscle. Proximal postural muscles demonstrated the largest anticipatory increase in the background activity during movements in one of the two opposite directions (forward or backwards). These changes progressively decreased when movements deviated from the preferred direction and frequently disappeared during movements in the opposite direction. The patterns in distal muscles varied across subjects and could demonstrate larger anticipatory changes during movements forward and backwards as compared to movements in intermediate directions. Bilateral addition of inertial loads to the wrists did not change the general anticipatory patterns, while making some of their features more pronounced. Anticipatory postural adjustments were followed by later changes in the activity of postural muscles, also reflected in the mechanical variables. Changes in leg joint angles revealed a "hip-ankle strategy" during shoulder flexions and an "ankle strategy" during shoulder extensions. The study demonstrates different behaviors of proximal and distal muscles during anticipatory postural adjustments in preparation for fast arm movements. We suggest that the proximal muscles produce a general pattern of postural adjustments, while distal muscles take care of fine adjustments that are more likely to vary across subjects.

Adult↗
PubMed1998

Static posture tests for the assessment of postural instability after virtual environment use.

The aim of this experiment was to measure the effect of immersion in a virtual environment (VE) on postural stability and examine the relationship between postural stability and self-reported simulator sickness. Forty healthy subjects were exposed to 20 min of immersion in an interactive VE with restricted user movement. The VE was viewed on a head mounted display (HMD) and the subject remained standing throughout the immersion period. Two static postures, normal stance and tandem romberg, were recorded before immersion, immediately after immersion and again at 10 min postimmersion. Performance in each posture was simultaneously measured by recording time that the posture could be maintained and mm path length of body sway over a 30-s period. The results demonstrated differences in the sensitivity of postural stability measurement techniques and variations in inter- and intraindividual responses to measures. Sway magnetometry measured a significant increase in postural instability in normal stance after VE immersion. None of the other measures were sensitive to this change. Postimmersion reports of simulator sickness symptoms indicate that the VE stimulus was provocative and correlation was found between reports of simulator sickness and balance-related symptoms. However, no association between self-reported symptoms and performance measures of postural instability was found.

Adolescent↗
PubMed1997

The relationship between ortho head posture and head posture measured during walking.

Murphy, Preston, and Evans recognized the dynamic nature of head posture and developed instrumentation capable of measuring and recording this posture in a continuous manner. The aim of the current project was to use the newly developed instrumentation to determine whether the difference is statistically significant between the mean natural head ortho posture, measured in a controlled manner, and the mean dynamic head posture obtained during 5 minutes of walking activity in an experimental situation. The mean ortho head posture and the mean walking head posture were measured in each of 30 men. The differences between these two sets of mean head postures were statistically significant (p < or = 0.05). In 23 persons, the mean walking head posture was tipped backward relative to the mean natural head ortho position.

Adult↗
PubMed1996

Correcting trunk muscle geometry obtained from MRI and CT scans of supine postures for use in standing postures.

Many studies have reported the geometry of the trunk muscles for use in models to predict spine loads. However, all have reported data collected from subjects positioned in a prone or supine posture which is required by CT or MRI scan techniques. This study compared the abdominal and extensor muscle moment arms obtained with muscles relaxed and activated and in both supine and upright postures. Both internal ultrasound measurements and external anthropometer measurements were collected. The anterior abdominal wall increased its flexor moment arm by approximately 30% when in a standing posture compared to the supine posture. The effect of an upright posture on the moment arm of erector spinae at the level of L3 was much smaller (3% increase in males and 12% increase in females). There was no moment arm change due to activating the muscles when compared to the relaxed condition for either posture. Modelers should be aware of the need to scale muscle moment arms obtained from MRI/CT scans in order to more accurately predict spine loads in upright postures.

Abdominal Muscles↗
PubMed2005

Development and validation of a novel rating system for scoring standing foot posture: the Foot Posture Index.

INTRODUCTION: The limitations of clinical methods for appraising foot posture are well documented. A new measure, the Foot Posture Index is proposed, and its development and validation described. METHODS: A four-phase development process was used: (i) to derive a series of candidate measures, (ii) to define an appropriate scoring system, (iii) to evaluate the validity of components and modify the instrument as appropriate, and (iv) to investigate the predictive validity of the finalised instrument relative to static and dynamic kinematic models. Methods included initial concurrent validation using Rose's Valgus Index, determination of inter-item reliability, factor analysis, and benchmarking against three dimensional kinematic models derived from electromagnetic motion tracking of the lower limb. RESULTS: Thirty-six candidate components were reduced to six in the final instrument. The draft version of the instrument predicted 59% of the variance in concurrent Valgus Index scores and demonstrated good inter item reliability (Cronbach's alpha = 0.83). The relevant variables from the motion tracking lower limb model predicted 58-80% of the variance in the six components retained in the final instrument. The finalised instrument predicted 64% of the variance in static standing posture, and 41% of the variance in midstance posture during normal walking. CONCLUSION: The Foot Posture Index has been subjected to thorough evaluation in the course of its development and a final version is proposed comprising six component measures that performed satisfactorily during the validation process. The Foot Posture Index assessment is quick and simple to perform and allows a multiple segment, multiple plane evaluation that offers some advantages over existing clinical measures of foot posture.

Adult↗
PubMed2004

Is there a transfer of postural ability from specific to unspecific postures in elite gymnasts?

The purpose of this study was to investigate the transfer of postural ability by comparing the level of performance and postural control of elite gymnasts in postures specifically trained or not. Fifteen elite gymnasts were asked to stand as still as possible with eyes opened in three conditions: bipedal, unipedal and handstand. Surface and mean velocity of the centre of pressure motions were used to quantify respectively performance and postural control. A ranking was made for each parameter to determine the level of each subject. As a whole, the subject's level of postural performance and control in one condition was not correlated to the corresponded level in another condition. Therefore, postural ability of elite gymnasts in the handstand is not transferable to upright standing postures.

Adolescent↗
PubMed2002

Effects of postural muscle fatigue on the relation between segmental posture and movement.

The purpose of this study was to examine whether fatigue of postural muscles might influence the coordination between segmental posture and movement. Seven healthy adults performed series of fifteen fast wrist flexions and extensions while being instructed to keep a dominant upper limb posture as constant as possible. These series of voluntary movements were performed before and after a fatiguing submaximal isometric elbow flexion, and also with or without the help of an elbow support. Surface EMG from muscles Deltoïdeus anterior, Biceps brachii, Triceps brachii, Flexor carpi ulnaris, Extensor carpi radialis were recorded simultaneously with wrist, elbow and shoulder accelerations and wrist and elbow displacements. Fatigue was evidenced by a shift of the elbow and shoulder muscles EMG spectra towards low frequencies. Kinematics of wrist movements and corresponding activations of wrist prime-movers, as well as the background of postural muscle activation before wrist movement were not modified. There were only slight changes in timing of postural muscle activations. These data indicate that postural fatigue induced by a low-level isometric contraction has no effect on voluntary movement and requires no dramatic adaptation in postural control.

Adult↗
PubMed2005

Reach and posture hand preferences during arboreal feeding in Sifakas (Propithecus sp.): a test of the postural origins theory of behavioral lateralization.

Sixteen sifakas (11 Propithecus verreauxi coquereli, 2 Propithecus verreauxi verreauxi form majori, and 3 Propithecus tattersalli) were videotaped as they fed on leaves in an arboreal context. The hand used to feed and the hand used to maintain postural stability was coded. For each subject, the lateral bias of the hand used to feed was opposite the hand used in postural support. Seven sifakas displayed no bias for feeding or posture-related hand use, 7 sifakas displayed significant feeding-related reach preferences for pulling branches to the mouth (5 left- and 2 right-hand preferences), and 9 sifakas exhibited significant hand preferences for postural support (2 left-, 7 right-hand preferent). Although these data do not strongly support the postural origins theory of behavioral lateralization, the modal preference pattern for sifakas that displayed significant hand preferences for posture and feeding involve a left bias for feeding and a right bias for postural support. s reserved).

Animals↗
PubMed1991

Interactions between automatic postural adjustments and anticipatory postural patterns accompanying voluntary movement.

In order to examine interactions between centrally initiated postural activity preceding voluntary arm movements and compensatory postural activity, we studied patterns of postural muscle activity preceding a vigorous bilateral reach and grasp task or triggered by support surface motion. The reaching task required movement onset to be coincident with a predictable stimulus, and in some trials a brief backward platform perturbation was timed to occur before, during, or after the reach onset. Centrally initiated anticipatory postural activity was subject-specific and was very often absent when perturbation-induced postural activity was elicited just prior to movement onset. Likewise, compensatory postural activity patterns elicited by the platform perturbation did not occur when they would have coincided with the anticipatory postural activity. These data support the idea that the central neural processes which determine the specific activation pattern of the supporting limb musculature are influenced by both the intended dynamic outcome and the current dynamic status of the body.

Adult↗
PubMedDate not supplied

Relationship between static posture and rearfoot motion during walking in patellofemoral pain syndrome: effect of a reference posture for gait analysis.

The reference posture used in angular motion calculations may play an important role in the relationship found between static posture and rearfoot motion in the frontal plane in a clinical population such as patients with patellofemoral pain syndrome. This study examined the relationship between rearfoot inversion and eversion during the stance phase of walking and the static relaxed standing measurement in women (aged 18 years and older) with patellofemoral pain syndrome and controls and examined the influence of the reference posture used when calculating dynamic motion. Two reference postures were investigated: vertical alignment between the rearfoot and the lower leg and relaxed calcaneal standing. When using the latter reference posture, a significant correlation was found between the static relaxed standing measurement and peak eversion in controls only. When using the vertical alignment reference posture, significant correlation was found only in the patellofemoral pain syndrome group for peak eversion and inversion. The positive relationship found in the patellofemoral pain syndrome group between dynamic angular measures, based on a neutral reference posture, and static relaxed standing indicated that for subjects with patellofemoral pain syndrome, the clinical rearfoot measurement of relaxed standing can be used to explain the pattern of rearfoot motion during walking.

Adolescent↗
PubMed1989

Contribution of postural muscle tone to full expression of posture and locomotor movements: multi-faceted analyses of its setting brainstem-spinal cord mechanisms in the cat.

In this minireview, I have summarized and discussed our results concerning the neuronal mechanisms of postural suppression, and our thoughts about contribution of postural muscle tone to the full expression of locomotion. The identified brainstem-spinal cord system is schematically illustrated in Fig. 1 with its neuronal constituents (A). When cells of origin of this system (cells in the nucleus reticularis pontis oralis), or the pathway descending from these cells (DTF area) are tonically activated, cells in the nucleus reticularis gigantocellularis (gc cells) are also tonically activated, and with this process the system as a whole exerts generalized or non-reciprocal tonic inhibitory effects upon alpha-motoneurons innervating hindlimb extensor and flexor muscles. In consequence, postural muscle tone, especially that of the hindlimbs, is tonically suppressed and results in sustained suppression of postural support both in acute decerebrate cats (locomotor preparation) and in awake, freely moving cats, terminating locomotor movements. Since postural control and locomotor control are not separate phenomena, our results indicate that interaction of the above-described two control systems should be studied at each level of the brainstem and the spinal cord. In fact, contribution of brainstem neurons and of spinal interneurons has already been studied. It may also be interesting to elucidate supra-pontine structures which activate the identified brainstem-spinal cord inhibitory system. Such a study may elucidate the neuronal structures related not only to the termination of on going movements but also to the muscular atonia observed during active sleep. As demonstrated, even for the understanding of the brainstem-spinal cord system involved in postural suppression, multi-faceted and mutally related analytical approaches have been necessary as suggested by Brookhart, and these approaches allowed us to approach a much better understanding of the problem one faces. They were neuroanatomical analyses of plausible neuronal structures, electrophysiological analyses of their synaptic organizations, the neuropharmacological analyses of their putative neurotransmitters, and finally the most important, behavioral analyses. For a thorough understanding of the dynamics of postural and locomotor control systems, the problems we are now concerned with are to identify both the "hardware" and the "software" of these two systems. Understanding of the hardware requires an elucidation of the neuronal circuits including synaptic organizations, and that of the software an identification of the putative neurotransmitters that set the identified neuronal circuit to work, so that the systems as a whole exhibit a meaningful external manifestation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Effects of different treatments on postural performance in patients with cervical root compression. A randomized prospective study assessing the importance of the neck in postural control.

Patients with cervical root compression were used as a "model" to investigate the possible importance of neck disorders and cervical sensory information in postural control. We assessed postural performance with posturography before and after treatment in 71 consecutive patients with MRI-verified cervical root compression without medullary compression. The patients were randomized to surgery (n = 22), physiotherapy (n = 24) or treatment with cervical collars (n = 25). There were no differences in postural performance or pain intensity between the groups before treatment. After treatment, the surgery group manifested significant improved postural performance and reduced neck pain scores, as compared to the two conservative treatment groups, and their postural performance had improved to the same level manifested by healthy controls. The conservative treatment groups manifested no consistent significant changes in postural performance or pain scores. Decreased muscular tension due to reduction of cervical pain after surgery and normalization of cervical proprioception are suggested as possible explanations of the improved postural control.

Female↗