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PubMed2004

Effect of computerized feedback postural training on posture and attentional demands in older adults.

BACKGROUND AND AIMS: Previous research on various fall prevention strategies, in an effort to help the aging population has lead to inconsistent results. In this experiment, an 8-week computerized training program with a feedback fading protocol was given to 12 community-dwelling elderly subjects twice a week. METHODS: Postural sway (force plate measures), attentional demands (dual-task paradigm), the Berg Balance Scale and the Activities-specific Balance Confidence Scale (ABC) were measured in pre-, post-, and retention test assessments. RESULTS: Results indicated that the experimental group showed a significant decrease in reaction time during standing compared with the control group, and the difference remained significant even after a two-week period (retention test). Postural sway and ABC results showed no significant changes between groups in either post-test or retention test. The Berg Balance Scale scores were significantly higher in the post-test compared with the pre-test. The Berg scale is a functional mobility scale, and the increase observed may be associated with a decrease of at least 4% in the risk of falling. This study further illustrates that postural sway (mode frequency) may not be the best variable to measure the efficiency of a treatment or training protocol. Reaction time in the dual-task paradigm, which was used to measure attentional demands during posture, was found to be affected more by the training program. CONCLUSIONS: Postural training in combination with a feedback fading protocol seems to improve the automaticity of posture significantly.

Accidental Falls↗
PubMed2005

Detecting altered postural control after cerebral concussion in athletes with normal postural stability.

OBJECTIVE: To determine if approximate entropy (ApEn), a regularity statistic from non-linear dynamics, could detect changes in postural control during quiet standing in athletes with normal postural stability after cerebral concussion. METHODS: The study was a retrospective, case series analysis of centre of pressure (COP) data collected during the Sensory Organization Test (SOT) from NCAA Division I (USA) athletes prior to and within 48 h after injury. Subjects were 21 male and six female athletes from a variety of sports who sustained a cerebral concussion between 1997 and 2003. After injury, athletes displayed normal postural stability equivalent to preseason levels. For comparison, COP data also were collected from 15 male and 15 female healthy non-athletes on two occasions. ApEn values were calculated for COP anterior-posterior (AP) and medial-lateral (ML) time series. RESULTS: Compared to healthy subjects, COP oscillations among athletes generally became more regular (lower ApEn value) after injury despite the absence of postural instability. For AP time series, declines in ApEn values were much larger in SOT conditions 1 and 2 (approximately three times as large as the standard error of the mean) than for all other conditions. For ML time series, ApEn values declined after injury in all sensory conditions (F(1,55) = 6.36, p = 0.02). CONCLUSIONS: Athletes who demonstrated normal postural stability after concussion nonetheless displayed subtle changes in postural control. Changes in ApEn may have represented a clinically abnormal finding. ApEn analysis of COP oscillations may be a valuable supplement to existing concussion assessment protocols for athletes.

Adolescent↗
PubMed1999

Validation of a standardized assessment of postural control in stroke patients: the Postural Assessment Scale for Stroke Patients (PASS).

BACKGROUND AND PURPOSE: Few clinical tools available for assessment of postural abilities are specifically designed for stroke patients. Most have major floor or ceiling effects, and their metrological properties are not always completely known. METHODS: The Postural Assessment Scale for Stroke patients (PASS), adapted from the BL Motor Assessment, was elaborated in concordance with 3 main ideas: (1) the ability to maintain a given posture and to ensure equilibrium in changing position both must be assessed; (2) the scale should be applicable for all patients, even those with very poor postural performance; and (3) it should contain items with increasing difficulty. This new scale has been validated in 70 patients tested on the 30th and 90th days after stroke onset. RESULTS: Normative data obtained in 30 age-matched healthy subjects are presented. The PASS meets the following requirements: (1) good construct validity: high correlation with concomitant Functional Independence Measure (FIM) scores (r=0.73, P=10(-6)), with lower-limb motricity scores (r=0.78, P<10(-6)), and with an instrumental measure of postural stabilization (r=0.48, P<10(-2)); (2) excellent predictive validity: high correlation between PASS scores on the 30th day and FIM scores on the 90th day (r=0.75, P<10(-6)); (3) high internal consistency (Cronbach alpha-coefficient=0.95); and (4) high interrater and test-retest reliabilities (average kappa=0.88 and 0.72). CONCLUSIONS: Our results confirm that the PASS is one of the most valid and reliable clinical assessments of postural control in stroke patients during the first 3 months after stroke.

Cerebrovascular Disorders↗
PubMed1998

Postural modulation of the segmental reflex: effect of body tilt and postural sway.

This purpose of this study was to clarify the relationship between segmental reflex excitability and posture and to investigate potential mechanisms responsible for modulation of the H-reflex (HR) in unsupported standing. Soleus (S) and lateral gastrocnemius (LG) HRs were recorded from subjects (N=12S, N=11LG) while their static posture was altered from supine to vertical (5 positions). This was compared to an unsupported standing position in which the subjects naturally underwent a small degree of postural sway, a dynamic posture condition. Although individual profiles suggested varied relationships between the S and LGHR and the angle of body tilt, the group data did not reveal significant differences. There was, however, a significant (p < .01) decrease in the S (43% 49%) and LG (34%-46%) HR when subjects stood without support compared to all static postures. This decrease occurred even though the tonic or background activity of the S and LG was present only when subjects were free standing. To determine whether weight-bearing was responsible for the HR depression, 3 additional conditions were compared (N=3), supported standing without weight-bearing (90 degrees NWB), supported standing with weight-bearing (90 degrees WB), and free standing. Again, S and LGHRs were depressed only when subjects were free standing. Presynaptic inhibition presumably accounts for the depression of the HR in unsupported standing. Data from 8 of the subjects were collected under the same 6 conditions using a shorter interstimulus interval (1 Hz stimulus instead of 0.1 Hz) which produced low frequency depression (LFD) of the S and LG HR. LFD reduced the amplitude of the S HR an average of 43% (p < .05) when subjects were in a supported static position but only 21% when subjects were free standing. Although tonic activity of the S was present only when subjects were free standing, in 2 (of 8) individuals the EMG in free standing was not measurably different from static conditions. In these individuals, free standing still depressed the SHR by 35%; however, the shorter stimulus interval now produced the same degree of LFD when subjects were free standing (35%) as when they were standing with support (37%). The data suggest that 2 presynaptic mechanisms, although independent, interact to control spindle afferent feedback when subjects are free standing. Postural sway appears to be necessary to reduce the gain of the HR when subjects are standing, whereas, LFD is influenced by the degree of muscle activation.

Adolescent↗
PubMed1994

Is there an optimal arm posture? Deterioration of finger localization precision and comfort sensation in extreme arm-joint postures.

Processing of joint redundancy is one of the most important problems in motor control. For instance, gaze orientation can be obtained with an infinite number of eye and head combinations. It has been proposed that a solution to this problem might be the minimization of eye and head position-signal errors. For arm movements, where the excess of degrees of freedom is even higher, cost function was proposed as a criterion for movement selection, reflecting some comfort variable evoked from the peripheral inputs, e.g. optimal muscular energy cost or glucose consumption. However, no biological implication of comfort on motor control has yet been demonstrated. We have further investigated this approach by hypothesizing that arm posture choice also relies on a minimization of position-signal errors arising from individual joints. The prediction is that accuracy of fingertip localization by pointing made by the contralateral hand would be enhanced for comfortable postures of the target arm and degraded for uncomfortable postures using extreme joint positions. Results show an increase in pointing variability when extreme joint postures are used (wrist flexion, shoulder elevation, or both). This increase in pointing variability is proportional to the increase in subjective discomfort rating. Individual joint effects can be added arithmetically into a whole arm value for both discomfort rating and pointing variable and constant error. These results suggest that the choice of comfortable postures for the arm corresponds to an optimization of arm position-signal reliability. This new constraint might be a useful tool for further investigation on posture or trajectory formation.

Arm↗
PubMed2005

Coordination between posture and movement: interaction between postural and accuracy constraints.

We examined the interaction between the control of posture and an aiming movement. Balance control was varied by having subjects aim at a target from a seated or a standing position. The aiming difficulty was varied using a Fitts'-like paradigm (movement amplitude=30 cm; target widths=0.5, 1.0, 2.5 and 5 cm). For both postural conditions, all targets were within the reaching space in front of the subjects and kept at a fixed relative position with respect to the subjects' body. Hence, for a given target size, the aiming was differentiated only by the postural context (seated vs. upright standing). For both postural conditions, movement time (MT) followed the well-known Fitts' law, that is, it increased with a decreasing target size. For the smallest target width, however, the increased MT was greater when subjects were standing than when they were seated suggesting that the difficulty of the aiming task could not be determined solely by the target size. When standing, a coordination between the trunk and the arm was observed. Also, as the target size decreased, the center of pressure (CP) displacement increased without any increase in CP speed suggesting that the subjects were regulating their CP to provide a controlled referential to assist the hand movement. When seated, the CP kinematics was scaled with the hand movement kinematics. Increasing the index of difficulty led to a strong correlation between the hand speed and CP displacement and speed. The complex organization between posture and movement was revealed only by examining the specific interactions between speed-accuracy and postural constraints.

Adaptation, Physiological↗
PubMed2000

Do anticipatory postural adjustments occurring in different segments of the postural chain follow the same organisational rule for different task movement velocities, independently of the inertial load value?

Dynamic phenomena, termed anticipatory postural adjustments (APA), are known to precede the onset of voluntary movement. Their anticipatory nature confers a particular status on APAs: as they cannot be triggered reflexly by afferent signals induced by a voluntary movement, it can be asked whether the APA parameters are centrally programmed as a function of some task movement parameters or are only the peripheral consequence of control variables. To this end the present study aims to determine whether the APAs occurring at the different sites of the postural chain yield the same accelerometric patterns and follow the same organisational rules when the task movement velocity changes, independently of the inertial load value. Subjects performed unilateral shoulder flexions at maximal and submaximal velocities, with (IUF) and without (OUF) an additional inertial load. Accelerometers were attached to the wrist and trunk, and on both sides of the body at shank, thigh, hip and shoulder. The results show that: 1) there was evidence of anticipatory acceleration in all segments of the postural chain; 2) each acceleration profile for the anticipatory phase was maintained over different focal movement velocities whether there was an additional load or not; 3) there were significant linear relationships between the amplitude of each segmental anticipatory acceleration and the square of the task movement velocity, the slope of which differs as a function of the inertial load; 4) there were close intersegmental correlations between these anticipatory accelerations which did not depend on the inertial load. In addition the correlation between the lower limbs and the opposite side of the body was positive, suggesting a diagonal postural pattern. A comparison of the present kinematic data with the corresponding EMG data reported in the literature argues in favour of a centrally determined kinematic pattern. It is proposed that the diagonal postural pattern between postural segments be considered as one of the order rules which could simplify the control process of asymmetrical movement. The anticipatory kinematics of each of the body segments would be calibrated with the velocity and the inertial load and scaled to the other segments to counteract the perturbing effect of the asymmetrical focal movement on body balance.

Acceleration↗
PubMedDate not supplied

Implications for the use of postural analysis as a clinical diagnostic tool: reliability of quantifying upright standing spinal postures from photographic images.

OBJECTIVES: A repeated measures design was used to test the reliability of standing spine postures within subjects using a biologically relevant measure determined by digitization of images and to compare the results to a previously tested vertical reference method. METHODS: Twenty subjects attended 3 sessions consisting of 5 trials each. Photographs of the sagittal and posterior views of normal upright standing were taken. Landmarks were digitized and cervical, thoracic, and lumbar spinal angles were calculated using the algebraic dot product. Intraclass correlation coefficients were used to evaluate intrasubject reliability across sessions. RESULTS: According to the intraclass correlation coefficients, posture had good to excellent reliability in the sagittal view and provided a more stable measure of spinal angles than the posterior view. Mean repositioning errors were less than 6 degrees and 2 degrees in the sagittal and posterior views, respectively. CONCLUSIONS: Although the repeatability of posture was improved in the sagittal view, when a biological measure was used instead of an external vertical reference to calculate spinal angles, individual subject posture was still variable. This brings into question the effectiveness and validity of using surface skin markers to track postural changes due to clinical interventions. If the postural analysis approach is to be used to detect changes due to clinical treatment, such changes must be larger than the baseline repositioning errors seen in healthy subjects.

Adult↗
PubMedDate not supplied

Does sitting posture in chronic obstructive pulmonary disease really matter? An analysis of 2 sitting postures and their effect [corrected] on pulmonary function.

PURPOSE: The purpose of this study was to investigate changes that occur in pulmonary function when postural changes in the sagittal plane are made in a seated position in patients diagnosed with chronic obstructive pulmonary disease (COPD). METHODS: Fourteen patients diagnosed with COPD participated in this study. Standard spirometric measurements (minute ventilation, forced vital capacity, and forced expiratory volume in 1 second) were taken for each patient in each of 2 sitting postures: slumped and upright. Breathing frequency, heart rate, and blood oxygen saturation were also recorded for each of the 2 postures. Patients assumed each posture for 5 minutes before any measurements were taken, after which measurements were recorded each minute for an additional 5 minutes. RESULTS: A 2-factor (posture and time) analysis of variance with repeated measures on both factors was used to analyze the data. There were no significant differences between the means for heart rate, blood oxygen saturation, and breathing frequency. Paired t tests likewise did not reveal any significant differences between the slumped and upright positions for forced expiratory volume in 1 second, forced vital capacity, and minute ventilation. CONCLUSIONS: These results suggest that there are no differences in measures of pulmonary function (minute ventilation, forced vital capacity, and forced expiratory volume in 1 second) and breathing frequency, heart rate, and blood oxygen saturation between slumped and upright sitting in patients with COPD. Based on this evidence alone, it may be inappropriate to instruct a patient with COPD to sit upright to improve respiratory function. However, further study is warranted before any definite recommendations can be made regarding sitting posture and respiratory performance in individuals with COPD.

Aged↗
PubMed1995

Effect of a postural support nappy on 'flattened posture' of the lower extremeties in very preterm infants.

OBJECTIVE: To determine whether the use of a postural support nappy (PSN) would reduce the features of 'flattened posture' in the lower extremities of infants < 31 weeks gestation who are nursed prone. METHODOLOGY: Randomized, observer blind, controlled trial conducted at King Edward Memorial Hospital for Women, Perth, Western Australia. Infants were randomly assigned and stratified by gestational age to be nursed in a conventional nappy (n = 29) or a PSN (n = 31) when in the prone position. The features of 'flattened posture' were measured as angles and assessed by blinded observers prior to commencement of the intervention, 4 weeks post intervention, then bi-weekly until discharge. RESULTS: A significant reduction in the features of 'flattened posture' occurred in the PSN group after 4-6 weeks of intervention and stabilized by 8 weeks until discharge. No changes were detected in the control group. No significant difference was observed between infants < 29 weeks gestation compared to infants of 29-30 weeks gestation in either treatment group. CONCLUSIONS: Use of the PSN in infants < 31 weeks gestation who are nursed in the prone position significantly reduces the features of 'flattened posture' in the lower extremities. This is of benefit in the short term, and follow up of these infants into childhood will demonstrate whether the long-term effects of 'flattened posture' can be prevented.

Chi-Square Distribution↗
PubMed1992

Comparison of the effect of castration on the development of postural and non-postural muscles of mice.

The effect of castration on the development of muscle mass of postural and non-postural muscles was studied in 18 male mice (9 castrated, 9 uncastrated). Results obtained indicated that the castrated males grew faster and were bigger in body size and weight at maturity than the intact males. The bigger body size of castrated males was not due to larger muscle mass but was probably due to increased subcutaneous fat deposition. Atrophy of muscles usually observed following castration was significantly greater in the non-postural (biceps brachii) muscle of the forelimb as compared to the postural (triceps brachii) muscle of the forelimb. Conversely, the amount of reduction in muscle mass was similar in both postural (soleus) and non-postural (tibialis cranialis) muscles of the hindlimb.

Animals↗
PubMed2004

The representation of self reported affect in body posture and body posture simulation.

It is taken for granted that the non-verbal information we acquire from a person's body posture and position affects our perception of others. However, to date human postures have never been described on an empirical level. This study is the first approach to tackle the unexplored topic of human postures. We combined two approaches: traditional behavior observation and modern anthropometric analysis. Photographs of 100 participants were taken, their body postures were transferred to a three dimensional virtual environment and the occurring body angles were measured. The participants were asked to fill in a questionnaire about their current affective state. A principal component analysis with the items of the affect questionnaire (Positive Negative Affect Scales, PANAS) revealed five main factors: aversion, openness, irritation, happiness, and self-confidence. The body angles were then regressed on these factors and the respective postures were reconstructed within a virtual environment. 50 different subjects rated the reconstructed postures from the positive and negative end of the regression. We found the ratings to be valid and accurate in respect to the five factors.

Adult↗
PubMed1987

[Studies on the posture of the healthy Japanese child--a classification of posture and their relation to changes in different age groups].

The human standing posture in childhood was analyzed and classified quantitatively utilizing moiré topography and a semi-automated computer system. Three thousand forty-five children ranging from three to twelve years of age were measured. Change in mid-sagittal spinal curvature was analyzed with age. The standing posture in childhood was categorized into three phases. The criteria of the classification of the postures in each phases were defined by alpha. Early juvenile posture: before 7 years of age in both male and female. The main characteristics of this phase is the development in the muscles of lower extremities. Late juvenile posture: 7-9 years old in male and 7-8 years old in female. The development of the lumbar lordosis is most characteristic. Adolescent posture: 10 years or older in male and 9 years or older in female. The increase in segmental length and magnitude of the thoracic kyphosis is most characteristic.

Adolescent↗
PubMed1998

Recovery from stress in two different postures and in Shavasana--a yogic relaxation posture.

The recovery from induced physiological stress in Shavasana (a yogic relaxation posture) and two other postures (resting in chair and resting supine posture) was compared. Twenty one males and 6 females (age 21-30 yrs) were allowed to take rest in one of the above postures immediately after completing the scheduled treadmill running. The recovery was assessed in terms of Heart Rate (HR) and Blood pressure (BP). HR and BP were measured before and every two minutes after the treadmill running till they returned to the initial level. The results revealed that the effects of stress was reversed in significantly (P < 0.01) shorter time in Shavasana, compared to the resting posture in chair and a supine posture.

Adult↗
PubMed2005

Effects of Pronated and Supinated Foot Postures on Static and Dynamic Postural Stability.

Context: The foot is the most distal segment in the lower extremity chain and represents a relatively small base of support on which the body maintains balance (particularly in single-leg stance). Although it seems reasonable that even minor biomechanical alterations in the support surface may influence postural-control strategies, the implications of a hypermobile or hypomobile foot on balance have received little attention to date.Objective: To determine if supinated and pronated foot types influence measures of static and dynamic balance.Design: Participants were assigned to 1 of 3 groups depending on foot type, as defined by navicular-drop measures: pronated (>/=10 mm), neutral (5-9 mm), or supinated (</=4 mm). Measures of static and dynamic balance were obtained for each participant and compared across groups.Setting: Sports medicine and athletic training research laboratory.Patients or Other Participants: Sixteen individuals with pronated (navicular drop = 13.0 +/- 3.7 mm), neutral (navicular drop = 6.2 +/- 1.1 mm), or supinated (navicular drop = 2.2 +/- 1.7 mm) foot postures volunteered to participate in the study.Main Outcome Measure(s): We used the Chattecx Balance System to measure center of balance, stability index, and postural sway during static single-limb stance under eyes-open and eyes-closed conditions. Center of balance was defined as the point on the foot at which the body weight was equally distributed between the medial-lateral and anterior-posterior quadrants and was recorded in centimeters. Stability index was defined as the mean deviation in sway around the center of balance. Postural sway was expressed as the maximum sway distance recorded (cm) in the medial-lateral and anterior-posterior directions. The Star Excursion Balance Test was used to measure dynamic balance, which was reported as the reach distance (cm) in each of the 8 directions tested. The average of 3 trials of each measure was calculated and normalized to the subject's height.Results: We found no difference in center of balance or postural sway as a function of foot type. The stability index was greater in pronators than in supinators, but neither group was different from those with neutral foot types. Dynamic reach differed among groups but only in some directions. Generally, pronators reached farther in the anterior and anterior medial directions and supinators reached farther in the posterior and posterio-lateral directions. In the lateral direction, supinators reached farther than pronators but not farther than neutrals.Conclusions: Our results suggest that postural stability is affected by foot type under both static and dynamic conditions. These differences appear to be related to structural differences as opposed to differences in peripheral input. These effects should be considered when clinicians use such balance measures to assess injury deficits and recovery.

Journal Article↗
PubMed2001

[Influence of a typical "posture-balance-motivity" motor practice on the postural capacities of elderly subjects].

OBJECTIVE: The object of this work was to observe the influence of the "Posture-Balance-Motivity" (PBM) activity on the total motivity in older adults. SUBJECTS AND METHOD: After 12 weeks of practice, to observe the effects on the control of static postural sway by the intermediary of a force platform of 15 subjects (mean age 75.5, SD = 6.6). RESULTS: Scores on "Posture", "Balance" and "Motivity" show respectively and significantly improvements. All scores of a clinical balance assessment scale, the POMA, have also improved. On the platform, parameters of spontaneous postural sway in the lateral (X) and antero-posterior (Y) axis have been evaluated with eyes open, eyes closed, on firm floor and foam floor condition. Values on the lateral axis did not show any significant decrease. But values on the antero-posterior axis showed a significant decrease for all modalities translating a better postural stability in this plan. CONCLUSION: These first results show the advantages of a typical "PBM" activity.

Accidental Falls↗
PubMed2000

The direction of postural instability affects postural reactions to ankle muscle vibration in humans.

Postural instability changes the weighting of different types of sensory information and the state of the equilibrium maintenance system. We have recently found that the effect of Achilles tendon vibration (so-called 'vibration-induced falling') strongly diminishes during unstable posture. However, it is unclear whether the state of postural instability has directionally specific or non-specific effects on the attenuation of proprioceptive influences from ankle muscles. To check this hypothesis, we varied the direction of support mobility and applied shank muscle vibration to subjects standing on a rocking platform movable in the sagittal, frontal or both directions. Postural reactions were present only on those supports that were stable in the sagittal direction. We suggest that the direction of postural instability affects information processing from ankle muscle receptors.

Adult↗
PubMed1998

Anticipatory postural adjustments in conditions of postural instability.

OBJECTIVES: The purpose of this study was to investigate anticipatory postural adjustments (APAs) in standing subjects who performed a standard motor action triggering a standard postural perturbation (releasing a 2.2 kg load from extended arms) in conditions of different stability requirements. METHODS: The degree of stability was varied either by balancing on special boards with long and narrow support beams or by instructions to the subjects. In the first series of experiments 13 subjects stood on the board facing either perpendicular to the beam (instability in a sagittal plane) or along the beam (instability in frontal plane); different widths of the beam were used to vary the degree of instability. During the second series of experiments (6 subjects) inclined and one-legged postures were used to induce instability in sagittal and frontal planes respectively. EMG activity of rectus abdominis, erector spinae, rectus femoris, biceps femoris, tibialis anterior, and soleus muscles were recorded. Statistical methods included repeated measures analysis of variance (ANOVA) with direction of instability and level of instability being major factors, descriptive statistics, and post hoc Student's t tests. RESULTS: The integral measure of changes in the background electromyographic activity of postural muscles during APAs depended on two factors related to the postural task: (1) standing on a platform with a narrow support area led to an attenuation of the APAs; and (2) these effects were stronger when instability was in a sagittal rather than in the frontal plane. The anticipatory component in the displacement of the center of pressure did not show a clear attenuation that would depend on the direction of instability. CONCLUSIONS: We suggest a hypothesis that, in conditions of high stability demands, the central nervous system may suppress APAs as a protection against their possible destabilizing effects. These effects are more pronounced when the direction of an expected perturbation is in the plane of instability.

Adult↗