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PubMedDate not supplied

A new force-plate technology measure of dynamic postural stability: the dynamic postural stability index.

CONTEXT: New measures of dynamic postural stability are needed to address weaknesses of previous measures. OBJECTIVE: To assess the feasibility, reliability, and precision of a new measure of dynamic postural stability. DESIGN: A single within-subjects design was used to determine optimal sampling interval as well as intersession reliability. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Eighteen subjects (7 men [age = 22 +/- 3 years, height = 175 +/- 5 cm, mass = 75 +/- 16 kg] and 11 women [age = 23 +/- 2 years, height = 163 +/- 6 cm, mass = 68 +/- 13 kg]) without lower extremity impairment. INTERVENTION(S): A jump protocol that required subjects to perform a 2-legged jump to a height equivalent to 50% of their maximum vertical leap and land on a single leg. MAIN OUTCOME MEASURE(S): The Dynamic Postural Stability Index (DPSI) and the directional components (medial-lateral, anterior-posterior, and vertical) after a jump landing. RESULTS: We observed a significant sampling-interval main effect (F(2,51) = 26.88, P < .01) for the DPSI; the 10-second trial duration produced significantly smaller means than the 5- and 3-second trial durations, whereas the 5-second trial result was also significantly smaller than that of the 3-second trial. The DPSI was highly reliable between test sessions (intraclass correlation coefficient = .96) and very precise (SEM = .03). CONCLUSIONS: These results suggest that the DPSI can be used in conjunction with a functional single-leg hop stabilization test and is a reliable and precise measure of dynamic postural stability. We believe the shortest sampling interval (3 seconds) is the best choice for studying and mimicking athletic performance as closely as possible.

Journal Article↗
PubMed2006

Changes in postural sway and its fractions in conditions of postural instability.

We investigated changes in postural sway and its fractions associated with manipulations of the dimensions of the support area. Nine healthy adults stood as quietly as possible, with their eyes open, on a force plate as well as on 5 boards with reduced support area. The center of pressure (COP) trajectory was computed and decomposed into rambling (Rm) and trembling (Tr) trajectories. Sway components were quantified using RMS (root mean square) value, average velocity, and sway area. During standing on the force plate, the RMS was larger for the anterior-posterior (AP) sway components than for the mediolateral (ML) components. During standing on boards with reduced support area, sway increased in both directions. The increase was more pronounced when standing on boards with a smaller support area. Changes in the larger dimension of the support area also affected sway, but not as much as changes in the smaller dimension. ML instability had larger effects on indices of sway compared to AP instability. The average velocity of Rm was larger while the average velocity of Tr was smaller in the AP direction vs. the ML direction. The findings can be interpreted within the hypothesis of an active search function of postural sway. During standing on boards with reduced support area, increased sway may by itself lead to loss of balance. The findings also corroborate the hypothesis of Duarte and Zatsiorsky that Rm and Tr reveal different postural control mechanisms.

Adult↗
PubMed1995

Spinal mobility and posture: changes during growth with postural defects, structural scoliosis and spinal osteochondrosis.

A number of case studies were followed for 10 years. Children suffering from postural defects, structural scoliosis and spinal osteochondrosis were separated from a normal group. Spinal mobility and posture were compared with the mobility of normal, healthy boys and girls aged 5-14 years. In postural defects curves similar to the physiologic one were observed. The range of motion was not physiologic in scoliosis. In this disease, rotation-flexion thoracic hypermobility with decreased lumbar flexion ability was found. A physiologic trend was found in spinal osteochondrosis, although sometimes the rotational mobility of the spine was reduced. An extremely high increase of thoracic kyphosis was found only in children aged 14 years.

Adolescent↗
PubMed2002

Relationship between comfort and back posture and mobility in sitting-posture.

The objective of this work is to analyze the causes of lumbar discomfort while sitting on a chair, by analyzing the relationship of lumbar curvature, pelvic inclination and their mobilities with discomfort. An experiment has been performed with healthy subjects, in which comfort, postural and mobility parameters have been measured. Their relationship has been analyzed with multivariate analysis. Factorial analysis has been used to represent all the correlated variables measured. Logistic regression and discriminant analyses have been used to classify discomfort/absence of discomfort. The results show that great changes of posture are a good indicator of discomfort, and that lordotic postures with forward leaned pelvis and low mobility are the principal causes of the increase of discomfort.

Ergonomics↗
PubMed2002

Attentional focus on supra-postural tasks affects postural control.

We examined whether the attentional focus adopted on a supra-postural task has an influence on postural control. Similar to Riley, Stoffregen, Grocki, and Turvey (Human Movement Science 18 (1999) 795), participants were instructed to stand still while lightly touching a loosely hanging sheet with their fingertips. However, instructions varied slightly under two conditions: Participants were either asked to minimize movements of the finger (internal focus) or to minimize movements of the sheet (external focus). In contrast to Riley et al.'s findings, both touch conditions resulted in increased postural sway, compared to a baseline condition (no touch). However, in line with previous findings (e.g., Wulf, McNevin, & Shea, Quarterly Journal of Experimental Psychology 54A (2001) 1143), frequency of responding (fast Fourier transformation) was greater under the external focus condition, compared to both internal focus and baseline conditions. The findings indicate improved static balance responses under external focus conditions and compromised static balance response under internal focus conditions.

Adult↗
PubMed1997

Postural load during VDU work: a comparison between various work postures.

The aim of this study was to compare the postural load during VDU work in the following work postures: (1) Supporting and not supporting the forearms on the table top, (2) Sitting and standing positions, and (3) Sightline to the centre of the screen at an angle of 15 degrees and 30 degrees below the horizontal. The muscle load from the upper part of musculus trapezius and from the lumbar part of musculus erector spinae (L3 level) was measured by electromyography (EMG). Postural angles of head, upper arm and back were measured by inclinometers. The load on m. trapezius when using the keyboard was significantly less in sitting with supported forearms compared to sitting and standing without forearm support. Further, the time and number of periods when the trapezius load was below 1% MVC was significantly greater with support versus no support. The load on the right erector spinae lumbalis was also significantly less and the time when the load was below 1% MVC was significantly longer in a sitting work position with support versus standing without support. In addition, when using a mouse supporting the forearms reduced the static trapezius load in sitting. The results from this study document clearly the importance of giving the operator the possibility of supporting the forearms on the table top.

Adult↗
PubMed2001

The School of Posture as a postural training method for Paraíba Telecommunications Operators.

This work proposes to show the experience of posture training accomplished in the Paraíba State Telecommunication Company, using the knowledge of the Back School. The sample was composed of 12 operators, employees of the company, representing 31% of this population. The model applied in TELPA (Paraíba Telecommunication Company, Brazil) was based on the models of Sherbrooke, Canada, and of the School of Posture of Paraìba Federal University. Fifty-eight point four percent of participants showed a reduction of column pain, 25% improved the quality of the rest and the received training was considered enough for the learning of correct postures at work in 75% of the cases. The whole population approved of the training, and 83.3% of the cases considered that this training influenced their lives very positively.

Adult↗
PubMed2005

Postural pseudoanemia: posture-dependent change in hematocrit.

OBJECTIVE: To determine the magnitude of posture-related changes in blood components. SUBJECTS AND METHODS: Twenty-eight healthy subjects were studied between 1995 and 2004 at the Vanderbilt Autonomic Dysfunction Center, Nashville, Tenn. Lying and standing plasma volume (PV) and hematocrit (Hct) values were determined for each subject. RESULTS: Individual PV decreases on standing ranged from 6% to 25%. The absolute mean +/- SD PV shift was 417+/-137 mL (range, 149-717 mL). The mean +/- SD change in Hct was from 37.7%+/-2.8% while supine to 41.8%+/-3.2% within 30 minutes of standing. This absolute increase in Hct of 4.1%+/-1.3% represents a relative increase of 11.0%+/-3.6% from lying to standing. CONCLUSIONS: Changes in posture can lead to substantial changes in Hct, which may be attributed mistakenly to blood loss or acute anemia and result in a cascade of unnecessary diagnostic costs. In reality, these changes represent postural pseudoanemia, a normal physiological response to a change in position from standing to lying (and vice versa).

Adult↗
PubMedDate not supplied

Toward standards for posture. Postural characteristics of the lower back system in normal and pathologic conditions.

On theoretic grounds it can be assumed that aberrations of posture may play a role in the generation of low-back pain by creating concentrations of stress. However, this assumption remains speculative because of the absence of criteria for normal posture. This study considers some of these criteria, especially as they are related to the lumbar spine and pelvis. The relations between the angle of declivity of the sacrum and radius and inclination of the lordotic curvature of the lumbar spine show good correlation. Mean values of postural parameters in the group of spondylolysis patients differ significantly from those in the group of healthy volunteers.

Adolescent↗
PubMed1989

Posture recording: a model for sitting posture.

A model for posture recording has been developed in order to provide for some features of sitting. Briefly, these features were related to seated subjects undergoing classroom activities, for whom positions of different body segments had to recorded as accurately as possible. The proposed procedure has allowed the identification of a great number of different postures presented by the subjects as well as their relative frequency of occurrence. The model may also be applicable to a wide range of situations involving general sitting posture in factories, offices, schools, etc, allowing some adjustments for specific cases.

Journal Article↗
PubMed1991

Microcomputer video image processing technology in working posture analysis: application to seated postures of keyboard operators.

A new two-dimensional video-based technique for the recording and analysis of working posture has been developed and applied to seated work. After initial set-up of the portable equipment in the workplace, and attachment of small adhesive retroreflective joint markers on the subject, an operator is not required for the remainder of the recording session. Analysis of the video recording is conducted in the laboratory using custom-written software and a commercially available image-processing package running on an IBM AT-compatible computer. After interactive set-up of a reference frame, the system is able to analyse the full video tape automatically, extracting video frames for analysis at approximately 30-s intervals. Poor image quality may occasionally necessitate interactive analysis. The system is capable of determining postural angles to an accuracy of 1-2 degrees , and thus represents a substantial improvement on other postural analysis systems which are able to be used readily in the workplace.

Journal Article↗
PubMed2002

Coexistence of stability and mobility in postural control: evidence from postural compensation for respiration.

This study evaluated the extent to which movement of the lower limbs and pelvis may compensate for the disturbance to posture that results from respiratory movement of the thorax and abdomen. Motion of the neck, pelvis, leg and centre of pressure (COP) were recorded with high resolution in conjunction with electromyographic activity (EMG) of flexor and extensor muscles of the trunk and hip. Respiration was measured from ribcage motion. Subjects breathed quietly, and with increased volume due to hypercapnoea (as a result of breathing with increased dead-space) and a voluntary increase in respiration. Additional recordings were made during apnoea. The relationship between respiration and other parameters was measured from the correlation between data in the frequency domain (i.e. coherence) and from time-locked averages triggered from respiration. In quiet standing, small angular displacements ( approximately 0.5 degrees ) of the trunk and leg were identified in raw data. Correspondingly, there were peaks in the power spectra of the angular movements and EMG. While body movement and EMG were coherent with respiration (>0.5), the coherence between respiration and COP displacement was low (<0.2). The amplitude of movement and coherence was increased when respiration was increased. The present data suggest that the postural disturbance that results from respiratory movement is matched, at least partly, and counteracted by small angular displacements of the lower trunk and lower limbs. Thus, stability in quiet stance is dependent on movement of multiple body segments and control of equilibrium cannot be reduced to control of a single joint.

Abdomen↗
PubMed2002

Effect of vibration-induced postural illusion on anticipatory postural adjustment of voluntary arm movement in standing humans.

We investigated the contribution of sensory signals arising from muscle proprioceptive receptors to anticipatory postural adjustments (APAs). During vibration applied to ankle (tibialis anterior; TA, soleus; Sol) or neck muscles, subjects generally describe having illusory sensations of whole-body movement, namely, whole-body movement in a backward and forward direction induced by vibration of the Sol or TA, respectively, and the front or back surface of the neck muscles, respectively. Preceding electromyographic (EMG) activity of the ipsilateral biceps femoris (BFi) muscle induced by rapid voluntary arm movement and the typical phenomenon of APA were changed dependent on these illusory whole-body movements, with preceding EMG activities of BFi appearing earlier in vibration applied to TA and later in vibration applied to Sol muscle. In vibration applied to the back surface of neck muscle, preceding EMG activities of BFi appeared earlier, as with vibration applied to TA. On the contrary, in vibration applied to the front surface of neck muscles, preceding EMG activities of BFi appeared later, as with vibration applied to Sol. Based on these results, we discuss changes in the central processing of proprioceptive signals used for coding of the spatial orientation of the body and its contribution to postural stabilization.

Adult↗
PubMed2006

Postural hypocapnic hyperventilation is associated with enhanced peripheral vasoconstriction in postural tachycardia syndrome with normal supine blood flow.

Previous investigations have demonstrated a subset of postural tachycardia syndrome (POTS) patients characterized by normal peripheral resistance and blood volume while supine but thoracic hypovolemia and splanchnic blood pooling while upright secondary to splanchnic hyperemia. Such "normal-flow" POTS patients often demonstrate hypocapnia during orthostatic stress. We studied 20 POTS patients (14-23 yr of age) and compared them with 10 comparably aged healthy volunteers. We measured changes in heart rate, blood pressure, heart rate and blood pressure variability, arm and leg strain-gauge occlusion plethysmography, respiratory impedance plethysmography calibrated against pneumotachography, end-tidal partial pressure of carbon dioxide (Pet(CO2)), and impedance plethysmographic indexes of blood volume and blood flow within the thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations while supine and during upright tilt to 70 degrees. Ten POTS patients demonstrated significant hyperventilation and hypocapnia (POTS(HC)) while 10 were normocapnic with minimal increase in postural ventilation, comparable to control. While relative splanchnic hypervolemia and hyperemia occurred in both POTS groups compared with controls, marked enhancement in peripheral vasoconstriction occurred only in POTS(HC) and was related to thoracic blood flow. Variability indexes suggested enhanced sympathetic activation in POTS(HC) compared with other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTS(HC).

Adolescent↗
PubMed1976

[The study of control of posture by frequency analysis of surface electromyogram: an analysis of changes in muscular activity under the controlled posture (author's transl)].

In order to examine the function of muscle for control of posture a frequency analysis was performed of surface EMGs taken from the arm (M. deltoideus) held at the shoulder level. The results indicate that: (a) Power spectra first with a dominant especially with respect to 45-55 Hz component changed significantly 2 components of 5-60 Hz and 65-75 Hz when a 5 min experiment were repeated 3 times, and (b) the ratios of increased power was remarkable in both bands of 10-15 Hz and 30-35 Hz with repeating trials. The control of posture was discussed from the standpoint of behavioral psychology.

Adult↗
PubMedDate not supplied

[Assessment of a postural reference frame as a diagnostic test for lumbar lordotic posture].

INTRODUCTION: Studying lumbar lordosis (LL) in large patient populations is not a practical approach due to the technical limitations of the gold standard. OBJECTIVE: Determine the specificity of a postural reference frame (PRF) in the diagnosis of LL. METHODS: A PRF (wooden frame using strings as a reference for measuring the distance between lumbar curvature and the glutei) was used as a diagnostic test to asses LL. The Ferguson angle, a radiologic evaluation, was used as gold standard. Specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of the PRF were determined. RESULTS: One hundred and ten subjects were studied (58 women, 52 men). Mean age was 18.8 +/- 3 years, weight 63 +/- 12 kg, height 164 +/- 8 cm and body mass index (BMI) 23.2 +/- 4 kg/m2. With a cut-off point 37 cm, test specificity was 94%, sensitiivity was 17%, PPV was 50%, and NPV was 75%. CONCLUSION: The postural reference frame as an assessment tool is highly specific and can aid in the diagnosis of LL among young asymptomatic patients.

Adolescent↗
PubMed1993

Evaluation of the postural stability in man: movement and posture interaction.

The stability of upright posture was evaluated in 13 young and 13 elderly subjects by measuring the amplitude of centre of foot pressure (COFP) excursion in the anteroposterior and mediolateral directions while performing voluntary motor tasks requiring precise center of gravity control i.e., circular and forward-backward sways, squatting and rising on toes. The elderly subjects exhibited a significantly smaller COFP excursion than the young in the circular and forward-backward sways and a nonsignificant reduction in the COFP progression in the rise on toes and squatting tasks. The data document significant reorganization of the motor program execution due to decline in the postural stability in old adults.

Adult↗
PubMed1977

Ergonomics of posture--review of various problems of standing and sitting posture.

Medical and ergonomic field studies indicate that bad standing and sitting postures are sometimes accompanied by pains in muscle and connective tissues of tendons, joint capsules and ligaments. There is evidence that such pains can become the symptoms of chronic diseases attributed to rheumatic disorders. Recent orthopaedic research revealed that inadequate standing and sitting postures provoke excessive increases of intradiscal pressure. These orthopaedic findings, together with ergonomic investigations on sitting behaviour and somatic troubles, provide good bases for the construction of rest chairs and work seats.

Journal Article↗