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At least 217 records · Page 12Linked to original sources

PubMed1997

Lateralizing value and semiology of ictal limb posturing and version in temporal lobe and extratemporal epilepsy.

PURPOSE: Unilateral dystonic limb posturing in partial seizures has been shown to be an accurate lateralizing sign indicating seizure onset in the contralateral hemisphere. However, its clinical utility may be reduced by confusion with other lateralized ictal motor phenomena. In this study, the ictal phenomena of dystonic limb posturing, tonic limb posturing, unilateral immobile limb, and version were distinguished and examined in patients with temporal and extratemporal seizures. METHODS: Partial seizures in 54 patients, successfully treated by surgery (34 temporal, 20 extratemporal; 14 frontal, 3 parietal, and 3 occipital), were analyzed blindly by 3 reviewers. Interobserver agreement was tested with kappa indexes and positive predictive value (PPV) was determined for each sign. RESULTS: In patients with temporal lobe epilepsy (TLE), dystonic posturing occurred in 35.3% (kappa 0.78, positive predictive value (PPV) for the sign being contralateral to seizure onset 92%); tonic limb posturing occurred in 17.7% (kappa 0.36, PPV 40%); unilateral immobile limb occurred in 11.8% (kappa 0.23, PPV 100%); and version occurred in 35.3% (kappa 0.77, PPV 100%). In patients with extratemporal epilepsy, dystonic posturing occurred in 20.0% (kappa 0.31, PPV 100%); tonic limb posturing occurred in 15.0% (kappa 0.08, PPV 67%); and version occurred in 40.0% (kappa 0.54, PPV 100%). The higher kappa indexes were significant for dystonic posturing (p < 0.001) and tonic limb posturing (p = 0.032) in TLE. Dystonic posturing (p = 0.034), tonic posturing (p = 0.07), and version (p = 0.0038) occurred earlier in extratemporal seizures than in temporal seizures. CONCLUSIONS: Of the limb ictal motor phenomena, only dystonic posturing was accurate and had good interobserver agreement.

Adolescent↗

PubMed2006

Early development of postural adjustments in standing with and without support.

This study investigates the early development of postural adjustments during external perturbations in two different standing positions: standing with support and standing without support. The aim of the study was to assess a group of 13 infants four times during the period in life when independent standing is achieved; at 8, 10, 12 and 14 months. However, longitudinal data could be achieved only in four infants. Muscle activations of the neck, hip and ankle were recorded using surface electromyography. Based on earlier studies and controversies, three main issues were addressed: (1) Is direction specificity present before independent standing is established? (2) How do postural adjustments change with increasing age (8-14 months)? (3) Are postural adjustments task-specific in the young child? The results showed that our small sample of infants aged 8 and 10 months, who were not yet able to stand independently, exhibited direction-specific postural adjustments both during standing with and without support, though not consistently during all trials and at all body levels. Therefore, we argue that direction specificity might constitute a prerequisite for the development of independent standing. We also found that the development of postural adjustments in standing with support resembles that of sitting, i.e. great variation in the postural adjustments at early age, and fine-tuning to the situation with increasing age and experience. This, we find that this is in agreement with the proposal that postural control develops through a selection process of the most suitable postural adjustments for the situation from a repertoire of direction-specific postural adjustments. The development of postural adjustments during standing without support is discussed. Additionally, differences in response rates were noted between the two standing positions, indicating that even before independent standing is established, sophisticated sensorimotor integration enables task-specific postural adjustments.

Age Factors↗

PubMed1992

Postural inflexibility in parkinsonian subjects.

In order to identify the types of postural deficits seen in parkinsonian patients with postural instability, we compared the performance of parkinsonian subjects with young and old control subjects in 3 aspects of postural control: (1) the use of sensory information for postural orientation, (2) the coordination of postural movement patterns in response to surface displacements, and (3) the flexible modification of postural response patterns to changes in support conditions. Parkinsonian subjects had very small sway, even under altered sensory conditions. Postural response latencies to displacements were also normal. Postural instability was associated with abnormal patterns of postural responses including excessive antagonist activity and inflexibility in adapting to changing support conditions. Some parkinsonian subjects appeared to have difficulty sequencing motor programs for postural correction. The parkinsonian subjects appeared stiffer since the rate-of-change of sway in response to displacements was reduced. Levodopa improved postural coordination but not the flexible adaptation to changing support conditions.

Adult↗

PubMed2005

Direction-specific postural instability in subjects with Parkinson's disease.

The purpose of this study was to determine whether and why subjects with Parkinson's disease (PD) have greater instability in response to specific directions of perturbations than do age-matched control subjects and how instability is affected by stance width. This study compared postural responses to 8 directions of surface translations in PD subjects and age-matched control subjects while standing in a narrow and wide stance. PD subjects were tested in their practical OFF state. A postural stability margin was quantified as the difference between peak center of pressure (CoP) and peak center of mass (CoM) displacement in response to surface translations. The control subjects maintained a consistent stability margin across directions of translations and for both narrow and wide stance by modifying rate of rise of CoP responses. PD subjects had smaller than normal postural stability margins in all directions, but, especially for backwards sway in both stance widths and for lateral sway in narrow stance width. The reduced stability margin in PD subjects was due to a slower rise and smaller peak of CoP in the PD subjects than in control subjects. Lateral postural stability was compromised in PD subjects by lack of trunk flexibility and backwards postural stability was compromised by lack of knee flexion, resulting in excessive displacements of the body CoM. Stability margins in PD subjects were related to their response on the pull test in the Unified Parkinson's Disease Rating Scale. Thus, PD patients have directionally specific postural instability due to an ineffective stiffening response and inability to modify their postural responses for changing postural demands related to direction of perturbation and initial stance posture. These results suggest that the basal ganglia, in addition to regulating muscle tone and energizing postural muscle activation, also are critical for adapting postural response patterns for specific biomechanical conditions.

Aged↗

PubMed2005

The effect of postural correction on muscle activation amplitudes recorded from the cervicobrachial region.

In clinical practice, postural correction is a common treatment approach for individuals with neck and shoulder pain. As chronic static muscle use is thought to be associated with the onset of some neck and shoulder pain syndromes, it is important to understand the impact a postural correction program might have on muscle activation amplitudes in the neck and shoulder regions. Normalized surface electromyographic data were recorded from the levator scapulae, upper trapezius, supraspinatus, posterior deltoid, masseter, rhomboid major, cervical erector spinae, and sternocleidomastoid muscles of the dominant side of each of eighteen healthy subjects. Subjects performed five repetitions of each of four seated typing postures (habitual, corrected, head-forward and slouched) and four standing postures (habitual, corrected, and head-forward and slouched). Repeated-measures analysis of variance models (alpha=0.05) revealed that in sitting postural correction tended to decreased the level of muscle activation required in all muscles studied during seated computer work, however this finding was not statistically significant. Corrected posture in sitting did, however produce a statistically significant reduction in muscle activity compared to forward head posture. Corrected posture in standing required more muscle activity than habitual or forward head posture in the majority of cervicobrachial and jaw muscles, suggesting that a graduated approach to postural correction exercises might be required in order to train the muscles to appropriately withstand the requirements of the task. A surprising finding was that muscle activity levels and postural changes had the largest impact on the masseter muscle, which demonstrated activation levels in the order of 20% maximum voluntary electrical activation.

Adult↗

PubMed2004

Obstacle negotiation kinematics: age-dependent effects of postural threat.

This study investigated whether obstacle negotiation kinematics among younger (YA) and older adults (OA) are influenced by postural threat. Obstacle negotiation kinematics among YA and OA were examined under four conditions of postural threat. Seventeen older and 15 YA negotiated a fixed virtual obstacle while walking at a self-determined velocity along a 7.2 m walkway. Postural threat was manipulated by varying the width (0.60 vs. 0.15 m) and height (0.00 vs. 0.60 m) of the walkway. Increasing postural threat resulted in elevated levels of physiological arousal and altered crossing kinematics for all subjects. Specifically, crossing step length, lead limb velocity, trail limb velocity, and whole body center of mass (COM) velocity decreased and lead limb crossing height increased in the condition of greatest postural threat compared with the condition of least postural threat. Although both YA and OA altered obstacle negotiation kinematics under conditions of postural threat, the changes observed among older adults were considerably different from those of YA. In particular, OA demonstrated more marked reductions in the crossing velocity of the lead limb, trail limb, and COM than YA between the condition of least postural threat and the condition of greatest postural threat. The results of this study reveal that postural threat influences negotiation kinematics among YA and OA and illustrate that age-dependent differences exist for obstacle negotiation kinematics when postural threat increases. These findings may imply a beneficial effect of fear of falling on reducing fall probability among healthy OA.

Accidental Falls↗

PubMedDate not supplied

[Can an insufficient posture of children and adolescents be verified instrumentally?].

UNLABELLED: 144 children aged 6 to 17 years were examined with the Lasar-Posture device which raises a perpendicular through the centre of gravity. To make an indirect postural examination possible and to classify posture, the courses of the gravity perpendicular, the shoulder centre, the greater trochanter femoris and the lateral ankle and their change during the Matthiass' test were determined. Additionally, spinal alignment, spine flexibility and the sufficiency of posture were assessed. RESULTS: The ability to achieve a sufficient posture correlated with age (p = 0,0004). The spinal alignment itself did not differ in the age groups but the hollow-round back showed a decreased ability to attain a sufficient posture (p < 0.0001). The spine flexibility measured with the Ott's test decreased with age (p = 0.0001). In relation to the gravity perpendicular, the shoulder centre moved forward with increasing postural insufficiency (p = 0.0379). The course of the gravity perpendicular did not differ in the different types of spinal alignment but was always found in front of the lateral ankle. The greater trochanter of the children with a II degrees insufficiency at the beginning (p = 0.03/0.01) and end (p = 0.2/0.05) of the Matthiass' test was always in front of the gravity perpendicular in contrast to the other children. As expected, the shoulder centre was always behind the gravity perpendicular. It was found to be more ventral in healthy children than in those with a postural insufficiency (p = 0.01/0.004/0.005). CONCLUSION: Overall, a high rate of children with postural insufficiency was found. It is impossible to determine or classify them with the Lasar-Posture device. The future aim should be to develop a measuring technique that allows a standardised definition of posture and age related developmental variants.

Adolescent↗

PubMedDate not supplied

A new symmetry-based scoring method for posture assessment: evaluation of the effect of insoles with mineral derivatives.

BACKGROUND: There is a need for a validated rapid procedure for the evaluation of posture, defined as lateral balance/imbalance at the pelvic, shoulder, and neck levels. This would enable clinicians to determine the importance of symmetry in the pathophysiology of musculoskeletal disorders and to assess the efficacy of devices and treatments claiming to normalize or improve posture. In this investigation, the efficacy of such a device, a set of insoles with a hypothesized proprioceptive-like action, was evaluated through use of the described procedure. OBJECTIVES: To develop a new scoring system to evaluate body posture on the basis of symmetry and to use this scoring system to investigate the efficacy of insoles containing a combination of mineral derivatives designed to balance posture through a neurophysiological effect. METHODS: The posture score was based on the evaluation of 4 postural parameters: pelvic and shoulder lateral balance/imbalance, static shoulder rotation, and amplitude of head rotation. In the placebo-controlled study, 32 patients were tested in a double-blind fashion, either with placebo insoles or with insoles containing mineral derivatives. The same study was repeated in unblind conditions in 137 patients selected from 2 chiropractic clinics in an open-label protocol. STUDY DESIGNS: A crossover placebo-controlled, double-blind study and a multicenter, large-scale, open-label study in patients selected from chiropractic clinics. RESULTS: A basal postural evaluation in 137 patients revealed that no patient had a perfect symmetry-ie, a perfectly or nearly perfectly balanced posture. The insoles with mineral derivatives induced a highly significant and similar improvement in the postural score in both the crossover double-blind study (32 patients; 56.7% improvement) and the open-label study (137 patients; 60.7% improvement, P < 0.001). CONCLUSIONS: All patients tested and selected in chiropractic clinics exhibited asymmetries and postural imbalances according to the newly developed scoring method, and this method was successful in assessing the efficacy of insoles exerting a profound and immediate postural effect through a hypothesized neurophysiological mode of action.

Adolescent↗

PubMed1997

Practice modifies the developing automatic postural response.

The purpose of this study was to examine effects of experience with a postural task on components of the automatic postural response including: (1) probability of activation of functionally appropriate postural muscles; (2) number of functionally appropriate postural muscles activated; and (3) onset latencies of functionally appropriate postural muscles in infants. Infants (n=15; age 36-48 weeks old) able to pull themselves into a standing position but not able to walk independently were tested using a postural task requiring the infant to stand and balance, with support, following a forward or backward movement of the support surface (platform perturbation). Infants were tested twice at 5-day intervals. One-half of the infants, the training group, were given intense platform perturbation training on the days between test sessions. Infants in the second group were also brought into the laboratory on the days between test sessions but were not exposed to platform perturbations during those days. Electromyograms of six leg and trunk muscles were recorded during test sessions to provide muscle onset latencies, probability of muscle activation data, and the number of postural muscles activated following a perturbation. Training infants demonstrated significant increases in probability of activating functionally appropriate muscles with tibialis anterior, quadriceps, and abdominal muscles activated in response to backward sway and gastrocnemius muscle in response to forward sway. The number of functionally appropriate postural muscles activated in a single trial also increased in the training group. There were no significant changes in mean postural muscle onset latencies or number of trials with antagonist muscle coactivation for either training or control groups. These findings suggest that during development selective parameters of the automatic postural response are affected by experience with the postural task.

Child Development↗

PubMed2006

Rasterstereographic analysis of axial back surface rotation in standing versus forward bending posture in idiopathic scoliosis.

The forward bending test according to Adams and rib hump quantification by scoliometer are common clinical examination techniques in idiopathic scoliosis, although precise data about the change of axial surface rotation in forward bending posture are not available. In a pilot study the influence of leg length inequalities on the back shape of five normal subjects was clarified. Then 91 patients with idiopathic scoliosis with Cobb-angles between 20 degrees and 82 degrees were examined by rasterstereography, a 3D back surface analysis system. The axial back surface rotation in standing posture was compared with that in forward bending posture and additionally with a scoliometer measurement in forward bending posture. The changes of back shape in forward bending posture were correlated with the Cobb-angle, the level of the apex of the scoliotic primary curve and the age of the patient. Averaged over all patients, the back surface rotation amplitude increased from 23.1 degrees in standing to 26.3 degrees in forward bending posture. The standard deviation of this difference was high (6.1 degrees ). The correlation of back surface rotation amplitude in standing with that in forward bending posture was poor (R (2)=0.41) as was the correlation of back surface rotation in standing posture with the scoliometer in forward bending posture measured rotation (R (2)=0.35). No significant correlation could be found between the change of back shape in forward bending and the degree of deformity (R (2)=0.07), likewise no correlation with the height of the apex of the scoliosis (R (2)=0.005) and the age of the patient (R (2)=0.001). Before forward bending test leg length inequalities have to be compensated accurately. Compared to the standing posture, forward bending changes back surface rotation. However, this change varies greatly between patients, and is independent of the type and degree of scoliosis. Furthermore remarkable differences were found between scoliometer measurement of the rib hump and rasterstereographic measurement of the vertebral rotation. Therefore the forward bending test and the identification of idiopathic scoliosis rotation by scoliometer can be markedly different compared to rasterstereographic surface measurement in the standing posture.

Back↗

PubMed2006

Validation of a computer analysis to determine 3-D rotations and translations of the rib cage in upright posture from three 2-D digital images.

Since thoracic cage posture affects lumbar spine coupling and loads on the spinal tissues and extremities, a scientific analysis of upright posture is needed. Common posture analyzers measure human posture as displacements from a plumb line, while the PosturePrint claims to measure head, rib cage, and pelvic postures as rotations and translations. In this study, it was decided to evaluate the validity of the PosturePrint Internet computer system's analysis of thoracic cage postures. In a university biomechanics laboratory, photographs of a mannequin thoracic cage were obtained in different postures on a stand in front of a digital camera. For each mannequin posture, three photographs were obtained (left lateral, right lateral, and AP). The mannequin thoracic cage was placed in 68 different single and combined postures (requiring 204 photographs) in five degrees of freedom: lateral translation (Tx), lateral flexion (Rz), axial rotation (Ry), flexion-extension (Rx), and anterior-posterior translation (Tz). The PosturePrint system requires 13 reflective markers to be placed on the subject (mannequin) during photography and 16 additional "click-on" markers via computer mouse before a set of three photographs is analyzed by the PosturePrint computer system over the Internet. Errors were the differences between the positioned mannequin and the calculated positions from the computer system. Average absolute value errors were obtained by comparing the exact inputted posture to the PosturePrint computed values. Mean and standard deviation of computational errors for sagittal displacements of the thoracic cage were Rx=0.3+/-0.1 degrees , Tz=1.6+/-0.7 mm, and for frontal view displacements were Ry=1.2+/-1.0 degrees , Rz=0.6+/-0.4 degrees , and Tx=1.5+/-0.6 mm. The PosturePrint system is sufficiently accurate in measuring thoracic cage postures in five degrees of freedom on a mannequin indicating the need for a further study on human subjects.

Biomechanical Phenomena↗

PubMed1992

Effects on platelet aggregation and fibrinolytic activity during upright posture and exercise in healthy men.

The circadian variation of acute myocardial infarction suggests that daily activities such as assuming the upright posture and performing different daily activities may trigger the onset of coronary thrombosis. Such triggering may result from unfavorable alterations in the balance between the prothrombotic and antithrombotic properties of the blood. The present study compares the effects of 2 common daily activities, assuming the upright posture and exercise, on platelet aggregation and fibrinolytic activity. In healthy male subjects, assuming the upright posture in the morning significantly increased platelet aggregation and produced only a moderate increase in fibrinolytic activity within 10 minutes. These changes were still present after 90 minutes in the upright posture. Supine posture for 45 minutes resulted in levels of fibrinolytic activity and platelet aggregation comparable to that observed before initially assuming the upright posture in the morning. Return to the supine posture for 45 minutes resulted in levels of fibrinolytic activity and platelet aggregation comparable to that observed before the initial assumption of upright posture. The changes recurred when upright posture was taken later in the day. Exercise did not increase platelet aggregation to levels beyond that produced by the upright posture, but was associated with a marked increase in fibrinolytic activity. Thus, exercise and upright posture produce distinctive alterations in the thrombogenic potential of the blood that may influence the timing of clinical vascular events.

Adult↗

PubMed1997

Postural control and strength and mood among older adults.

Falls are a significant problem among older adults. Reported correlates of older adult falls have included determinations in leg muscle strength and declines in postural control. However, some investigators have reported low correlations between measures of strength and postural control among older adults. Other investigators have reported that attention demands in this group are inversely related to their postural control. No study has attempted to predict postural control from mood precursors or from knee and ankle strength among older adults. The purpose of this study was to examine relationships between postural control and strength and mood precursors to attention among older adults. Twenty-seven older adults (m = 73.8 years) completed the 16-item Mood Response Scale, which measures total mood, and three subscales conceptualized to be precursors of the subject's ability to focus attention: alertness, contentedness, and calmness. Measures of each subject's isometric knee and ankle strength and postural control also were collected. Using stepwise regression analysis the investigators found that alertness accounted for the greatest amount of variance in all three measures of postural control (R2 = 20 to 27). Additionally, ankle strength, calmness, and age considerably increased the explained variance in postural sway with eyes closed (total R2 = 416). Age was not a significant predictor of the other two measures of postural control. The findings suggest that alertness, a precursor to attention among older adults, is a significant predictor of postural control when vision is intact but that other factors assume importance when vision is impaired. These findings indicate that the postural stability of older adults may be improved, and falls reduced, through interventions which enhance the alertness and attention among older adults.

Accidental Falls↗

PubMed2003

Posture-dependent trunk extensor EMG activity during maximum isometrics exertions in normal male and female subjects.

Posture-dependent trunk function data are important for appropriate normalization of submaximal trunk exertions, and is also necessary to define a more precise and specific use for strength testing in the prevention and diagnosis of spinal disorders. The aim of the current study was to quantify maximal effort trunk muscle extensor activity and trunk isometric extension torque over a functional range of sagittal standing postures. Twenty healthy, young adult male and female subjects performed isometric extension tasks over a sagittal posture range of -20 degrees extension to +50 degrees flexion, in 10 degrees increments. Erector spinae muscle activity was recorded bilaterally at the level of L3 using surface EMG electrodes. Isometric trunk extension torque was measured using a trunk dynamometer. EMG and trunk torque differed significantly between genders, but there were no differences between male and female subjects when the data were normalized with respect to the upright posture. For the combined male and female population, upright posture normalized L3 EMG activity (EMGn) and trunk extension torque (Tn) increased 1.7-fold and 3.5-fold, respectively, over the 70 degrees range of sagittal postures examined. The ratio (Tn/EMGn) increased two-fold (0.83 to 1.67) from -20 degrees extension to +50 degrees flexion, indicating that the neuromuscular efficiency increases with flexion. Trunk extension torque normalized with respect to the upright posture was linearly and positively correlated (r = 0.59, P < 0.001) to similarly normalized L3 EMG activity. This relatively weak correlation suggests that trunk muscle synergism and/or intrinsic muscle length-tension relationships are also modulated by posture. This study provides data that can be used to estimate trunk extensor muscle function over a broad range of sagittal postures. Our findings indicate that appropriate postural normalization of trunk extensor EMG activity is necessary for studies where submaximal trunk exertions are performed over a range of upright postures.

Adult↗

PubMed2001

The boundaries for joint angles of isocomfort for sitting and standing males based on perceived comfort of static joint postures.

This study presents data for the joint angles of isocomfort (JAI) in sitting and standing males based on perceived comfort ratings for static joint postures maintained for 60 s. The JAI value was defined as a boundary indicating joint deviation (an angle) from neutral posture, within which the perceived comfort for different body joint postures is expected to be the same. An experiment for quantifying perceived comfort ratings was conducted using the free modulus method of magnitude estimation. Based on experimental results, regression equations were derived for each joint posture, to represent the relationships between different levels of joint deviation/joint posture and corresponding normalized comfort scores. The JAI values were developed for nine verbal categories of joint comfort. The JAIs with the marginal comfort levels, one of the nine verbal categories used, for most joint postures around the wrist, elbow, neck and ankle were similar to the maximum range of motion (ROM) values for these joints. However, the JAIs with the marginal comfort category for back and hip postures were much smaller than the maximum ROM values for these joints. There were no significant differences in JAI expressed in terms of the percentage of the corresponding maximum ROM values between sitting and standing postures. The relative 'marginal comfort index', defined as the percentage of JAIs for the marginal comfort relative to the corresponding maximum ROM values, for the hip was the smallest among all joints. This was followed, in an increasing order of the marginal comfort index, by the lower back and shoulder, while the marginal comfort index for the elbow joint was the largest. The results of this study suggest that static postures maintained for 60 s cause greater discomfort for the hip joint than for the other joints studied, and less discomfort for the elbow than for the other joints. The data about JAIs can be used as guidelines for enhancing postural comfort when designing a variety of human-machine tasks where static postures cannot be eliminated.

Adult↗

PubMed1993

Effect of posture on lung and regional chest wall mechanics.

BACKGROUND: Little is known about the extent to which changes in postures in clinical situations affect respiratory mechanics, even in humans with healthy respiratory systems. This study tested the hypothesis that posture has only small effects on overall respiratory system mechanics in healthy subjects, despite changes in parts of the respiratory system in some postures. METHODS: Measurements were made of airway flow, airway and esophageal pressures, and rib cage and abdominal volume displacements (with inductance plethysmography) of awake, healthy subjects, relaxed at functional residual capacity, during external forcing at 0.2 Hz with a tidal volume of 8-10 ml/kg. From these measurements, discrete Fourier transform was used to calculate elastances (E) and resistances (R) of the total respiratory system, lungs, total chest wall, and compartments of the chest wall (rib cage, diaphragm-abdomen, and belly wall). Measurements were made while the subjects were in nine different postures: in six of these, the torso was straight; in three, the torso was bent or twisted. RESULTS: Although changes in mechanics of parts of the respiratory system were evident in certain postures, overall respiratory mechanics were not greatly affected by posture. Changing from sitting to supine decreased E and R of the diaphragm-abdomen about 50% (P < .05), but total chest wall E and R changed only slightly. Lung E increased 24% (P < .05), but total respiratory E did not change (P < .05). Lung and total respiratory R increased 40-50% (P < .05) with this same change in posture. As long as the torso was straight, however, changes in orientation of 30 degrees from the horizontal or a shift to lateral posture resulted in only minor changes in the variables measured. Postures in which the torso was twisted or bent increased E of the total chest wall 20-30% compared to supine (P < .05), due to increases in E of one or more compartments. Respiratory system E also increased, at most 14%. Although lung R decreased 30-45% (P < .05) in these postures compared to supine with a straight torso, chest wall and total respiratory R generally were unchanged. CONCLUSIONS: Changes in respiratory system mechanics over a wide range of postures that may be encountered clinically are relatively small in healthy awake subjects due to adaptability of total chest wall mechanical behavior.

Adult↗

PubMed1997

Trunk extension strength and muscle activity in standing and kneeling postures.

STUDY DESIGN: A split-plot experimental design was used to evaluate the influence of posture, trunk angle, and rotational velocity on peak torque output and myoelectric activity during maximal trunk extension maneuvers. OBJECTIVES: To determine whether the kneeling posture alters extension torque capabilities in isometric and isokinetic exercises as compared with standing. Also, to ascertain whether recruitment of trunk muscles is modified by such a postural change. SUMMARY OF BACKGROUND DATA: Factors such as workplace geometry may force workers to adopt awkward or unusual postures in the performance of manual tasks. An understanding of the limitations placed on strength in unconventional working postures is crucial to the proper design of jobs. METHODS: Twenty-one healthy male subjects (mean age = 36 years +/- 7 SD) performed 12 trunk extension exertions in standing and kneeling postures. Isometric tests were performed at 22.5 degrees, 45 degrees, and 67.5 degrees of trunk flexion. Isokinetic tests were done at three velocities: 30 degrees/sec, 60 degrees/sec, and 90 degrees/sec. Electromyographic data were collected from eight trunk muscles to assess muscle recruitment under each condition. A priori orthogonal contrasts were specified for analysis of both torque and electromyographic data. RESULTS: The kneeling posture was associated with a 15% decrease in peak torque output when contrasted with standing: however, no concomitant change in trunk muscle activity was evident. Trunk hyperflexion (isometric tests) and increasing rotational velocity (isokinetic tests) were associated with reduced torque in both postures. Trunk muscle activity was primarily affected by changes in trunk angle and velocity of contraction. CONCLUSIONS: A reduced extensor capability exists in the kneeling posture, despite equivalent trunk muscle activity. The similar activation patterns in both postures suggest that the strength deficit does not result from alterations in trunk muscle function. Rather, it may be the consequence of a reduced capability to rotate the pelvis in the kneeling posture, due to a disruption of the biomechanical linkage of the leg structures.

Adult↗

PubMed2002

The effects of side-posture positioning and spinal adjusting on the lumbar Z joints: a randomized controlled trial with sixty-four subjects.

STUDY DESIGN: A blinded, randomized controlled trial was conducted. OBJECTIVE: To test the hypothesis that chiropractic side-posture manipulation (adjusting) of the lumbar spine separates (gaps) the zygapophysial (Z) joints. SUMMARY OF BACKGROUND DATA: Spinal adjusting is thought to gap the Z joints, yet no studies have conclusively validated this hypothesis, and some investigators have reported that the lumbar Z joints do not gap during rotation. METHODS: For this study, 64 healthy student volunteers (32 men and 32 women) ages 22 to 30 years with no history of significant low back pain were randomized into four groups of 8 men and 8 women each. Interventions included lumbar side-posture spinal adjusting (manipulation) and side-posture positioning. Anterior to posterior measurements of the Z joints from MRI scans taken before and after side-posture spinal adjusting and before and after side-posture positioning were compared. RESULTS: Observers performing the measurements were blinded as to group and first and second scans. Reliability of the measurements was established. Differences were found between the groups (F = 24.15; P < 0.000, analysis of variance). Side-posture positioning showed greater gapping than the control condition (mean difference, 1.18; P < 0.000); side-posture adjusting showed greater gapping than the control condition (mean difference, 1.89; P < 0.000), and side-posture adjusting showed greater gapping than side-posture positioning (mean difference, 0.71; P = 0.047). CONCLUSIONS: Spinal adjusting produced increased separation (gapping) of the Z joints. Side-posture positioning also produced gapping, but less than that seen with lumbar side-posture adjusting. This study helps to increase understanding about the mechanism of action for spinal manipulation.

Adult↗