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PubMed2006

The control system for the Honda humanoid robot.

To avoid tipping over either during walking or on standing up, humans will first push down hard on the ground with a part of the sole of the foot. Then, when the tipping force can no longer be resisted, a change in body position or an extra step (stepping out) may be required to stabilise the posture. Our biped robot's control system attempts to reproduce and execute the same postural control operations carried out by humans. In this article, we present the history of robot development at Honda, fundamental dynamics for robots and the principles of posture control.

Artificial Intelligence↗

PubMed1998

The clinical diagnosis of the narcoleptic syndrome.

Sleep-wake habits and control of postural muscle tone were investigated by self-report questionnaire in 183 subjects considered to have the narcoleptic syndrome, 62 subjects with hypersomnia and 10 with obstructive sleep apnoea. Results were compared with those in a group of 188 control subjects with normal sleep wake habits. Excessive daytime sleepiness, determined by the Epworth Sleepiness Scale (ESS), was five times greater in the narcoleptic syndrome than in control subjects (score range 0-24, mean scores +/-SD 19.6+/-3.0; and 4.5+/-3.3 respectively; P<0.001). The propensity to cataplexy, as determined by a rating scale developed to estimate the likelihood of loss of postural tone in response to sudden emotional stimuli, including laughter, was 10 times greater in narcoleptic syndrome than in control subjects (postural atonia total score range 0-600; mean + SD 334+/-122 and 28+/-45, respectively; P<0.001). Narcoleptics had more disturbances of night sleep than controls with episodes of muscle jerking, sleep walking, sleep talking and sleep terrors, as well as sleep paralysis, and higher insomnia self-rating scores. Sleep latency from bedtime to sleep-onset time was shorter in narcoleptics than controls. The hypersomniac group of 62 subjects was heterogeneous. Subsequent investigation showed that 18 subjects (29%) had idiopathic hypersomnia, four (6%) 'incomplete' narcolepsy without cataplexy and 10 (16%) hypersomnia accompanying a mood disorder. The mean ESS scores in this group and in subjects with obstructive sleep apnoea were comparable to those of the narcoleptic syndrome subject group. Mean postural atonia scores were similar to those of control subjects.

Adult↗

PubMed1993

Vestibular induced postural responses in Parkinson's disease.

We have tested the hypothesis that dysfunction of the vestibular control of posture is a principal cause of parkinsonian instability by measuring the body sway response induced by galvanic vestibular stimulation (0.5 mA for 2 s) in a group of patients with Parkinson's disease (n = 15). Responses were compared with those obtained from a group of age-matched control subjects (n = 10). Subjects were stimulated (randomized polarity) whilst standing with feet together, eyes closed and maintaining one of five head yaw angles. The motion of the body and the ground reaction forces were measured in three dimensions. There was no significant difference between patients and controls in the speed or direction of the induced body sway response. When the patients were subdivided into two groups according to a clinical assessment of postural deficit, the more disabled group was found to respond with significantly greater body speed than either the control group or the mildly affected patient group. However, the baseline speed of spontaneous body sway was also greater in these patients and it was found that response speed was linearly related to baseline body sway even for the control group. There were no significant differences between any of these groups in the latency to onset, latency to peak or peak amplitude of the initial horizontal ground reaction force response to the stimulus. We conclude that vestibular dysfunction does not explain the postural deficits of patients who are mildly or moderately affected by Parkinson's disease.

Biomechanical Phenomena↗

PubMed1976

Effect of posture on renal lithium clearance.

1. Renal lithium clearance in healthy men was elevated while the subject was reclining, decreased upon standing and increased upon lying down during 45-60 min tests. 2. Parallel changes in renal clearance of creatinine, sodium and potassium, and urine flow rate occurred in response to the changes in posture. 3. The findings demonstrate for the first time that posture is a factor that can influence lithium excretion. Control of posture during lithium excretion tests is recommended.

Adult↗

PubMedDate not supplied

Effects of regular walking on postural stability in the elderly.

BACKGROUND: Both age and lack of physical activity may be responsible for poor health and poor balance control. Conversely, physical activity may modulate postural control in elderly people. OBJECTIVE: An observational study was performed in older adults to explore whether walking on a regular basis might prove to be beneficial not only to the cardiovascular system but also to maintaining a good balance. METHODS: Twenty-two healthy older subjects walking on a regular basis (DW group) and 121 healthy control older subjects who did not walk regularly (NW group) were studied. The subjects included in the study were free from major gait and postural disorders. An instrumented force platform was used to measure the time-varying displacements of the center of pressure under eight static conditions and postural limit tests. An isometric test was performed to evaluate lower limb muscle strength, and a static two-point discrimination test evaluated the innervation density of the slowly adapting receptors of the sole of the first toe. RESULTS: The DW group had a significantly better (p < 0.05) postural stability under static conditions than the NW group. There were no significant differences in postural limit tests and in two-point discrimination between the groups. The DW group had significantly higher values of ankle plantar flexor and knee extensor strengths, while there were no significant differences in ankle dorsiflexors and knee flexors. None of the DW group reported experiencing a fall during the previous 6 months compared with 16% in the NW group who reported at least two falls during the last half year. CONCLUSIONS: Walking on a regular basis in old age may have the potential to modulate stability. It was found that healthy older subjects, who walked on a regular basis since their retirement, have better postural control, especially in their static balance, than those who do not. The laboratory results were accompanied by the important finding that although older subjects who walk on a regular basis walked much more than nonwalkers, they did not suffer from falls.

Accidental Falls↗

PubMed1978

Dynamic features of standing and their correlation with neurological disorders.

Standing posture is a result of complex activity of the human control system. Irregularities of postural control may be expected to result in deviations from normal standing. In the present study a ballistic monitoring technique was employed to establish criteria for assessment of postural disorders. Two "Kistler" force plate dynamometers were used to measure changes in the weight bearing components of each foot and displacement of the center of pressure of each foot. The patterns were analysed separately, and it was found that each of the monitored parameters demonstrated three modes of oscillation--termed Tremor, Ataxia and Sway. Statistical analysis conducted on three groups of subjects (normals, post-C.V.A. hemiplegics and brain injured) revealed significant intergroup differences in movement patterns. Good agreement was found between the interpretation of the ballistic features and the clinical diagnosis.

Ataxia↗

PubMed1985

Motor behavior underlying the control of an upside-down vertical posture.

The present study examines the control of equilibrium by trained acrobats standing balanced upside-down on their hands. The focus of the experiment was to analyze the postural attitudes of various body segments and the underlying motor activity, and to evaluate the influence of vision. We found a strong correlation between the motor activity of two antagonist muscles of the forearm and the anteriorposterior position of the center of gravity. The upside-down standing posture was most stable when the neck was dorsiflexed, indicating that the tonic neck reflex and the tonic labyrinthine reflex play an important role in the stability of this posture. Comparison between known data about the normal standing posture, on the feet, and the upside-down standing posture, on the hands, shows that motor behavior of the two postures is similarly organized.

Electromyography↗

PubMed2004

A quantitative measure of postural sway deficits in schizophrenia.

Clinicians rely on observational methods to assess obvious signs of postural abnormalities in schizophrenia, yet subtle signs of postural deficits may go unnoticed. Posture is controlled, in large part, by the cerebellum, which has been implicated in numerous reports of structural and functional deficits in schizophrenia. Given the possibility of an underlying disruption of cerebellar function in schizophrenia, this study used an objective, quantitative measure to assess the magnitude of postural stability in this disorder. A total of 36 schizophrenia patients and 36 non-psychiatric age-matched controls stood on a pressure-sensitive platform that recorded shifts in weight (body sway) through pressure points in the feet. Patients demonstrated more postural sway than did healthy controls (p<0.01). When patients with noticeable signs of tardive dyskinesia were removed from analyses, group differences remained (p<0.01). There was no significant correlation between neuroleptic medication level and degree of postural sway (r=0.16, p=0.37). These results indicate that patients with schizophrenia have subtle, yet quantifiable, disturbances in the control of posture and balance. Quantitative measures of postural sway may provide a more sensitive means of detecting disturbances of movement than do standard clinical observations alone.

Adult↗

PubMed2005

Evaluation of segmental postural characteristics during quiet standing in control and Idiopathic Scoliosis patients.

BACKGROUND: The complex skeletal deformations that accompany Idioapthic Scoliosis pose a challenge to the clinician to non-invasively discriminate Idiopathic Scoliosis patients from children with no pathology. Therefore, the focus of this study is to non-invasively evaluate the position and amplitude of displacement of the pelvis, shoulders and thorax during quiet standing of Idiopathic Scoliosis patients and control subjects. METHODS: The quiet standing posture of 18 healthy adolescent females and 22 Idiopathic Scoliosis subjects was evaluated using an Optotrak 3020 position sensor over a period of 120 s, with 4 repeat trials. Outcome measures included the mean position, root mean square amplitude and range over the duration of 120 s trials for both linear and angular measures of the pelvis, thorax and shoulders. Appropriate sample times were chosen and evaluated for stability over the 120 s period, and between trial reliability was evaluated. FINDINGS: There was a significant difference between groups for the mean position of the shoulder blade rotation in reference to the base of support and to the pelvis. The Idiopathic Scoliosis patients had a significantly larger root mean square amplitude of anterior-posterior displacement of the T1 and S1 spinous processes in reference to the base of support. There was no difference between the sample durations to estimate the mean position of the body segments, however the root mean square increased significantly. INTERPRETATION: This study demonstrates that postural abnormalities are evident during quiet standing in Idiopathic Scoliosis patients.

Child↗

PubMed1987

Differential effects of cortical lesions in humans.

The best-known example of motor deficits after cortical lesions is contralateral paresis and spasticity after damage to the precentral motor strip. After recovery the residual motor functions can be used in a purposive and skillful manner. In patients with lesions of the supplementary motor area (SMA) and cingulate gyrus transient akinesia and mutism have been described. Lesions restricted to more lateral parts of the premotor field interfere with proximal muscle function and interlimb coordination, whereas distal motor activity and bimanual coordination are unimpaired. In contrast, hand function in patients with parietal lesions is severely disturbed. This dysfunction includes deficits such as ataxia, dysmetria and postural instability that are typically observed in deafferented patients. Severe disturbances of the purposive behaviour of the hand during exploratory finger movements and manipulation of objects are seen in patients with posterior parietal lesions. Observations in human patients are compatible with the hypothesis that lesions of the frontal agranular motor fields interfere with the control of postural and force control whereas parietal lesions are associated with motor programme disorders affecting the use of the hand or the eye as a sense organ or affecting more complex motor behaviour.

Apraxias↗

PubMed2006

Postural responses to multidirectional stance perturbations in cerebellar ataxia.

Previous studies of patients with focal cerebellar damage underscored the importance of the cerebellum for balance control. These studies were restricted to postural control in the pitch plane, and focused mainly on leg muscle responses. Here, we examined the effect of degenerative cerebellar lesions on postural control in multiple directions, and studied how such lesions affect intersegmental coordination of the legs, trunk and arms. We formulated two main questions. (a) Do patients with cerebellar ataxia predominantly have balance problems in the sagittal or frontal planes? (b) Is instability in cerebellar ataxia associated with increased joint motion or with reduced joint motion? We selected nine patients with autosomal dominant spinocerebellar ataxia (SCA)--three with pure ataxia and six with mild extra-cerebellar features--and 12 matched controls. Upright standing subjects received support surface rotations (7.5 degrees at 60 degrees /s) that were randomly delivered in eight different directions of pitch or roll. We used full body kinematics to determine displacements of the center of mass (COM) and of individual body segments. We also collected surface EMG from 10 leg, trunk and arm muscles. Primary variables of interest were COM displacement and trunk control (angles and muscle responses). Secondary analyses focused on angles and muscle responses of the legs and arms. COM analysis demonstrated that SCA patients had greatest instability following backward and laterally directed perturbations. Major factors in causing this instability were, first, a marked reduction of stimulus-induced knee flexion and, second, excessive "hypermetric" motion of the pelvis (in roll) and trunk (in pitch). Muscle responses of SCA patients were characterized by increased late balance correcting activity. Responses of patients with pure ataxia were comparable to those of patients with mild extra-cerebellar features. A main underlying cause of postural instability in SCA patients appears to be "locking" of the knees, which may reflect compensation (by reducing interaction between body links) or reduced vestibulocerebellar control over leg muscles. The observed pathophysiology is very different from that seen in other patient populations.

Adult↗

PubMed1992

Increased sympathetic and decreased parasympathetic cardiac innervation in patients with Alzheimer's disease.

To assess whether Alzheimer's disease affects the sympathetic and parasympathetic influences on the heart rate, we used power spectrum analysis of heart rate variability derived from simple body-surface electrocardiography. We calculated the energy ratio of low- to high-frequency bands. This ratio was significantly higher in patients with Alzheimer's disease than in normal controls (upright posture, 0.41 +/- 0.21 vs 0.23 +/- 0.08). The parasympathetically mediated baroreceptor activity reflected by the energy ratio of medium- to low- and high-frequency bands was significantly depressed in patients with Alzheimer's disease (upright posture, 0.12 +/- 0.02 vs 0.07 +/- 0.03; supine posture, 0.11 +/- 0.02 vs 0.085 +/- 0.025). Compared with normal volunteer controls, patients with Alzheimer's disease manifested a relatively hypersympathetic, hypoparasympathetic state.

Aged↗

PubMedDate not supplied

Pulmonary rehabilitation in patients with chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality in India. Drug treatment alone does not optimize therapy. Pulmonary rehabilitation has been found to improve the physical efficiency of COPD patients. Therefore, we evaluated the effect of domiciliary pulmonary rehabilitation programme in patients of COPD. METHODS: Forty patients of stable COPD having severe airflow obstruction were included in the study. They were divided into control and experimental groups randomly. Rehabilitation included walking, breathing exercises, postural drainage, controlled coughing and changes in life style activities. Exercises of 30 minutes duration were performed at home twice daily for four weeks supervision. Six-minute walking distance, forced expiratory volume in one seocond (FEV1) and various indices of chronic respiratory disease questionnaire (CRDQ) were measured in both experimental and control groups before and after completion of the study. RESULTS: In the experimental group, after four weeks, the mean (+/- SD) difference in six-minute walking distance, dyspnoea, mastery, fatigue and emotion scores were 54.2 (26.7) meters, 0.96 (0.26), 0.89 (0.44), 0.90 (0.40) and 0.91 (0.32) respectively. Changes in all these parameters were statistically significant (p < 0.001) as compared to the control group. There was no significant change in FEV1. CONCLUSION: It was concluded that domiciliary pulmonary rehabilitation for four weeks results in significant improvement in the quality of life and exercise tolerance, even without improvement in FEV1.

Aged↗

PubMed1987

Measurement of blood pressure and heart-rate variation while resting supine and standing for the evaluation of autonomic dysfunction.

Blood pressure and R-R interval variation were studied during postural changes using a tilting table. The subjects were 64 normal controls and 52 patients with various disorders. None of the normal controls showed postural falls of more than 15 mm Hg in mean blood pressure. The mean loge coefficient of variation of 100 R-R intervals was significantly reduced in groups with Parkinson's disease, spinocerebellar degeneration, Shy-Drager syndrome and diabetes mellitus, compared with a normal control group. Reduced heart-rate variation was frequently associated with sphincter disturbance and orthostatic hypotension.

Adolescent↗

PubMed1996

Angular biofeedback device for sitting balance of stroke patients.

BACKGROUND AND PURPOSE: Impaired sitting balance is an important and time-consuming complication for stroke patients. We examined the effect of the use of an angular biofeedback device in addition to physical therapy in training stroke patients with impaired sitting balance compared with outcome in patients receiving conventional physical therapy only. METHODS: The biofeedback group consisted of 24 patients who received angular biofeedback training in addition to conventional physical therapy. The number of biofeedback signals and the lengths of time a patient could sit balanced throughout a period of 5 minutes before the training program, after 10 days of treatment, and at discharge were recorded and compared with those of the control group of 13 patients who received conventional physical therapy only. RESULTS: It was found that 75% of the biofeedback group gained sitting balance after 10 days of treatment in comparison with 15.4% of the control group (P < .001). At discharge, 91.6% of the biofeedback group and 84.6% of the control group gained sitting balance (P = .510), and 45.8% of the biofeedback group and 46.2% of the control group managed independent ambulation (P = .985). The mean rehabilitation periods among the ambulatory patients of the biofeedback and control groups were 9.45 +/- 0.71 and 13.83 +/- 1.70 weeks, respectively (P = .049). The mean training time in which the biofeedback group gained sitting balance was significantly shorter than that of the control group (P < .001). CONCLUSIONS: Angular biofeedback intervention, by providing earlier postural trunk control, is a useful adjunct to conventional physical therapy in the rehabilitation of stroke patients with impaired sitting balance.

Biofeedback, Psychology↗

PubMed1989

Blood pressure during induction and termination of the dorsal immobility response.

Evidence has indicated that afferent baroreceptor input may play a role in the induction of the dorsal and tonic immobility responses, which are behaviorally similar, but involve opposite posture changes upon induction (i.e., upright versus inverted, respectively). Information is lacking on the topography of the blood pressure response during periods of dorsal immobility. The blood pressure response of the adult Wistar rat during induction and termination of dorsal immobility was compared to the blood pressure response during a condition which controlled for posture change. Each animal received two control trials, ten dorsal immobility trials and then two control trials in two successive sessions four and ten days after surgery. A precise second-by-second topographical analysis of the dorsal immobility response revealed a sharp rise in blood pressure at trial onset of 18.4 mmHg, followed by a return below pretrial levels and then subsequent recovery back to pretrial levels by the tenth-trial second. This level was maintained until the last five seconds of immobility when a rapid blood pressure elevation occurred. This terminating elevation correlated highly with the observation of large movement and probably reflected motor activity that eventually culminated in escape from immobility. The vertical posture change of the control condition, on the other hand, resulted in a gradual diminution of blood pressure, which implied that the initial blood pressure elevation during initiation of the dorsal immobility response could not be accounted for simply by posture change.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Postural stability after vestibular schwannoma surgery.

Factors related to postural stability and the course of recovery after vestibular schwannoma surgery were analyzed in a retrospective study of 177 patients and in a prospective study of 44 patients. Before surgery, 7 of the 44 patients in the prospective group complained of postural instability. The body sway velocity was measured. In the retrospective study, the sway velocity was abnormal under nonvisual control in 63% of the patients and under visual control in 34%. The sway velocity correlated with tumor size, smooth pursuit deficit, and postoperative work history. We compared patients with abnormal postural control to those with normal postural control, and found that the former relied to a greater extent on visual information and the latter on proprioceptive information. In the prospective study, the sway velocity increased after the operation, and 1 year after surgery it had not returned to preoperative values. In the logistic regression analysis, a translabyrinthine approach, rehabilitation, the patient's age, and preserved function of the facial nerve predicted a good outcome of postural stability. The retrosigmoid approach and depression were the most significant risk factors for postoperative gait difficulties. Vestibular rehabilitation increased the reliance on proprioception for maintenance of postural control and improved postural stability.

Adult↗

PubMed1996

Loop gain of reflexes controlling human standing measured with the use of postural and vestibular disturbances.

1. In this study we measured the loop gain of postural reflexes in standing human subjects. Reflex activity is conventionally described in terms of the muscle activation arising from a perturbation, but in this study the ability of the evoked muscle activity to correct the perturbation was also measured, and the behavior of the entire feedback loop is described. 2. A weak continuous random perturbation was applied at waist level to standing subjects. The effects of the perturbation on body sway and soleus electromyogram (EMG) were identified by cross-correlation, and spectral analysis was used to estimate the open-loop reflex transmission characteristics (i.e., sway to EMG). Under the same conditions, activity in the leg muscles was evoked by galvanic vestibular stimulation with the use of a continuous randomly varying current. The effects on soleus EMG and the subsequent body sway were identified by cross-correlation. This allowed calculation of the open-loop muscle and load behavior (i.e., EMG to sway). From these open-loop reflex and muscle and load transfer functions, the loop gain and phase were calculated. 3. In addition to the gain of the feedback loop, the study describes the transmission characteristics of reflex responses in the leg muscles associated with body sway and the effects of excluding visual and proprioceptive contributions to the response; the transfer function of human soleus with a stimulus that preserves the normal recruitment of motoneurons, including the effects of different load conditions on the muscle; and the transmission characteristics of vestibular pathways that evoke responses in the leg muscles during standing in situations that might modify the reflexes. 4. When standing, the loop gain of reflex feedback is approximately unity and is unchanged by eye closure and stability of support. Reflex transmission introduced a marked phase advance, and this served to offset most of the phase lag introduced by muscle and load. The residual phase lag could explain the frequency of tremor observed during standing (6-8 Hz). 5. The gain of the feedback loop (approximately 1) is higher than suggested by both previous estimates and theoretical considerations, but is still insufficient to explain the stability of normal human standing. This implies that, although sensory information is used to control posture, it does not do so exclusively through a negative feedback control process. The experimental findings are consistent with a reflex response based on a feed-forward process, and this would result in prediction of the response necessary to counteract a postural disturbance.

Adult↗