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At least 19 recordsLinked to original sources
PubMed1984

Elderly inpatients: postural reflex impairment.

We examined postural reflexes in 50 patients in a geriatric care facility. Patients aged 60 years and older who did not have orthostatic hypotension were subjected to a standing postural perturbation, and the degree of postural instability was recorded. Sixteen patients with leg amputations, recent stroke, and leg deformities were excluded. Of the remaining 34 patients, 44% had severe postural reflex impairment, and 24% had moderate impairment. Although the etiology for postural reflex impairment may be multivariant, the high percentage suggests that postural reflex dysfunction may be an important cause of unexplained falls in the elderly.

Aged↗
PubMed1995

Postural reflexes in Parkinson's disease during 'resist' and 'yield' tasks.

Postural reflexes in leg muscles appear to be set at a fixed gain in Parkinson's disease. To further investigate gain adaptation, we instructed 16 patients with idiopathic Parkinson's disease (studied during the 'off' phase) and 21 healthy controls to either 'resist' or 'yield' in response to 20 serial 4 degrees toe-up perturbations of a supporting platform on which they were standing. We bilaterally recorded destabilizing medium latency (ML) reflexes from stretched gastrocnemius muscles and corrective long latency (LL) reflexes from shortened tibialis anterior muscles. We also assessed changes in center of foot pressure (CFP) and center of gravity (COG). During the 'resist' condition, patients had increased destabilizing ML reflexes, decreased corrective LL reflexes, increased backward displacement of the COG and increased forward (destabilizing) displacement of the CFP. In addition, the backward (corrective) displacement of CFP between 150 and 250 ms was delayed. During the 'yield' condition, reflex gains were modified in controls: LL reflexes were markedly attenuated, whereas ML reflexes were markedly increased. Although this reflex pattern resembled the 'resist' condition in patients, it was not associated with an increased forward displacement of the CFP, but only with a strongly delayed backward displacement of CFP which started after 150 ms. In patients, ML reflex amplitudes remained unchanged during the 'yield' condition, suggesting a fixed reflex gain. LL reflex amplitudes were reduced in patients but significantly less compared to controls, which again suggests a fixed reflex gain. This 'inflexibility' of postural reflexes was reflected by the CFP which showed much smaller changes between 0 and 250 ms in patients than controls. These results could not be ascribed to a different ability to yield because posterior displacement of the COG was identical in patients and controls during the 'yield' condition. We conclude that (1) patients with Parkinson's disease have abnormal and 'inflexible' postural reflexes, associated with delayed corrective movements about the ankle joint and increased body sway; and (2) the increased forward displacement of the CFP in patients likely reflects high stiffness in ankle muscles because reflex changes in controls only affected the CFP more than 150 ms after the perturbation. The increased muscle stiffness and inflexibility of postural reflexes in Parkinson's disease may contribute to balance impairment in daily life.

Adaptation, Physiological↗
PubMed2004

Modulation of ankle muscle postural reflexes in stroke: influence of weight-bearing load.

OBJECTIVE: Given the known sensorimotor deficits and asymmetric weight-bearing posture in stroke, the aim of this study was to determine whether stroke affects the modulation of standing postural reflexes with varying weight-bearing load. METHODS: Ten individuals with chronic stroke and 10 healthy older adult controls were exposed to unexpected forward and backward platform translations while standing. Three different stance conditions were imposed: increased weight-bearing load, decreased weight-bearing load, and self-selected stance. Surface electromyography from bilateral ankle dorsiflexors (tibialis anterior) and extensors (gastrocnemius) were recorded and the magnitude of background muscle activity (prior to the platform translation) and postural reflex onset latency and magnitude (75 ms following reflex onset) were determined. RESULTS: Load modulation of ankle extensors was found in controls and individuals with stroke. Although controls demonstrated modulation of ankle dorsiflexors to different loads, individuals with stroke did not show this modulation. Further, load did not change the onset latency of postural reflexes of the individuals with stroke. CONCLUSIONS: The delayed paretic muscle onset latencies in conjunction with impaired modulation of ankle dorsiflexor postural reflexes may contribute to the instability and frequent falls observed among individuals with stroke. SIGNIFICANCE: The results provide some insight into standing postural reflexes following stroke.

Aged↗
PubMed1989

Age, functional postural reflexes, and voluntary sway.

This experiment considered age-related changes in functional relationships between postural reflexes and voluntary movement. Young and older adults received horizontal perturbations during normal stance and when engaged in voluntary sway. Electromyographic activity showed that (a) older adults had poorer coordination between postural reflexes and voluntary movement, and (b) their stabilizing responses to postural disturbances during voluntary sway were slower. In addition, the onsets of activity of functionally important muscles were less tightly bilaterally coupled, and patterns of muscle onsets were less stereotypically organized in older adults. The results suggest that older adults experience some breakdown in the timing and sequencing of muscle activity and in the functional coordination of their postural reflexes with voluntary sway.

Adolescent↗
PubMed2005

Exercise leads to faster postural reflexes, improved balance and mobility, and fewer falls in older persons with chronic stroke.

OBJECTIVES: To determine the effect of two different community-based group exercise programs on functional balance, mobility, postural reflexes, and falls in older adults with chronic stroke. DESIGN: A randomized, clinical trial. SETTING: Community center. PARTICIPANTS: Sixty-one community-dwelling older adults with chronic stroke. INTERVENTION: Participants were randomly assigned to an agility (n=30) or stretching/weight-shifting (n=31) exercise group. Both groups exercised three times a week for 10 weeks. MEASUREMENTS: Participants were assessed before, immediately after, and 1 month after the intervention for Berg Balance, Timed Up and Go, step reaction time, Activities-specific Balance Confidence, and Nottingham Health Profile. Testing of standing postural reflexes and induced falls evoked by a translating platform was also performed. In addition, falls in the community were tracked for 1 year from the start of the interventions. RESULTS: Although exercise led to improvements in all clinical outcome measures for both groups, the agility group demonstrated greater improvement in step reaction time and paretic rectus femoris postural reflex onset latency than the stretching/weight-shifting group. In addition, the agility group experienced fewer induced falls on the platform. CONCLUSION: Group exercise programs that include agility or stretching/weight shifting exercises improve postural reflexes, functional balance, and mobility and may lead to a reduction of falls in older adults with stroke.

Accidental Falls↗
PubMed2004

[The influence of the cervical proprioception on the postural reflexes--experimental and clinical study].

The aim of the study was to estimate the effect of the neck proprioception on the postural reflexes in the cases of the cervical pathology in the whiplash injury and degenerative disease of the cervical vertebral column. The investigation using ENG and stabilometry was performed in 81 patients. Experimental observations were done among 10 pigeons with limitation of the neck proprioceptors action by special neck tutor. Their postural reflexes were analysed during balance test on the seesaw. Our conclusion is, that disorders of the proprioceptors impulastion can damage the postural reflexes even in patients with normal labyrinth function.

Adolescent↗
PubMed1982

Abnormalities in postural reflexes and voluntarily induced automatic movements in Parkinson patients.

Postural abnormalities were systematically studied in 41 Parkinson patients in relation with the other Parkinson symptomatology. Evidence was collected that kinetic postural mechanisms, including turning in recumbant position, rising from the floor and walking, to be considered as volitional automatic movements, reacted differently on Levodopa therapy compared with static postural reflexes and the classical Parkinson symptoms. This suggests that the neuro-biochemical substrate of these postural movements may involve other than dopaminergic pathways as well.

Basal Ganglia↗
PubMed1996

Long-term effects of antidepressants on balance, equilibrium, and postural reflexes.

To assess the long-term effects of antidepressant medication on balance, equilibrium, and postural reflexes, we studied 30 patients, ages 20-76 years, who had a diagnosis of depressive disorder (as defined by DSM-III-R criteria) and had been treated with tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs) for > or = 1 year. They were assessed by a Balance Master System. The assessment included three tasks: static balance, rhythmic weight shift, and limits of stability. When compared with 30 nonhospitalized healthy controls (of comparable age and the same sex), patients who took TCAs showed impaired balance function in all main indices. The results suggest that the impairment of balance function includes motor coordination, fine-motor control, postural reflexes, maintaining equilibrium, and reaction time. No obvious impairment of balance function was observed in patients who took SSRIs.

Adult↗
PubMed1991

Postural reflexes in patients on long-term neuroleptic medication.

It is not conclusively known whether the amplitude of medium latency postural reflexes is controlled by dopamine. To further assess the influence of supraspinal dopaminergic pathways on postural reflexes, we studied short (SL), medium (ML) and long latency (LL) reflexes in the lower extremity of 10 patients on long term (greater than 6 months) neuroleptic medication, 5 with and 5 without mild drug induced parkinsonism. A control group consisted of 10 age and sex matched healthy volunteers. In both patient groups, latencies and amplitudes of all 3 responses were identical to normal controls. These findings suggest that a moderate postsynaptic inhibition of central dopaminergic pathways is insufficient to cause enhanced amplitudes of ML responses.

Adult↗
PubMed2005

Comparison of tap-evoked and tone-evoked postural reflexes in humans.

To find an easy clinical test of postural reflexes, we compared tone and tap stimuli for eliciting postural reactions in leg muscles in 13 healthy subjects during upright stance. Tones (1000 Hz, 90 dB nHl) were presented monaurally via headphones; taps were applied with a reflex hammer to the forehead. Surface EMG was recorded from the medial gastrocnemius and the sternocleidomastoid muscles, and rectified and averaged. Tapping the forehead of a standing subject evoked leg muscle reflexes that began 50 ms after the stimulus in all subjects. Tone-evoked leg muscle reflexes behaved differently, i.e., they had smaller amplitudes and could be recorded in only 5 of 13 subjects. However, this same acoustic stimulus elicited reflex activity in the neck muscles of all subjects. There were also other differences (amplitudes, dependence on pre-activation) between these two reflexes. Tone-evoked leg muscle responses and tone-evoked neck muscle responses seem to be mediated by different structures, i.e., the latter by an oligosynaptic pathway and the former by polysynaptic neural circuits. We conclude that tap-evoked leg muscle responses are not or not solely mediated by saccular receptors but other receptors (i.e., proprioceptors, semicircular canals) are probably also involved.

Acoustic Stimulation↗
PubMed1992

Altered postural reflexes in Parkinson's disease: a reverse hypothesis.

In subjects standing on a movable platform, sudden dorsiflexion of the ankle joint elicits a set of reflexes in leg muscles. These responses include a short latency (SL) and medium latency (ML) stretch reflex in the gastrocnemius muscle and a distal to proximal innervation sequence of long latency (LL) reflexes in the shortened tibialis anterior and vastus lateralis muscles. Because of their role in maintaining upright stance these responses have been termed postural reflexes. In patients with Parkinson's disease (PD), the following abnormalities have been described: 1) enhanced ML-amplitudes; 2) a reversed LL innervation sequence; and 3) delayed onset latencies. These abnormalities are thought to be due to defective motor programming and disturbed control of spinal and supraspinal reflex centers by basal ganglia circuits. The altered reflexes have been held responsible for some of the clinical features of PD, including balance impairment and rigidity. In this paper, we argue the reverse hypothesis that postural reflexes are essentially normal in PD, and that the observed alterations are at least in part consequence rather than cause of balance impairment, the stooped parkinsonian posture and rigidity of PD patients.

Humans↗
PubMed2002

Classical conditioning of postural reflexes.

Unexpected external perturbations of body equilibrium elicit compensatory postural reflexes. The reflex patterns change only minimally, even after repetitive perturbations. This study addressed the question of whether classical conditioning can alter the reflex patterns. In the first session 27 healthy subjects were tested when standing on an unexpectedly tilting platform. Electromyographic (EMG) activity from different leg muscles and the vertical ground forces, from which the centre of vertical pressure (CVP) was computed, were recorded. In a subsequent session subjects were tested using the classical conditioning paradigm with the tilting platform as the unconditioned stimulus (US) and a prior auditory signal as the conditioning stimulus (CS). The decay of the unconditioned response (UR) observed in the first session was similar and small in all subjects. During conditioning, 22% of the subjects established conditioned responses (CR) in all muscles recorded (strategy 1). UR amplitudes of the anterior tibialis (TA) decayed more than in the first session. The resulting CVP excursions were similar to those observed in US-alone trials. The remaining subjects exhibited CR only in the gastrocnemius muscle but developed a substantial decay of UR, resulting in very small CVP excursions (strategy 2). Our data suggest that processing of US-preceding conditioning stimulus leads to different strategies in the control of postural adjustment with assumed underlying associative and non-associative plastic processes.

Adult↗
PubMed1984

Development and maturation of postural reflexes in normal kittens.

In order to evaluate neurologic development, postural reflexes were tested in normal kittens from birth through 7 weeks of age until stable adult patterns of performance were attained. These reflex tests included: body and air righting, visual placing, chin placing, tactile placing, hopping, and locomotion. A protocol for scoring responses was designed for each individual reflex to differentiate their progression. The first reflexes to mature were visual placing, chin placing, and body righting which attained a maximal score during the 3rd week of life. This was followed by maturation of the forelimb hopping reflex and independent locomotion during the 4th week. Forelimb tactile placing responses, hind limb hopping reflexes, and air righting developed by the 5th week. Hind limb tactile placing responses were the last to mature. They became fully expressed in the 6th week. The pattern of ontogeny of these reflexes proceeded in a cephalocaudal direction. This is in agreement with earlier observations of others who correlated the maturation of reflex responses in kittens with myelination in the central nervous system.

Aging↗
PubMed2001

[Toe phasic posture reflex: description and distribution among patients with neurological disease and in the general population].

A clinical sign is described consisting of a brief extension of the toes after upward tapping of the plantar surface of their terminal phalanges. Electrological data support the hypothesis of a long loop reflex, which we call the "toe phasic posture reflex" (TPPR). In a preliminary study, this sign was observed in patients with central nervous system disease, especially in subcortical brain disorders regardless of etiology. In Parkinson's disease, it was seen mostly in severe and postural forms. Among 237 healthy subjects, it was observed in none of those under 70 years old (n=116), and in 10p. cent of those over 69 years and doing no sport (n=132), but in none of those doing regularly gymnastics or swimming (n=29). TPPR could thus be a sign of motor and especially postural aging.

Adult↗