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  • 1
    Electronic Resource
    Electronic Resource
    The coordination of posture and voluntary movement in patients with hemiparesis (1993)
    Springer
    Journal of neurology 240 (1993), S. 161-167 
    Details
    ISSN: 1432-1459
    Keywords: Hemiparesis ; Posture ; Voluntary movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Postural adjustments associated with the task of raising oneself on tiptoes were investigated in a reaction time paradigm in six normal subjects and six patients with hemiparesis due to stroke. Body and ankle position in space were measured by means of a movement analysis system (ELITE). The findings indicate that the task of going up on tiptoes is performed in two steps. First, the centre of gravity is shifted forward to a position per pendicular to the forefoot. This movement is initiated by a phasic burst of EMG activity in the tibialis anterior (TA). The activity of the quadriceps femoris (QUA) aids the forward shift and together with the biceps femoris (BF) stabilizes the knee. Following these postural adjustments, the action of going up on tip-toes is performed mainly by the gastrocnemius medialis (MG). The basic pattern of preparatory (TA, QUA, BF) and focal (MG) activity was disturbed in its temporal sequence in patients with hemiparesis. The analysis of the biomechanical data showed smaller movement velocities for leaning forward and going up on tiptoes in patients, with increased duration of going up on tiptoes and decreased movement amplitude on the paretic side. In addition, the correlation between the start of horizontal (leaning forward) and vertical (going up on tiptoes) hip movement was lost in patients. The preserved correlation between the latency of MG activity and the onset of the vertical hip movement on the paretic side in patients and the loss of correlation on the non-paretic side indicates that the EMG activity on the healthy side is adapted to the functional requirements of the affected side. The findings demonstrate that preparatory and executional activity are not programmed as a unit, but are more likely to be generated by a hierachically organized structure using proprioceptive and exteroceptive feedback.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00857522
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Direction and amplitude precuing has no effect on automatic posture responses (1991)
    Springer
    Experimental brain research 84 (1991), S. 219-223 
    Details
    ISSN: 1432-1106
    Keywords: Posture ; Movement precuing ; Cerebellar disease ; Parkinson's disease ; Motor control ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Automatic postural responses of leg muscles to the sudden displacement of standing support were investigated under four different conditions of information given to subjects in advance. Results from three groups of subjects were compared: 6 normal subjects, 10 patients with cerebellar disease, and 9 patients with Parkinson's disease. Specifically, each subject was provided with visual information about the direction and/or the amplitude of an upcoming platform tilt. For the control situation no advance information on the characteristics of platform tilt was provided. Neither the latencies nor the integrals of postural EMG-responses showed alterations with advance information. In contrast, in a control experiment in which 3 normal subjects had to perform large or small forward or backward voluntary movements of the body around the ankle joint, shorter onset-latencies of leg muscle EMG responses were observed with increasing complexity of the advance information. These results suggest that, unlike voluntary movements, postural responses to rapid surface tilts do not benefit from advance visual information on direction or amplitude of a postural disturbance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231777
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Postural strategies associated with somatosensory and vestibular loss (1990)
    Springer
    Experimental brain research 82 (1990), S. 167-177 
    Details
    ISSN: 1432-1106
    Keywords: Posture ; Somatosensory ; Vestibular ; Movement ; EMG ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study examines the roles of somatosensory and vestibular information in the coordination of postural responses. The role of somatosensory information was examined by comparing postural responses of healthy control subjects prior to and following somatosensory loss due to hypoxic anesthesia of the feet and ankles. The role of vestibular information was evaluated by comparing the postural responses of control subjects and patients with bilateral vestibular loss. Postural responses were quantified by measuring 1) spatial and temporal characteristics of leg and trunk EMG activation; 2) ankle, knee, and hip joint kinematics, and 3) surface forces in response to anterior and posterior surface translations under different visual and surface conditions. Results showed that neither vestibular nor somatosensory loss resulted in delayed or disorganized postural responses. However, both types of sensory deficits altered the type of postural response selected under a given set of conditions. Somatosensory loss resulted in an increased hip strategy for postural correction, similar to the movement strategy used by control subjects while standing across a shortened surface. Vestibular loss resulted in a normal ankle strategy but lack of a hip strategy, even when required for the task of maintaining equilibrium on a shortened surface. Neither somatosensory nor vestibular loss resulted in difficulty in utilizing remaining sensory information for orientation during quiet stance. These results support the hypothesis that cutaneous and joint somatosensory information from the feet and ankles may play an important role in assuring that the form of postural movements are appropriate for the current biomechanical constraints of the surface and/or foot. The results also suggest that vestibular information is necessary in controlling equilibrium in a task requiring use of the hip strategy. Thus, both somatosensory and vestibular sensory information play important roles in the selection of postural movement strategies appropriate for their environmental contexts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230848
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    Paper (German National Licenses)
    Fulltext
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