Head stabilization during various locomotor tasks in humans. I. Normal subjects.
TL;DR: The study emphasizes the importance of head stabilization as part of the postural control system and described as a basis for inertial guidance.
Abstract: Head kinematics were studied in ten normal subjects while they executed various locomotor tasks The movement of the body was recorded with a video system which allowed a computer reconstruction of motion of joint articulations and other selected points on the body in three dimensions Analyses focus on head translation along the vertical axis and rotation in the sagittal plane This was done by recording the displacement of a line approximating the plane of horizontal semi-circular canals (the Frankfort plane: F-P) Four conditions were studied: free walking (W) walking in place (WIP) running in place (R) and hopping (H) In the 4 experimental conditions, amplitude and velocity of head translation along the vertical axis ranged from 1 cm to 25 cm and 015 m/s to 18 m/s In spite of the disparities in the tasks regarding the magnitude of dynamic components, we found a significant stabilization of the F-P around the earth horizontal Maximum amplitude of F-P rotation did not exceed 20° in the 4 situations Vertical angular velocities increased from locomotion tasks to the dynamic equilibrium task although the maximum values remained less than 140°/s Predominant frequencies of translations and rotations in all the tasks were within the range 04–35 Hz and harmonics were present up to 6–8 Hz During walking in darkness, mean head position is tilted downward, with the F-P always below the earth horizontal Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, WIP and R, but during H the amplitude decreased by 37% Residual head angular displacement is found to compensate for head translation during the 4 conditions Our study emphasizes the importance of head stabilization as part of the postural control system and described as a basis for inertial guidance
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TL;DR: An operational meaning to ” controlled” and ”uncontrolled” is given and a method of analysis through which hypotheses about controlled and uncontrolled degrees of freedom can be tested is described, finding that, for the task of sit-to-stand, the position of the center of mass in the sagittal plane was controlled.
Abstract: The degrees of freedom problem is often posed by asking which of the many possible degrees of freedom does the nervous system control? By implication, other degrees of freedom are not controlled. We give an operational meaning to "controlled" and "uncontrolled" and describe a method of analysis through which hypotheses about controlled and uncontrolled degrees of freedom can be tested. In this conception, control refers to stabilization, so that lack of control implies reduced stability. The method was used to analyze an experiment on the sit-to-stand transition. By testing different hypotheses about the controlled variables, we systematically approximated the structure of control in joint space. We found that, for the task of sit-to-stand, the position of the center of mass in the sagittal plane was controlled. The horizontal head position and the position of the hand were controlled less stably, while vertical head position appears to be no more controlled than joint motions.
1,333 citations
TL;DR: This document summarizes current capabilities, research and operational priorities, and plans for further studies that were established at the 2015 USGS workshop on quantitative hazard assessments of earthquake-triggered landsliding and liquefaction in the Czech Republic.
Abstract: .........................................................................................................................................................322 III.
1,051 citations
TL;DR: The sections in this article are: Neural Control of Postural Orientation and Equilibrium, Sensory Control, and Concluding Remarks.
Abstract: The sections in this article are:
1
Neural Control of Postural Orientation and Equilibrium
1.1
Behavioral Goals
1.2
Biomechanical Principles
1.3
Postural Strategies
2
Postural Orientation
2.1
Stiffness and Tonic Muscle Activation
2.2
Controlling Postural Orientation
2.3
Internal Representation of Postural Orientation
3
Coordination of Postural Equilibrium
3.1
Triggered Reactions to External Disturbances
3.2
Anticipatory Postural Adjustments for Voluntary Movement
3.3
Modeling of Postural Coordination
4
Sensory Control of Postural Orientation and Equilibrium
4.1
Sensory Integration
4.2
Somatosensory System
4.3
Vestibular System
4.4
Visual System
5
Central Neural Control of Posture
5.1
Spinal Cord and Brainstem
5.2
Basal Ganglia
5.3
Cerebellum
5.4
Cerebral Cortex
6
Concluding Remarks
990 citations
TL;DR: Méthodes : Sur une série de 31 femmes présentant des varices périnéales d’origine extrasaphéniennes ayant bénéficié d”une exploration radiologique veineuse pelvienne et de l’embolisation des veines incontinentes nous avons étudié les résultats et les corrélations anatomo-clinique entre
Abstract: Méthodes : Sur une série de 31 femmes présentant des varices périnéales d’origine extrasaphéniennes ayant bénéficié d’une exploration radiologique veineuse pelvienne et de l’embolisation des veines incontinentes nous avons étudié les résultats et les corrélations anatomo-clinique entre les varices et les signes cliniques de l’insuffisance veineuse pelvienne. Un sous-groupe B de 23 patientes présentant une insuffisance veineuse pelvienne et des signes cliniques a été comparé à un groupe A de 4 patientes qui ne présentaient pas d’insuffisance veineuse pelvienne à l’exploration. Nous avons choisi d’étudier 3 signes cliniques : la douleur pelvienne et la douleur des membres inférieurs survenant au début ou pendant les règles ainsi que la dyspareunie. La symptomatologie a été évaluée sur une échelle analogique de 0 à 10 et un score clinique (de 0 à 30) a été établi en ajoutant ces 3 chiffres.
705 citations
TL;DR: The results show that standing and walking conditions required more attention than sitting in a chair, and the attentional cost for walking was also significantly greater than for standing.
Abstract: Upright standing and walking tasks require the integration of several sources of sensory information In a normal and highly predictable environment, locomotor synergies involving several muscles may take place at lower spinal levels with neural circuitry tuned by local loops of assistance or self-organizing processes generated in coordinative networks When ongoing regulation of gait is necessary (obstacles, changes in direction) supraspinal involvement is necessary to perform movements adapted to the environment Using a classical information processing framework and a dual-task methodology, it is possible to evaluate the attentional demands for performing static and dynamic equilibrium tasks The present experiment evaluates whether the attentional requirements for a control sitting condition and for standing and walking conditions vary with the intrinsic balance demands of the tasks The results show that standing and walking conditions required more attention than sitting in a chair The attentional cost for walking was also significantly greater than for standing For the walking task, reaction times when subjects were in singlesupport phase (small base of support) were significantly longer than those in double-support phase, suggesting that the attentional demands increased with an increase in the balance requirements of the task Balance control requires a continuous regulation and integration of sensory inputs; increasing balance demands loads the higher level cognitive system
667 citations
References
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Book•
01 Jan 1967
6,041 citations
"Head stabilization during various l..." refers background in this paper
...In addition, the subject could take advantage of head inertia as "nonmuscular forces" (Bernstein 1967) which acts in the same direction as head compensatory rotation....
[...]
Book•
01 May 1979
TL;DR: The Vestibular System and the Cerebellum are studied as well as the Vestibulospinal System, which consists of the vestibular nucleus, the cerebellum, and theocular system.
Abstract: 1 Introduction.- 2 Peripheral Morphology.- 3 Biophysics of the Peripheral End Organs.- 4 Mechanoneural Transduction and the Primary Afferent Response.- 5 Labyrinthine Input to the Vestibular Nuclei and Reticular Formation.- 6 The Vestibular System and the Cerebellum.- 7 The Vestibulospinal System.- 8 The Vestibuloocular System.- References.
789 citations
TL;DR: The presence of a form of stretch reflex, previously described in the arm by other authors, has been confirmed in the gastrocnemius muscle of the human leg and is referred to in this article as the Functional Stretch Reflex (FSR).
Abstract: 1. The presence of a form of stretch reflex, previously described in the arm by other authors, has been confirmed in the gastrocnemius muscle of the human leg. The electromyographic (e.m.g.) manifestation of this reflex occurred 120 msec (S.E. of mean = 3.5 msec) following a sharply applied, and maintained, dorsiflexing force to the foot. This form of response is referred to in this article as the Functional Stretch Reflex (FSR).2. To determine the contribution of the FSR to the control of normal leg movement, the e.m.g. activity in the above muscle was monitored during single downward steps of 12.7, 25.4 and 38.1 cm and during repetitive, rhythmic, hopping movements on one foot.3. It was found that e.m.g. activity associated with steps to the ground began 141 msec (S.E. of mean = 8.5 msec) before contact with the ground and ended 131 msec (S.E. of mean = 7.6 msec) after contact, when the e.m.g. usually became temporarily inactive.4. It is inferred from these results that the muscular deceleration associated with landing was brought about by the release of a pre-programmed pattern of neuromuscular activity which was inaccessible to reflex activity resulting from the mechanical event of landing, rather than by a stretch reflex.5. It was found that subjects chose their preferred frequency of hopping with great accuracy and consistency. The mean value obtained was 2.06 Hz (S.E. of mean = 0.02 Hz).6. At the preferred frequency, e.m.g. activity began 84 msec (S.E. of mean = 9.6 msec) before and terminated 263 msec (S.E. of mean = 10 msec) after contact with the ground.7. It is inferred that in rhythmical hopping and perhaps also in running, each landing is effected, as in single steps, by a predetermined pattern of neuromuscular activity. However, when hopping at the preferred frequency, the take-off phase of muscular activity is timed to make maximal use of the FSR, i.e. between 120 and 260 msec after initial contact.8. The results emphasize the importance of pre-programming complex muscular contractions suitable for opposing sudden passive stretching forces, and of initiating them prior to the onset of these forces.
559 citations
TL;DR: The system illustrated in this paper has been designed and developed particularly for automatic and reliable analysis of body movement in various conditions and environments and is based on real-time processing of the TV images to recognize multiple passive markers and compute their coordinates.
Abstract: The system illustrated in this paper has been designed and developed particularly for automatic and reliable analysis of body movement in various conditions and environments. It is based on real-time processing of the TV images to recognize multiple passive markers and compute their coordinates. This performance is achieved by using a special algorithm allowing the recognition of markers only if their shape matches a predetermined "mask." The main feature of the system is a two-level processing architecture, the first of which includes a dedicated peripheral fast processor for shape recognition (FPSR), designed and implemented by using fast VLSI chips. The second level consists of a general purpose computer and provides the overall system with high flexibility. The main characteristics are: no restriction on the number of markers, resolution of one part in 2500, and a 50 Hz sampling rate independent of the number of markers detected. The prototype has been fully developed, and preliminary results obtained from the analysis of several movements are illustrated.
477 citations
TL;DR: During locomotion, the head is stabilized in space incompletely but adequately so that the vestibulo-ocular reflex (VOR) is not saturated and during vigorous, voluntary head rotations, the maximum head velocity exceeds the range where the VOR can stabilize gaze.
Abstract: We used the magnetic search coil technique to record horizontal (yaw) and vertical (pitch) head rotations of 20 normal subjects during (1) walking in place, (2) running in place, (3) vigorous, voluntary, horizontal head rotation and (4) vigorous, voluntary, vertical head rotation. During walking or running, the predominant frequency of pitch rotations was at least twice that of yaw rotations. During running, the median, predominant pitch frequency from all subjects was 3.2 Hz, but significant harmonics were present up to 15-20 Hz in several subjects. Group median maximal head velocity during walking or running did not exceed 90 degrees/ second. During vigorous, voluntary head rotations median frequency for yaw and pitch was similar and did not exceed 2.6 Hz. However, group median maximal head velocity during vigorous voluntary yaw rotation was 780 degrees/second. Thus, (1) during locomotion, the head is stabilized in space incompletely but adequately so that the vestibulo-ocular reflex (VOR) is not saturated, (2) during vigorous, voluntary head rotations, the maximum head velocity exceeds the range where the VOR can stabilize gaze, (3) the frequencies of head rotations that occur during locomotion greatly exceed frequencies conventionally used in the laboratory for testing the VOR.
461 citations