Scaling of postural responses to transient and continuous perturbations

Abstract Scaling of postural ankle-muscle responses was compared for transient (forward and backward acceleration pulses) and continuous (pseudorandom acceleration) platform-translation perturbations. The two types of perturbation were designed to be unpredictable, to have similar frequency content, and to represent similar levels of challenge to stability. A repeated measures experimental design was used to test 12 healthy young (20–45 years) males. Each type of perturbation was administered at three acceleration levels, in random order, and the tests were repeated under eyes-open and blindfolded conditions, while controlling for order of testing. Individual ankle-muscle responses were quantified and, in addition, used to estimate a net response measure (proportional to net ankle torque) and measures of antagonist activation and relative co-contraction level. The results failed to show strong evidence of differences between transient and continuous postural control with regard to the influence of vision, as both types of response were largely unaffected by vision deprivation; however, the results did demonstrate some substantial perturbation-dependent differences in the scaling of the responses to perturbations of differing magnitude. The most pronounced differences, seen in tibialis anterior, appeared to be related to a tendency to lean slightly further forward during continuous perturbations. Substantial co-contraction of antagonistic muscles was frequently observed, for both types of perturbation, and antagonist activation tended to increase at larger perturbation magnitudes. The observed differences in the scaling of the transient and continuous responses raise some concerns about the generalizability of posture control models derived from continuous-perturbation tests.

[1]  V. Dietz,et al.  Interlimb coordination of leg-muscle activation during perturbation of stance in humans. , 1989, Journal of neurophysiology.

[2]  H C Diener,et al.  On the role of vestibular, visual and somatosensory information for dynamic postural control in humans. , 1988, Progress in brain research.

[3]  J Dichgans,et al.  Role of visual and static vestibular influences on dynamic posture control. , 1986, Human neurobiology.

[4]  I W Hunter,et al.  System identification of human joint dynamics. , 1990, Critical reviews in biomedical engineering.

[5]  A. Berthoz,et al.  Visual contribution to rapid motor responses during postural control , 1978, Brain Research.

[6]  D. Winter,et al.  Quantitative assessment of co-contraction at the ankle joint in walking. , 1985, Electromyography and clinical neurophysiology.

[7]  David J. Anderson,et al.  Parametric analysis of dynamic postural responses , 1984, Biological cybernetics.

[8]  Brian E. Maki,et al.  A Posture Control Model and Balance Test for the Prediction of Relative Postural Stability , 1987, IEEE Transactions on Biomedical Engineering.

[9]  W. E. McIlroy,et al.  Task constraints on foot movement and the incidence of compensatory stepping following perturbation of upright stance , 1993, Brain Research.

[10]  F. Horak,et al.  Influence of stimulus parameters on human postural responses. , 1988, Journal of neurophysiology.

[11]  A. M. Smith The coactivation of antagonist muscles. , 1981, Canadian journal of physiology and pharmacology.

[12]  B E Maki,et al.  Influence of expectation and arousal on center-of-pressure responses to transient postural perturbations. , 1993, Journal of vestibular research : equilibrium & orientation.

[13]  F. Horak,et al.  Central programming of postural movements: adaptation to altered support-surface configurations. , 1986, Journal of neurophysiology.

[14]  F. Horak,et al.  Influence of central set on human postural responses. , 1989, Journal of neurophysiology.

[15]  C. D. De Luca,et al.  Surface myoelectric signal cross-talk among muscles of the leg. , 1988, Electroencephalography and clinical neurophysiology.

[16]  Måns Magnusson,et al.  Identification of human postural dynamics , 1988 .

[17]  B. E. Maki,et al.  Chapter 26 A system identification approach to balance testing , 1988 .

[18]  R. Dickstein,et al.  Postural responses of normal geriatric and hemiplegic patients to a continuing perturbation , 1988, Experimental Neurology.

[19]  Fel'dman Ag On the functional tuning of the nervous system in movement control or preservation of stationary pose. II. Adjustable parameters in muscles , 1966 .

[20]  B E Maki,et al.  Do postural responses to transient and continuous perturbations show similar vision and amplitude dependence? , 1993, Journal of biomechanics.