Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 97 (3), 515-27

Postural Adjustments in Sitting Humans Following External Perturbations: Muscle Activity and Kinematics

Affiliations

Postural Adjustments in Sitting Humans Following External Perturbations: Muscle Activity and Kinematics

H Forssberg et al. Exp Brain Res.

Abstract

There are several controversies concerning the organization and induction of postural adjustments in standing humans. Some investigators suggest the responses are triggered by somatosensory inputs (especially from the ankle in standing subjects), while others emphasize the vestibular input induced by head acceleration. We examined postural responses in sitting subjects in order to describe the muscle activation pattern during various perturbations and to test whether somatosensory or vestibular stimulation elicited the responses. The kinematics and EMG patterns in response to perturbations caused by movements of the support surface were studied in adults. The postural muscle activation following a backward sway was mainly the same, whether it was elicited by a forward translation or a legs-up rotation. This is remarkable, since, except for pelvis rotation, the movements of all body segments including the head differed in the two conditions. Furthermore, a second experiment showed that the direction of the initial head movement could be reversed with retainment of the same postural muscle activation pattern. The results suggest that somatosensory signals derived from the backward rotation of the pelvis, and not vestibular information from the head, trigger postural responses during sitting. There was a slight but consistent difference in the muscle activation pattern, whether the backward sway was elicited by a forward translation or legs-up rotation. The difference seemed to reflect the sensory information from head and other body parts (except the pelvis). This finding allowed us to speculate in a central pattern generator for postural adjustments containing two levels. At the first level, a simple format of the muscle activation would be generated; at the second level, the centrally generated pattern could be shaped and timed by interaction from the entire somatosensory, vestibular, and visual input.

Similar articles

See all similar articles

Cited by 39 PubMed Central articles

See all "Cited by" articles

References

    1. Exp Brain Res. 1988;71(3):455-66 - PubMed
    1. Adv Otorhinolaryngol. 1988;42:65-71 - PubMed
    1. Exp Brain Res. 1984;56(1):126-34 - PubMed
    1. IEEE Trans Biomed Eng. 1985 Nov;32(11):943-50 - PubMed
    1. Exp Brain Res. 1976 Aug 27;26(1):59-72 - PubMed

Publication types

LinkOut - more resources

Feedback