title: Modulations of muscle modes in automatic postural responses induced by external surface translations.
abstract: The authors applied principal component analysis to investigate muscle activation patterns (M-modes) involved in the automatic postural responses induced by external surface perturbations. They focused on M-mode modulations as responses to the effects of practice, stability of the conditions and perturbed directions. While peak center of mass velocity reduced with practice, M-modes were similar with practice and across stability conditions. In contrast, atypical sway mode coactivations that combined proximal trunk muscles with distal muscles of the opposite lower extremity of the ventral-dorsal side were observed under the unstable conditions in both forward and backward perturbations after practice. In addition, M-modes in the forward translations were characterized by increased cocontraction patterns. Results suggest that compositions of the underlying M-modes show minor differences in each perturbed direction, but practice enhances coactivation patterns combining proximal muscles with distal muscles, and with accompanying cocontraction patterns, under more challenging conditions.
authors.affiliation: Research Faculty of Health Sciences, Hokkaido University, Kita-ku, Sapporo, Japan. ask-chu@hs.hokudai.ac.jp
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Asaka
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yahata
authors.forename: Hiroki
authors.initials: H
authors.lastname: Mani
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods; D025461:Feedback, Physiological / Q000502:physiology; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011214:Practice, Psychological; D025341:Principal Component Analysis; D013909:Thorax / Q000502:physiology