title: Age effects on multi-muscle modes during voluntary body sway.
abstract: The aim of this article was to explore age-related differences in the muscle modes (M-modes) during voluntary body sway (VS). M-modes were defined as trunk and leg muscles organized into groups with parallel scaling of muscle activation level within a group. We hypothesized that, in comparison with young performers, older adults would show changes in the compositions of M-modes stabilizing the anterior-posterior (AP) center of pressure (COP) displacement. Young (27.5 ± 7.3 yr, 164.6 ± 9.7 cm and 58.4 ± 10.6 kg) and older (69.4 ± 6.4 yr, 160.0 ± 7.0 cm and 58.9 ± 7.5 kg) subjects performed the VS task in the AP direction while trying to minimize sway in the medio-lateral direction. EMG signals of 10 postural muscles were recorded and analyzed. Principal component analysis (PCA) was used to identify three M-modes within the space of integrated indices of muscle activity. The main findings were (1) that there were no age-related differences in magnitude of the COP displacement or amount of variance explained by the principal components (m-modes), and (2) that the number of times co-contraction and mixed m-modes were used were significantly higher for older adults, and the number of times reciprocal m-modes were used were significantly higher for young adults. These observations suggest that aging is associated with a reduced ability to unite dorsal and ventral muscles of the body, which may be reflective of the CNS developing a useful strategy when faced with self-triggered perturbations.
authors: a Tianjin Key Lab of Exercise Physiology and Sports Medicine, Department of Health and Exercise Science , Tianjin University of Sport , Hexi District , Tianjin , China.
authors: Yun
authors: Y
authors: Wang
authors: Kazuhiko
authors: K
authors: Watanabe
authors: Tadayoshi
authors: T
authors: Asaka
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D025341:Principal Component Analysis; D060726:Torso / Q000502:physiology
keywords: aging; muscle modes; posture; principal component analysis