Changes in posture control across the life span--a systems approach.

In this article, a systems approach to the development of posture control across the life span and its integration with voluntary tasks such as walking is described. Research shows a clear cephalocaudal gradient in the development of postural responses. Postural muscle synergies develop appropriate temporal organization through experience in each new level of postural skill development. Sensory inputs contributing to posture control influence postural responses very early in development, with responses being elicited by vision alone, or by somatosensory and vestibular cues in isolation. Studies of older adults indicate small, but significant, increases in onset latencies and disruptions in the temporal organization of postural muscle responses when subjects are given external threats to balance. In addition, older adults, like young children, use antagonist muscles more often in coactivation with agonist muscles. Older adults also have more difficulty balancing when sensory inputs are reduced experimentally or pathologically. Ankle dorsiflexor muscle weakness is also a factor in balance dysfunction in the older adult.