Abstract
Human stepping is a commonly executed control strategy for maintaining standing balance in the natural environment. Aging changes in the initiation triggering of both voluntary (longer latency) and perturbation-induced (shorter latency) stepping are associated with falling, and are a complex function of altered sensorimotor, neuromuscular, and cognitive system factors. The aim of this study was to determine the effect of contextual uncertainty about balance stability on the triggering of protective stepping in young and older individuals. Subjects initiated forward stepping during simple reaction time and waist-pull perturbation conditions with and without contextual uncertainty about balance stability. The results showed that, regardless of age, the initiation timing for triggering both voluntary and induced stepping was delayed substantially (100-300 ms) by the presence of balance uncertainty, and that age-associated timing differences were exacerbated with contextual uncertainty. The initiation timing of the first step liftoff for perturbation-induced stepping did not reflect entirely an immediate necessity or last resort strategy to balance instability determined directly by specific sensory input, but rather a decision to step. Moreover, the time to liftoff onset for perturbation-induced stepping was similar for the old and young with contextual certainty, and occurred 130 ms earlier for the old than for the young when balance stability was uncertain. Overall, we concluded that older individuals can retain a residual capacity to sustain stationary standing stability as a function of the prevailing task conditions, and that the reduced timing threshold with age may involve a pre-selected strategy triggered earlier by non-specific event-related sensory input rather than specific movement-related information.
Original language | English (US) |
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Pages (from-to) | 192-198 |
Number of pages | 7 |
Journal | Cognitive Brain Research |
Volume | 16 |
Issue number | 2 |
DOIs | |
State | Published - Apr 2003 |
Funding
This work was supported by the National Institutes of Health grants K01 AG00581 and R01 AG16780 to MWR. The contributions of M. Payton, L. Vervaeke-Robinson, A. Ross, A. Smith and R. Weir are gratefully acknowledged. We thank Dr. Richard Fitzpatrick for helpful discussion. Portions of this work were presented at the Combined Sections Meeting of the American Physical Therapy Association, New Orleans, LA, 2000.
Keywords
- Aging
- Balance
- Intention and context
- Protective stepping
ASJC Scopus subject areas
- Experimental and Cognitive Psychology
- Cognitive Neuroscience
- Behavioral Neuroscience