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Neural control of posture during small magnitude perturbations: effects of aging and localized muscle fatigue.

Authors
Davidson-BS; Madigan-ML; Southward-SC; Nussbaum-MA
Source
IEEE Trans Biomed Eng 2011 Jun; 58(6):1546-1554
NIOSHTIC No.
20039653
Abstract
This study investigated the effects of aging and localized muscle fatigue on the neural control of upright stance during small postural perturbations. Sixteen young (aged 18-24 years) and 16 older (aged 55-74 years) participants were exposed to small magnitude, anteriorly-directed postural perturbations before and after fatiguing exercises (lumbar extensors and ankle plantar flexors). A single degree of freedom model of the human body was used to simulate recovery kinematics following the perturbations. Central to the model was a simulated neural controller that multiplied time-delayed kinematics by invariant feedback gains. Feedback gains and time delay were optimized for each participant based on measured kinematics, and a novel delay margin analysis was performed to assess system robustness. A 10.9 percent longer effective time delay ( p = 0.010) was found among the older group, who also showed a greater reliance upon velocity feedback information (31.1 percent higher differential gain, p = 0.001) to control upright stance. Based on delay margins, older participants adopted a more robust control scheme to accommodate the small perturbations, potentially compensating for longer time delays or degraded sensory feedback. No fatigue-induced changes in neural controller gains, time delay, or delay margin were found in either age group, indicating that integration of this feedback information was not altered by muscle fatigue. The sensitivity of this approach to changes with fatigue may have been limited by model simplifications.
Keywords
Biomechanics; Humans; Posture; Age-factors; Muscle-function; Muscles; Fatigue; Age-groups; Physical-exercise; Motion-studies; Simulation-methods; Musculoskeletal-system; Sensory-motor-system; Feedback-controls; Physiological-fatigue
Contact
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
CODEN
IEBEAX
Publication Date
20110601
Document Type
Journal Article
Email Address
bradley.davidson@du.edu
Funding Type
Grant
Fiscal Year
2011
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-007882; B09282011
Issue of Publication
6
ISSN
0018-9294
Source Name
IEEE Transactions on Biomedical Engineering
State
VA
Performing Organization
Virginia Polytechnic Institute and State University
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