Extreme levels of noise constitute a key neuromuscular deficit in the elderly

PLoS One. 2012;7(11):e48449. doi: 10.1371/journal.pone.0048449. Epub 2012 Nov 6.

Abstract

Fluctuations during isometric force production tasks occur due to the inability of musculature to generate purely constant submaximal forces and are considered to be an estimation of neuromuscular noise. The human sensori-motor system regulates complex interactions between multiple afferent and efferent systems, which results in variability during functional task performance. Since muscles are the only active component of the motor system, it therefore seems reasonable that neuromuscular noise plays a key role in governing variability during both standing and walking. Seventy elderly women (including 34 fallers) performed multiple repetitions of isometric force production, quiet standing and walking tasks. No relationship between neuromuscular noise and functional task performance was observed in either the faller or the non-faller cohorts. When classified into groups with either nominal (group NOM, 25(th) -75(th) percentile) or extreme (either too high or too low, group EXT) levels of neuromuscular noise, group NOM demonstrated a clear association (r(2)>0.23, p<0.05) between neuromuscular noise and variability during task performance. On the other hand, group EXT demonstrated no such relationship, but also tended to walk slower, and had lower stride lengths, as well as lower isometric strength. These results suggest that neuromuscular noise is related to the quality of both static and dynamic functional task performance, but also that extreme levels of neuromuscular noise constitute a key neuromuscular deficit in the elderly.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Accidental Falls
  • Aged
  • Factor Analysis, Statistical
  • Female
  • Gait / physiology
  • Humans
  • Isometric Contraction / physiology*
  • Neuromuscular Diseases / physiopathology*
  • Posture / physiology
  • Principal Component Analysis
  • Task Performance and Analysis

Grants and funding

This research was supported by the EU framework 7 VPHOP project FP7–223864. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.