title: Aging, visuomotor correction, and force fluctuations in large muscles.
abstract: OBJECTIVE
  To determine the contribution of visuomotor correction to increased force fluctuations in the elbow flexor and knee extensor muscles of elderly adults.
  
  
  METHODS
  Young (N = 22, 23 +/- 3 yr) and elderly (N = 23, 74 +/- 7 yr) adults performed constant-force contractions at target forces of 2.5, 30, and 65% MVC. Visual feedback was provided (6-8 s) and then removed (6-8 s). After removal of drift (< 0.5 Hz) from the force, the standard deviation (SD) and coefficient of variation (CV) of force were calculated from vision and no-vision data.
  
  
  RESULTS
  Maximal voluntary contraction (MVC) force was 19% lower for elbow flexors and 37% lower for knee extensors in elderly adults than in young adults. Overall, the CV of force was 27% greater in the vision condition compared with the no-vision condition. The CV of force for vision was greater for elderly adults than for young adults at the 2.5% MVC target force and lower at 30 and 65% MVC. For the 2.5% MVC target force, the decline in CV of force from vision to no vision was greater for elderly adults than for young adults. At 30 and 65% MVC, the decline was significant but similar for young and elderly adults. For elbow flexors, the change in power from vision to no vision was greater for 0- to 4-Hz (reduced power) and 8- to 12-Hz (increased power) frequencies for elderly adults compared with young adults.
  
  
  CONCLUSIONS
  Visuomotor correction contributed to force fluctuations in large proximal muscles. The contribution was greater for healthy elderly adults at low forces. Visuomotor processes thus contributed to the age-related increase in force fluctuations.
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, CO 80523-1582, USA. tracybl@cahs.colostate.edu
authors.forename: Brian L
authors.initials: BL
authors.lastname: Tracy
authors.forename: Devin V
authors.initials: DV
authors.lastname: Dinenno
authors.forename: Bjorn
authors.initials: B
authors.lastname: Jorgensen
authors.forename: Seth J
authors.initials: SJ
authors.lastname: Welsh
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D004550:Elbow / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010865:Pilot Projects; D014785:Vision, Ocular / Q000502:physiology*