title: Lower-extremity force decrements identify early mobility decline among community-dwelling older adults.
abstract: BACKGROUND
  Many apparently independent older adults modify daily tasks. Task modifications strongly predict future mobility disability. Clinically intuitive, easily measured "biomarkers" associated with task modifications would offer quantifiable treatment targets for prevention of age-related functional limitations.
  
  
  OBJECTIVE
  The objective of the study was to examine lower-extremity muscle strength deficits and functionally relevant cutoff points associated with daily task modifications in community dwelling older adults living independently.
  
  
  METHODS
  This was a cross-sectional observational study.
  
  
  METHODS
  Fifty-three participants (mean age=76.4 years, SD=5.2) were tested for task modifications and leg strength. Task modifications were assessed using a previously described tool (summary task modification score). Twenty-six of the participants were classified as task modifiers (TM group), and 27 participants were classified as non-task modifiers (NTM group). A net antigravity leg force in the sagittal plane (NETforce) was calculated by summing the normalized isometric and isokinetic torques from the hip extensors, knee extensors, and ankle plantar flexors.
  
  
  RESULTS
  Compared with the NTM group, the TM group exhibited 30.0% and 33.5% reduction in lower-extremity isometric and isokinetic NETforces, respectively. Isometric and isokinetic NETforce cutoff points for task modifications were ≤ 4.24 and 2.77 N · m/kg body weight, respectively. The isometric and isokinetic models both yielded sensitivity and specificity values of 74.1% and 80.8%, respectively (positive likelihood ratio=3.852, 95% confidence interval=1.699-8.735; negative likelihood ratio=0.321, 95% confidence interval=0.167-0.618). Isometric and isokinetic NETforces were significantly associated with task modifications (odds ratio=2.50 and 2.42, respectively).
  
  
  CONCLUSIONS
  The cross-sectional design of this study does not allow for a test of causal relationships. This study used a modest yet adequate sample size that may limit generalization of the results.
  
  
  CONCLUSIONS
  Isometric and isokinetic NETforce cutoff points provide quantifiable biomarkers that discriminate community-dwelling older adults who modify daily tasks from those who do not.
authors.affiliation: Department of Physical Therapy Education, College of Health Professions, SUNY Upstate Medical University, Room 2232, Silverman Hall, 750 Adams St, Syracuse, NY 13210-1834, USA. markom@upstate.edu
authors.forename: Moshe
authors.initials: M
authors.lastname: Marko
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Neville
authors.forename: Mark A
authors.initials: MA
authors.lastname: Prince
authors.forename: Lori L
authors.initials: LL
authors.lastname: Ploutz-Snyder
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D015577:Geriatric Assessment / Q000379:methods; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D051346:Mobility Limitation; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D019415:Torque