title: Age-related changes in physical functioning: correlates between objective and self-reported outcomes.
abstract: OBJECTIVE
  To quantify the variance attributable to age and estimate annual decline in physical function and self-reported health using a battery of outcome measures in healthy older females. To determine whether self-reported functional losses are similar to those measured objectively and which best represent overall physical capacity.
  
  
  METHODS
  Experimental study, cross-sectional analysis.
  
  
  METHODS
  Human Performance Laboratory, University setting.
  
  
  METHODS
  Thirty-nine community-dwelling women (mean [SD] age=71.5 [7.3] years, range 60 to 83 years) completed a battery of objective measures of function and a self-reported health status survey.
  
  
  METHODS
  Objective measures: gait speed; TUG test; sit-to-stand; concentric knee flexor and extensor moments; self-reported: the SF-36.
  
  
  RESULTS
  Using a cross-sectional approach, annual declines were estimated for: TUG time (2.1%); gait speed (1.2%); knee extensor (2.2%) and flexor moments (3.0%); and self-reported Physical Functioning (0.9 to 1.2%) (p≤0.001). Linear regression indicated that age explained moderate variance in the objective (R(2)=21 to 34%) and self-reported (R(2)=14 to 28%) outcomes. TUG time and gait speed was significantly correlated with all objective outcomes except sit-to-stand (r=0.46 to 0.83) and most of the self-reported (r=0.40 to 0.63) outcomes (p<0.01).
  
  
  CONCLUSIONS
  Age-related functional deterioration was estimated precisely across both objective and self-reported outcomes. Greater strength losses for the knee flexors compared to the extensors indicate an unequal strength loss of antagonistic muscle pairs which has implications for the safe completion of many functional tasks including obstacle negotiation, stair locomotion, postural transitions, and ultimately knee joint stability. Furthermore, walking speed and TUG time correlated most strongly with many of the outcomes highlighting their importance as global indicators of physical capacity.
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE4 5PL, UK; Department for Sport, Health and Exercise Science, University of Hull, Hull HU6 7RX, UK. Electronic address: lisa.alcock@newcastle.ac.uk.
authors.forename: Lisa
authors.initials: L
authors.lastname: Alcock
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool L3 3AF, UK; School of Sport, Health and Exercise Sciences, Bangor University, Bangor LL57 2PZ, UK. Electronic address: t.d.obrien@ljmu.ac.uk.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: O'Brien
authors.affiliation: Department for Sport, Health and Exercise Science, University of Hull, Hull HU6 7RX, UK; Discipline of Exercise and Sport Science, Faculty of Health Sciences, The University of Sydney, Sydney NSW 2141, Australia. Electronic address: n.vanicek@hull.ac.uk.
authors.forename: Natalie
authors.initials: N
authors.lastname: Vanicek
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003430:Cross-Sectional Studies; D003625:Data Collection; D004185:Disability Evaluation; D005260:Female; D006304:Health Status; D006801:Humans; D008875:Middle Aged; D053580:Muscle Strength; D026741:Physical Therapy Modalities; D057566:Self Report
keywords: Functional performance; Healthy ageing; Objective and self-reported outcomes; Physical capacity