title: Concordance and discordance between two measures of lower extremity function: 400 meter self-paced walk and SPPB.
abstract: OBJECTIVE
  The purpose of the study was to assess the concurrent validity of the 400 meter self-paced walk test (400-m W) against the commonly used short physical performance battery (SPPB). A secondary purpose was to determine whether the 400-m W could better discriminate physical performance among high functioning older adults by examining the distribution of 400-m W scores.
  
  
  METHODS
  101 men and women (80.8+/-0.4 years) were recruited to participate in the study. The 400-mW and SPPB assessed lower extremity function. Lower extremity muscle strength, power, and contraction velocity was assessed using bilateral leg press (LP). Health history was obtained with questionnaire.
  
  
  RESULTS
  400-m W demonstrated moderate correlations with SPPB (Pearson r=0.74; p< 0.001). In 36 high functioning individuals (SPPB score= 10, 11, 12), participants above the median 400-m W performance time (n=20) had more medical conditions (2.8+/-0.4 vs 1.7+/-0.3; p=0.038), more reported falls (0.80+/-0.2 vs 0.19+/-0.1; p=0.016), more medications (3.7+/-0.4 vs 1.8+/-0.4; p=0.001), had lower LP power at 70% of the one repetition maximum (1RM) (336+/-45 W vs 663+/-78 W; p=0.001) and 40% 1RM (329+/-43 W vs 580+/-75 W; p=0.005), and had slower LP contraction velocity at 40% 1RM (77+/-5.5 m/s vs 112+/-8.4 m/s; p=0.001) compared with those below the median (n=16).
  
  
  CONCLUSIONS
  A substantial number of apparently well functioning older adults demonstrated some limitations in the ability to walk 400 meters. Use of the 400-m W may be justified to obtain information to better discriminate among high functioning elderly.
authors.affiliation: Human Physiology Laboratory, Department of Health Sciences, Sargent College of Rehabilitation Sciences, Boston University, USA. sayerss@missouri.edu
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Sayers
authors.forename: Jack M
authors.initials: JM
authors.lastname: Guralnik
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Brach
authors.forename: Roger A
authors.initials: RA
authors.lastname: Fielding
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D015577:Geriatric Assessment / Q000379:methods*; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D051346:Mobility Limitation; D009119:Muscle Contraction / Q000502:physiology; D011237:Predictive Value of Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011795:Surveys and Questionnaires; D013647:Task Performance and Analysis; D016138:Walking / Q000502:physiology*