title: Physical Activity Minimum Threshold Predicting Improved Function in Adults With Lower-Extremity Symptoms.
abstract: To identify an evidence-based minimum physical activity threshold to predict improved or sustained high function for adults with lower-extremity joint symptoms.
  
  
  
  Prospective multisite data from 1,629 adults, age ≥49 years with symptomatic lower-extremity joint pain/aching/stiffness, participating in the Osteoarthritis Initiative accelerometer monitoring substudy were clinically assessed 2 years apart. Improved/high function in 2-year gait speed and patient-reported outcomes (PROs) were based on improving or remaining in the best (i.e., maintaining high) function quintile compared to baseline status. Optimal thresholds predicting improved/high function were investigated using classification trees for the legacy federal guideline metric requiring 150 minutes/week of moderate-vigorous (MV) activity in bouts lasting 10 minutes or more (MV-bout) and other metrics (total MV, sedentary, light intensity activity, nonsedentary minutes/week).
  
  
  
  Optimal thresholds based on total MV minutes/week predicted improved/high function outcomes more strongly than the legacy or other investigated metrics. Meeting the 45 total MV minutes/week threshold had increased relative risk (RR) for improved/high function (gait speed RR 1.8, 95% confidence interval [95% CI] 1.6, 2.1 and PRO physical function RR 1.4, 95% CI 1.3, 1.6) compared to less active adults. Thresholds were consistent across sex, body mass index, knee osteoarthritis status, and age.
  
  
  
  These results supported a physical activity minimum threshold of 45 total MV minutes/week to promote improved or sustained high function for adults with lower-extremity joint symptoms. This evidence-based threshold is less rigorous than federal guidelines (≥150 MV-bout minutes/week) and provides an intermediate goal towards the federal guideline for adults with lower-extremity symptoms.
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Dorothy D
authors.initials: DD
authors.lastname: Dunlop
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Jungwha
authors.initials: J
authors.lastname: Lee
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Abigail L
authors.initials: AL
authors.lastname: Gilbert
authors.affiliation: Rush University, Chicago, Illinois.
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Semanik
authors.affiliation: Rehabilitation Institute of Chicago, Chicago, Illinois.
authors.forename: Linda
authors.initials: L
authors.lastname: Ehrlich-Jones
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Pellegrini
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pinto
authors.affiliation: Arizona State University, Phoenix.
authors.forename: Barbara
authors.initials: B
authors.lastname: Ainsworth
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Rowland W
authors.initials: RW
authors.lastname: Chang
mesh_terms: D056044:Actigraphy; D000368:Aged; D001696:Biomechanical Phenomena; D018450:Disease Progression; D015444:Exercise; D017079:Exercise Tolerance; D005260:Female; D006304:Health Status; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology / Q000517:prevention & control*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D020127:Recovery of Function; D012307:Risk Factors; D057185:Sedentary Behavior; D013997:Time Factors; D014481:United States