title: Relationship between physical activity and aerobic fitness.
abstract: OBJECTIVE
  Physical activity (PA) and cardiorespiratory fitness (CRF) are indicators of cardiovascular disease risk and all-cause mortality. Many health advocates use PA and CRF interchangeably. However, quantification of the relationship between objectively measured PA and CRF is rarely found.
  
  
  METHODS
  The association between objectively measured PA volume (PAv), intensity (PAi), and CRF indexed by V.O(2max) was assessed in a cross-sectional study; 275 women (40.1+/-3.0 years) wore accelerometers at the hip for seven days. They performed a graded maximal treadmill test to measure CRF and had their percent body fat (%BF) assessed.
  
  
  RESULTS
  PAv (F=12.33, P<0.0001) and PAi (F=48.5, P<0.0001) were both significant predictors of CRF, together accounting for 26.9% of the variance (P<0.0001). However, with PAi controlled, PAv was not related to CRF. Yet, with PAv controlled, PAi remained a strong predictor. %BF explained 47% (P<0.0001) of the variance in CRF.
  
  
  CONCLUSIONS
  CRF is more a function of PAi than PAv in middle-aged women. More than 70% of the variance in CRF can be explained by factors other than PA, particularly %BF, suggesting that CRF may not be an appropriate surrogate for PA.
authors.affiliation: College of Health and Human Performance, Brigham Young University, Provo, UT 84602, USA. nnokes@hotmail.com
authors.forename: N
authors.initials: N
authors.lastname: Nokes
mesh_terms: D050154:Adiposity / Q000502:physiology; D000328:Adult; D003430:Cross-Sectional Studies; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D009043:Motor Activity / Q000502:physiology*; D010101:Oxygen Consumption; D010809:Physical Fitness / Q000502:physiology*