title: Dose-response relationship of cardiorespiratory fitness adaptation to controlled endurance training in sedentary older adults.
abstract: BACKGROUND
  The purpose of this investigation was to identify a quantitative dose-response relationship for enhancing maximal oxygen consumption (VO2max) in healthy sedentary older adults after controlled endurance training.
  
  
  RESULTS
  This meta-analysis of controlled clinical trials included 1257 exercisers and 845 controls with a mean age of 67.45 ± 5.25 years. Effect sizes were calculated for training-induced VO2max changes. Different training regimens were analyzed and compared. The weighted net change of the mean VO2max values showed a significant increase of 3.78 ml/kg per min (95% confidence interval = 3.29 to 4.27; p < 0.0001) in response to aerobic training. Interstudy differences in VO2max changes were significantly related to exercise intensity, and explained approximately 11% of the variance of the VO2max responses. VO2max improved significantly at 35%-50% heart rate reserve (HRR) and continued improving at a greater rate with increasing "dose". The largest VO2max-improvement adaptation was achieved with a mean intensity of 66%-73% HRR. The magnitudes of the VO2max adaptation are identical to exercise at 57%-65% HRR and at 75%-80% HRR. Higher intensity doses more than 75-80% HRR did not lead to greater enhancement of VO2max improvements but, conversely, resulted in large declines.
  
  
  CONCLUSIONS
  Our data provide quantitative insight into the magnitude of VO2max alterations as affected by exercise intensity, duration, frequency, and program length. The shapes of the dose-response curves are not simply linear, but with many similar trends and noteworthy characteristics. Aerobic training at a mean intensity of 66%-73% HRR with 40-50 min per session for 3-4 day/week for 30-40 weeks appears to be effective and optimal for maximum cardiorespiratory benefits in healthy sedentary older adults.
authors.affiliation: Pott College of Science, Engineering & Education, University of Southern Indiana, Evansville, USA College of Exercise Science, Shanghai University of Sport, China ghuang@usi.edu.
authors.forename: Guoyuan
authors.initials: G
authors.lastname: Huang
authors.affiliation: College of Exercise Science, Shanghai University of Sport, China.
authors.forename: Ru
authors.initials: R
authors.lastname: Wang
authors.affiliation: College of Exercise Science, Shanghai University of Sport, China.
authors.forename: Peijie
authors.initials: P
authors.lastname: Chen
authors.affiliation: Pott College of Science, Engineering & Education, University of Southern Indiana, Evansville, USA Carver College of Medicine, University of Iowa, Iowa City, USA.
authors.forename: Sunny C
authors.initials: SC
authors.lastname: Huang
authors.affiliation: Department of Internal Medicine, University of Kansas Medical Center, Kansas City, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Donnelly
authors.affiliation: College of Arts & Letters, University of North Georgia, Dahlonega, USA.
authors.forename: Jon P
authors.initials: JP
authors.lastname: Mehlferber
mesh_terms: D000222:Adaptation, Physiological; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D018849:Controlled Clinical Trials as Topic; D005081:Exercise Therapy / Q000379:methods*; D017079:Exercise Tolerance; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D010807:Physical Endurance; D010809:Physical Fitness; D057185:Sedentary Behavior; D013997:Time Factors; D016896:Treatment Outcome
keywords: Controlled clinical trials; VO2max; aerobic exercise; aerobic fitness; aging; elderly; intensity; meta-analysis; optimal prescription; sedentary