title: Is a threshold-based model a superior method to the relative percent concept for establishing individual exercise intensity? a randomized controlled trial.
abstract: BACKGROUND
  Exercise intensity is arguably the most critical component of the exercise prescription model. It has been suggested that a threshold based model for establishing exercise intensity might better identify the lowest effective training stimulus for all individuals with varying fitness levels; however, experimental evidence is lacking. The purpose of this study was to compare the effectiveness of two exercise training programs for improving cardiorespiratory fitness: threshold based model vs. relative percent concept (i.e., % heart rate reserve - HRR).
  
  
  METHODS
  Apparently healthy, but sedentary men and women (n = 42) were randomized to a non-exercise control group or one of two exercise training groups. Exercise training was performed 30 min/day on 5 days/week for 12weeks according to one of two exercise intensity regimens: 1) a relative percent method was used in which intensity was prescribed according to percentages of heart rate reserve (HRR group), or 2) a threshold based method (ACE-3ZM) was used in which intensity was prescribed according to the first ventilatory threshold (VT1) and second ventilatory threshold (VT2).
  
  
  RESULTS
  Thirty-six men and women completed the study. After 12weeks, VO2max increased significantly (p < 0.05 vs. controls) in both HRR (1.76 ± 1.93 mL/kg/min) and ACE-3ZM (3.93 ± 0.96 mL/kg/min) groups. Repeated measures ANOVA identified a significant interaction between exercise intensity method and change in VO2max values (F = 9.06, p < 0.05) indicating that VO2max responded differently to the method of exercise intensity prescription. In the HRR group 41.7 % (5/12) of individuals experienced a favorable change in relative VO2max (Δ > 5.9 %) and were categorized as responders. Alternatively, exercise training in the ACE-3ZM group elicited a positive improvement in relative VO2max (Δ > 5.9 %) in 100 % (12/12) of the individuals.
  
  
  CONCLUSIONS
  A threshold based exercise intensity prescription: 1). elicited significantly (p < 0.05) greater improvements in VO2max, and 2). attenuated the individual variation in VO2max training responses when compared to relative percent exercise training. These novel findings are encouraging and provide important preliminary data for the design of individualized exercise prescriptions that will enhance training efficacy and limit training unresponsiveness.
  
  
  BACKGROUND
  ClinicalTrials.gov Identifier: ID NCT02351713 Registered 30 January 2015.
authors.affiliation: Recreation, Exercise, and Sport Science Department, Western State Colorado University, 600 N. Adams St., Gunnison, CO 81230 USA.
authors.forename: Ali E
authors.initials: AE
authors.lastname: Wolpern
authors.affiliation: Recreation, Exercise, and Sport Science Department, Western State Colorado University, 600 N. Adams St., Gunnison, CO 81230 USA.
authors.forename: Dara J
authors.initials: DJ
authors.lastname: Burgos
authors.affiliation: Department of Kinesiology, University of Wisconsin - Eau Claire, 105 Garfield Ave, PO Box 4004, Eau Claire, WI 54702 USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Janot
authors.affiliation: Recreation, Exercise, and Sport Science Department, Western State Colorado University, 600 N. Adams St., Gunnison, CO 81230 USA.
authors.forename: Lance C
authors.initials: LC
authors.lastname: Dalleck
keywords: Cardiorespiratory fitness; Cardiovascular Disease; Exercise prescription; Primary prevention; VO2max