title: High-intensity compared to moderate-intensity training for exercise initiation, enjoyment, adherence, and intentions: an intervention study.
abstract: BACKGROUND
  Understanding exercise participation for overweight and obese adults is critical for preventing comorbid conditions. Group-based high-intensity functional training (HIFT) provides time-efficient aerobic and resistance exercise at self-selected intensity levels which can increase adherence; behavioral responses to HIFT are unknown. This study examined effects of HIFT as compared to moderate-intensity aerobic and resistance training (ART) on exercise initiation, enjoyment, adherence, and intentions.
  
  
  METHODS
  A stratified, randomized two-group pre-test posttest intervention was conducted for eight weeks in 2012 with analysis in 2013. Participants (n = 23) were stratified by median age (< or ≥ 28) and body mass index (BMI; < or ≥ 30.5). Participants were physically inactive with an average BMI of 31.1 ± 3.5 kg/m2, body fat percentage of 42.0 ± 7.4%, weight of 89.5 ± 14.2 kg, and ages 26.8 ± 5.9 years. Most participants were white, college educated, female, and married/engaged. Both groups completed 3 training sessions per week. The ART group completed 50 minutes of moderate aerobic exercise each session and full-body resistance training on two sessions per week. The HIFT group completed 60-minute sessions of CrossFit™ with actual workouts ranging from 5-30 minutes. Participants completed baseline and posttest questionnaires indicating reasons for exercise initiation (baseline), exercise enjoyment, and exercise intentions (posttest). Adherence was defined as completing 90% of exercise sessions. Daily workout times were recorded.
  
  
  RESULTS
  Participants provided mostly intrinsic reasons for exercise initiation. Eighteen participants adhered (ART = 9, 81.8%; HIFT = 9, 75%). HIFT dropouts (p = .012) and ART participants (p = .009) reported lower baseline exercise enjoyment than HIFT participants, although ART participants improved enjoyment at posttest (p = .005). More HIFT participants planned to continue the same exercise than ART participants (p = .002). No significant changes in BMI or body composition were found. Workouts were shorter for HIFT than ART (p < .001).
  
  
  CONCLUSIONS
  HIFT participants spent significantly less time exercising per week, yet were able to maintain exercise enjoyment and were more likely to intend to continue. High-intensity exercise options should be included in public health interventions.
  
  
  BACKGROUND
  ClinicalTrials.gov Identifier: http://NCT02185872. Registered 9 July 2014.
authors.affiliation: Department of Kinesiology, Kansas State University, Functional Intensity Training Lab, 1A Natatorium, Manhattan, KS 66506, USA. kmhphd@ksu.edu.
authors.forename: Katie M
authors.initials: KM
authors.lastname: Heinrich
authors.forename: Pratik M
authors.initials: PM
authors.lastname: Patel
authors.forename: Joshua L
authors.initials: JL
authors.lastname: O'Neal
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Heinrich
mesh_terms: D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D015897:Comorbidity; D015444:Exercise; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D033182:Intention; D008297:Male; D009765:Obesity / Q000150:complications / Q000628:therapy*; D050177:Overweight; D010349:Patient Compliance; D005082:Physical Exertion; D057181:Pleasure; D055070:Resistance Training; D055815:Young Adult
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