title: Low-volume, high-intensity, aerobic interval exercise for sedentary adults: VO₂max, cardiac mass, and heart rate recovery.
abstract: OBJECTIVE
  The aim of this study was to compare the effects of low-volume, high-intensity aerobic interval training (HAIT) on maximal oxygen consumption (VO₂max), left ventricular (LV) mass, and heart rate recovery (HRR) with high-volume, moderate-intensity continuous aerobic training (CAT) in sedentary adults.
  
  
  METHODS
  Twenty-four healthy but sedentary male adults (aged 29.2 ± 7.2 years) participated in an 8-week, 3-day a week, supervised exercise intervention. They were randomly assigned to either HAIT (18 min, 180 kcal per exercise session) or CAT (45 min, 360 kcal). VO₂max, LV mass (3T-MRI), and HRR at 1 min (HRR-1) and 2 min (HRR-2) after maximal exercise were measured pre- and post-intervention.
  
  
  RESULTS
  Changes in VO₂max during the 8-week intervention were significant (P < 0.01) in both groups (HAIT, 8.7 ± 3.2 ml kg(-1) min(-1), 22.4 ± 8.9%; CAT, 5.5 ± 2.8 ml kg(-1) min(-1), 14.7 ± 9.5%), while the VO₂max improvement in HAIT was greater (P = 0.02) than in CAT. LV mass in HAIT increased (5.1 ± 8.4 g, 5.7 ± 9.1%, P = 0.05), but not in CAT (0.9 ± 7.8 g, 1.1 ± 8.4%, P = 0.71). While changes in HRR-1 were not significant in either group, change in HRR-2 for HAIT (9.5 ± 6.4 bpm, 19.0 ± 16.0%, P < 0.01) was greater (P = 0.03) than for CAT (1.6 ± 10.9 bpm, 3.9 ± 16.2%, P = 0.42).
  
  
  CONCLUSIONS
  This study suggests that HAIT has potential as a time-efficient training mode to improve cardiorespiratory capacity and autonomic nervous system function in sedentary adults.
authors.affiliation: Hazard Evaluation and Epidemiology Research Group, National Institute of Occupational Safety and Health, Japan, 6-21-1 Nagao, Tama-ku, Kawasaki, 214-8585, Japan, matsuo.tomoaki11@gmail.com.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Matsuo
authors.forename: Kousaku
authors.initials: K
authors.lastname: Saotome
authors.forename: Satoshi
authors.initials: S
authors.lastname: Seino
authors.forename: Miki
authors.initials: M
authors.lastname: Eto
authors.forename: Nobutake
authors.initials: N
authors.lastname: Shimojo
authors.forename: Akira
authors.initials: A
authors.lastname: Matsushita
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Iemitsu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohshima
authors.forename: Kiyoji
authors.initials: K
authors.lastname: Tanaka
authors.forename: Chiaki
authors.initials: C
authors.lastname: Mukai
mesh_terms: D000328:Adult; D002306:Cardiac Volume; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D020127:Recovery of Function; D057185:Sedentary Behavior