title: Effects of a low-volume aerobic-type interval exercise on VO2max and cardiac mass.
abstract: OBJECTIVE
  The aim of this study was to compare the effects of time-efficient, low-volume interval exercises on cardiorespiratory capacity and left ventricular (LV) mass with traditional continuous exercise in sedentary adults.
  
  
  METHODS
  Forty-two healthy but sedentary male subjects (age 26.5 ± 6.2 yr) participated in an 8-wk, five times per week, supervised exercise intervention. They were randomly assigned to one of three exercise protocols: sprint interval training (SIT, 5 min, 100 kcal), high-intensity interval aerobic training (HIAT, 13 min, 180 kcal), and continuous aerobic training (CAT, 40 min, 360 kcal). Cardiorespiratory capacity (V˙O2max) and LV mass (3T-MRI) were measured preintervention and postintervention.
  
  
  RESULTS
  We observed significant (P < 0.01) increases in V˙O2max in all three groups, and the effect of the HIAT was the greatest of the three (SIT, 16.7% ± 11.6%; HIAT, 22.5% ± 12.2%; CAT, 10.0% ± 8.9%; P = 0.01). There were significant changes in LV mass, stroke volume (SV), and resting HR in both the SIT (LV mass, 6.5% ± 8.3%; SV, 5.3% ± 8.3%; HR, -7.3% ± 11.1%; all P < 0.05) and HIAT (LV mass, 8.0% ± 8.3%; SV, 12.1% ± 9.8%; HR, -12.7% ± 12.2%; all P < 0.01) but not in the CAT (LV mass, 2.5% ± 10.1%; SV, 3.6% ± 6.6%; HR, -2.2% ± 13.3%; all P > 0.05).
  
  
  CONCLUSIONS
  Our study revealed that V˙O2max improvement with the HIAT was greater than with the CAT despite the HIAT being performed with a far lower volume and in far less time than the CAT. This suggests that the HIAT has potential as a time-efficient training mode to improve V˙O2max in sedentary adults.
authors.affiliation: 1Space Biomedical Research Office, Japan Aerospace Exploration Agency, Tokyo, JAPAN; 2Hazard Evaluation and Epidemiology Research Group, National Institute of Occupational Safety and Health, Kawasaki, JAPAN; 3Center for Cybernics Research, University of Tsukuba, Tsukuba, JAPAN; 4Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, JAPAN; and 5Faculty of Sport and Health Science, Ritsumeikan University, Kyoto, JAPAN.
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: 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; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006352:Heart Ventricles / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D010101:Oxygen Consumption / Q000502:physiology*; D057185:Sedentary Behavior; D013318:Stroke Volume; D055815:Young Adult