title: Effect of 24 sessions of high-intensity aerobic interval training carried out at either high or moderate frequency, a randomized trial.
abstract: OBJECTIVE
  The training response of an intensified period of high-intensity exercise is not clear. Therefore, we compared the cardiovascular adaptations of completing 24 high-intensity aerobic interval training sessions carried out for either three or eight weeks, respectively.
  
  
  METHODS
  Twenty-one healthy subjects (23.0±2.1 years, 10 females) completed 24 high-intensity training sessions throughout a time-period of either eight weeks (moderate frequency, MF) or three weeks (high frequency, HF) followed by a detraining period of nine weeks without any training. In both groups, maximal oxygen uptake (VO2max) was evaluated before training, at the 9(th) and 17(th) session and four days after the final 24(th) training session. In the detraining phase VO2max was evaluated after 12 days and thereafter every second week for eight weeks. Left ventricular echocardiography, carbon monoxide lung diffusion transfer factor, brachial artery flow mediated dilatation and vastus lateralis citrate maximal synthase activity was tested before and after training.
  
  
  RESULTS
  The cardiovascular adaptation after HF training was delayed compared to training with MF. Four days after ending training the HF group showed no improvement (+3.0%, p = 0.126), whereas the MF group reached their highest VO2max with a 10.7% improvement (p<0.001: group difference p = 0.035). The HF group reached their highest VO2max (6.1% increase, p = 0.026) twelve days into the detraining period, compared to a concomitant reduction to 7.9% of VO2max (p<0.001) above baseline in the MF group (group difference p = 0.609).
  
  
  CONCLUSIONS
  Both HF and MF training of high-intensity aerobic exercise improves VO2max. The cardiovascular adaptation following a HF programme of high-intensity exercise is however delayed compared to MF training.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00733941.
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Håvard
authors: H
authors: Hatle
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Per Kristian
authors: PK
authors: Støbakk
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Harald Edvard
authors: HE
authors: Mølmen
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway ; Department of Pulmonary Medicine, St Olav University Hospital, Trondheim, Norway.
authors: Eivind
authors: E
authors: Brønstad
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Arnt Erik
authors: AE
authors: Tjønna
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway ; Department of Pulmonary Medicine, St Olav University Hospital, Trondheim, Norway.
authors: Sigurd
authors: S
authors: Steinshamn
authors: Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Eirik
authors: E
authors: Skogvoll
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Ulrik
authors: U
authors: Wisløff
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Charlotte Björk
authors: CB
authors: Ingul
authors: K.G. Jebsen Centre of Exercise in Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Circulation and Medical Imaging, NTNU, Trondheim, Norway.
authors: Øivind
authors: Ø
authors: Rognmo
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001916:Brachial Artery / Q000502:physiology; D004452:Echocardiography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D012129:Respiratory Function Tests; D013318:Stroke Volume / Q000502:physiology; D016896:Treatment Outcome; D016276:Ventricular Function / Q000502:physiology*; D055815:Young Adult