title: Modified high-intensity interval training increases peak cardiac power output in patients with heart failure.
abstract: OBJECTIVE
  Although high-intensity interval aerobic training (HIT) effectively improves aerobic fitness, the risk of cardiac arrest transiently increases during strenuous physical exertion in patients with cardiovascular disease. For safety and efficacy concerns, this investigation explored the effect of a modified HIT (mHIT) on exertional ventilatory-hemodynamic efficiency in heart failure patients with reduced ejection fraction (HFREF).
  
  
  METHODS
  HFREF patients were prospectively assigned to two groups: mHIT and usual healthcare (UC). The former comprised supervised continuous aerobic training at ventilatory anaerobic threshold for 50 min/day, 3 days/week for 4 weeks, and then 3-min intervals at 40 and 80% VO₂ reserve for 50 min/day, 3 days/week for 8 weeks. The latter received optimal medical treatment only. Ventilatory and hemodynamic responses during exercise were measured before and after the intervention. Paired-t and repeated measures ANOVA with post hoc tests were adopted.
  
  
  RESULTS
  Each group had an N of 33. The mHIT and UC group had matched baseline characteristics including health-promotion concept and behavior score. The mHIT for 12 weeks (1) increased VO₂, cardiac output, and notably, cardiac power output at peak workload (1,151 ± 573 vs. 1,306 ± 596 L/min/mmHg); (2) reduced V E/VO2 (32.4 ± 4.6 vs. 30.0 ± 4.0), breathing frequency, ventilation, and enhanced stroke volume compliance at identical submaximal intensity (50% peak workload at pre-intervention evaluation). No significant changes in ventilatory and hemodynamic responses to exercise were observed following the UC.
  
  
  CONCLUSIONS
  The mHIT regimen improves peak cardiac pumping capacity with reducing cardiac after-load and simultaneously increases ventilation efficiency during exercise in patients with HFREF. Thereby, aerobic fitness is ameliorated.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkuo, Taiwan.
authors.forename: Shu-Chun
authors.initials: SC
authors.lastname: Huang
authors.forename: Mei-Kuen
authors.initials: MK
authors.lastname: Wong
authors.forename: Pyng-Jing
authors.initials: PJ
authors.lastname: Lin
authors.forename: Feng-Chun
authors.initials: FC
authors.lastname: Tsai
authors.forename: Tieh-cheng
authors.initials: TC
authors.lastname: Fu
authors.forename: Ming-Shien
authors.initials: MS
authors.lastname: Wen
authors.forename: Chi-Tai
authors.initials: CT
authors.lastname: Kuo
authors.forename: Jong-Shyan
authors.initials: JS
authors.lastname: Wang
mesh_terms: D000368:Aged; D015308:Anaerobic Threshold; D002302:Cardiac Output; D015444:Exercise; D005081:Exercise Therapy; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange