# Effects of High Intensity Interval versus Moderate Continuous Training on Markers of Ventilatory and Cardiac Efficiency in Coronary Heart Disease Patients PMID: 25741531 Journal: The Scientific World Journal Published: 2015-02-09 Authors: Cardozo GG, Oliveira RB, Farinatti PT ## Question Do 16 weeks of HIIT improve peak VO2, VE/VCO2 slope, oxygen uptake efficiency slope, and oxygen pulse more than moderate continuous training or no exercise in coronary heart disease patients? ## Summary This randomized controlled trial compared 16 weeks of supervised treadmill HIIT, moderate continuous training, and no exercise in stable coronary heart disease patients. HIIT used 30 minutes of alternating 2-minute bouts at 90% and 60% peak heart rate, with 5-minute warm-up and cool-down, 3 times per week. All subjects completed the program and no untoward events occurred. HIIT improved peak VO2, peak oxygen pulse, and oxygen pulse slope, while moderate training did not improve peak VO2 and ventilatory efficiency markers were not significantly changed by either exercise regimen. ## Population - Stable coronary heart disease patients referred to cardiac rehabilitation with optimized treatment and ejection fraction greater than 50%. - Sample size: 71 - Age: HIIT 56 +/- 12 years; MIT 62 +/- 12 years; CG 64 +/- 12 years. - Sex: Male: HIIT 63%, MIT 66%, CG 76%. - Fitness level: Sedentary for at least one year; baseline peak VO2 about 20.6-21.9 mL/kg/min. - Health status: Coronary artery disease with preserved ejection fraction; recent MI/revascularization, pacemaker, medication changes, and limiting musculoskeletal conditions excluded. ## Methodology - Randomized controlled trial with HIIT, moderate continuous training, and nonexercise control groups. - 16 weeks - Supervised cardiac rehabilitation treadmill training with laboratory cardiopulmonary testing. - Randomized and controlled study design. ## Protocol - HIIT treadmill cardiac rehabilitation. - Modality: Treadmill aerobic training. - Work intervals: 2 minutes at 90% peak HR. - Recovery: 2 minutes at 60% peak HR. - Sets or repetitions: Alternating bouts for 30 minutes. - Intensity: 90% peak HR high bouts and 60% peak HR low bouts. - Session duration: 40 minutes including 5 minute warm-up, 30 minute interval block, and 5 minute cool-down. - Frequency: 3 times/week. - Program length: 16 weeks. - Moderate continuous training and nonexercise control. - Modality: MIT: treadmill aerobic training; CG: no exercise training. - Work intervals: MIT continuous 30 minutes; CG none. - Intensity: MIT 70-75% peak HR; CG instructed not to engage in physical activity programs. - Session duration: MIT 40 minutes including 5 minute warm-up, 30 minutes continuous exercise, and 5 minute cool-down; CG none. - Frequency: MIT 3 times/week; CG none. - Program length: 16 weeks. ## Outcomes ### Peak VO2 Status: improved HIIT increased peak VO2 from 20.6 +/- 5 to 24.4 +/- 5 mL/kg/min; MIT remained 21.8 +/- 6 to 21.9 +/- 6; CG decreased 21.9 +/- 6 to 18.6 +/- 6. Interaction P = 0.04; HIIT within-group P < 0.05; CG within-group decrease P < 0.05 and CG versus HIIT P < 0.05. ### Peak oxygen pulse Status: improved HIIT increased peak oxygen pulse from 12.4 +/- 4 to 14.2 +/- 4 mL/beat; MIT was stable; CG decreased from 13.7 +/- 4 to 11.7 +/- 4. Interaction P = 0.05; HIIT within-group P < 0.05; CG within-group decrease P < 0.05 and CG versus HIIT P < 0.05. ### O2 pulse slope Status: improved O2 pulse slope increased in HIIT by about 22%, was stable in MIT at about 2%, and decreased in CG by about 20%. HIIT P < 0.05; MIT P > 0.05; CG P < 0.05; CG lower versus HIIT P = 0.03; differences versus CG after 70% of CPX duration P < 0.05. ### VE/VCO2 slope and OUES Status: no clear change No differences among groups were found for VE/VCO2 slope or OUES before versus after training. VE/VCO2 slope interaction P = 0.48; OUES interaction P = 0.16. ### Safety Status: no clear change All subjects completed the program and no untoward events occurred during exercise testing or training procedures. ## Practical Insights - For stable CHD patients in supervised rehabilitation, 2-minute 90%/60% peak-HR treadmill intervals improved peak VO2 where 30-minute moderate continuous training did not. - The protocol included explicit warm-up and cooldown and medical monitoring, which are core safety features for clinical HIIT. - Ventilatory efficiency markers did not improve, so claims should distinguish fitness/oxygen pulse outcomes from VE/VCO2 or OUES. ## Limitations - Participants had mild or moderate CHD with preserved ejection fraction, limiting generalization to more severe cardiac disease. - Mechanisms were not directly tested with invasive measures of lung perfusion, arterial blood gases, or ventricular function. - Training was supervised and medically monitored, limiting translation to unsupervised app exercise. - Actual achieved training intensity and exact interval count/order were not reported. - HIIT group was younger on average than MIT and CG, although baseline group differences were not statistically significant. ## Safety And Adherence - All subjects completed the program. - No untoward events occurred during exercise testing or training procedures. - No patient was limited by angina. - No patients showed ECG evidence of ischemia during baseline CPX. - Exercise testing used termination criteria including moderately severe angina, ST depression greater than 2.0 mm, sustained systolic blood pressure drop, or clinically relevant rhythm disturbance. - A cardiologist checked ECG responses once weekly at the beginning and end of training sessions. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/25741531/) (pubmed) - [DOI](https://doi.org/10.1155/2015/192479) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4337271/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.