Exercise-based cardiac rehabilitation (CR) is a recommended clinical practice in Class 1 for patients with selected cardiovascular disease (CKD) and reduced ejection fraction (HFrEF). For patients with coronary heart disease and heart failure (HF), the cardiorespiratory season is a strong predictor of mortality. Therefore, exercise optimizes the improvement of cardiorespiratory pressure and exercise.
Systematic studies of coronary heart disease showed that between 2004 and 2011, CRs based on physical activity reduced hospitalizations by 31%, CV deaths by 26%, and all-cause mortality rates by 20% compared to regular medical care. Since then, however, the results of RAMIT (Myocardial Infarction Rehabilitation Trial) and subsequent systematic reviews have questioned the effectiveness of exercise-based CR in reducing these results.
This recent review examined data from multiple studies on the effects of HIIT on CR programs, such as beneficial physiological adaptations for the lung, heart, vascular, and skeletal muscle systems in patients with ECB and HF.
“Most of the guidelines for physical exercise training recommend prescribing aerobic exercise based on relative exercise competency indices,” the authors wrote. The following competency indices are:
- Percentage of maximum workload (Wpeak)
- Percentage of maximum heart rate (% HRpeak)
- Percentage of VO2peak (% VO2peak)
- Percentage of HR reserve (% HRR)
- Percentage of VO2 reserve (% VO2R)
The review found 3 studies that looked at the long-term outcomes of HIIT compared to MICT in coronary artery disease (CAD) at 6 months and 12 months.
Moholdt et al found that HIIT improved VO2peak and HR recovery more than MICT in patients undergoing coronary artery bypass surgery for 6 months. The study also found similar improvements in quality of life (QOL) and adiponectin in both HIIT and MICT.
SAINTEX-CAD and FITR Heart studies found similar improvements between HIIT and MICT in patients with CAD for 12 months. These improvements were seen in VO2peak and other exercise variables, including CVD risk factors, QOL, fibromuscular dysplasia, body composition, and moderate to severe physical activity. No change was seen in the dietary intake.
The improvement in VO2peak in the FITR Heart Study was numerically higher in MICT (1.8 ml / kg / min) than HIIT (1.8 ml / kg / min) and the authors suggested that it could have a longer long-term survival.
Two other studies in the review measured adherence. SMARTEX HF research has followed patients with HFrEF, while OptimEX-Clin has followed patients with HFpEF, and both have shown a reversal of supervised workout improvements over 12 months, regardless of exercise intensity.
The FITR Heart Study and OptimEx-Clin study ordered participants to undergo HIIT or MICT at home until a 12-month follow-up after the supervised training period, with adherence as prescribed for 70% of the measured sessions. The FITR Heart Study reported 53% adherence to HIIT and 41% to MICT, and the Optimex-Clin study measured 56% adherence to HIIT and 60% to MICT.
However, the FITR Heart Study reported that 38% of MICT-mandated participants started exercising with greater intensity and 24% of participants underwent HIIT with lower intensity. After excluding non-adherent participants, HIIT significantly improved VO2peak (5.2 ml / kg / min) compared to MICT (2.2 ml / kg / min).
In contrast, Moholdt et al found that after 5 months of training at home, higher proportions of participants stopped HIIT in favor of MICT (35%) and only 4% of participants prescribed MICT began high-intensity exercise. The proportion of participants who performed 3 sessions per week was similar in the case of HIIT (74%) and MICT (68%), and HIIT had better improvements at 6 months of VO2peak.
“Short-term HIIT protocols may be a strong stimulus to enhance peripheral mitochondrial adaptations and provide similar VO2 peak enhancements for MICTs, longer-duration and high-volume HIIT protocols appear to be better for achieving stroke volume and vascular adaptations, and with higher VOTs.” .
They are credited with high-intensity exercise for maximum exercise in making VO2 improvements, which is also important for performing general daily activities.
Taylor JL, Bonikowske AR, Olson TP. Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity. Front Cardiovasc Med.Posted on the Internet September 3, 2021. doi: 10.3389 / fcvm.2021.734278