HIIT versus MICT in cardiac rehabilitation
Worldwide, coronary heart disease (CHD) results in one in four deaths, an increase compared to one in five deaths 20 years ago. CHD was ranked in 2012 by a systematic analysis for the Global Burden of Disease Study as the leading cause of years of life lost (YLL) to premature death that transcends the infections of the lower respiratory tract. The YLL attributed to CHD has increased by 28% over the past 20 years.
Cardiac rehabilitation (CR) is an important tool in the secondary prevention of cardiovascular diseases. This form of prevention, while reducing the chance of subsequent heart incidents, is intended to help participants lead a full, healthy life. CR concerns education, behavioral change in lifestyle, exercise programs and psychosocial support under supervision. These exercise programs are aimed at increasing cardio respiratory function and muscle strength of CR participants; however, international CR guidelines are inconsistent in their recommendations regarding training intensity.
The training component of CR programs must ensure that prescribing exercises result in significant improvements in cardio respiratory function and also adequately evaluates the changes resulting from participation. Prescribing a rehabilitation program, which increases cardio respiratory function to the greatest extent, could have a superior effect on the reduction of all causes and cardiovascular mortality.
Aerobic capacity has turned out to be equivalent to cardiovascular mortality and morbidity. There is also growing evidence that, with regard to improving cardio respiratory function in the heart population, interval training with high intensity (HIIT) seems to be more effective than training with moderate intensity (MICT). Previously published systematic reviews in cardiovascular disease have neither examined the effect of the number of weeks of intervention on cardio respiratory fitness changes, nor have any side effects been reported. Within the cardiac population that examined cardio respiratory fitness changes as a result of HIIT versus MICT, a systematic review and meta-analysis of randomized controlled trials (RCTs) were sought, as well as side effects.
The ability to determine whether HIIT or MICT resulted in greater cardio respiratory functional gain for participants with CAD who did not have a diagnosis of heart failure was the main goal of this systematic review and meta-analysis. Furthermore, they wanted to measure whether the duration of the interventions had an effect on the results. The hypothesis that HIIT improves cardio respiratory function to a greater extent than MICT was supported by the assessment and meta-analysis. Interventions of >12 weeks showed, as expected, no greater increase in cardio respiratory function of continued HIIT training. In addition, programs of ≤6 weeks did not result in significant changes.
After a systematic search by Hannan et al. of relevant databases up to July 2017, a critical narrative synthesis and meta-analysis were performed. We looked for RCTs in which cardio respiratory function and functioning were compared that resulted from HIIT versus MICT interventions within the cardiac population. In the analysis, 17 studies with 953 participants (465 for HIIT and 488 for MICT) were included. In improving cardio respiratory function, HIIT was significantly better than MICT, in general (SMD 0.34 ml / kg / min, 95% confidence interval [CI, 0.2-0.48], p <0.00001, I2 = 28%). There were cardiac events or deaths for which hospitalization was reported during a training session. As a result of the MICT (n = 14) intervention than the HIIT intervention (n = 9), more side effects were usually reported. However, some side effects (n = 5) were not classified per intervention group.
HIIT is more effective (better) compared to MICT in improving cardio respiratory function in participants in cardiac rehabilitation (CR). Improvements in cardio respiratory function are significant for CR programs with a duration of more than 6 weeks. The major improvements in programs with a duration of 7-12 weeks resulted in cardio respiratory function for patients with coronary heart disease. For CR participants, HIIT appears to be just as safe as MICT. This assessment may allow countries with guidelines that recommend lower intensity to have more confidence in including HIIT in their guidelines and in improving international consensus.
Source: Hannan et al.
Physical Therapy Science