HIIT(High-intensity interval training) is an umbrella term for a time-efficient exercise that features cardio-based and/or multimodal exercise intervals (30-240 seconds) with interspersed active or passive recovery bouts. HIIT intervals typically range from 85%-100% of the highest heart rate attained during a peak or symptom-limited exercise test. HIIT has been widely adopted in healthy populations as an alternative to moderate-intensity continuous training (MICT); or the ubiquitous application of moderate intensity exercise (50%-75% of maximal heart rate [HRmax]) utilized in rehabilitation settings. Quindry JC et al., conducted a study which overviews risks and benefits of HIIT for coronary artery disease (CAD) patients. Mitigating factors central to the HIIT risk-benefit ratio were patient compliance, safety, risk stratification, and cardiovascular outcomes.
- The adaptive stimulus of HIIT was often believed to be superior to moderate intensity continuous training (MICT)
- HIIT provided equivalent or greater adaptive responses to MICT with a shortened time investment
- A HIIT regimen induced improvements in aerobic capacity and body composition at a fraction of the exercise time devoted to MICT
- HIIT enrolled short duration intervals that approach near maximal/maximal intensity than MICT which emphasizes continuous moderate intensity exercise of extended duration
- HIIT showed a remarkable increase in aerobic capacity, particularly in previously sedentary patients with chronic disease
- HIIT showed a sustained increase in post exercise oxygen consumption, often exceeding 24 hours in duration
- Although metabolic responses to HIIT remain elevated when normalized for exercise duration and caloric expenditure
- HIIT also had independent effects on appetite suppression
- Short-term exercise performance advantages and cardiac performance outcomes were improved slightly following HIIT interventions as compared to MICT (Figure 1)
HIIT in CAD patients
- HIIT training improved ventricular compliance (evaluated by strain rate and mitral flow as compared to MICT
- The diastolic relaxation improved more in cardiac patients that engaged in HIIT in-depth investigation of exercise training intensity on left ventricular function in low-risk CAD patients
- Aerobic capacity was further improved by HIIT training in CAD patients as compared with MICT interventions
The safety and effectiveness of HIIT can be confirmed and widely adopted in patients with known or suspected CAD, especially in unsupervised, non-medical settings
