High intensity interval training (HIIT) is hugely popular in the exercise world at the moment, leading to an explosion of “HIIT” style group classes and work outs. Unfortunately though, many of these classes and work outs are not actually HIIT programs as used in the research literature. Therefore the results individuals achieve won’t be inline with the results HIIT research supports. Is this a bad thing? Probably not, if it means people are exercising this far outweighs the difference in health outcomes comparing HIIT and vigorously intensive classes.
An example of a true HIIT program which was used in a research study using HIIT to treat patients with heart failure involved 4, 30 second sprints at 90% of max HR on an inclined treadmill with 4 minute rest intervals, building up to 6 sprints.