High intensity interval training (HIIT) is only effective for improving fitness when performed at 60-second intervals.
That is according to new research from Liverpool John Moores University, which focused on HIIT, meaning short bursts (anywhere from 20 to 90 seconds) of intense cardio exercises. The research compared two popular HIIT protocols (60HIIT and 30HIIT) performed for six weeks, three times a week, in a sample of 26 previously sedentary men and women; 60HIIT means six-10 60 second intervals with 60 seconds of rest, whereas 30HIIT means four-eight 30 second intervals, with 120 seconds of rest.
They kept track of training adherence and intensity remotely via a heart rate monitor that fed info through a mobile app, finding that aerobic capacity increased after six weeks of 60HIIT, but there was no difference for 30HIIT. This means that 60HIIT should be used over 30HIIT because the former improves fitness, whereas the latter doesn’t.
Hannah Church, one of the researchers, commented “In order for people to get the most out of HIIT, which may be the answer to the difficulties of paying for and getting to the gym, we need to get the timing right. Our research showed just how important this is, because we found that 30 second intervals with 120 seconds of rest meant that participants’ heart rates didn’t stay up; 120 seconds is just too long to be resting for!”