High-intensity interval training (HIIT) is a form of interval training, a cardiovascular exercise strategy alternating short periods of intense anaerobic exercise with less intense recovery periods, until too exhausted to continue.
https://en.wikipedia.org/wiki/High-inte ... l_training
I thought I'd pass on my own experience. For context I'm a 63 yr old male and about the right weight. I have an exercise bike and turn it to the maximum resistance. I then pedal as hard as I can for 20 seconds, rest for 10 seconds and repeat another 3 times. All done in less than 2 minutes. That's the first attraction for me, only 2 minutes. I've been doing this for a couple of months every other day. I'm impressed with the results, I recover much more quickly than I did when I first started and I've put on about 7lbs in weight which has clearly gone to my legs which haven't looked as muscular since I was in my 20's and did a lot of cycling. More to the point I feel fitter. And it takes less than 8 minutes a week It must be a very efficient way of exercising.
RC