People spend longer in the gym than they need too. A lot of people follow the same exercise programme for a number of months, which is great as they have a plan to follow and a good routine. However, after a while, your body gets used to the exercises that you do which can lead to the person not seeing as much progress/change to their body as they would like too.
High-intensity interval training (HIIT) is a form of interval training, an exercise strategy alternating short periods of intense anaerobic exercise with less-intense recovery periods. This type of training is great for people who do not have much time to spend exercising.
HIIT means working at a high level by doing short bursts of exercise. This allows your heart rate to stay up in the high zone which means you will burn fat effectively without having to spend hours in the gym.
I would recommend HIIT to everyone who would like to hit their own individual fitness targets without becoming bored and demotivated.