HIIT or High Intensity Interval Training is when you perform an exercise for a short period of time at a high intensity level, followed by a period of complete or active rest. Most individuals performHIIT with sprinting or other forms of cardio.
I've recently been using HITT with bodyweight and dumbbell exercises and have seen tremendous results in fat loss, mass gain, and athletic performance. These workouts are extremely simply to set up.
All you do is choose on exercise, a work interval, and a rest interval. For example, lets say I decide to use Dumbbell Alternating Hanging High Pulls as my exercise of choice. A great intervalscheme would have to perform the exercise for 30 seconds straight, then rest 15 seconds.
You can repeat this interval for as long as you'd like. You can even perform more than one exercise per workout. For example, lets say you were performing 2 exercises, each with a 30 seconds work and 15 seconds rest interval.
My personal favorite is to alternate between two exercises. For example, you can perform the first exercise for 30 seconds, then rest 15 seconds. Then move onto the second exercise and perform it for 30 seconds followed by a 15 second rest period.
Along the fat loss and mass gain benefits of HIIT, there is another very important benefit to this training style: time savings. You can literally construct a simple interval training workout based on how much time you have to workout.
For example, if you only have 15 minutes to workout, then you perform 10 rounds of 2 exercises with a 30 seconds work and 10 seconds rest interval. This entire workout would last just 15 minutes, but you'll be able to complete a lot of work within that short period of time.