"Training density" technically refers to the amount of work being performed per unit of time. When it comes to strength training, the easiest way to increase density is to gradually reduce the amount of rest between sets.
With density-dominant training, you perform a moderate volume of work for each muscle group (9 to 12 total sets) and use very short rest intervals (15 to 45 seconds). Or you can use density techniques such as antagonist supersets (e.g. supersetting a back and a chest exercise).
Two Ways to Progress
- Use more weight without resting more
- Use the same weight while resting less
How It Works
This approach has the advantage of stimulating the release of hormones that burn more fat. Contrary to what its name implies, "growth" hormone mobilizes fatty acids. By increasing its release, you positively affect the amount of fat you burn during your workout.
For this reason, density-dominant workouts are good for a fat loss phase, as well as for "endomorphs" who aren't normally efficient at mobilizing fat. However, it's not optimal for those in a mass gaining or pure strength phase.