One muscle-building strategy is a concept known as time under tension. The idea is that the longer you can keep tension in your muscles during a set, the more you’ll exhaust them, forcing them to grow to adapt.
One way to increase TUT is by doing more reps (duh). The other is to pause an exercise at a point in its range of motion and hold it for time. With countdown sets, you accomplish both simultaneously, delivering the maximum stimulus.
How it works
The problem with doing high reps (12 or more, typically) is that your form tends to break down, increasing your risk of injury. It also forces you to use lighter weights, sacrificing muscular tension. With countdown sets, you can fatigue your muscles while keeping your reps low by interspersing isometric holds (pausing a movement), effectively creating a long-lasting,…