Every exercise has two components or movements: the positive and the negative.
The exertion half of the exercise, such as raising the dumbbell while doing biceps curls, or raising the barbell when performing the bench press, is called the positive.
Returning to the starting position is called the negative.
Most people put all their effort and attention into the positive movement but ignore and thus discard the enormous benefits provided by attentively performing the negative movement.
The negative is just as essential to shaping the muscle and building the muscle as is the positive.
You can amplify and accelerate your growth by paying as close attention to the negative as to the positive, but it will require increased effort and further depletion of your stores of energy.
The negative is all about keeping the target muscle flexed, rather than relaxing the muscle as we return it to the starting position, and maintaining control over the weight while doing so.
Most people concentrate on a number — the number written on the side of the weight — and once we achieve a larger number, graduating from a 25 lb. dumbbell to a 30 lb. dumbbell for example, it is anathema to consider going back to the 25. But since utilizing the negative takes far more energy than allowing the weight to just drop without resistance, backing off on the weight will be necessary.
Remember that this is just a NUMBER, and that the added component of the well-performed negative will MORE than make up for the lessened weight.
It is as much the intensity of the exercise as the weight of the dumbbell or barbell that provides us the results we seek.