If you understand the strength curve of a particular muscle you will better understand how to build optimal strength/hypertrophy/power in that muscle group and pack on some serious quality size as well.
Ascending, descending, and bell-curve are the three curves of strength training.
Ascending resistance curve – The weight gets harder to lift as you get closer to the completion in the range of motion. Difficulty is highest at the top, and your strength descends as you lift (descending strength curve). Dumbbell lateral raises are an example of this.
Descending resistance curve – Difficulty is highest at the beginning of the movement, and the weight gets easier to lift as you get closer to the completion in the range of motion (ascending strength curve). Incline dumbbell curls are an example of this.
Bell-shaped resistance curve – The resistance, and thus difficulty, is greatest at the mid-point in the exercise, which is also where the strength curve is at its lowest point. A standing barbell curl is a great example of this.