Are isometric exercises a good way to ToneUp?

Isometrics are defined as static (HOLDING... SQUEEZE WITHOUT MOVING) exercises in which neither the muscle length nor the joint angle change. Any exercise in which you contract a group of muscles and sustain that contraction for a given amount of time, without moving at the joints, essentially would be considered an isometric exercise.   For example, a classic biceps curl is considered a dynamic exercise because as one pulls the weight up toward the shoulder, the bicep muscle is shortened on the concentric contraction and then is lengthened as the weight is released and lowered back down on the eccentric contraction. In contrast, when one holds a plank position, the muscles of the back, abdomen, and shoulders are all contracted, but they are held in that contraction for a substantial amount of time with no change in the length of the muscles. A plank is a static exercise and therefore considered an isometric. If you have ever practiced Yoga, Pilates or Barre, then you are already familiar with isometric contractions, as many of the poses and exercises performed in these formats involve various types of isometrics.