We all have exercises we avoid and for me it is isometrics. Isometrics basically means holding the taxing positions so the joint angle and muscle length do not change during the contraction, the work.
Holding a yoga pose, holding an elbow plank, holding bridge pose, holding a bicep mid-range, trying to push a wall. When you do isometrics you are really working the endurance of the muscle, the slow twitch fibers. Isometric training is a great way to target toning specific muscles. The one drawback to isometric training is that it doesn't strengthen the muscle through a range of motion, since you are not moving the joint. Remember, isometrics is a part of a strength training regimen, not the only component.
Just as it is good to mix up your cardio training, it is also a good idea to vary your strength training methods too. So try some isometrics.