Isometric exercise involves contraction against an immovable resistance. Strength is increased at the specific angle of exertion with up to 20% overflow surrounding joint angles. At other joint angles, there is no corresponding increase in strength. The use of isometric exercises is widely practiced in injury rehabilitation or reconditioning. Isometric training is typically implemented when full range of motion exercises may otherwise exacerbate a condition or ailment if introduced too early in the rahab process. Isometrics are also used by powerlifters to break sticking points, a specific angle in the range of motion at which smooth movement is difficult because of insufficient strength. They may use an isometric contraction against an immovable resistance to increase strength at this sticking point so that a smooth, coordinated lift can ultimately be performed through a full range of motion.