Isometric exercises are the tightening (contraction) of a specific muscle or group of muscles and are performed in a static position. Typically the position will be held for 20-40 seconds. The muscle does not lengthen during this type of movement and there will be no movement around the joint. Isometric exercises help maintain strength and improve stabilization, but won't build power or explosiveness. Since the muscle does not lengthen, isometric exercises will give you less DOMS compared to other strength movements. By incorporating these less physically demanding (but still challenging) movements into your strength plan, it will compliment your heavier lifts and provide a good balance in your strength session.