Final answer:
The correct instruction for isometric exercises is to contract the muscle for several seconds, then relax for a few seconds, and repeat. Isometric exercises involve increasing muscle tension without changing joint angles and are used for strengthening and stabilizing muscles.
Step-by-step explanation:
When instructing a patient on performing isometric exercises, the nurse should include the following instruction: Contract the muscle for several seconds, then relax the muscle for a few seconds, and contract it again. Isometric exercises are characterized by the muscle creating tension without changing the angle of a skeletal joint. This involves sarcomere shortening and an increase in muscle tension, but the muscle does not move a load. It is an exercise where the muscle acts against resistance with the goal of strengthening and/or stabilizing the muscle without producing movement.
For instance, pushing against a static object such as a wall, where the arms exert force without bending at the elbows, is a form of isometric exercise. These exercises are beneficial for maintaining posture and joint stability. The other options listed involve either isotonic contractions, where the muscle length changes as it moves a load, or passive movements done by a family member, which are not isometric in nature.