Final answer:
An isometric contraction occurs when a muscle produces tension without changing the angle of a skeletal joint. It involves sarcomere shortening and increasing muscle tension, but no movement of the load. Isometric contractions are important for maintaining posture and bone and joint stability.
Step-by-step explanation:
An isometric contraction occurs as the muscle produces tension without changing the angle of a skeletal joint. Isometric contractions involve sarcomere shortening and increasing muscle tension, but do not move a load, as the force produced cannot overcome the resistance provided by the load.
For example, if one attempts to lift a hand weight that is too heavy, there will be sarcomere activation and shortening to a point, and ever-increasing muscle tension, but no change in the angle of the elbow joint. Isometric contractions are active in maintaining posture and maintaining bone and joint stability. Most actions of the body are the result of a combination of isotonic and isometric contractions working together to produce a wide range of outcomes.