Final answer:
Isometric contractions occur without changing joint angle and can be used to start resistive training with little movement.
Step-by-step explanation:
An isometric contraction occurs when a 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. They are often used to maintain posture and stability in the body. In contrast, isotonic contractions involve the muscle changing length as it moves a load and can be either concentric (shortening) or eccentric (lengthening). Isometric contractions may be a good way to start resistive training when there is little movement, as they can help activate and strengthen muscles without putting excessive strain on the joints.