Which type of muscle contraction occurs without joint movement?

Which type of muscle contraction occurs without joint movement?

• A. Isometric
• B. Isotonic
• C. Concentric
• D. Eccentric

Answer: (A)

The correct answer is isometric contraction. In an isometric contraction, the muscle generates force without changing its length, which means there is no movement at the joint. This occurs when a muscle is activated and holds a position against a resistance, such as pushing against an immovable object or holding a weight steady without moving it. This type of contraction is essential for stabilizing joints and maintaining posture. In contrast, isotonic contractions involve joint movement, where the muscle changes length during the contraction. This can include concentric contractions, where the muscle shortens as it contracts (like lifting a weight), and eccentric contractions, where the muscle lengthens while still generating force (like lowering a weight). Both isotonic types lead to visible movements at the joints, which is why they do not fit the definition of a contraction occurring without joint movement.

The correct answer is isometric contraction. In an isometric contraction, the muscle generates force without changing its length, which means there is no movement at the joint. This occurs when a muscle is activated and holds a position against a resistance, such as pushing against an immovable object or holding a weight steady without moving it. This type of contraction is essential for stabilizing joints and maintaining posture.

In contrast, isotonic contractions involve joint movement, where the muscle changes length during the contraction. This can include concentric contractions, where the muscle shortens as it contracts (like lifting a weight), and eccentric contractions, where the muscle lengthens while still generating force (like lowering a weight). Both isotonic types lead to visible movements at the joints, which is why they do not fit the definition of a contraction occurring without joint movement.