Which type of contraction occurs when the muscle lengthens while generating force?

Which type of contraction occurs when the muscle lengthens while generating force?

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

Answer: (B)

The concept tested is how muscle length changes while it is generating force. When a muscle produces force and its length increases, that is called an eccentric contraction. A practical example is slowly lowering a dumbbell during a bicep curl—the muscle is actively resisting the downward force, still generating tension, but it is lengthening. This differs from a concentric contraction, where the muscle shortens while generating force (like lifting the dumbbell). It also differs from an isometric contraction, where the muscle tenses but does not change length. Isokinetic refers to movement performed at a constant speed, which can occur with either concentric or eccentric contractions depending on the direction of movement, but the defining feature here is the lengthening under load, which identifies the eccentric type.

The concept tested is how muscle length changes while it is generating force. When a muscle produces force and its length increases, that is called an eccentric contraction. A practical example is slowly lowering a dumbbell during a bicep curl—the muscle is actively resisting the downward force, still generating tension, but it is lengthening.

This differs from a concentric contraction, where the muscle shortens while generating force (like lifting the dumbbell). It also differs from an isometric contraction, where the muscle tenses but does not change length. Isokinetic refers to movement performed at a constant speed, which can occur with either concentric or eccentric contractions depending on the direction of movement, but the defining feature here is the lengthening under load, which identifies the eccentric type.