Which muscle action occurs when the muscle shortens during contraction?

Which muscle action occurs when the muscle shortens during contraction?

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

Answer: (C)

Shortening a muscle while it contracts is called a concentric contraction. When the muscle fibers actively shorten, they pull on the bones to produce movement against resistance, such as lifting a dumbbell or flexing the elbow. The key idea is the length of the muscle decreases during the contraction. In contrast, an eccentric contraction occurs when the muscle lengthens while generating force (like slowly lowering a weight). An isometric contraction generates tension without any change in muscle length (holding a weight steady). Isokinetic contraction refers to a movement performed at a constant speed, typically with special equipment, and isn’t defined by whether the muscle shortens or lengthens.

Shortening a muscle while it contracts is called a concentric contraction. When the muscle fibers actively shorten, they pull on the bones to produce movement against resistance, such as lifting a dumbbell or flexing the elbow. The key idea is the length of the muscle decreases during the contraction.

In contrast, an eccentric contraction occurs when the muscle lengthens while generating force (like slowly lowering a weight). An isometric contraction generates tension without any change in muscle length (holding a weight steady). Isokinetic contraction refers to a movement performed at a constant speed, typically with special equipment, and isn’t defined by whether the muscle shortens or lengthens.