What type of muscle contractions are characterized by tension development while the muscle lengthens?

Eccentric contractions are characterized by the muscle generating tension while lengthening. This typically occurs when a muscle is working against a load that is greater than the force the muscle can produce, causing it to elongate during the contraction. An example of this type of contraction is when lowering a weight, where the muscle must control the descent and effectively 'brake' against gravity.

In contrast, concentric contractions involve the muscle shortening as it generates force, often seen during the lifting phase of an exercise. Isometric contractions occur when the muscle exerts force without any change in length, such as holding a position steady against a resistance. Isokinetic contractions involve muscle contractions at a constant speed throughout the range of motion, often requiring specialized equipment to maintain that speed. Therefore, the defining feature of eccentric contractions is their ability to create tension while the muscle is actively lengthening, making it the correct choice for this question.