College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What occurs during an isotonic contraction?

1. The muscle remains static

2. The muscle fibers lengthen

3. The muscle contracts and shortens

4. The muscle undergoes stretching with force

The correct answer is: The muscle contracts and shortens

During an isotonic contraction, the muscle contracts and shortens, resulting in movement of the attached bones. This type of contraction is characterized by a change in muscle length while the tension remains constant. This can occur during various physical activities such as lifting weights or performing any action that requires movement. When a muscle contracts isotonicly, it generates enough force to overcome the resistance, allowing for dynamic movement. In contrast, during isometric contractions, which would be relevant to the static muscle option, there is no change in muscle length despite the force being applied. This is not applicable to isotonic contractions. While muscles can stretch and lengthen, that typically describes eccentric contractions rather than isotonic contractions specifically. Therefore, the primary defining feature of isotonic contractions is the shortening and movement enabled by the muscle fibers contracting.