ACSM Personal Trainer Certification Practice Exam

Which contraction type results in no change in muscle length?

1. Isotonic Contraction

2. Isometric Contraction

3. Eccentric Contraction

4. Concentric Contraction

The correct answer is: Isometric Contraction

The type of contraction that results in no change in muscle length is the isometric contraction. During an isometric contraction, the muscle generates force without changing its length, meaning that the tension in the muscle increases, but the angle of the joint remains constant. This happens when the muscle is activated but is not allowed to shorten or lengthen; for example, when pushing against a wall. In contrast, isotonic contractions involve changes in muscle length; they are further categorized into eccentric and concentric contractions. Eccentric contractions occur when the muscle lengthens while producing force, and concentric contractions happen when the muscle shortens while contracting. Therefore, isometric contractions are unique in that they maintain muscle length, a key characteristic that distinguishes them from the others.