ACSM Personal Trainer Certification Practice Exam

What type of contraction occurs when muscle fibers shorten while producing force?

1. Eccentric Contraction

2. Isometric Contraction

3. Concentric Contraction

4. Isokinetic Contraction

The correct answer is: Concentric Contraction

The type of contraction where muscle fibers shorten while producing force is known as concentric contraction. During a concentric contraction, the tension in the muscle is sufficient to overcome the resistance placed upon it, resulting in the muscle fibers getting shorter as they actively contract. This process is commonly observed in movements like lifting weights, where the muscles shorten as they exert force to move an object against gravity. In contrast, eccentric contractions occur when muscles lengthen while producing force, typically against resistance, such as lowering a weight. Isometric contractions occur when muscles generate force without any visible change in length, meaning the muscle remains the same length while contracting. Isokinetic contractions involve the muscle shortening and lengthening at a constant speed with accommodating resistance, which is not the primary focus when discussing simple shortening of muscle fibers while producing force. Understanding these different types of contractions is crucial for developing effective training programs as each plays a distinct role in muscle performance and rehabilitation.