ACSM Personal Trainer Certification Practice Exam

When does eccentric contraction occur?

1. When muscle fibers shorten

2. When muscle fibers stabilize

3. When muscle fibers lengthen under load

4. When muscle fibers remain static

The correct answer is: When muscle fibers lengthen under load

Eccentric contraction occurs when muscle fibers lengthen under load. This type of contraction is commonly experienced during activities where the muscle is actively resisting an external force while it is being elongated. For instance, during a controlled descent in a squat or while lowering a weight, the muscles involved are generating force while they are stretching, which is a defining characteristic of eccentric contractions. This process is important for maintaining control of movement, decelerating body parts, and absorbing shock, which can help prevent injury. Understanding eccentric contraction is critical for trainers to effectively design programs that promote strength, balance, and flexibility, as it plays a significant role in functional activities and overall musculo-skeletal health.