IFPA Trainer Practice Exam

Which type of contraction involves a muscle shortening as it contracts?

1. Eccentric

2. Concentric

3. Isometric

4. Dynamic constant resistance

The correct answer is: Concentric

The type of contraction that involves a muscle shortening as it contracts is known as concentric contraction. When a muscle contracts concentrically, it generates force while shortening, which typically occurs during movements such as lifting weights or performing a bicep curl. For instance, when you lift a dumbbell towards your shoulder, the bicep muscle contracts concentrically, resulting in the shortening of the muscle fibers and allowing for the upward movement of the forearm. In contrast, eccentric contractions occur when a muscle lengthens while under tension, such as during the lowering phase of a squat. Isometric contractions involve no change in muscle length, as the muscle generates force without shortening or lengthening, like when holding a plank position. Dynamic constant resistance involves varied muscle contractions, including both concentric and eccentric movements, usually against a constant resistance but does not specifically refer only to shortening contractions. Understanding these distinctions is fundamental for trainers and coaches when developing effective exercise programs and biomechanics.