ACE Personal Trainer Practice Exam

When controlling the weight at a slow pace, eccentric action is the type of muscle action that is primarily taking place. This is characterized by the lengthening of the muscle fibers as they contract under load. For example, when lowering a weight in a controlled manner, the muscle is actively working to resist the force of gravity while elongating, which leads to greater tension and promotes muscle growth as well as increased strength.

Eccentric actions are particularly important in strength training because they allow for more tension to be generated within the muscle compared to concentric actions, where the muscle shortens while contracting. The control during lowering, or the eccentric phase, is crucial for injury prevention as it requires stability and strength.

In contrast, concentric actions involve the muscle shortening to lift a weight, isometric actions refer to muscle contractions where the muscle length does not change, and isotonic actions combine both concentric and eccentric actions without changing tension. Thus, eccentric action is specifically associated with the control involved in lowering weights slowly, making it the correct choice in this scenario.