Which of the following is NOT one of the major muscle groups trained in weightlifting?

The trapezius is indeed an important muscle group often worked during various exercises, particularly those that involve pulling or lifting motions. However, it is not typically classified as one of the primary muscle groups targeted specifically in traditional weightlifting routines.

In contrast, the pectorals (chest muscles), hamstrings (back of the thighs), and deltoids (shoulder muscles) are major muscle groups that are commonly emphasized in weightlifting and strength training programs. The pectorals are primarily engaged during pressing movements such as bench presses, hamstrings play a significant role during lower body lifts such as deadlifts and leg curls, and the deltoids are worked during shoulder presses and lateral raises.

Understanding the focus of traditional weightlifting allows for better programming and muscle group targeting, hence why recognizing the trapezius as less central in this context is important for personal trainers.