What is the primary focus of back rowing prep 4 with biceps curls?

The primary focus of back rowing prep 4 with biceps curls emphasizes the engagement of the biceps, anterior deltoids, and pectoralis major. This exercise is designed to strengthen the upper body, particularly by targeting these key muscle groups during the rowing movement combined with the bicep curl.

In back rowing prep 4, the activity requires the participant to pull against the resistance of the reformer, which actively engages the biceps as they contract to perform the curl. Simultaneously, the anterior deltoids contribute to the movement, helping with shoulder flexion during the exercise. The pectoralis major is also involved as it aids in stabilizing the shoulder joint and supporting the forward pulling motion. Therefore, by focusing on these muscle groups, the exercise enhances strength and stability in the upper body, making option A the correct choice.