What is the primary source of dysfunction in the cocking phase of throwing, and which muscles are especially important for this phase?

• A. Insufficient positional timing of contralateral rotation between the pelvis and trunk; the lower trapezius, internal oblique, and bilateral serratus anterior are essential.
• B. Over-activation of pectoralis major.
• C. Weak rotator cuff.
• D. Excessive biceps activation.

Answer: (A)