Review Question - QID 219784

A 28-year-old professional baseball pitcher presents to the clinic for evaluation of medial-sided elbow pain that occurred acutely while pitching in a game two days ago. On examination, there is pain and swelling overlying the medial epicondyle. Moreover, pain is reproduced with valgus stress when pulling on the patient's thumb with the elbow flexed at 90 degrees, in addition to throughout elbow flexion and extension. The structure suspected to be injured in this patient is most commonly injured during which phase of throwing?